NAVAIR 01 1A 35

NAVAIR 01-1A-35 31 August 2005 TECHNICAL MANUAL MAINTENANCE INSTRUCTIONS ORGANIZATIONAL, INTERMEDIATE, AND DEPOT AIRC...
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NAVAIR 01-1A-35 31 August 2005

TECHNICAL MANUAL

MAINTENANCE INSTRUCTIONS ORGANIZATIONAL, INTERMEDIATE, AND DEPOT

AIRCRAFT FUEL CELLS AND TANKS

This revision supercedes NAVAIR 01-1A-35, dated 15 January 2001 and incorporates IRACs 11, 12, and 13.

DISTRIBUTION STATEMENT A. Approve for public release; distribution is unlimited. DESTRUCTION NOTICE - For unclassified, limited documents, destroy by any method that will prevent disclosure of contents or reconstruction of the document.

PUBLISHED BY DIRECTION OF THE COMMANDER, NAVAL AIR SYSTEMS COMMAND

0801LP1046199

NAVAIR 01-1A-35 Page A NUMERICAL INDEX OF EFFECTIVE WPS/PAGES List of Current Changes Original ......................... 0...................... 31 Aug 2005 (Includes IRAC 11, 12, and 13) Only those pages assigned to the manual are listed in this index. If changed pages are issued, insert the changed pages and dispose of superseded pages, including classified data, in accordance with applicable regulations. The portion of text affected by the change is indicated by change bars or the symbol “R” in the outer margin of each column of text. Changes to illustrations are indicated by pointing hands, change bars, or shaded areas as applicable. Total number of pages in this manual is 384 consisting of the following:

WP/Page No.

*Change No.

Title ....................................... 0 A - B ...................................... 0 C Blank ................................. 0 TPDR-1................................. 0 TPDR-2 Blank....................... 0 HMWS-1 1 – 6.................................. 0 001 00 1 - 3 .................................. 0 4 Blank.............................. 0 002 00 1 -25 ................................. 0 26 Blank ........................... 0 003 00 1 - 5 .................................. 0 6 Blank.............................. 0 004 00 1 - 19 ................................ 0 20 Blank ........................... 0 005 00 1 - 3 .................................. 0 4 Blank.............................. 0 006 00 1 - 20 ................................ 0

WP/Page No.

*Change No.

007 00 1 - 10 ................................ 0 008 00 1 - 5 .................................. 0 6 Blank ............................. 0 009 00 1 - 4 .................................. 0 010 00 1 - 13 ................................ 0 14 Blank ........................... 0 011 00 1 - 6 .................................. 0 012 00 1 - 10 ................................ 0 013 00 1 - 58 ................................ 0 014 00 1 - 12 ................................ 0 015 00 1 - 54 ................................ 0 016 00 1 - 54 ................................ 0 017 00 1 – 8 ................................. 0

*Zero in this column indicates an original page.

WP/Page No.

*Change No.

018 00 1 - 18 ............................... 0 019 00 1 - 4 ................................. 0 020 00 1 - 8 ................................. 0 021 00 1 - 15 ............................... 0 16 Blank .......................... 0 022 00 1 - 11 ............................... 0 12 Blank .......................... 0

NAVAIR 01-1A-35 Page B/(C Blank)

LIST OF TECHNICAL PUBLICATIONS DEFICIENCY REPORT INCORPORATED MAINTENANCE INSTRUCTIONS ORGANIZATIONAL, INTERMEDIATE, AND DEPOT AIRCRAFT FUEL CELLS AND TANKS

The TPDRs listed below have been incorporated in this issue. Identification No. 09122 2004 0001 09281 2004 0002 09674 2004 0008 30338 2002 N001 30338 2002 N002 30338 2002 N008 30338 2003 N032 30338 2003 N033 30338 2003 N034 30338 2003 N035 30338 2003 N036 30338 2003 N037 30338 2003 N038 30338 2003 N039 30338 2003 N040 33207 2002 0001 39501 2004 0001 44328 2004 0040 52813 2003 0001 52814 2001 0027 52814 2001 0031 52873 2004 0012 53823 1995 0004 55584 2004 0203 5Z623 2005 0147 65886 2004 0521 65886 2004 0580 65888 2001 0215 65888 2003 0868 80338 2001 N007 80338 2001 N008 97819 2002 0115 N3168 2003 0002

VFA82 VF143 PATRON 40 NATEC New Orleans NATEC New Orleans NATEC New Orleans NATEC New Orleans NATEC New Orleans NATEC New Orleans NATEC New Orleans NATEC New Orleans NATEC New Orleans NATEC New Orleans NATEC New Orleans NATEC New Orleans NATEC Camp Pendleton VR-51 COMAEWWINGPAC DET AIMD Raytheon Aerospace Sikorsky Support Services, Inc Sikorsky Support Services, Inc HSL-37 Patrol Wing Five HSL-51 DET 2 Cecil Field NAVAIRDEPOT JAX NAVAIRDEPOT JAX NADEP NORIS NADEP NORIS NATEC New Orleans NATEC New Orleans COMTRAWING ONE NRLFSD

Location WP 004 WP 018 WP 004 WP 004, pgph 26 WP 004, pgph 48a WP 004 WP 004 WP 004 WP 004 WP 004 WP 004 WP 004 WP 004 WP 004 WP 004, pgph 64 WP 006, pgph 26 WP 002, Table 2-6 WP 018 WP 004, pgph 70 WP 006, pgph 26 WP 004, pgph 70, WP 003, pgph 15 WP 005, pgph 4 WP 009, pgph 2g(7) WP 004 WP 006, pgph 26 WP 009, pgph 2g(7) WP 018 WP 012, pgph 3a(10) WP 015, Table 15-1 WP 004 WP 004 WP 004 WP 004

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141601Z MAR 07 P INTERIM RAPID ACTION CHANGE (IRAC) 16 TO TECHNICAL MANUAL NA 01-1A-35 OF 31 AUG 2005 MSGID/GENADMIN/NAVAIRDEPOT CHERRY PT NC// REF/A/DESC:DOC/NA 01-1A35/31AUG2005// AMPN/REF A IS THE AIRCRAFT FUEL CELLS AND TANKS MANUAL.//AIG 7658 POC/A. KOONCE/ENGR/4.9.7.5/LOC:CHERRY PT NC/TEL:(2520 464-9341 /TEL:DSN 451-9341/EMAIL:[email protected]// GENTEXT/REMARKS/1. RESPONSIBLE CODE: NAVAIRDEPOT CHERRY PT NC, MATERIALS ENGINEERING, CODE 4.9.7.5, A. KOONCE, PRIPHN DSN 451-9341, EMAIL: [email protected]. GENERAL SERIES PUBLICATIONS, CODE 6.8.5.1, K. FOSTER, PRIPHN DSN 451-5580, EMAIL: [email protected]. 2. CONDITION AND PURPOSE OF CHANGE: TO PREVENT UNNECESSARY EXPENDITURES OF MAN HOURS AND MATERIALS AND INCREASE MISSION CAPABILITY/READINESS. 3. DETAILED INFORMATION: A. PEN AND INK CHANGES TO THE TECHNICAL CONTENT OF A MANUAL ARE NOT AUTHORIZED. THE FOLLOWING TECHNICAL CONTENT CHANGE INFORMATION APPLIES TO THE FOLLOIWNG REFERENCED PAGES AND PARAGRAPHS OF THE SUBJECT MANUAL UNTIL THE FORMAL CAHNGE IS RELEASED. B. CHANGE WORK PACKAGE 4, PARAGRAPH 38D, PAGE 6 TO READ: THE CO OR A DESIGNATED INDIVIDUAL SHALL SIGN AND DATE LETTERS OF CERTIFICATION FOR ENTRY AUTHORITIES. THE CO MAY DELEGATE ENDORSEMENT OF CERTIFICATION LETTERS THROUGH WRITTEN INSTRUCTIONS WHICH ARE AVAILABLE FOR REVIEW. THE CERTIFICATION LETTER FOR AND ENTRY AUTHORITY SHALL STATE THE FUNCTIONS FOR WHICH THE INDIVIDUAL IS QUALIFIED TO PERFORM (SUCH AS HOT WORK). A SAMPLE CERTIFICATION LETTER, FIGURE 4-1, IS AN EXAMPLE FOR CONTENT ONLY, AND MAY BE ALTERED TO FIT THE COMMAND'S REQUIREMENTS. 4. VALIDATED BY: NAVAIRDEPOT CHPT, CODE 4.9.7.4, A. KOONCE, PRIPHN 451-9341. 5. RELATED INSTRUCTIONS: A. FOR PAPER COPY - MAINTAIN THIS IRAC WITH THE APPLICABLE MANUAL BY PLACING OR ATTACHING IT DIRECTLY BEHIND THE TITLE PAGE. MARK THE SPECIFIC CHANGE AREA IN TEH MARGIN OF EACH PAGE AFFECTED WITH A VERTICAL LINE, AND INCLUDE HTE IRAC NUMBER AND DATE TIME GROUP (DTG) OF THE IRAC MSG. THIS IRAC SHALL NOT BE REMOVED UNTIL RECEOPT OF THE FORMAL CAHNGE PAGES. B. FOR IRACS AFFECTING MANUALS ON CD-ROM: AFFIX AND ADHESIVE LABLE TO THE CD-ROM CASE, ANNOTATED WITH TE4H APPLICABLE PUBLICATION NUMBER, IRAC NUMBER AND DTG OF THE IRAC MSG. THE LABEL SHOULD BE POSITIONED TO ALLOW FOR ADDITIONAL UPDATES AS THE OCCUR. MAINTAIN THE IRAC ON FILE UNTIL RECEIPT OF THE SUPERSEDING CD-ROM. \ C. SUBJ. IRAC SHALL BE INCORPORATED INTO APPLICABLE MANUAL NO LATER THAN 12 MONTHS AFTER IRAC ISSUE DATE BY NAVAIRDEPOT CHPT NC, CODE 3.3.1. D. TO ASSIST US IN MEASURING OUR PERFORMANCE, PLEASE PROVIDE FEEDBACK ON THE QUALITY OF THIS PRODUCT BY ACCESSING HTTP:/WWW.NADEPCP.NAVY.MIL/FEEDBACK/PRODUTCOMMENTS.CFM//

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081346Z SEP 06 P INTERIM RAPID ACTION CHANGE (IRAC) NO. 15 TO TECHNICAL MANUAL 01-1A-35 PASS TO OFFICE CODES: FM NAVAIRDEPOT CHERRY PT NC//4.9.7.5// TO AIG 165 AIG 7658 AIG 13734 INFO COMNAVAIRFOR SAN DIEGO CA COMNAVAIRFORES SAN DIEGO CA COMNAVAIRSYSCOM PATUXENT RIVER MD NATEC SAN DIEGO CA NAVAIRDEPOT CHERRY PT NC //N04730// MSGID/GENADMIN/NAVAIRDEPOT CHERRY PT NC// REF/A/DOC/NA 01-1A-35/31AUG2005// REF/B/DOC/NA 00-25-100/01JUL2006// NARR/REF A IS TECHNICAL MANUAL NAVAIR 01-1A-35, MAINTENANCE INSTRUCTIONS ORGANIZATIONAL INTERMEDIATE, AND DEPOT AIRCRAFT FUEL CELLS AND TANKS. REF B IS THE NAVAL AIR SYSTEMS COMMAND TECHNICAL MANUAL PROGRAM.// POC/A. S. KOONCE/ENGR/4.9.7.4/NAVAIRDEPOT CHPT NC/TEL:(252) 464-9341 /TEL:DSN 451-9341/EMAIL:[email protected]// GENTEXT/REMARKS/ 1. RESPONSIBLE CODE: A. S. KOONCE, NAVAIRDEPOT CHERRY POINT, NC, AIR-4.9.7.4, TEL: (252)464-9341, DSN 451-9341, EMAIL: [email protected]. K. FOSTER, NAVAIRDEPOT CHERRY POINT, NC, CODE 3.3.1, TEL: (252)464-5514, DSN: 451-5514, EMAIL: [email protected]. 2. CONDITION AND PURPOSE OF CHANGE: TO PREVENT UNNECESSARY EXPENDITURES OF MAN-HOURS AND MATERIALS AND INCREASE MISSION CAPABILITY/READINESS BY UPDATING AVIATION CONFINED SPACE SAFETY INSPECTIONS. 3. DETAILED INFORMATION: A. PEN AND INK CHANGES TO THE TECHNICAL CONTENT OF A MANUAL ARE NOT AUTHORIZED. THE FOLLOWING TECHNICAL CONTENT CHANGE INFORMATION APPLIES TO THE FOLLOWING REFERENCED PAGES AND PARAGRAPHS OF THE SUBJECT MANUAL UNTIL THE FORMAL UPDATE IS RELEASED. B. IN WP 004 00, PAGE 14, TABLE 4-1 OF REF A: (1) CHANGE THE WORDING OF THE CLASS 6 DESCRIPTION TO READ AS FOLLOWS: For HAZARD FREE CONDITION FUEL CELLS, DROP TANKS, EXTENDED RANGE TANKS, ETC. C. IN WP 004 00, PAGE 16, PARAGRAPH 73 OF REF A: (1) ADD NOTE UNDER PARAGRAPH 73: NON-INTRINSICALLY SAFE RADIOS ARE ALLOWED ON AIRCRAFT WHILE ALL FUEL CELLS OR TANKS ON THAT AIRCRAFT ARE IN THIS CONDITION. (2) ADD NOTE UNDER PARAGRAPH 73: WEARING OF WHITE COTTON COVERALLS IS NOT REQUIRED WHILE FUEL CELLS OR TANKS ARE IN THIS CONDITION. 4. VALIDATED BY: A. S. KOONCE, NAVAIRDEPOT CHPT, AIR-4.9.7.4, TEL: (252)464-9341, EMAIL: [email protected]. 5. RELATED INSTRUCTIONS: A. FOR IRACS AFFECTING MANUALS IN PAPER COPY - MAINTAIN THIS IRAC WITH THE APPLICABLE MANUAL BY PLACING OR ATTACHING IT DIRECTLY BEHIND THE TITLE PAGE. MARK THE SPECIFIC AREA AFFECTED AND ANNOTATE THE CHANGED PAGE OR CARD LISTED ON THE A PAGE WITH A VERTICAL LINE IN THE MARGIN NEXT TO THE CHANGED DATA OPPOSITE THE BINDING. FOR DOUBLE COLUMN MATERIAL MARK THE CENTER MARGIN WHEN THE INNER

PARAGRAPH IS AFFECTED. NOTE THE IRAC NUMBER IN THE MARGIN. THIS IRAC SHALL NOT BE REMOVED UNTIL RECEIPT OF THE FORMAL CHANGE PAGES. B. FOR IRACS AFFECTING MANUALS ON CD-ROM - AFFIX AN ADHESIVE LABEL TO THE CD-ROM CASE ANNOTATED WITH THE APPLICABLE PUBLICATION NUMBER AND IRAC NUMBER. THE LABEL SHOULD BE POSITIONED TO ALLOW FOR ADDITIONAL IRACS AS THEY OCCUR AND SHOULD NOT COVER THE DATE OR CD TITLE. MAINTAIN THE IRAC ON FILE UNTIL RECEIPT OF THE SUPERSEDING CD-ROM. C. IAW REF B SUBJECT IRAC SHALL BE INCORPORATED INTO APPLICABLE MANUAL NO LATER THAN 12 MONTHS AFTER IRAC ISSUE DATE BY NAVAL AIR DEPOT, CHPT NC, CODE 3.3.1. D. TO ASSIST US IN MEASURING OUR PERFORMANCE, PLEASE PROVIDE FEEDBACK ON THE QUALITY OF THIS PRODUCT BY ACCESSING HTTP:/WWW.NADEPCP.NAVY.MIL/CUSTSATSURVEY/CUSTSATSURVEY.CFM//

PRIORITY P 261905Z JAN 06 PSN 617202Q18 FM NAVAIRDEPOT CHERRY PT NC TO AIG 13734 ZEN/MENT/OU=DOD/OU=NAVY/OU=ADDRESS LISTS(UC)/CN=AL 7658(UC) ZEN/AIG 7658 ZEN/NMENT/OU=DOD/OU=NAVY/OU=ADDRESS LISTS(UC)/CN=AL 165(UC) ZEN/AIG 165 ZEN/ENT/OU=DOD/OU=NAVY/OU=ADDRESS LISTS(UC)/CN=AL 13734(UC) INFO ZEN/COMNAVAIRFOR SAN DIEGO CA ZEN/COMNAVAIRSYSCOM PATUXENT RIVER MD ZEN/NATEC SAN DIEGO CA ZEN/NAVAIRDEPOT CHERRY PT NC BT UNCLAS QQQQ SUBJ: (261905Z JAN 06) INTERIM RAPID ACTION CHANGE (IRAC) NO. 14 TO T ECHNICAL MANUAL UNCLASSIFIED// UNCLAS //N04730// MSGID/GENADMIN/NAVAIRDEPOT CHERRY PT NC// SUBJ/INTERIM RAPID ACTION CHANGE (IRAC) NO. 14 TO TECHNICAL MANUAL// REF/A/DOC/NA 01-1A-35/31AUG2005// POC/A. S. KOONCE/ENGR/4.9.7.4/NAVAIRDEPOT CHPT NC/TEL:(252) 464-9341 /TEL:DSN 451-9341/EMAIL:[email protected]// GENTEXT/REMARKS/ 1. RESPONSIBLE CODE: A. S. KOONCE, NAVAIRDEPOT CHERRY POINT, NC, AIR-4.9.7.4, PRIPHN DSN: 451-9341, TEL: (252) 464-9341, EMAIL: [email protected]. K. FOSTER, NAVAIRDEPOT CHERRY POINT, NC, CODE 3.3.1, PRIPHN DSN: 451-5514, TEL: (252) 464-5514, EMAIL: [email protected]. 2. CONDITION AND PURPOSE OF CHANGE: TO PREVENT UNNECESSARY EXPENDITURES OF MAN-HOURS AND MATERIALS AND INCREASE MISSION CAPABILITY/READINESS BY UPDATING INSPECTION CRITERIA FOR FUEL CELL FITTINGS. 3.

DETAILED INFORMATION: A. PEN AND INK CHANGES TO THE TECHNICAL CONTENT OF A MANUAL ARE NOT AUTHORIZED. THE FOLLOWING TECHNICAL CONTENT CHANGE INFORMATION APPLIES TO THE FOLLOWING REFERENCED PAGES AND PARAGRAPHS OF THE SUBJECT MANUAL UNTIL THE FORMAL UPDATE IS RELEASED. B. ADD THE FOLLOWING PARAGRAPHS AFTER THE LAST ENTRY INTO TABLE 16-1, PAGE 4, WP 016: (1) COLUMN 1: DEFECT: DAMAGED DOME NUT. COLUMN 2: LIMITATION: UNACCEPTABLE (2) COLUMN 1: DEFECT: CUTS, TEARS, OR DEEP INDENTATIONS TO THE

FITTING INSERT OR DOME NUT RUBBER END CAP AND SEALANT OVERCOAT. COLUMN 2: LIMITATION: PHYSICAL DAMAGE UNACCEPTABLE. INDENTATIONS ACCEPTABLE PROVIDED SERVICEABILITY IS NOT AFFECTED. (SEE NOTE 1). (3) NOTES: 1. CERTAIN FITTINGS HAVE BOTH LONG AND SHORT INSERT OR DOME NUT RUBBER END CAPS WHERE LONGER END CAPS ARE USED FOR POSITIONING FITTING IN CELL. DAMAGE TO LONGER END CAP IS ACCEPTABLE ONLY IF ALL INSERTS AND BOLTS IN FITTING ARE SAME LENGTH, AND DAMAGE IS LIMITED ONLY TO PORTION OF RUBBER CAP ABOVE HEIGHT OF ADJACENT SHORTER END CAPS. C. INSERT NOTE AFTER PARAGRAPH 13, WP 003, PAGE 4: MAINTENANCE IS NOT AUTHORIZED ON THE XP-25A. UNDERWRITERS LABORATORIES (UL) REQUIRES THAT THE EXPLOSION PROOF LIGHT GLOBE REPLACEMENT BE MADE BY THE MANUFACTURER. BULB AND GLOBE GASKETS ARE NOT AVAILABLE IN THE SUPPLY SYSTEM. 4. VALIDATED BY: A. S. KOONCE, NAVAIRDEPOT CHPT, AIR-4.9.7.4, TEL: (252) 464-9341, EMAIL: [email protected]. 5.

RELATED INSTRUCTIONS: A. FOR IRACS AFFECTING MANUALS IN PAPER COPY - MAINTAIN THIS IRAC WITH THE APPLICABLE MANUAL BY PLACING OR ATTACHING IT DIRECTLY BEHIND THE TITLE PAGE. MARK THE SPECIFIC AREA AFFECTED AND ANNOTATE THE CHANGED PAGE OR CARD LISTED ON THE A PAGE WITH A VERTICAL LINE IN THE MARGIN NEXT TO THE CHANGED DATA OPPOSITE THE BINDING. FOR DOUBLE COLUMN MATERIAL MARK THE CENTER MARGIN WHEN THE INNER PARAGRAPH IS AFFECTED. NOTE THE IRAC NUMBER IN THE MARGIN. THIS IRAC SHALL NOT BE REMOVED UNTIL RECEIPT OF THE FORMAL CHANGE PAGES. B. FOR IRACS AFFECTING MANUALS ON CD-ROM - AFFIX AN ADHESIVE LABEL TO THE CD-ROM CASE ANNOTATED WITH THE APPLICABLE PUBLICATION NUMBER AND IRAC NUMBER. THE LABEL SHOULD BE POSITIONED TO ALLOW FOR ADDITIONAL IRACS AS THEY OCCUR AND SHOULD NOT COVER THE DATE OR CD TITLE. MAINTAIN THE IRAC ON FILE UNTIL RECEIPT OF THE SUPERSEDING CD-ROM. C. SUBJECT IRAC SHALL BE INCORPORATED INTO APPLICABLE MANUAL NO LATER THAN 12 MONTHS AFTER IRAC ISSUE DATE BY NAVAL AIR DEPOT, CHPT NC, CODE 3.3.1. D. TO ASSIST US IN MEASURING OUR PERFORMANCE, PLEASE PROVIDE FEEDBACK ON THE QUALITY OF THIS PRODUCT BY ACCESSING WWW.NADEPCP.NAVY.MIL/FEEDBACK/PRODUCTCOMMENTS.CFM.// BT #4684 NNNN

NAVAIR 01-1A-35

HMWS-1

31 August 2005 1.

GENERAL SAFETY INSTRUCTIONS.

The following general safety precautions are not related to any specific procedure and therefore do not appear elsewhere in this publication. These are precautions that personnel must understand and apply during all phases of operation and maintenance. a. KEEP AWAY FROM LIVE CIRCUITS. Operating personnel must observe safety precautions at all times. Do not replace components or make adjustments inside any equipment with the high voltage supply turned on. Under certain conditions, dangerous potentials may exist when the power control is in the off position, due to charges retained by capacitors. To avoid casualties, always remove power, discharge, and ground a circuit before touching it. b. DO NOT SERVICE OR ADJUST ALONE. Under no circumstances shall any person reach into or enter an enclosure for the purpose of servicing or adding the equipment, except in the presence of someone who is capable of rendering aid. c. RESUSCITATION. Personnel working with or near high voltages should be familiar with modern methods of resuscitation. Such information may be obtained from the Bureau of Medicine and Surgery. d. ENGINE NOISE. Personnel must observe the following precautions when working within danger areas of jet engines. (1) Wear the proper protection (earplugs and/or earmuffs). (2) Do not exceed the time limits of exposure to various sound intensities. (3) Have periodic checks on hearing ability. The wearing of regulation earplugs or earmuffs will raise the time limits of exposure. All personnel working within danger areas should be familiar with calculated sound levels (as specified in the general information section of applicable Maintenance Instruction Manual) and should wear the necessary protection equipment. e. FLIGHT LINE SAFETY PRECAUTIONS. Personnel working in or around aircraft on the flight line shall observe flight line safety precautions and regulations. f. USE SAFETY SHIELDS. Observe applicable safety regulations and use safety shields on power tools where provided. Adequate shielding to protect eyes and face shall be used at all times when operating power tools or performing pressure tests. g. HANDLING FLUIDS AND GASSES. Observe applicable safety precautions when using fluids or gasses, which are flammable or toxic. Do not use gasses or fluids, which are not positively identified. h. SEAT EJECTION MECHANISMS. Safety precautions shall be strictly observed when working around

aircraft equipped with an ejection seat. These safety precautions cannot be overemphasized. Each ejection seat has several ground safety pins. These safety pins are provided on red-flagged lanyards for use at every point of potential danger. They shall be installed whenever the aircraft is on the ground or deck, and must never be removed until the aircraft is ready for flight. The following general precautions should always be kept in mind: (1) Ejection seats shall be treated with the same respect as a loaded gun. (2) Always consider an ejection seat system as loaded and armed. (3) Before entering a cockpit, know where the ejection seat safety pins are and be certain of their installation. (4) Only authorized personnel may work on or remove/install ejection seats and components, and only in authorized area. 2.

WARNINGS AND CAUTIONS USED IN TEXT.

a. Warnings for hazardous substances have been developed from dated manufacturer's Material Safety Data Sheets (MSDSs), when available. Each warning is valid as of its specific preparation date. To ensure compliance with current precautionary information: Read and follow specific instructions in MSDS for types of personal protective equipment (safety glasses, gloves, apron, etc.), for use of ventilators or respirators, for types of fire extinguishers, and for treating medical emergencies. Read and follow the hazardous materials label posted on the container for the specific substance and the MSDS supplied by the manufacturer. Follow established shop practices and procedures when using, handling, and storing hazardous materials. Dispose of hazardous materials by complying with existing federal, state, or local regulations. b. Warnings, cautions, and notes will be found throughout the manual in various procedures. It is important that the significance of each be thoroughly understood by personnel using the manual. Their definitions are:

NAVAIR 01-1A-35

HMWS-2 identifier assigned at its initial appearance. The following is an explanation of the general hazard symbols used in this manual.

An operating or maintenance procedure, practice, condition, statement, etc., which if not strictly observed, could result in injury or death of personnel.

In the text of the manual, the caption WARNING will not be used for hazardous materials. Such warnings will be identified by an icon and numeric identifier. The material nomenclature will also be provided. The user is directed to refer to the corresponding numeric identifier listed, beginning on page vi, for the complete warning applicable to the hazardous materials. 4.

An operating or maintenance procedure, practice, condition, statement, etc., which if not strictly observed, could result in damage to, or destruction of, equipment or loss of mission effectiveness.

NOTE An essential operating or maintenance procedure, condition, or statement, which, must be highlighted. 3.

HAZARDOUS MATERIALS WARNINGS.

Warnings for hazardous materials listed in this manual are designed to warn personnel of hazards associated with such items when they come in contact with them by actual use. Additional information related to hazardous materials is provided in OPNAVINST 5100.23 Series, Navy Occupational Safety and Health (NAVOSH) Program Manual, NAVSUPINST 5100.27 Series, Navy Hazardous Material Control Program, and the DOD 6050.5, Hazardous Materials Information System (HMIS) series publications. For each hazardous material used within the Navy, a material safety data sheet (MSDS) is required to be provided and available for review by users. Consult your local safety and health staff concerning any question on hazardous chemicals, MSDS's, personal protective equipment requirements, and appropriate handling and emergency procedures and disposal guidance. The selection of personal protective equipment should be made by the material user, based on the particular conditions; where and how the material is to be used, together with information provided by the safety and health staff. Complete warnings for hazardous materials referenced in this manual are identified by use of an icon, nomenclature and specification or part number of the material and a numeric identifier. The numeric identifiers have been assigned to the hazardous materials in the order of their appearance in the manual. Each hazardous material is assigned only one numeric identifier. Repeated use of a specific hazardous material references the numeric

HAZARDOUS MATERIALS ICONS.

Icons are used in this manual to identify dangers associated with hazardous materials. The icons used and their definitions are as follows. Biological - The abstract symbol bug shows that material may contain bacteria or viruses that present a danger to your life or health. Chemical - The symbol of drops of a liquid onto a hand shows that a material will cause burns or irritation of human skin or tissue. Cryogenic - The symbol of a human hand in a block of ice shows that the material is extremely cold and can injure human skin or tissue. Explosion - The rapidly expanding symbol shows that the material may explode if subjected to high temperatures, sources of ignition, or high pressure. Eye - The symbol of a person wearing goggles shows that the material will injure your eyes. Fire - The symbol of a flame shows that a material can ignite and burn you. Poison - The symbol of a skull and crossbones shows Radiation – The symbol of three circular wedges shows that a material emits radioactive energy and can injure human tissue or organs. Vapor – The symbol of a human figure in a cloud shows that vapors of a material present a danger to your life and health through inhalation.

NAVAIR 01-1A-35 5.

HMWS-3

HAZARDOUS MATERIALS WARNING STATEMENTS Index

Material

Warning

1

CORROSION PREVENTIVE COMPOUND MIL-C-81309

MIL-C-81309 Corrosion Preventive Compound may cause eye and skin irritation. Overexposure may cause dizziness or other nervous system effects. For safety, use: Chemical splash proof goggles, gloves, and good ventilation. Consult the applicable Material Safety Data Sheet (MSDS) and local Occupational Safety and Health (OSH) regulations for appropriate safety precautions.

2

CLEANING COMPOUND MIL-PRF-85570

MIL-PRF-85570 Aircraft Cleaning Compound is irritating to skin and eyes. Prolonged contact may cause dermatitis. Wear chemical splash proof goggles and gloves. Use only with adequate ventilation. Consult the applicable Material Safety Data Sheet (MSDS) and local Occupational Safety and Health (OSH) regulations for appropriate safety precautions.

3

ISOPROPYL ALCOHOL TT-I-735

TT-I-735 Isopropyl Alcohol is flammable. Do not use near open flame or other sources of ignition. May irritate skin and eyes. Inhalation may cause dizziness, headaches and irritation to respiratory tract. PPE: Chemical splash proof goggles and gloves. Consult the applicable Material Safety Data Sheet (MSDS) and local Occupational Safety and Health (OSH) regulations for appropriate safety precautions.

4

DRY CLEANING SOLVENT MIL-PRF-680, Type II or III

MIL-PRF-680 Dry Cleaning Solvent may cause eye and skin irritation. Over exposure may cause dizziness and other central nervous system effects. PPE: Nitrile gloves, chemical protective goggles. Consult the applicable Material Safety Data Sheet (MSDS) and local Occupational Safety and Health (OSH) regulations for appropriate safety precautions.

5

LUBRICATING OIL MIL-PRF-6081

Oil, MIL-PRF-6081, Grade 1010 may cause skin and eye irritation. Avoid contact with skin and eyes. Always use with adequate ventilation. PPE: gloves, goggles, adequate ventilation. Consult the applicable Material Safety Data Sheet (MSDS) and local Occupational Safety and Health (OSH) regulations for appropriate safety precautions.

6

CORROSION PREVENTIVE COMPOUND MIL-DTL-85054

Corrosion preventive compound MIL-DTL-85054 is a skin, eye and respiratory tract irritant. High vapor concentration may cause dizziness, headache, or unconsciousness. Do not use in confined areas. PPE: Chemical splash proof goggles and gloves. Consult the applicable MSDS and local OSH regulations for safety precautions.

NAVAIR 01-1A-35 Index

Material

HMWS-4 Warning

7

ACETONE ASTM D329

ASTM D329 Acetone is flammable. Do not breathe vapors. Do not use near heat, sparks, open flames, or any other source of ignition. Use only in well-ventilated area. Do not allow contact with skin or eyes. PPE: Butyl rubber gloves, goggles. Consult the applicable Material Safety Data Sheet (MSDS) and local Occupational Safety and Health (OSH) regulations for appropriate safety precautions.

8

ADHESIVE MIL-PRF-9117

MIL-PRF-9117 Adhesive is toxic, flammable, and may cause eye and skin irritation. PPE: gloves, goggles Consult the applicable Material Safety Data Sheet (MSDS) and local Occupational Safety and Health (OSH) regulations for appropriate safety precautions.

9

ADHESIVE 82C18

82C18 adhesive is toxic and can cause eye and skin irritation. Avoid prolonged contact with skin or eyes and inhalation of any vapors. PPE: gloves, goggles/faceshield. Consult the applicable Material Safety Data Sheet (MSDS) and local Occupational Safety and Health (OSH) regulations for appropriate safety precautions.

10

COMPOUND, SILICONE SAE-AS8660

Silicone compound, SAE-AS8660, is a skin and eye irritant. Avoid skin and eye contact. Avoid contact with extreme heat or oxidizing materials. PPE: gloves, goggles. Consult the applicable Material Safety Data Sheet (MSDS) and local Occupational Safety and Health (OSH) regulations for appropriate safety precautions.

11

SEALING COMPOUND AMS-S-4383

Sealing Compound, AMS-S-4383, is toxic and flammable. Keep away from all sources of ignition. Avoid breathing vapors. Avoid skin and eye contact. Use only in well ventilated area. PPE: gloves, goggles. Consult the applicable Material Safety Data Sheet (MSDS) and local Occupational Safety and Health (OSH) regulations for appropriate safety precautions.

12

PHENOLPHTHALEIN

Phenolphthalein can irritate skin and eyes. Wear gloves and chemical protective goggles during use. Consult the applicable Material Safety Data Sheet (MSDS) and local Occupational Safety and Health (OSH) regulations for appropriate safety precautions.

13

LEAK DETECTION COMPOUND MIL-PRF-25567

Leak detection compound, MIL-PRF-25567, is a skin and eye irritant. Avoid contact with strong oxidizing agents and reducers, particularly alkaline materials. PPE: rubber gloves and chemical goggles. Consult the applicable Material Safety Data Sheet (MSDS) and local Occupational Safety and Health (OSH) regulations for appropriate safety precautions.

NAVAIR 01-1A-35 Index

HMWS-5

Material

Warning

14

SEALING COMPOUND AMS 3276

Sealing compound is flammable and irritating to the skin and eyes. Avoid prolonged breathing of vapors. Keep away from sources of ignition. PPE: gloves, goggles/ faceshield. Consult the applicable Material Safety Data Sheet (MSDS) and local Occupational Safety and Health (OSH) regulations for appropriate safety precautions.

15

SEALANT AMS-S-8802

AMS-S-8802 Sealant is toxic and can cause skin and eye irritation. Avoid skin and eye contact. PPE: gloves, apron, and goggles or faceshield. Consult the applicable Material Safety Data Sheet (MSDS) and local Occupational Safety and Health (OSH) regulations for appropriate safety precautions.

16

SEALANT MIL-S-22473

MIL-S-22473 sealant may cause eye and skin irritation. Wear gloves and goggles. Consult the applicable Material Safety Data Sheet (MSDS) and local Occupational Safety and Health (OSH) regulations for appropriate safety precautions.

17

DRY ICE CGA-G6.2

Dry Ice, Carbon Dioxide (solid), CGA-G6.2, can cause severe skin burns and frostbite. Do not handle with bare hands. Use in well ventilated area. PPE: cryogenic gloves, goggles and faceshield. Consult the applicable Material Safety Data Sheet (MSDS) and local Occupational Safety and Health (OSH) regulations for appropriate safety precautions.

18

SEALANT PR-2200

PR 2000 Sealing Compound may irritate the skin and eyes. High concentration can cause dizziness or drowsiness. Contains ingredients that can cause cancer. Do not grind, cut or otherwise create a respirable dust from cured material. For safe use, wear chemical resistant gloves and safety glasses with side-shields. Consult the applicable MSDS and local OSH regulations for additional information.

19

SEALANT AMS-3277

Sealant is toxic and can cause skin and eye irritation. Do not inhale vapors. Use only in well ventilated area. PPE: gloves, goggles. Consult the applicable Material Safety Data Sheet (MSDS) and local Occupational Safety and Health (OSH) regulations for appropriate safety precautions.

20

SEAL/COAT COMPOUND INHIBITIVE MIL-PRF-81733

CORROSION

MIL-PRF-81733, Type I-1/2 Corrosion Inhibitive Sealing and Coating Compound may contain chromate compounds, suspected carcinogens. Avoid contact with skin and eyes. Avoid breathing vapors. PPE: gloves, goggles. Consult the applicable Material Safety Data Sheet (MSDS) and local Occupational Safety and Health (OSH) regulations for appropriate safety precautions.

NAVAIR 01-1A-35 Index

Material

HMWS-6 Warning

21

SEALANT AMS-3284

AMS-3284, is toxic and flammable. Avoid contact with skin and eyes. Use in a well ventilated area and avoid breathing vapors. PPE: gloves, goggles. Consult the applicable Material Safety Data Sheet (MSDS) and local Occupational Safety and Health (OSH) regulations for appropriate safety precautions.

22

PRIMER PR1826 B-1

PR1826 B-1 Primer may cause eye and skin irritation upon overexposure. PPE: rubber gloves, safety goggles. Consult the applicable Material Safety Data Sheet (MSDS) and local Occupational Safety and Health (OSH) regulations for appropriate safety precautions.

23

AMMONIUM HYDROXIDE A-A-59370

Ammonium Hydroxide is severely irritating to all body tissue and will burn eyes, skin and mucous membranes. PPE: rubber gloves, chemical goggles. Consult the applicable Material Safety Data Sheet (MSDS) and local Occupational Safety and Health (OSH) regulations for appropriate safety precautions.

24

ETHYL ALCOHOL A-A-51693

Ethyl alcohol A-A-51693 is flammable and irritating to the skin, eyes, and respiratory tract. Do not use in confined spaces. Avoid breathing vapors. Wear chemical splash proof goggles and butyl gloves. Consult the applicable Material Safety Data Sheet (MSDS) and local Occupational Safety and Health (OSH) regulations for appropriate safety precautions.

25

ENAMEL A-A-2787

Enamel A-A-2787 is flammable. It is irritating to the eyes, skin, and respiratory tract. Overexposure can cause brain or nervous system damage. Avoid breathing vapors. Use chemical resistant goggles, gloves, and good ventilation. Keep sparks, flames, and heat away. Keep off skin, eyes, and clothes. Spray application may require a respirator. Consult the applicable Material Safety Data Sheet (MSDS) and most recent industrial hygiene survey for more information.

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Page 1 of 4

TABLE OF CONTENTS AND ALPHABETICAL INDEX MAINTENANCE INSTRUCTIONS ORGANIZATIONAL, INTERMEDIATE, AND DEPOT AIRCRAFT FUEL CELLS AND TANKS

Table of Contents WP Number

Title

Hazard Warnings Statements ..................................................................................................................................HMWS-1 Table of Contents and Alphabetical Index .................................................................................................................. 001 00 Introduction ................................................................................................................................................................. 002 00 Support Equipment Required............................................................................................................................... 002 00 Materials Required............................................................................................................................................... 002 00 General Safety Instructions ......................................................................................................................................... 003 00 Aircraft Confined Space Program ............................................................................................................................... 004 00 Aircraft Fuel System Maintenance Facilities and Areas ............................................................................................. 005 00 Defueling, Depuddling, Purging, Hot Work, and Inerting .......................................................................................... 006 00 Aircraft Fuels and Fuel Contamination ....................................................................................................................... 007 00 Decontamination Procedures....................................................................................................................................... 008 00 Fuel Cell Foam Baffles................................................................................................................................................ 009 00 Fuel Cell Removal, Installation, Preservation, and Packaging for Shipment and Storage .......................................... 010 00 Leak Detection of Installed Fuel Cells ........................................................................................................................ 011 00 Cleaning, Testing, and Closure Requirements of Uninstalled Fuel Cells.................................................................... 012 00 Integral Fuel Tanks, Leak Detection, Repair, and Sealing .......................................................................................... 013 00 Inspection and Assessment of Self-Sealing, Self-Sealing Crash Resistant, and Non Self-Sealing Crash Resistant Fuel Cells ................................................................................................ 014 00 Self-Sealing Fuel Cell Repairs .................................................................................................................................... 015 00 Self-Sealing Fuel Cell Fittings .................................................................................................................................... 016 00 Reinforcement of Self-Sealing Fuel Cells and Repair of Fuel Cell Components........................................................ 017 00 Inspection and Assessment of Urethane (Non-Self Sealing) Bladder Fuel Cells ........................................................ 018 00 Repair of Urethane Fuel Cells ..................................................................................................................................... 019 00 Inspection and Assessment of Non-Self Sealing (Bladder) Fuel Cells........................................................................ 020 00 Repair of Non Self-Sealing (Bladder) Fuel Cells ........................................................................................................ 021 00 Non-Self Sealing (Bladder) Fuel Cell Fittings ............................................................................................................ 022 00 Alphabetical Index Title

WP Number

Aircraft Confined Space Program, The ....................................................................................................................... 004 00 Alphabetical Index ...................................................................................................................................................... 001 00 Aviation Fuels ............................................................................................................................................................. 007 00 Batteries....................................................................................................................................................................... 003 00 Bonding and Grounding .............................................................................................................................................. 006 00 Characteristics of Aviation Fuels ................................................................................................................................ 007 00 Combination Self-Sealing and Non-Self Sealing Fuel Cell Damage / Defect Repair Procedures .............................. 015 00

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001 00 Page 2 Alphabetical Index (Cont)

Title

WP Number

Contamination of Aircraft Fuels ..................................................................................................................................007 00 Contractor Relations ....................................................................................................................................................004 00 Crash Resistant Self Sealing Fuel Cell (ARM) Damage / Defect Repair Procedures..................................................015 00 Defueling .....................................................................................................................................................................006 00 Depuddling ..................................................................................................................................................................006 00 Detection of Weakened Fuel Cell Structure.................................................................................................................017 00 Enclosed Fuel Cell Maintenance..................................................................................................................................005 00 Evaluation of Non-self Sealing (Bladder) Fuel Cells for Damage and Defect ............................................................020 00 Fire Extinguishers ........................................................................................................................................................003 00 Foam Baffle Maintenance Procedures .........................................................................................................................009 00 Fuel Cell Baffles ..........................................................................................................................................................017 00 Fuel Cell Cleaning .......................................................................................................................................................012 00 Fuel Cell Fitting Corrosion Removal...........................................................................................................................016 00 Fuel Cell Hangers ........................................................................................................................................................017 00 Fuel Cell Installation....................................................................................................................................................010 00 Fuel Cell Packaging For Shipment and Storage...........................................................................................................010 00 Fuel Cell Preservation..................................................................................................................................................010 00 Fuel Cell Reconfiguration and Fitting Relocation .......................................................................................................016 00 Fuel Cell Removal .......................................................................................................................................................010 00 Fuel Cell Storage .........................................................................................................................................................010 00 Fuel Cell Testing..........................................................................................................................................................012 00 Fuel Exposure Hazards ................................................................................................................................................003 00 Fuel Sampling ..............................................................................................................................................................007 00 Fuel System Repair Area Checklist .............................................................................................................................005 00 Gaskets.........................................................................................................................................................................012 00 Generation and Accumulation of Static Electricity......................................................................................................003 00 Glossary of Terms........................................................................................................................................................002 00 Hot Work .....................................................................................................................................................................006 00 Inerting.........................................................................................................................................................................006 00 Integral Fuel Tank Leak Detection ..............................................................................................................................011 00 Integral Fuel Tanks ......................................................................................................................................................013 00 Introduction..................................................................................................................................................................002 00 Leak Detection.............................................................................................................................................................011 00 Lockring Threaded Insert (ROSAN) and Fitting Locating Pin Replacement ..............................................................016 00 Materials Required.......................................................................................................................................................002 00 Methods of Preventing Contamination ........................................................................................................................007 00 Microbiological Growth Decontamination Procedures................................................................................................008 00 Nitrile (BUNA-N) Synthetic Rubber Bladder Fuel Cell Repair ..................................................................................021 00 Non-Molded Self-Sealing Fuel Cell Fitting Repair .....................................................................................................016 00 Non-Self Sealing Fuel Cell Fitting Repair ...................................................................................................................022 00 Non-Self Sealing Fuel Cell Fitting Replacement.........................................................................................................022 00 Open Fuel Cell Maintenance........................................................................................................................................005 00 O-Ring Fittings ............................................................................................................................................................012 00 O-Ring Groove Area Fitting Repair.............................................................................................................................016 00 Permitting of Fuel Cells and Tanks..............................................................................................................................004 00 Personnel......................................................................................................................................................................004 00 Protective Clothing ......................................................................................................................................................003 00 Protective Equipment...................................................................................................................................................003 00 Purging.........................................................................................................................................................................006 00 Quick Cure Repair Method (Bladder Fuel Cell) ..........................................................................................................021 00 Quick Cure Repair Method (Urethane Fuel Cell) ........................................................................................................019 00 Record Keeping Requirements ....................................................................................................................................004 00 Reinforcement of Weakened Fuel Cell Structure ........................................................................................................017 00

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001 00 Page 3/(4 Blank) Alphabetical Index (Cont)

Title

WP Number

Repair of Urethane Fuel Cells ..................................................................................................................................... 019 00 Rescue Plans................................................................................................................................................................ 004 00 Rigid, Non-Metallic, Self-Sealing Fuel Cell Damage / Defect Repair Procedures ..................................................... 015 00 Safety Wiring .............................................................................................................................................................. 012 00 Salt Water Decontamination Procedures..................................................................................................................... 008 00 Sealants ....................................................................................................................................................................... 013 00 Self Sealing Fuel Cell / Defect Repair Procedures – Lightweight and Standard Construction .................................. 015 00 Self-Sealing Fuel Cell Defects and Acceptable Limitations ....................................................................................... 014 00 Self-Sealing Fuel Cell Fitting Insert Replacement ...................................................................................................... 016 00 Self-Sealing Fuel Cell Fitting Replacement ................................................................................................................ 016 00 Shipping Container Markings ..................................................................................................................................... 010 00 Specific Properties of Aviation Fuels.......................................................................................................................... 007 00 Static Electricity .......................................................................................................................................................... 003 00 Stencils and Decalomanias .......................................................................................................................................... 012 00 Support Equipment Required ...................................................................................................................................... 002 00 Susceptibility of Aviation Fuel Vapors to Electrostatic Ignition................................................................................. 003 00 Testing Procedures ...................................................................................................................................................... 004 00 Torque Requirements .................................................................................................................................................. 012 00 Urethane Fuel Cell Defects and Acceptable Limitations............................................................................................. 018 00 Use of Dye in JP-Fuel Systems to Detect Fuel System Leaks..................................................................................... 011 00

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Page 1 of 26 INTRODUCTION AIRCRAFT FUEL CELLS AND TANKS

1. INTRODUCTION This Maintenance Instruction Manual (MIM) provides information for the Organizational, Intermediate and Depot maintenance of Naval aircraft fuel cells and tanks. 2.

PURPOSE AND SCOPE. NOTE Where fuel cells and tanks are referred to together, they are labeled as fuel cells in this manual. Where a tank is specifically referred to it is labeled as tank.

a. Supporting Instructional Manuals. This manual shall be used in conjunction with and in support of the appropriate MIM and Structural Repair Instruction Manual (SRIM). However, in the event of conflicts between this manual and the fuel cell maintenance materials and procedures specified for a specific aircraft, the materials and procedures in this manual shall take precedence. b. Scope. The material in this manual is divided into twenty two work packages, the hazard warnings, tables for support equipment and materials required and a table of term definitions . The scope of each is described below. (1) HMWS-1. Hazard Warnings Statements. Lists the hazard warnings for hazardous materials presented in the manual (2) Work Package 001 00, Table of Contents and alphabetical index of major topics covered in the manual. (3) Work Package 002 00, Purpose and scope of the manual, list of abbreviations and acronyms, and list of references used in the manual. It also contains a list of acceptable consumable materials and non-consumable equipment used during fuel cell maintenance. A glossary provides and defines terms commonly used by fuel cell maintenance personnel.

(6) Work Package 005 00, Aircraft Fuel System Maintenance Facilities and Areas. This WP covers the requirements of the facilities and areas for safe fuel cell maintenance. (7) Work Package 006 00, Defueling, Depuddling, Purging, Hot Work, and Inerting. This WP provides definitions and general information for defueling, depuddling, inerting, hot work, and purging of fuel cells for inspections, repair or entry by maintenance personnel. (8) Work Package 007 00, Aircraft Fuels and Fuel Contamination. This WP provides information and procedures for sampling fuels to detect contamination. It includes inspection techniques, identification of contaminants, their harmful effects, and contamination sources. (9) Work Package 008 00, Decontamination Procedures. This WP describes decontamination procedures to be followed after it has been determined that a fuel system is contaminated with salt water or microbiological growth. (10) Work Package 009 00, Fuel Cell Foam Baffles. This WP contains general information and procedures for the removal, inspection and repair of reticulated foam baffles used in aircraft fuel cells. It also includes fuel sample analysis to be performed after replacement, repair or reinstallation of reticulated foam baffles. (11) Work Package 010 00, Fuel Cell Removal, Installation, Preservation, and Packaging For Shipment and Storage. This WP provides general instructions to be observed during the removal or installation of self-sealing and bladder fuel cells in an aircraft. In order to reduce further damage to cells, instructions for the preparation of damaged cells prior to return to supply and procedures necessary to protect fuel cells from damage during handling, preservation, packaging, shipment and storage.

(4) Work Package 003 00, General Safety Instructions. Safety summary for maintenance on and around fuel cells and tanks, introduction to hazards of fuel and fuel vapors, and personal protective equipment.

(12) Work Package 011 00, Leak Detection of Installed Fuel Cells. This WP contains general information procedures and leak detection methods which, when used in conjunction with the applicable aircraft maintenance manuals, can aid maintenance personnel in locating the source of an aircraft fuel system leak.

(5) Work Package 004 00, Aircraft Confined Space Program requirements. This WP describes the procedures to be followed to ensure safe operations when performing fuel cell maintenance.

(13) Work Package 012 00, Cleaning, Testing, and Closure Requirements of Uninstalled Fuel Cells. This WP contains instructions, procedures, and materials for cleaning and testing uninstalled fuel cells. It includes methods to

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locate leaks prior to repair and fuel cell integrity after repairs. Additionally, it includes fuel cell O-ring installation, gasket application, and other closure requirements. (14) Work Package 013 00, This WP defines integral tanks and describes sealing methods, leaks, theory, temporary and permanent repairs, and the use of related materials/equipment. (15) Work Package 014 00, Inspection and Assessment of Self-Sealing, Self-Sealing Crash Resistant, and Non Self-Sealing Crash Resistant Fuel Cells. This WP presents the inspection criteria and safe damage limits for combinations of self-sealing and/or crash resistant fuel cell constructions.

construction design, and instructions for repair of non selfsealing fuel cells. (23) Work Package 022 00. Non-Self Sealing (Bladder) Fuel Cell Fittings. This WP provides instructions for evaluating damage to non-self-sealing fuel cell fittings. Additionally, it contains repair and replacement techniques, materials and procedures. 3. NONSTANDARD ABBREVIATIONS.

TERMS,

SYMBOLS

AND

a. There are no nonstandard terms, symbols, and abbreviations used in the manual, unless listed below. 4. QUALITY ASSURANCE PROCEDURES.

(16) Work Package 015 00, Self-Sealing Fuel Cell Repair. This WP provides definitions, construction design and instructions for techniques, materials and procedures for repairing of self-sealing and/or crash resistant fuel cells. (17) Work Package 016 00. Self-Sealing Fuel Cell Fittings. This WP provides instructions for evaluating damage to self-sealing fuel cell fittings. Additionally, it contains repair and replacement techniques, materials and procedures. (18) Work Package 017 00. Reinforcement of SelfSealing Fuel Cells and Repair of Fuel Cell Components. This WP provides general information and procedures for detecting and correcting defects in self-sealing fuel cell structures, and the repair of fuel cell components. (19) Work Package 018 00. Inspection and Assessment of Urethane (Non Self-Sealing) Bladder Fuel Cells. This WP presents the inspection criteria and safe damage limits for non-self sealing urethane fuel cell constructions manufactured by Engineered Fabrics Corporation. (20) Work Package 019 00. Repair of Urethane Fuel Cells. This WP provides general information and procedures for detecting and correcting defects in urethane fuel cells manufactured by Engineered Fabrics Corporation. (21) Work Package 020 00. Inspection and Assessment of Non Self-Sealing (Bladder) Fuel Cells. This WP presents the inspection criteria and safe damage limits for non self-sealing fuel cell constructions (excluding urethane). (22) Work Package 021 00. Repair of Non-SelfSealing (Bladder) Fuel Cells. This WP provides definitions,

a. Instructions that are essential to quality assurance are shown in italics throughout this manual. Quality assurance required procedures, shall be highlighted by the addition of the abbreviation (QA) following the procedure/step. 5. RECORD OF APPLICABLE DIRECTIVES. a. Each technical content Work Package (WP) in this manual has a Record of Applicable Technical Directives listing technical directives affecting data within that respective WP. Table 2-3 is a consolidated record of all technical directives incorporated in this manual and lists each by type, number, issue date, title, incorporation date and WP(s) number in which incorporated. 6. REQUISITION DISTRIBUTION MANUALS.

OF

AND NAVAIR

AUTOMATIC TECHNICAL

a. Procedures to be used by Naval activities and other Department of Defense activities requiring NAVAIR technical manuals are defined in NAVAIR 00-25-100 and NAVAIRINST 5605.5.5. b. To automatically receive future changes and revisions to NAVAIR technical manuals, an activity must be established on the Automatic Distribution Requirements List (ADRL) maintained by the Naval Air Technical Data and Engineering Service Command (NATEC). To become established on the ADRL, notify your activity central technical publications librarian. If your activity does not have a library, you may establish your automatic distribution by contacting the Commanding Officer, NATEC, Attn: Distribution, NAS North Island, Bldg. 90, P.O. Box 357031, San Diego, CA 92135-7031. Annual reconfirmation of these requirements is necessary to remain on automatic distribution. Please use your NATEC assigned account

NAVAIR 01-1A-35

002 00 Page 3

number whenever referring to automatic distribution requirements.

materials presented in this manual are listed in Work Package HMWS.

c. If additional or replacement copies of this manual are required with no attendant changes in the ADRL, they may be ordered by submitting a MILSTRIP requisition in accordance with NAVSUP 485 to Routing Identifier Code “NFZ”. MILSTRIP requisitions can be submitted through your supply office, Navy message, or SALTS to DAAS (Defense Automated Address System), or through the DAAS or NAVSUP web sites. For assistance with a MILSTRIP requisition, contact the Naval Inventory Control Point (NAVICP) Publications and Forms Customer Service at DSN 442-2626 or (215) 697-2626, Monday through Friday, 0700 to 1600 Eastern Time.

b. Warnings and cautions for hazardous materials listed in this manual are designed to apprise personnel of hazards associated with such items when they come in contact with them by actual use. Additional information related to hazardous materials is provided in OPNAVINST 5100.23 Navy Occupational Safety and Health (NAVOSH) Program manual and the DOD 6050.5 Hazardous Materials Information System (HMIS) series publications. Consult your local safety and health staff concerning specific personnel protective requirements and appropriate handling and emergency procedures.

7. WARNINGS, CAUTIONS AND NOTES.

9. REFERENCE MATERIAL. a. Each work packages (003 00 and subsequent) contain a list of materials required to perform procedures in each work package. Table 1 is a consolidated list of reference material relevant to the procedures in this manual.

Refers to a procedure that, if not correctly followed, could result in injury, death, or long- term health hazard.

Refers to a procedure that, if not correctly observed, could result in damage to, or destruction of, equipment.

NOTE Refers to a procedure or condition that requires additional emphasis or explanation. 8. WARNINGS AND CAUTIONS APPLICABLE TO HAZARDOUS MATERIALS. a. Applicable warning statements for all hazardous

10. SUPPORT EQUIPMENT REQUIRED. a. Each Work Package (003 00 and subsequent) contains a list of support equipment required. Table 4 is a consolidated list of support equipment required to perform the procedures in this manual. When an item of support equipment is not available an approved alternate identified in the activity’s Individual Materials Readiness List (IMRL) may be substituted. 11. MATERIALS REQUIRED. a. Each work package (003 00 and subsequent) contains a list of materials required to complete the procedures in the specific work package. Table 5 is a consolidated list of all materials required to perform the maintenance procedures in this manual.

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002 00 Page 4

Table 2-1. List of Abbreviations and Acronyms Abbreviation/term

Definition

ACSPM

Aircraft Confined Space Manager

CFA

Cognizant Field Activity

EA

Entry Authority

FSII

Fuel System Icing Inhibitor

FST

Fleet Support Team

IDLH

Immediately Dangerous to Life and Health

LEL

Lower Explosive Limit

LFL

Lower Flammable Limit

MALS

Marine Aviation Logistic Squadron

MIM

Maintenance Instruction Manual

MEK

Methyl Ethyl Ketone

MRC

Maintenance Requirement Cards

NIOSH

National Institute of Occupational Safety and Health

OPNAVINST

Office of Chief of Naval Operations Instruction

PDM

Program Depot Maintenance

PEL

Permissible Exposure Limit

PPE

Personal Protective Equipment

QAR

Quality Assurance Representative

SCBA

Self Contained Breathing Apparatus

SRIM

Structural Repair Instruction Manual

TMS

Type Model Series

UEL

Upper Explosive Limit

UFL

Upper Flammable Limit

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002 00 Page 5 Table 2-2. Glossary

A ABRADE - To remove shiny surface by roughening with emery cloth or sanding disc. ABRADED AREA - Scuffed area where the outer coat has been damaged or removed by buffing. ABRASION - Term used in fuel cell meaning wearing away of the fabric or coating by friction. ACCELERATOR - The curing agent used with base sealant compound. ACTIVATION - A condition which occurs in self-sealing cells and which is caused by fuel coming in contact with sealant, causing the sealant to swell. ADHESION - The strength of bond between cured adhesive and the surface to which the sealant is applied, or the strength of bond between a cured rubber surface or surfaces and a non-rubber surface.

B BARRIER - A film of pure nylon immediately behind the inner liner of all fuel cells, which prevents the diffusion of fuel through the remaining plies of the cells. BASE COMPOUND - The major component of adhesive without accelerator. BLISTER - A raised spot on a surface or a separation between layers, which usually forms a void or air-filled space in a vulcanized article of fuel cells. BUFFING - The abrasion of a surface of a cell which produces a roughened or velvety surface. BUILDING FORM - A reinforced plaster or cardboard structure built in the shape of a fuel cell cavity, upon which a fuel cell is built and cured.

C CELL, FUEL - Removable fuel container constructed of fabric, nylon and gum stock. CHANNEL - A void left between the joint of two sheets of material. CHECKING, WEATHER OR OZONE - Short, small cracks on a surface of a cell, generally caused by the destructive action of environmental conditions. COAT BLISTER - A separation between a rubber lacquer skin coating and a fabric of cell, which forms a void or air space that does not require repair. COLD FLOW - The deformation of rubber under stress. COLD FABRIC - A rubber-impregnated or coated fabric, used in manufacture and repair of cells, which has heavy-strength members running in one direction at close intervals; it is held together by lightweight cross-members at relatively wide intervals. COLD WORK - Any work, which does not exceed 400oF. CONFINED SPACE – A fuel cell or tank that is large enough and so configured that a person can bodily enter and perform assigned work.

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002 00 Page 6 TABLE 2-2. Glossary (Cont)

C - Continued CRAZING - A surface effect on rubber articles characterized by many hairline indentations or ridges. CRITICAL O-RING SEALING SURFACE - The critical area for an O-ring sealing surface consists of a groove and a band extending 0.010-inch on each side of the groove. CROSSLINKER - The tying together of large molecules and hence changing the physical properties of a material. CRUMBLE SEALANT - Sealant in a fuel tank that has become hard and which will crumble when touched. CURE - Act of vulcanization of uncured rubber or the setting up of adhesives.

D DEFUELING - Defueling is the process of removing fuel from the aircraft. DELAMINATION - The separation of ply layers in any material of cells. DEPUDDLING - Depuddling is the process of removing residual fuel from the aircraft fuel cell after defueling and low-point draining. DIFFUSION - The flow or loss of fuel by seepage through a rubber layer.

E ENCLOSED AREA - An area completely surrounded by other structure, which does not have proper ventilation, such as in the nacelles and center section areas. ENTRY – The action by which a person passes through an opening into a fuel cell or tank. It includes ensuing work activities in that cell or tank and is considered to have occurred as soon as any part of the entrant’s body breaks the plane of an opening into the cell or tank. EXPLOSION-PROOF - A unit enclosed in a case which is capable of withstanding an explosion of a specified gas or vapor which may occur from within, and preventing the igniting of vapors and gases surrounding the unit. EXTERNAL POWER - Any power source, AC or DC, used to operate any system or unit on an aircraft and not contained within the aircraft.

F FITTINGS, FUEL CELL - Attaching points of a call to a structure or functional equipment such as booster pumps, fuel outlets, vents, etc. FIT JIG - A structure built to accurately duplicate the fuel call cavity, as in the aircraft, in which a cured cell is placed to check for compliance with specifications on size of the cell and location of hangers and fittings. FLAMMABLE LIQUID - Any liquid, which produces vapors less than 100oF.

G GROUND - An approved ground is one with a resistance of less than 10,000 ohms resistance.

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002 00 Page 7 TABLE 2-2. Glossary (Cont)

H HANGER - An external assembly installed on a cell, which is used to attach bladder cells to an aircraft structure for support. HANGER STRAP - An exterior attachment to a cell, usually made in loops of webbing, which supports a cell installed in aircraft and storage containers. HOLES - Punctures, cuts, tears or breaks in the cell material caused by contact with a sharp object. HOT WORK - Any work which produces a temperature equal to or greater than 400oF, such as applicable soldering, heat shrink operations, welding, cutting, brazing, grinding, flame-spray/metal-spray, etc. I IMMEDIATELY DANGEROUS TO LIFE OR HEALTH (IDLH) – An atmosphere that poses an immediate threat to life, would cause irreversible adverse health effects, or would impair an individual's ability to escape from a dangerous atmosphere. INNER LINER - The first ply of material applied to a building form in the manufacture of a cell. It supports and protects the nylon barrier and may be constructed of fabric or rubber. INTEGRAL - The sealing of a structure to make a fuel-tight container. INTRINSICALLY SAFE - Equipment and wiring that is incapable of releasing sufficient electrical or thermal energy under normal or abnormal conditions to cause ignition of a specific hazardous atmospheric mixture in its most easily ignited concentration. INERTING - To render the flammable vapor in the cell/tank non-explosive and non-flammable, by adding a nonflammable gas (usually nitrogen) to the cell/tank to displace the oxygen required to support a fire or explosion. K KNUCKLE TEST - A test to determine if the adhesive applied to patch is tacky. The test consists of gently pressing a dry knuckle of a finger against the cemented surface and withdrawing the knuckle. The cement should feel tacky without adhering to the knuckle.

L LAP SEAM - A seam made by placing the flat edge of one piece of material over the edge of a second piece of material or over itself. LEAK PATH - The exit or path fuel follows to reach the external surface of a fuel tank. LEL - Lower Explosive Limit

M METAL INSERT - Metal ring used in molding rubber fittings to give rigidity to the finished fitting and hold the dome nuts in place. MIXED ADHESIVE - Adhesive in which the base compound and the accelerator have been properly mixed and which is ready for application.

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002 00 Page 8 Table 2-2. Glossary (Cont)

M - Continued MOLDED FITTING - A metal insert over which is molded rubber, which protects metal from corrosion and acts as a gasket surface for attaching hardware.

N NYLON BARRIER - A film of pure nylon immediately behind the liner of the fuel cell to prevent the rapid diffusion of fuel through remaining pieces of the fuel cell. Used on all fuel cells.

P PDM - Program Depot Maintenance PLASTICIZER - A material which, when incorporated in rubber, will change its hardness, flexibility and plasticity. PLY - Any layer of basic fuel cell construction of either fabric or non-fabric. POROSITY - Quality or state of being porous due to presence of minute structural voids. PRESERVATIVE - A substance added to or coated over a product to preserve the product against damage or deterioration. PURGING - The process of removing fuel vapors capable of producing a combustible or toxic atmosphere

R RUNNING LEAK - A leak where fuel is dripping or running from a structure.

S SCBA – Self Contained Breathing Apparatus – Portable breathing apparatus consisting of pressurized air tank, pressure regulator, delivery hose, and facemask. SCIM OR SKIM COAT - A layer of rubber material laid on a fabric but not forced into the weave. SEALANT - A special compounded natural or synthetic rubber, which reacts to fuel contact by a very pronounced and immediate swelling action. SEEP - A leak where fuel wets an area around the apparent leak source, and in which the moist area is not over 1 1/2inch in diameter. The fuel does not run, flow or drip when the area has been wiped clean and 30 minutes have elapsed. SEPARATIONS - Area of non-adhesion, which splits the plies into layers but shows no evidence of trapped fuel or liquid. SKIM COAT BLISTERS - A separation between the skim coating and the fabric, usually forming a void or air space. SLOW SEEP - A leak where fuel wets an area around the apparent leak source, and in which the moist area width is not over 3/4-inch in diameter after the area has been wiped clean and 30 minute have passed. STITCHING - This is the process in the application of an adhesive patch in which the adhesive coated patch and bladder are compressed together using a hand roller tool. This extrudes out air bubbles and initiates a strong cohesive bond between properly prepared surfaces.

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002 00 Page 9 Table 2-2. Glossary (Cont)

T TANK - Tank (fuel) is generally a metallic fuel container, such as integral wing tanks, or the droppable or refuelable tanks.

V VULCANIZATION - A chemical reaction in which the physical properties of a rubber are changed in the direction of decreased plastic flow, less surface tackiness, and increased tensile strength by reacting it with sulfur or other suitable chemicals.

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Table 2-3. Record of Applicable Technical Directives

Technical Directive

Issue Date

Change/revision Supplement Date

Title None

Table 2-4. Related Technical Publication Number

Title

BUMEDINST 6260.16

Isocyanates; Measures for Control of Health Hazards Related to

DoD 6050.5

DoD Hazard Communication Program

MIL-L-10547

Liners, Case and Sheet Overwrap, Water-Vaporproofing, Flexible

MIL-STD-2073-1

Standard Practice for Military Packaging

MIL-STD-129

Standard Practice for Military Marking

NASM33540

General Practice for Safety Wiring and Cotter Pinning

NAVAIR 0l-lA-507

General Use of Cements, Sealants and Coatings

NAVAIR 0l-lA-509

Aircraft Weapons Systems Cleaning and Corrosion Control

NAVAIR 15-01-500

Preservation of Naval Aircraft for Organizational, Intermediate and Depot Maintenance

NAVAIR 00-80T-109

Aircraft Refueling Manual

NAVSEA S6470-AA-SAF-010

Gas-Free Engineering (Shore)

NAVSEA S9086-CH-STM030, Chapter 074, Volume 3

Gas-Free Engineering (Shipboard)

NAVSUP Publication 4500

Consolidated Hazardous Item List, Storage and Handling

NFPA 410

National Fire Protection Association - Standard on Aircraft Maintenance

OPNAV 4790.2 Series

The Naval Aviation Maintenance Program (NAMP)

OPNAVINST 5100.23 Series

Navy Occupation Safety and Health (NAVOSH) Program Manual

T.O. 1-1-3

Aircraft Integral Tanks and Fuel Cells - Inspection and Repair of

29 CFR 1910.146

Occupational Safety and Health Standards, Permit-Required Confined Spaces

NAVAIR 01-1A-35

002 00 Page 11 Table 2-5. Support Equipment Required

Item No.

Nomenclature

National Stock No.

Unit Issue

MIL-B-7619

4140-00-302-9534

Ea.

For air purging and ventilating fuel cells/tanks.

4140-01-096-1596

Ea.

For air purging and ventilating fuel cells/tanks. For air purging and ventilating fuel cells/tanks.

Specification

1.

Air Blowers and Air Movers

a. (1)

Blower, Exhaust Electric Motor Driven, ExplosionProof (MA1)

Intended Use

12 –inch blowers/fans (2a)

Pneumatic Powered Fan, 12 inch

NV14-2A

(2a)

Pneumatic Powered Air Mover, 12 inch

APV-12

Ea.

8-inch blowers/fans (2b)

Electric Powered Blower, 8-inch

AF-178E

4140-01-306-9138

Ea.

(2b)

Pneumatic Powered Blower, 8-inch

NF17-8A

4140-01-105-6326

Ea.

(2b)

Pneumatic Powered Air Mover, 8 inch

APV-1N (supercedes NF17-8A)

(2b)

Pneumatic Powered Air Mover, 8 inch (For MAV-1 Kit)

APV-1

(3)

Hose, Air Ducting

(4)

Mobile aircraft Fuel Tank Ventilating System

MAV-1

(5)

Respirator/Ventilator Kit, Fuel Cell

b.

c.

For air purging and ventilating fuel cells/tanks. For air purging and ventilating fuel cells/tanks.

Ea.

For air purging and ventilating fuel cells/tanks.

Ea.

For air purging and ventilating fuel cells/tanks.

Ea.

Used in conjunction with the MA1 Air Blower, Item a(1).

1560-01-492-8256

Ea.

Complete, mobile system includes blower, ducting, container

NF35-1 NF20-1

4920-01-444-0714 4240-01-140-5458

Ea.

Complete ground kit, respirator and fuel cell ventilation systems

Blower Assembly Hot Air, Integral Fuel Cell, Ventilation

MMEP12B

4920-00-944-5765

Ea.

For warm air purging and ventilating fuel cells/tanks.

Eductor, Air Mover, Venturi-Type

DP32119

4730-00-313-0680

Ea.

To vent fuel vapors from fuel cell/tank.

5370-01-462-8941

NAVAIR 01-1A-35

002 00 Page 12

Table 2-5. Support Equipment Required (Cont) Item No.

Nomenclature

Specification

National Stock No.

Unit Issue

Intended Use

2.

Cleaners

a.

Cleaner, Aircraft Portable Foam Generator

Model 20 P/N 0020SS,

4940-01-058-5267

Ea.

For applying cleaning solution to interior and exterior of removable external metal tanks.

b.

Cleaner, Vacuum, Pneumatic

55-20

7910-00-632-9840

Ea.

Cleaning interior of fuel cells and tanks.

c.

Pump, Backpack

5100-254B

4320-00-289-8912

Ea., 5 Gal.

For flushing interior of fuel cells and tanks.

3.

Containers, Safety

a.

Container, Safety

RR-S-30

7240-00-177-4997

Ea., 5 Gal.

After defueling, residual fuel from cells and tanks is drained into this container.

b.

Container, Safety

RR-P-125

4940-00-684-0580

Ea., 2 Gal.

For containing the fuel that is removed during depuddling.

c.

Safety Streamers (MS51700)

Ea.

For safety purpose while work is being performed on fuel tanks.

4.

Inspection Lights, Explosion-Proof

a.

Flashlight, Explosion-Proof

6230-00-270-5417

Ea.

Illumination of fuel cell during inspection and cleaning.

b.

Inspection Light, Fuel Cell

57A42

6230-00-593-8576

Ea.

Illumination of fuel cell during inspection and cleaning.

c.

Light, Extension Explosion-Proof

MIL-F-16377/52

6230-00-283-9671

Ea.

Illumination of fuel cell during inspection and cleaning.

5.

Knives and Inert Gas Servicing Unit

a.

Knife, Electric Slicing, Heavy Duty (Not Explosion-Proof)

297

7340-00-937-1436

Ea.

For cutting polyurethane foam buns.

b.

Nitrogen Servicing Unit, Trailer

NAN3

3655-00-224-9142 or 3655-01-112-4943

Ea.

For inerting fuel cells/tanks.

NAVAIR 01-1A-35

002 00 Page 13

Table 2-5. Support Equipment Required (Cont) Item No.

Nomenclature

Specification

National Stock No.

Unit Issue

Intended Use

6.

Personnel Protective Clothing and Equipment

a. (1)

Air Breathing Pump, Pneumatic Driven

NF-1100A (supercedes NF15-3)

4240-01-363-4699 4310-01-084-9665

Ea.

Air Source for Item 6o.

(2)

Mobile Aircraft Fuel Tank Respiratory Protection System

MAV-5

1680-01-494-3033

Ea.

Complete mobile system includes pump, mask, hose, case

b.

Filter Cartridge Replacement

AS393

4240-01-084-0921

Bx. of 10

Line Filter for Item 6a.

c.

Air Pump Repair Kit

K231A

4320-01-084-1876

Ea.

Repair Kit for Item 6a.

d.

Air Motor Repair Kit

K208

2895-01-084-0525

Ea.

Repair Kit for Item 6a.

e.

Cap Set, Helmet, Medium Cap Set, Helmet, Large

765AS270-101

8745-01-077-8909

Ea.

Worn when performing repairs inside fuel cell.

765AS271-101

8745-01-077-8910

f.

Coveralls, Explosive Handlers

MIL-DTL-14610

8415-00-280-2455 8415-00-279-8719 8415-00-279-8720 8415-00-279-8721 8415-00-279-8722

Ea. XSm reg Ea. Sm reg Ea. Med reg Ea. Large reg Ea. XLg reg

Worn when performing maintenance inside fuel cell.

g.

Footwear covers

No reference

8430-00-508-0765 8430-00-508-0766

Pr. Large Pr. X-Large

To cover shoes when entering an integral fuel tank.

h.

Gloves, Cotton, AntiFlash

MIL-G-2874

8415-01-267-9661

Pr.

Protect hands when applying sealants.

i.

Gloves, Disposable, General Purpose

MR-100

6515-00-051-1950

Pkg. of 100 medium

For protecting hands when applying solvents.

j.

Gloves, Rubber, Industrial

MIL-DTL-32066 (ZZ-G-381)

8415-00-266-8679 8415-00-266-8677 8415-00-266-8675 8415-00-266-8673

Pr. size 9 Pr. size 10 Pr. size 11 Pr. size 12

Handling solvents, chemicals, fuel and some adhesives.

k.

Goggles, Industrial and Spectacles

ANSI Z87.1

Pr.

Eye protection when using solvents or during fuel cell buffing and grinding operations.

l.

Headset, Communication

79091

Ea.

Communications between person inside fuel cell/tank and safety observer outside the

5830-00-600-0848

NAVAIR 01-1A-35

002 00 Page 14

Table 2-5. Support Equipment Required (Cont) Item No.

Nomenclature

Specification

National Stock No.

Unit Issue

Intended Use cell/tank.

m.

Overshoes, Rubber

MIL-O-82295

Pr.

Worn when working inside of fuel cell or tank.

n.

Respirator, Air Line, (Air Supplied) Full Face

NIOSH Approved

Ea.

To be worn when entering a fuel cell or tank to perform maintenance.

o.

Respirator

GG-M-125/1

Ea.

Worn when applying polyurethane adhesive to the exterior of a fuel cell.

p.

Safety Shoes

Pr.

Worn when working in fuel system maintenance area.

q.

Socks, Cotton, White

Pr.

For fuel system maintenance personnel.

7.

Gas Detection Equipment

a.

MultiRae Gas Detector

Ea.

To detect and indicate Concentration of oxygen, combustible gasses, and toxic vapors in the air inside a fuel cell.

b.

Control Box

To identify leak source and leak path by the injection method.

c.

Cup, Vacuum

To identify leak source and leak path by the injection method.

d.

Cup Vacuum Pressure

To identify leak source and leak path by the injection method.

e.

Temporary Repair Kit Comp Air D236 Injection Kit Equipment Manometer, Water

8. a.

009-3001-01N

4240-00-022-2524

01-457-0472

4920-00-485-1213

4920-00-793-0650

Ea.

To pressurize fuel tank during leak testing.

NAVAIR 01-1A-35

002 00 Page 15

Table 2-5. Support Equipment Required (Cont) Item No.

Nomenclature

b.

Thermometer, Bimetallic Dial

9. a.

Sealant Accessories Nozzle, Sealant Gun (See Chapter 6 for sizes and shapes)

b.

Sealant Smoothing Tool

Specification

Part No.

Model No.

220538 220540 220542 220544 220548 220550 220552 220553 220555 220557 220559 220561 220563 220565 220568 220569 220572 220574 220581 220582 220582 220586 220588 220589 220606

252 254 410 420 430 440 600E 620 640 820 840 1002 1004 1010 8607 8608 8613 8615 8630 8630-9 8630 8643 8646 8648 8690

Part No.

Model No.

226244 11798-500

National Stock No.

Unit Issue

6685-00-996-8899

Ea.

Intended Use To test temperature of metal surface.

To apply sealant in a specific shape, size, and/or form. 5120-00-167-0150 5120-00-673-1855 5120-00-801-0949 5120-00-801-0949 5120-00-967-8151 5120-00-773-3791 5120-00-670-1187 5120-00-167-0152 5120-00-822-7194 5120-00-966-8270 5120-00-966-5372 5120-00-055-4055 5120-00-055-4054 5120-00-055-4058 5120-00-966-5381 5120-00-966-6244 5120-00-966-5379 5120-00-966-5378 5120-00-966-5377 5120-00-966-5376 5120-00-966-5376 5120-00-775-1670 5120-00-966-5374 5120-00-966-5375 5120-00-966-8243 Smooth sealant. 5120-00-056-3237

NAVAIR 01-1A-35

002 00 Page 16

Observe all cautions and warnings on containers when using consumables. When applicable, wear necessary protective gear during handling and use. If a consumable is flammable or explosive, MAKE CERTAIN consumable and its vapors are kept away from heat, spark, and flame. MAKE CERTAIN equipment is properly grounded and firefighting equipment is readily available prior to use. For additional information on toxicity, flashpoint, and flammability of chemicals, refer to DOD 6050.5.

Table 2-6. Materials Required Item No.

Nomenclature

Specification

National Stock No.

Unit Issue

Intended Use

1.

Abrasives

a.

Abrasive Mat, Nylon (non-woven)

MIL-A-9962, Type 1, Grade B, Class 1 (Fine)

5350-00-967-5093

Pkg. of 10

Cleaning abrasive used on fuel cell fittings.

b.

Cloth, Abrasive Aluminum Oxide

P-C-451, Type 1, Class 1, 180 Grit

5350-00-192-5051

Pkg. of 50

For sanding epoxy adhesive filler material.

P-C-451, Type 1, Class 1, 240 Grit

5350-00-161-9715

Pkg. of 50

Removal of corrosion from fuel cell fittings.

P-C-451, Type 1, Class 1, 320 Grit

5350-00-246-0330

Pkg. of 50

Removal of corrosion from fuel cell fittings.

MMM-A-125

8040-00-262-9002

CN 4oz.

For bonding plywood support braces.

D4001

Carton

For temporary repair of fuel leaks using a click patch.

2.

Glues

a.

Glue, Wood, Water and Mold Resistant

b.

Hardman Extra Fast Setting Epoxy

3.

Brushes, Cleaning Cloths and Sponges

a.

Brush, Acid Swabbing

H-B-643, Type II, Class 1

7920-00-514-2417

Bx. of 144

Applying adhesive to small areas.

b.

Brush, Dusting Bench

H-B-00190

7920-00-178-8315

Ea.

For lightly scrubbing fuel cells.

c.

Brush, Paint

H-B-420

8020-00-248-9309

Ea.

For cleaning fuel cell interior and components.

d.

Brush, Paint

H-B-451

8020-00-721-9646

Ea.

For application of red talcum powder.

NAVAIR 01-1A-35

002 00 Page 17 Table 2-6. Materials Required (Cont)

Item No.

Nomenclature

Specification

National Stock No.

Unit Issue

Intended Use

e.

Brush, Scrub

H-B-1490

7920-00-619-9162

Ea.

For cleaning around bolts and nuts.

f.

Cheesecloth, Cotton, bleached and unbleached

CCC-C-440

8305-00-205-3496 8305-00-205-3495 8305-00-262-3321

Bolt 10 yds Bolt 100 yds Bolt 50 yds

General purpose fuel cell wiping cloth.

g.

Sponge, Cellulose

L-S-00626

7920-00-633-9906

Ea.

Cleaning of fuel cells.

h.

Cloth Cleaning (Rymple Cloth)

7920-01-180-0556 7920-01-180-0557 7920-01-004-7847

i.

Gauze Pads, 4"x4"

Bx. of 2700 Bx. of 800 Roll of 111 sq. yds. Bag of 200

Lint free solvent cleaning and dry wiping of aircraft surfaces and support equipment General purpose, fuel tank wiping cloth.

4.

Cleaning Compounds and Solvents

a.

Cleaning Compound

MIL-PRF-85570, Type II

b.

Detergent, External Removable Fuel Tanks

MIL-D-81956

6850-01-060-5921 6850-01-268-1754

Dr. 55 gal. CN 5 gal.

For making a cleaning solution that is used for purging external, removable fuel tanks (drop tanks).

c.

Dry Cleaning Solvent

MIL-PRF-680, Type II or III

6850-01-474-2317 6850-01-474-2320

CN. 5 gal. CN. 5 gal.

A general purpose cleaning solvent for removal of oil, grease, dirt and preservatives.

d.

Isopropyl Alcohol

TT-I-735

6810-00-286-5435 6810-00-855-6160

CN. 1 gal. CN. 5 gal.

For making a wateralcohol solution for fuel cell/tank cleaning.

e.

Acetone

ASTM D329

For cleaning fuel cell repair areas and for activating adhesives.

f.

Cleaning Compound

A-A-59281, Type I or II

Mixed cleaning solvent for use in final cleaning of surfaces prior to bonding.

5. a.

Corrosion Preventive Compounds (Preservatives) and Corrosion Inhibitors Corrosion Preventive MIL-C-85054, Type I 8030-00-041-1596 CN. 16 oz. Compound, Water Displacing, Clear

MIL-C-87962, Type 2

7920-01-104-5406

Aqueous cleaner for cleaning contaminated fuel cells, tanks and components.

For use on metal fuel cell fittings.

NAVAIR 01-1A-35

002 00 Page 18 Table 2-6. Materials Required (Cont)

Item No.

Nomenclature

Specification

National Stock No.

Unit Issue

Intended Use

b.

Corrosion Preventive Compound, Water Displacing, UltraThin Film

MIL-C-81309, Type II, Class 1

8030-00-262-7358

CN. 5 gal.

Water displacing corrosion preventive. For use in protecting integral parts of fuel components.

c.

Lubricating Oil

MIL-L-6081, Grade 1010

9150-00-273-2388

Qt.

Internal preservation of rubber fuel cells and also used for fluid purging.

6. a.

Leak Detection Ammonium Hydroxide, Technical

0-A-451

6810-00-527-2476

Qt.

Used to pinpoint fuel cell leaks.

b.

Dye, Liquid, Red, Leak Detection

MIL-D-81298

6820-00-926-8887

Bt. 2 oz.

Added to the fuel to aid in locating leaks.

Dye, Liquid, Yellow, Leak Detection

MIL-D-81298

6820-00-412-2296

1 gal.

c.

Ethyl Alcohol

0-E-760

6810-00-264-6507

1 gal.

For making leak detection solution.

d.

Phenolphthalein

0-C-265

6810-00-223-7612

100 gm.

For making leak detection solution.

e.

Soap, Leak Detecting Fluid

372

6850-00-543-7692

50 lbs.

For locating fuel cell leaks and for cleaning fuel cell interior.

f.

Powder Dyed Red Talcum, Leak Test Compound

Ld-4

6850-01-417-4455

6 oz.

Leak detector for external use only.

g.

Compound, Leak Detection

MIL-PRF-25567

6850-00-185-0423

Gal.

Non-corrosive leak detection compound.

7. a.

Markers Crayon, Clay Base

SS-C-635

7510-00285-1731

Box of 8

Marking damaged area of a Fuel cell.

b.

Marker, Felt Tip, Black

GG-M-00114

7520-00-973-1059

Pkg. of 12

For marking polyurethane foam baffles.

c.

Pencil, Marking, Yellow

SS-P-196

7510-00-264-4612

Pkg. of 12

For marking fuel cell fitting locations.

NAVAIR 01-1A-35

002 00 Page 19 Table 2-6. Materials Required (Cont)

Item No.

Nomenclature

Specification

National Stock No.

Unit Issue

7510-00-240-1525

Pkg. of 12

For marking fuel cell fitting locations.

7510-00-537-6935 7510-00-537-6930 7510-00-111-6425

Box of 12 Box of 12 Box of 12

For marking integral fuel repair areas.

8010-00-290-6983

Pt. Spray can

d.

Pencil, Marking, White

SS-P-196

e.

Pencil, Acft Marking Red Yellow Silver

MIL-P-83953

Paint, Lacquer, White #17875

A-A-2787

f.

Intended Use

For stenciling information on fuel cells

8010-00-141-2952

Paint, Lacquer, Red #11136

8010-00-515-2487

Lacquer, Clear 8. a.

Sealants and Sealant Primers Primer, Sealing Compound

b.

Adhesive Promoter, Aerosol

c.

8030-00-560-8756

Pt.

For use on metal or coatings to promote adhesion of sealants.

Clean and Prime

8030-00-560-8756

Pt.

Adhesion Promoter, Water Based

Pro-Seal 152

8030-01-233-4041

Pt.

d.

Adhesive Promoter, Aerosol

Clean and Prime

8030-01-131-3228

Pt.

e.

Sealing Compound Class B2

MIL-S-8802

8030-00-579-8453

Gal. Kt.

Fuel resistant sealant for repair of fuel leaks in integral tanks.

f.

Sealing Compound Class B2

MIL-S-8802

8030-00-685-0915

Qt. Kt.

Fuel resistant sealant for repair of fuel leaks in integral tanks.

g.

Sealing Compound Class B2

MIL-S-8802

8030-00-878-8428

Kit, 5 gal.

Fuel resistant sealant for repair of fuel leaks in integral tanks.

h.

Sealing Compound Class A2

MIL-S-8802

8030-00-889-3531

Kit, 5 gal.

Fuel resistant sealant for repair of fuel leaks in integral tanks.

i.

Sealing Compound Class A2

MIL-S-8802

8030-00-723-5344

Kit, Qt.

Fuel resistant sealant for repair of fuel leaks in integral tanks.

NAVAIR 01-1A-35

002 00 Page 20 Table 2-6. Materials Required (Cont)

Item No.

Nomenclature

Specification

National Stock No.

Unit Issue

Intended Use

j.

Sealing Compound Class A2

MIL-S-8802

8030-00-753-5003

2-1/2 oz. Semkit

Fuel resistant sealant for repair of fuel leaks in integral tanks.

k.

Sealing Compound Class B-1/2

MIL-S-8802

8030-00-753-5004

6 oz. Semkit

Fuel resistant sealant for repair of fuel leaks in integral tanks.

l.

Sealing Compound Class B2

MIL-S-8802

8030-00-753-5005

6 oz. Semkit

Fuel resistant sealant for repair of fuel leaks in integral tanks

m.

Sealing Compound Class B2

MIL-S-8802

8030-00-753-5006

2-1/2 oz. Semkit

Fuel resistant sealant for repair of fuel leaks in integral tanks.

n.

Sealing Compound Class B-1/2

MIL-S-8802

8030-00-753-5007

2-1/2 oz. Semkit

Fuel resistant sealant for repair of fuel leaks in integral tanks.

o.

Sealing Compound Class A-1/2

MIL-S-8802

8030-00-753-5008

2-1/2 oz. Semkit

Fuel resistant sealant for repair of fuel leaks in integral tanks.

p.

Sealing Compound Class A2

MIL-S-8802

8030-00-753-5009

6 oz. Semkit

Fuel resistant sealant for repair of fuel leaks in integral tanks.

q.

Sealing Compound Class A-1/2

MIL-S-8802

8030-00-753-5010

6 oz. Semkit

Fuel resistant sealant for repair of fuel leaks in integral tanks.

r.

Sealing Compound Class A2

MIL-S-8802

8030-00-841-6832

Gal. Kt.

Fuel resistant sealant for repair of fuel leaks in integral tanks.

s.

Sealing Compound Class B4

MIL-S-8802

8030-00-850-0758

6 oz. Semkit

Fuel resistant sealant for repair of fuel leaks in integral tanks.

t.

Sealing Compound Class B4

MIL-S-8802

8030-00-850-0759

2 oz. Semkit

Fuel resistant sealant for repair of fuel leaks in integral tanks.

u.

Sealing Compound Class B-1/2

MIL-S-8784

8030-00-598-2910

Kit, 1/2 pt.

v.

Sealing Compound Class A-1/2

MIL-S-8784

8030-00-291-8380

Kit, 1/2 pt.

NAVAIR 01-1A-35

002 00 Page 21 Table 2-6.Materials Required (Cont)

Item No.

Nomenclature

Specification

National Stock No.

Unit Issue

w.

Sealing Compound Low Adhesion Class B-1/2

MIL-S-8784

8030-00-152-0022

2-1/2 oz. Semkit

x.

Sealing Compound Class B2

MIL-S-8784

8030-00-616-9191

Kit, 1 pt.

y.

Sealing Compound Class B2

MIL-S-8784

8030-00-680-2041

Kit, 1 qt.

z.

Desealant

SR-125A

8030-01-369-2646

55 Gal. Drum

To remove polysulfide sealant.

aa.

Sealing Compound, Low Temp Cure

MIL-S-83318

8030-00-474-1419

Kit, 1 qt.

Quick repair fuel tank sealant at low temperature.

ab.

Sealing Compound, High Temp Polysulfide Class A-1/2 Class A2 Class B-1//2 Class B2 Class B-1/2 Class B2

AMS 3276

Adhesive-Sealant Silicone, RTV Noncorrosive Type I Type I Type I, III Type I, III

MIL-A-46146 White White Clear Gray

8030-00-938-1535 8040-00-118-2695 8040-00-117-8510 8040-00-144-9774

Type I, III Type II Type II

Gray Clear Clear

8040-00-145-0020 8030-00-927-1513 8040-01-009-1562

12 oz. Cart. 3 oz. Tube 3 oz. Tube 12 oz. Tube, case 3 oz. Tube 1 pt. 3 oz. Tube

ad.

LocTite sealant, Grade A

MIL-S-22473

8030-00-081-2338

Bottle, 50cc.

9. a.

Parting Agents Cloth, Holland, Parting Agent

MIL-C-17564

8305-00-286-5050

b.

Silicone, Compound

MIL-S-8660

6850-00-880-7616

ac.

Intended Use

Integral fuel tank sealant for high temperature. 8030-00-602-0107 8030-01-387-1001 8030-00-348-7888 8030-00-485-3237 8030-00-602-0045 8030-00-560-8758

Kit, 1/2 pt. Case 6 oz. Kit, pt. Kit, pt. Case 6 oz. Case 6 oz. Semkit Adhesive-Sealant for use with sealant gun nozzles.

For sealing leaks around fasteners

Parting agent, place between the cell and heating plates. Tube, 8 oz.

Used as a parting agent.

NAVAIR 01-1A-35

002 00 Page 22 Table 2-6. Materials Required (Cont)

Item No.

Nomenclature

Specification

National Stock No.

Unit Issue

Intended Use

c.

Talc, Technical

MIL-T-50036

6810-01-080-9589

CN. 5 lb.

To dust fuel cells to reduce frictional abrasion.

10. a.

Packaging Materials Barrier Material, Greaseproof, Waterproof, Flexible

MIL-B-121, Grade A, Type I, Class 2

8135-00-753-4661

Ro. 36" x 100 yd.

Covering for workbench that is used for fuel cell repair and protection of fuel cells during shipment or storage.

b.

Barrier Material, Water-proof

PPP-B-1055

8135-00-171-1559

Ro. 36" x 200 yd.

Interior liner for fuel cell shipping containers.

c.

Barrier Material, Flexible, Electrostatic-Free, Water/Vaporproof

MIL-B-81705 MIL-PRF-81705

8135-01-419-1131

Ro. 36" x 200 yd.

Protect Polyurethane Reticulated foam baffles during storage.

d.

Boxes, Wood, Cleated Veneer, Paper, Overlaid

PPP-B-576

For shipment and storage of fuel cells.

e.

Boxes, Wood, WireBound

PPP-B-585

For shipment and storage of fuel cells.

f.

Boxes, Wood, Cleated, Plywood

PPP-B-601

Shipping and storage containers for fuel cells.

g.

Boxes, Wood, Nailed and Lock Corner

PPP-B-621

Shipping and storage containers for fuel cells.

h.

Corrugated Paperboard

PPP-P-291

i.

Corrugated Fiberboard

PPP-F-320

For covering large access door openings in fuel cells.

j.

Fiberboard Container

PPP-B-640

Domestic shipment of fuel cells.

k.

Plywood, 1/2"

NN-P-530, Grade AA

8135-00-242-5610 8135-00-281-3920 8135-00-290-3400 8135-00-290-3402 8135-00-782-3954

5330-00-171-6700

3' x 250' 2' x 250' 4' x 250' 3' x 250' 12" x 3000"

Pkg. of 6 sheets 4' x 8'

For cushioning bladder cell folds to prevent creasing.

For making fuel cell support braces.

NAVAIR 01-1A-35

002 00 Page 23 Table 2-6. Materials Required (Cont)

Item No.

Nomenclature

Specification

National Stock No.

Unit Issue

Intended Use

l.

Polyethylene Film

L-P-378, 6 mil.

8135-00-579-6489

Ro. 100' x 12'

Provide protection for fuel cells removed from the aircraft.

m.

Tube, Mailing

PPP-T-495

8110-00-291-0346 8110-00-291-0347 8110-00-291-0348

Ea. 42"x 2" Ea. 42"x 3" Ea. 42"x 4 1/2"

For placement in fuel cell folds to prevent creasing of the cell walls.

11. a.

Tapes Tape, Transparent, Polyurethane, Abrasion Resistant, Anti-Chaffing

SJ8560 SJ8561

9330-00-115-5036

Ro. 1"x 36 yd. 4"x 36 yd.

To cover protruding fasteners and sharp edges of a fuel cell cavity to prevent subsequent damage to the fuel cell.

9330-00-124-3730 9330-00-169-6407 9330-00-003-6171

b.

c.

Tape, Waterproof, Packaging and Sealing

PPP-T-60, Type III,

7510-00-079-7906

Class 1

7510-00-079-7905

Tape, Weather Resistant

MIL-T-22085, Type II

7510-00-852-8179

Ro. 2"x 36 yd. Ro. 3"x 36 yd Ro. 2"x 60 yd. Ro. 3"x 60 yd.

For packaging applications and for sealing barrier materials.

Ro. 1"x 36 yd. Ro. 4"x 36 yd.

For protection of fuel cell fitting surfaces.

4020-00-240-2146

2100 ft.

Used as lacing for fuel cell installation and fuel cell baffle installation.

7510-00-916-9659

12. a.

Miscellaneous Materials Cord, Nylon MIL-C-5040

b.

Cork and Rubber Composite Sheet

MIL-G-6183

5330-00-074-3042

.125" thk.

For making fuel cell fitting gaskets.

c.

Needle, Hypodermic, 17 gage

GG-N-196

6516-00-349-1900

Box of 12, 3" long Box of 12, 1 1/2" long

Fuel cell ply separation and blister repairs.

Cyl. 200 Ft3

For inerting fuel cells or tanks.

6516-00-349-2400 d.

Nitrogen, Gas, Dry

BB-N-411, Type I, Class 1, Grade B

e.

Polyurethane Foam Buns

MIL-DTL-83054, Type I

6830-00-264-9087

Replacement or repair material for the fuel cell/tank baffles.

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002 00 Page 24 Table 2-6. Materials Required (Cont)

Item No. f.

Nomenclature Protective Skin Compound

Specification

National Stock No.

Unit Issue

Intended Use

P-S-411

6850-00-244-4893

lb. Jar

For skin protection from fuel and fuel vapors.

6850-00-870-8995

5 oz. Tube

g.

Tubing, Aluminum Alloy

MIL-T-7081

4710-00-289-2785

h.

Sealing Compound, Top Coat, Fuel Tank, Buna N

MIL-S-4383

8030-00-664-4019

Pt.

8030-00-664-4954

Qt.

i.

Syringe, Hypodermic

GG-S-935, Type II, Size 1

6516-00-380-5500

Ea.

Fuel cell ply separation and blister repairs.

j.

Wire, Safety

MS20995C

9505-00-293-4208

.032" thk.

Used when safety wiring is required.

k.

Oylite Stick

8030-00-935-5841

Ea.

For the temporary repair of fuel leaks around fastener heads.

l.

Epoxy Tabs

8030-01-265-2895

Box of 24

For the temporary repair of integral tank fuel leaks.

m.

Click Patch Kit

8040-01-107-3972

Ea.

For the temporary repair of integral tank fuel leaks.

n.

Click Patch Kit

8040-01-107-3978

Ea.

For the temporary repair of integral tank fuel leaks.

o.

Click Patch Kit

8040-01-107-3979

Ea.

For the temporary repair of integral tank fuel leaks.

p.

Click Patch Kit

8040-01-107-3980

Kt.

For the temporary repair of integral tank fuel leaks.

q.

Click Patch Kit

8040-01-107-3981

Kt.

For the temporary repair of Integral tank fuel leaks.

r.

Click Patch Kit

8040-01-107-4932

Kt.

For the temporary repair of Integral tank fuel leaks.

Type O

To repair fuel cell baffle rods. Used as a general purpose, sealing compound.

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002 00 Page 25/(26 Blank) Table 2-6. Materials Required (Cont)

Item No.

Nomenclature

Specification

National Stock No.

Unit Issue

Intended Use

s.

Aluminum foil 0.0015

9535-00-242-5661

Roll, 1130’ x 24”

For temporary repair of fuel leaks using a click patch.

t.

Aluminum foil 0.0010

9535-00-721-9726

Roll, 1424” x 15”

For temporary repair of fuel leaks using a click patch.

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GENERAL SAFETY INSTRUCTIONS AIRCRAFT FUEL CELLS AND TANKS

Reference Material Navy Occupational Safety and Health (NAVOSH) Program Manual..................................... OPNAVINST 5100.23 Series

Alphabetical Index Subject

Page

Batteries................................................................................................................................................................................ 4 Bonding and Grounding ....................................................................................................................................................... 4 Fire Extinguishers ................................................................................................................................................................ 4 Fuel Exposure Hazards......................................................................................................................................................... 2 Fuel Absorbed Internally ........................................................................................................................................... 2 Fuel Vapor Exposure ................................................................................................................................................. 2 Injury to the Skin and Eyes........................................................................................................................................ 2 Lead Poisoning .......................................................................................................................................................... 2 Polyurethane Adhesives ............................................................................................................................................ 2 Generation and Accumulation of Static Electricity .............................................................................................................. 4 Aircraft in Flight........................................................................................................................................................ 5 Aircraft on the Ground .............................................................................................................................................. 5 Clothing ..................................................................................................................................................................... 5 Fueling....................................................................................................................................................................... 5 Personnel ................................................................................................................................................................... 5 Materials and Equipment Required ...................................................................................................................................... 5 Protective Clothing............................................................................................................................................................... 2 Caps ........................................................................................................................................................................... 3 Coveralls.................................................................................................................................................................... 3 Gloves........................................................................................................................................................................ 3 Shoes ......................................................................................................................................................................... 3 Socks ......................................................................................................................................................................... 3 Protective Equipment ........................................................................................................................................................... 2 Air Supply Equipment ............................................................................................................................................... 3 Respirator .................................................................................................................................................................. 3 Safety Goggles........................................................................................................................................................... 3 Static Electricity ................................................................................................................................................................... 4 Conditions of Discharges........................................................................................................................................... 4 Conductors and Insulators ......................................................................................................................................... 4 Electrostatic Ignition.................................................................................................................................................. 4 Susceptibility of Aviation Fuel Vapors to Electrostatic Ignition.......................................................................................... 5 Aviation Gasoline ...................................................................................................................................................... 5 Fuel to Air Proportions .............................................................................................................................................. 5 JP-4 Fuel.................................................................................................................................................................... 5 JP-5 Fuel.................................................................................................................................................................... 5 JP-8 Fuel.................................................................................................................................................................... 5 Support Equipment............................................................................................................................................................... 3 Battery Powered Flashlights ...................................................................................................................................... 3 Explosion-Proof Lights.............................................................................................................................................. 4 Hand Tools ................................................................................................................................................................ 4 Non Explosion-Proof Equipment .............................................................................................................................. 3 Power Tools............................................................................................................................................................... 4

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1.

FUEL EXPOSURE HAZARDS

2. Fuel Vapor Exposure. Maintenance personnel exposed to fuel vapors may suffer eye, nose, and throat irritation. Even at relatively low levels of exposure, nausea, vomiting, and loss of appetite may occur. At higher levels of exposure, there may be headaches, dizziness, euphoria, or loss of muscle coordination followed by loss of consciousness, convulsions, and eventually death. Excessive physical contact with fuel, such as wearing clothing that is soaked with fuel, produces a solvent action, which removes natural fats and oils from the skin. This will produce dryness, irritation of the skin, and may result in severe dermatitis.

Do not induce vomiting when petroleum products have been swallowed. Seek medical attention immediately. 3. Fuel Absorbed Internally. Some fuels are composed of elements that may be absorbed through the skin and cause damage to internal organs such as kidneys and liver. The accidental swallowing of fuels causes internal injuries and possible death. Fuel taken internally will produce abdominal pain, discomfort, prolonged constipation, fatigue, and palsy. Any person showing these physical signs while working around fuel shall report to the medical facility immediately. 4. Lead Poisoning. The tetraethyl lead in aviation gasoline is a very poisonous compound. It is harmful if the vapors are inhaled, or if the compound enters the body through the mouth or by contact with the skin. The principal danger of lead poisoning occurs when it is necessary to enter fuel cells, which have been used for leaded gasoline. Bathing after being in a fuel cell that has contained leaded fuel is mandatory.

Apply protective skin compound A-A-50169 (Table 2-5, item 12f) to exposed skin surfaces that may be wetted by any fuel. If a permanent eye wash facility is not available, ensure a portable one is available.

5. Injury to the skin and eyes. If fuel should accidentally contact the skin, it should be promptly washed off using soap and water. Any clothing or shoes, which may become soaked with fuel should be removed at once. Prolonged contact of fuels or solvents with the skin may result in dermatitis due to removal (defatting) of the natural body oils. Splashes or spills in the eyes produce immediate irritation and can result in loss of sight. Eyes must be flushed immediately and repeatedly with large quantities of fresh water for a minimum of 15 minutes and obtain treatment as soon as possible. 6. Polyurethane Adhesives. Polyurethane adhesives produce isocyanate vapors during preparation, application, and curing. Uncured isocyanates irritate eyes, skin, and respiratory tract, and may induce allergic sensitization of personnel exposed to vapors and mists during spray application. Sensitization is usually characterized by bronchial constriction, causing difficulty in breathing, dry cough, and shortness of breath. Once sensitized, many workers cannot tolerate even minimum subsequent exposure to isocyanates and must avoid work areas where such exposure can occur. In addition, solvents employed with polyurethane coatings are moderately toxic and tend to increase rate of absorption and severity of physiological effect. 7.

PROTECTIVE CLOTHING

8. Work involving inspection, repair, installation, and removal of fuel cells may require partial or complete entry of personnel into a cell. Protective clothing shall be provided to ensure safety of personnel while performing work in such space. Personal protective equipment shall be maintained in accordance with OPNAVINST 5100.23 Series. Personnel engaged in fuel system repairs shall wear the following clothing:

Do not remove any garment while in an open fuel cell or area adjacent to an open fuel cell. Normal activity can generate electrical charges on clothing. Do not wear clothing made of materials such as nylon, orlon, dacron, wool, or silk while working on an open fuel system component.

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a. Coveralls. Personnel entering a fuel cell to perform repairs shall remove all outer clothing and wear clean, cotton, coveralls, conforming to MIL-DTL-14610 (Table 26, item 6f). Authorized personnel performing concurrent maintenance on the same aircraft other than fuel cell maintenance shall wear 100 percent cotton clothing, which may be other than white coveralls.

entering a fuel cell to perform repairs. The local Industrial Hygienist will determine which respirator is authorized, depending on the type of repair. The hygienist will also provide respirator inspection, fit check, and cleaning instructions. Ensure continuous general ventilation (one complete air change every 3 minutes) when working inside a fuel cell.

b. Socks. Prior to entering a fuel cell, personnel shall remove shoes and personal socks and shall put on white cotton socks followed by rubber overshoes (Table 2-6, item 6m).

c. Air Supply Equipment. Use of an air supplied respirator is required when personnel enter cells which is noted on a Permit as Class 1 or Class 2 per Work Package 004. 11. SUPPORT EQUIPMENT

Wear safety shoes in fuel cell maintenance areas. Shoes with exposed tacks or metal shall not be worn.

12. Maintenance personnel shall be thoroughly familiar with the manual of operating instructions for the equipment involved and know emergency shutdown procedures and other precautionary measures, including the selection and the use of appropriate fire extinguishers. Operators shall review the maintenance and inspection records attached to the unit and inspect the equipment for leaks, damage or malfunction before operational use.

Shoes shall not be worn inside of bladder or self-sealing fuel cells. c. Shoes. Do not wear safety shoes, (Table 2-6, item 6p) in integral fuel cells unless footwear covers (Table 2-6, Item 6g) are worn over the shoes. d. Caps. Wear cap (Table 2-6, item 6e) when doing internal fuel cell repair to prevent contamination with hair oils. e. Gloves. Wear rubber gloves, MIL-DTL-32066, (Table 2-6, item 6j) during depuddling or when using solvents that require application by hand. Cotton gloves, MIL-G-2874, (Table 2-6, item 6h) shall be worn to protect the hands when applying sealants/adhesives. 9.

PROTECTIVE EQUIPMENT

10. The following equipment is required by personnel who perform repairs inside fuel cells:

Under no circumstances shall non-explosionproof power equipment be operated within the fuel cell maintenance area. All rolling equipment used in fuel cell maintenance areas shall be quipped with rubber tires or wheels. a. Nonexplosion-proof Equipment. Electrical and engine-driven equipment that is nonexplosion-proof shall be placed outside of the fuel cell maintenance area and upwind of the aircraft. External power units used to supply electrical power during refueling or defueling shall be positioned upwind of the aircraft away from the source of fuel vapors with power cable fully extended. Prior to use, inspect power cables for fraying, cuts, or damage to insulation. Inspect connections for damage or corrosion.

a. Safety goggles. Personnel engaged in exterior buffing of fuel cells shall wear safety goggles, ANSI Z87.1, (Table 2-6, item 6k) to prevent rubber dust from coming in contact with eyes. b. Respirator. NIOSH approved respiratory protection suitable to protect the entrant from exposure to repair adhesives and cleaning agents shall be worn when

Use only explosion-proof equipment meeting Class 1, Div 1, Group D, National Electrical Code for purging and ventilating fuel cells.

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003 00 Page 4

Do not rest lights on fuel cell surfaces. Light assemblies received from stock shall be inspected before use for frayed electrical wires and/or cracked bulbs.

NOTE The requirement for the use of special safety and approved flashlights has been deleted. The ordinary two or three cell flashlights using carbon zinc dry cells have not been found capable of igniting a flammable vapor air mixture under conditions of ordinary usage. 13. Explosion-proof Lights. Explosion-proof electric lights are the only lights authorized in the fuel cell maintenance area. Extension cords with explosion-proof fittings shall be long enough to make the electrical connection outside the fuel cell maintenance area. If the lamp, cord, plug, or any component of the light assembly is defective, do not use the light. Special care shall be taken to inspect the glass globe for nicks, scratches, or minor cracks in the surface of the glass. SEE IRAC #14 14. Power Tools. All power tools used in fuel system maintenance shall be air-driven. Tools powered by compressed air require careful handling to avoid accidents. Air is supplied under pressure from either an engine compressor or tanks. Before disconnecting, or leaving a pneumatic tool unattended, the air supply shall be turned off at the control valve and the tool bled of air.

been the result of a lack of understanding by maintenance personnel of how static electricity is generated, accumulated, discharged as a spark, and of the means of controlling such a hazard. a. Electrostatic Ignition. Electrostatic Ignition is the ignition of a flammable vapor-air mixture by a spark created during the discharge of electrostatic charges. The term "static charge" as used in this manual shall mean the accumulation of electrical charges on materials as a result of friction or induced charging due to the proximity of a nearby charged object. The discharge of these charges across an air gap creates a spark that constitutes a fire or explosion hazard. The generation of static charges cannot be totally prevented because its inherent origins are present at every interface. b. Conditions of Discharges. The accumulation of electrical charges may not be, in itself, a fire or explosion hazard. There must be a discharge across an air gap (spark) for static electricity to be the source of ignition. For this to occur, the following conditions must be fulfilled: (1) A means of generating the static charge. (2) A means of accumulating the charge. (3) Adequate voltage (potential difference) to cause a discharge across an air gap between two objects. (4) The discharge must occur in a flammable vapor mixture.

17. The fuel cell maintenance area shall be equipped with approved fire extinguishers as specified by the fire marshal. Extinguishers shall be in a readily accessible position. Seals and inspection dates shall be checked monthly. Extinguishers shall be removed after use and immediately replaced.

c. Conductors and Insulators. Static charges can move freely through certain substances. Generally, such substances are metal and are called conductors. In other substances, static charges move with difficulty. These substances are called nonconductors or insulators. Some of the more common insulators in the latter group include glass, rubber, and many plastic materials. When electric charges are present on the surface of a non-conductive substance, they cannot flow or move away from an area, thus permitting a potential buildup of the charges. Electric charges on a conductive material, which is completely surrounded by insulating material also are prevented from escaping and therefore, are non-mobile or static charged. In either case, the substance on which these charges are present is said to be statically charged, or have static electricity.

18. BATTERIES

22. BONDING AND GROUNDING

19. Disconnect batteries prior to any open fuel cell repair or fuel cell entry. Disconnect battery cables and label with a suitable warning sign to indicate that the cables are not to be connected. If the aircraft/support equipment is scheduled to be down for an extended period, the batteries shall be removed.

23. Refer to Work Package 006 paragraph 4 for proper grounding and bonding procedures. All aircraft must be properly grounded to an approved earth ground prior to maintenance procedures.

20. STATIC ELECTRICITY

25. Static electricity is most often generated by frictional effects during relative motion between two substances, particularly those of unlike materials.

15. Hand Tools. The requirement for non-sparking tools has been deleted. 16. FIRE EXTINGUISHERS

21. Static electricity has been the ignition source of numerous petroleum fires and explosions. Often these have

24. GENERATION AND STATIC ELECTRICITY

ACCUMULATION

OF

NAVAIR 01-1A-35

003 00 Page 5/(6 blank)

a. Personnel. The human body, especially in a dry atmosphere, can frequently accumulate a static charge as high as several thousand volts. This charge may be generated by rubbing contact of the shoes with the floor, sliding contact involving clothing, etc. b. Clothing. Clothing made of synthetic fabrics(nylon, dacron, orlon, rayon, etc.) are more active generators of static charges than natural fabrics, although wool and silk also generate charges when rubbed against certain materials. The removal or wearing of clothing of the above fabrics shall not be done in an area that may contain a flammable or explosive atmosphere. c. Aircraft in Flight. Static charges may be developed and accumulated by the relative motion between the aircraft and atmospheric particles, particularly snow, ice crystals, dust, or smoke. Also, the proximity of the aircraft to electrically charged clouds can induce a charged condition. d. Aircraft on the Ground. An aircraft can build up a static charge when in movement on the ground. Also, the rubber tires act as an insulator to prevent the dissipation of the charges when the aircraft is parked. The charging rate difference is principally one of magnitude because of the greater surface area of the aircraft. Charges may be generated by movement of air currents over aircraft surfaces where such currents carry particles of dust, snow, water, etc. Static charge buildup on an aircraft in a hangar heated by a blower system will usually be found to be greater during cold weather due to the lower humidity and increased circulation of dust particles in the air.

Limit fueling flow rate when fueling to minimize static charge buildup. A high static charge buildup in an air-enriched atmosphere can change the atmosphere into the flammable range.

27. Static discharges under ideal conditions can create a spark, which can ignite fuel vapors. A person walking across a dry area may accumulate several times the voltage necessary to cause such a spark. a. Fuel to Air Proportions. Aviation fuels must be in a vapor form within certain fuel to air proportions to burn. b. Aviation Gasoline. Aviation gasoline has a very strong tendency to vaporize and, as a result, will always have considerable vapors in the air over the surface of the fuel. In a closed tank, enough fuel can vaporize so that the fuel-air vapor mixture may be too rich to burn. c. JP-4 Fuel. The JP-4 vaporization temperature range and flammable fuel-to-air mixture (vapor) range falls within normal operational temperatures. Thus, of the fuels used for aircraft, JP-4 is the most apt to be ignited by static electrical discharges. In addition, in any cell closed or open, the vapor above JP-4 often tends to stabilize in the flammable range instead of becoming over-rich, as can occur in the case of aviation gasoline. d. JP-5 Fuel. JP-5 fuel will not give off enough fuel vapors to be flammable until it is heated above 136oF (60oC). Since the vapor concentration in the air above the surface of JP-5 at normal handling temperatures is below the lean limit, the discharge of a static spark over the surface should not result in a fire or explosion. However, if JP-5 fuel is mixed with a small amount of JP-4 or aviation gasoline, the amount of vapor given off can increase to the point where it will be in the flammable range at a much lower temperature and thus become susceptible to ignition by a static electricity spark. e. JP-8 Fuel. During typical ground fuel handling operations, where the ambient conditions are below 75°F, JP-8 falls below the lean limit. This means that a discharge of a static spark over the surface should not result in a fire or explosion. However, if the temperature is above 75°F then the JP-8 falls within the flammable fuel-to-air mixture and is more susceptible to ignite by static electrical discharges.

e. Fueling. To control the amount of static charges that may be generated by the flow of fuel through pipes, filters, hoses, and other equipment during aircraft fuel servicing, and to provide a path to equalize this charge or minimize the possibility of static discharge that could ignite fuel vapors, the fueling equipment and the aircraft shall be bonded to each other. Further, the fuel nozzle shall be brought in contact with a metal part of the aircraft remote from the fuel cells to minimize any differential in electrical charge potential. The fueling nozzle is then bonded to the aircraft by means of a bonding wire before fuel is dispensed.

a. Table 2-5 Consumable Materials Required. This table lists all consumable materials required for each work package of the manual.

26. SUSCEPTIBILITY OF AVIATION VAPORS TO ELECTROSTATIC IGNITION

b. Table 2-6 Equipment Required. This table lists all equipment required for each work package of the manual.

FUEL

28. MATERIALS AND EQUIPMENT REQUIRED 29. Table 2-5 and Table 2-6 list materials and equipment required to perform maintenance procedures for each work package.

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Page 1 of 20

AIRCRAFT CONFINED SPACE PROGRAM Reference Material Naval Aviation Maintenance Program .............................................................................. COMNAVAIRFORINST 4970.2 Navy Occupational Safety and Health (NAVOSH) Program Manual................................................OPNAVINST 5100.23 Naval Sea Systems Command Gas Free Engineering Program ........................................... NAVSEA S6470-AA-SAF-010 Naval Ships Technical Manual............................................................................................ NAVSEA S9086-CH-STM-030

Alphabetical Index Subject

Page

Aircraft Confined Space Program, The ................................................................................................................................ 4 Intermediate ‘I’, Organizational ‘O’, and Depot ‘D’ level requirements ...................................................................... 4 Supporting Documents.................................................................................................................................................. 4 Contractor Relations............................................................................................................................................................. 4 Definitions............................................................................................................................................................................ 3 Affected Persons ........................................................................................................................................................... 3 Aircraft Confined Space Program ................................................................................................................................. 3 Concurrent Maintenance ............................................................................................................................................... 3 Confined Space ............................................................................................................................................................. 3 Entry Authority ............................................................................................................................................................. 3 Fireguard / Fire Watch .................................................................................................................................................. 4 Fuel Cell and Fuel Tank ................................................................................................................................................ 4 Hot Work....................................................................................................................................................................... 4 Immediately Dangerous to Life and Health (IDLH) ..................................................................................................... 4 Non-Permit Required Confined Space .......................................................................................................................... 4 Permit / Certificate ........................................................................................................................................................ 4 Permit Required Confined Space .................................................................................................................................. 4 Sticker / Note / Tag ....................................................................................................................................................... 4 Discussion ............................................................................................................................................................................ 3 Entry and Work Restrictions .............................................................................................................................................. 17 Permitting of Fuel Cells and Tanks .................................................................................................................................... 13 Classification of Permits ............................................................................................................................................. 13 Class 1: Not Safe for Hot Work – Not Safe For Personnel ......................................................................................... 14 Class 2: Not Safe Fore Personnel Without Protection (Provisional Permit) ............................................................... 14 Class 3: Safe For Personnel – Not Safe For Hot Work ............................................................................................... 14 Class 4: Safe For Personnel – Safe For Hot Work ...................................................................................................... 15 Class 5: Hands-In/Tool-In Maintenance ..................................................................................................................... 15 Class 6: Reclassified Non-Permit Required Confined Space ...................................................................................... 15 Permit, The ......................................................................................................................................................................... 16 Cancellation of Permits ............................................................................................................................................... 17 Continuous or Periodic Testing and Maintaining Permits........................................................................................... 16 Permit Distribution..................................................................................................................................................... 17 Initial Permit ............................................................................................................................................................... 16 Permit Process, The..................................................................................................................................................... 16 Retesting Fuel Cells .................................................................................................................................................... 17 Personnel .............................................................................................................................................................................. 6 Aircraft Confined Space Program Manager, The.......................................................................................................... 6 Authorized Entrant ........................................................................................................................................................ 9 Backup Safety Observer.............................................................................................................................................. 10 Commanding Officer, The ............................................................................................................................................ 6 Entry Authority ............................................................................................................................................................. 8 Entry Supervisors .......................................................................................................................................................... 8

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Fire Watch ...................................................................................................................................................................11 Management Personnel..................................................................................................................................................9 Naval Air Technical Data and Engineering Service Command (NATEC)..................................................................11 Safety Observer ...........................................................................................................................................................10 Record Keeping Requirements .............................................................................................................................................5 Rescue Plans .........................................................................................................................................................................5 Civilian Only Depot ‘D’ level Rescue Plans .................................................................................................................6 ‘I’ and ‘O’ level Rescue Plans .......................................................................................................................................5 Personal Protective Equipment (PPE) ...........................................................................................................................6 Testing Procedures..............................................................................................................................................................11 General.........................................................................................................................................................................11 Hazard Mitigation........................................................................................................................................................13 Instrumentation ............................................................................................................................................................11 Procedure .....................................................................................................................................................................11

NAVAIR 01-1A-35

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1.

DISCUSSION

2. The Naval Aviation Maintenance Program (NAMP) COMNAVAIRFORINST 4790.2 directs COMNAVAIRSYSCOM to manage the Aviation Gas Free Engineering (AVGFE) Program (hereafter known as the Aircraft Confined Space Program) per this Maintenance Instruction manual (MIM). The Aircraft Confined Space Program (ACSP) is an extension of the OPNAVINST 5100.23 series NAVAIR Confined Space Entry Program. This work package establishes requirements and responsibilities of the ACSP for Naval aviation ashore and afloat. 3. The ACSP is concerned with the safety and health of personnel while handling or working with hazardous materials and equipment associated with fuel cell and fuel tank maintenance. Aircraft fuels must be handled with caution because of fire and explosion dangers. Additionally, there are health hazards associated with fuels (inhalation of vapors, absorption through the skin, moisture around the eyes, or ingesting by mouth, etc.). Other hazards relate to work areas and equipment used during fuel system maintenance. 4. Safety instructions and precautions in this work package are minimum requirements. It is not feasible to describe all situations that may arise. Basic knowledge and good judgment are required of all personnel involved with fuel cell maintenance in order to deal with hazardous conditions which may or may not be covered in this work package. 5. Strict compliance to prescribed standards is mandatory. Safety instructions as well as training and supervision of personnel are essential to accident-free fuel cell maintenance. Failure to comply with safety precautions could result in loss of life, injury, and/or destruction of valuable property. 6.

DEFINITIONS

7. Affected Persons Anyone whose duty is specifically defined and stated as required by this work package is an affected person. 8. Aircraft Confined Space Program. The Aircraft Confined Space Program (ACSP) describes the processes, means, and methods used for recognizing, evaluating, and controlling potential confined space hazards associated with fuel cell and fuel tank maintenance and for communicating those hazards to employees. The ACSP was formerly known as the Aviation Gas Free Engineering Program (AVGFE). 9. Concurrent Maintenance. Multiple maintenance procedures happing concurrently on a single aircraft are allowed

under certain circumstances. As defined in this work package, these are procedures that may take place anywhere on the aircraft and do not involve the use of external or battery power and may or may not involve hot work. 10. Confined Space. A “confined space” means a space that: a. is large enough and so configured that an employee can bodily enter and perform assigned work b. has limited or restricted means for entry or exit (for example, tanks, vessels, silos, storage bins, hoppers, vaults, and pits are spaces that may have limited means of entry c. is not designed for continuous employee occupancy. 11. Entry Authority In previous editions to this manual, the Entry Authority (EA) was the Aviation Gas Free Engineer (AVGFE). The EA is anyone who is specifically trained and authorized to test and certify the Permit to an aircraft confined space. In the context of this work package, the EA responsibilities may also be performed by the Aircraft Confined Space Manger, a local Confined Space Program Manager or Assistant CSPM, a Naval Gas Free Engineer, or a Certified Marine Chemist. The EA must be designated in writing by the CO or the CO’s designee. 12. Fireguard / Fire Watch In this instruction, the term Fireguard is equivalent to and interchangeable with the term Fire Watch. 13. Fuel Cell and Fuel Tank. Where fuel cells and fuel tanks (integral, wing tanks, or drop tanks) are referred to together, they are labeled as fuel cells in this manual. Where a fuel tank is specifically referred to it is labeled as such. 14. Hot Work Any procedure that generates temperatures of 400°F or more. This may include grinding, drilling, welding, flame heating, cutting, brazing, soldering, heat shrink operations, etc. 15. Immediately Dangerous to Life and Health – IDLH Any condition that poses an immediate or delayed threat to life or that would cause irreversible adverse health effects or that would interfere with an individual’s ability to escape unaided from a permit space. 16. Non-Permit Required Confined Space. A non-permit required confined space means a confined space that does not contain or, with respect to atmospheric hazards, have the potential to contain any hazard capable of causing death or serious physical harm.

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17. Permit / Certificate The term Permit is the preferred term and corresponds to OSHA standard terminology. The term Certificate will no longer be used in this program to describe the document that permits confined spaces. Permits may be issued only by the Aircraft Confined Space Program Manager (ACSPM) or Entry Authority (EA), as defined in this work package. 18. Permit Required Confined Space means a confined space that has one or more of the following characteristics: a. Contains or has a potential to contain a hazardous atmosphere, b. Contains a material that has the potential for engulfing an entrant,

23. Where no existing law, regulation, or standard applies, or where interpretation is necessary, the activity shall submit full particulars and details via the chain of command to the Materials Engineering Division, Code 4.9.7.4., NADEP Cherry Point. Action to control the hazard shall be taken in the interim. 24. Intermediate ‘I’, Organizational ‘O’, and Depot ‘D’ level requirements. Operationally, ‘I’ and ‘O’ level activities require slightly different work practices than the civilian only ‘D’ level activities. Where different operating procedures are required it will be stated as such. Specific requirements are located in paragraphs concerning: a.

Record Keeping

c. Has an internal configuration such that an entrant could be trapped or asphyxiated by inwardly converging walls or by a floor which slopes downward and tapers to a smaller cross-section, or

b.

Training

c.

Rescue Plans

d. Contains any other recognized serious safety or health hazard.

d.

Personnel

19. Sticker / Note / Tag At times additional warnings or information will be required to be posted on or near a fuel tank or cell. The terms sticker, note, or tag are representative terms for the additional signage that may be posted on a confined space and are to be used in conjunction with instructions presented on Permits. 20. THE AIRCRAFT CONFINED SPACE GRAM (ACSP)

PRO-

21. The purpose of the ACSP is to assure the safety and health of personnel required to work in and around aircraft fuel cells and tanks. All other requirements for confined space safety should be forwarded to the local Confined Space Program Manager (CSPM) for action. 22. Supporting Documents This chapter was written to conform to the strictest requirements of the Occupational Safety and Health Administration’s (OSHA) 29 CFR 1910.146 Permit Required Confined Spaces. It is adapted to reflect the unique operational requirements of Naval Aviation. The following documents, which address the requirements of a Confined Space Entry Program, were consulted in preparing this manual: NAVSEA S6470-AA-SAF-010 Naval Sea Systems Command Gas Free Engineering Program OPNAVINST 5100.23 series, Navy Occupational Safety and Health (NAVOSH) Program Manual NAVSEA S9086-CH-STM-030, Naval Ships Technical Manual, Chapter 074, Volume 3, Gas Free Engineering

25. All personnel whose name will appear on a permit will be regulated by this work package. 26. CONTRACTOR RELATIONS 27. As a matter of policy, military and civilian personnel employed by the Department of the Navy (DON) are prohibited from performing confined space testing services for contractor operations. The following provisions shall apply to avoid the assumption of liability by the Navy in the event of a mishap: a. Navy personnel may not perform any aircraft confined space safety related duties in support of contractors or contractor personnel. b. Navy personnel may not lend governmentcontrolled equipment to contractors or contractor personnel. Government owned and controlled equipment is equipment that has been issued to, and is in the possession of a Federal Government organization. c. Where Navy personnel and contractors are to occupy the same space at the same time, the ACSPM and the contractor representative(s) shall issue separate Permits. Government civilian employees are not to be considered as contractors. d. For extreme emergency situations, which could endanger personnel and property, an exception in writing shall be authorized by the Commanding Officer. Confined space safety services shall be personally conducted and supervised by the ACSPM. Where delays created by seeking Commanding Officer approval would create a greater danger, Navy Aircraft Confined Space services may be used without prior authorization to prevent catastrophic harm to personnel or property.

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e. Equipment purchasing decisions cannot be dictated by the DON on civilian contractors. Where conflict exists between this manual and the contractor with regards to equipment, the equipment owned by the contractor shall be allowed. The equipment shall meet all government regulations with regards to confined space entry safety as presented in OSHA 29 CFR 1910.146. f. Navy squadrons with a total civilian contractor maintenance force shall comply with the provisions of this manual. Contractors shall provide personnel qualified to test spaces and issue Permits. 28. RECORD KEEPING REQUIREMENTS 29. Copies of the following documents associated with the ACS Program shall be maintained by the ACSPM for the length of time indicated. a. Military personnel in ‘I’ and ‘O’ level activities, authorized to assess aircraft confined spaces (ACSPM or Entry Authority (EA)), must maintain personal logbooks containing the following: (1) A COPY of initial course completion certificate. (2) Current letter of certification. (3) A legible copy of each Permit issued. (4) Record of all training that applies to the ACS Program including, but not limited to, On the Job Training (OJT). (5) Hot work checklist (when applicable). b. Civilian ‘D’ level personnel are not required to maintain personal logbooks. c. Certificates of completed training (both formal and on-the-job) for each ACSPM or EA. Retain as long as the individual is performing in the capacity. d. Certification letter signed by the Commanding Officer or CO’s designee for each ACSPM or EA. Retain as long as the letter is valid. e. Calibration logs for each gas detector. Retain for a minimum of one year from the date of the last entry. f. A legible copy of each confined space permit. Retain for a minimum of one year from the date of issue.

30. RESCUE PLANS 31. Each activity that performs fuel cell and tank maintenance shall develop and implement procedures for rescuing incapacitated entrants from fuel cells and tanks. The rescue plan shall prevent unauthorized personnel from attempting a rescue. It must have procedures for summoning rescue and emergency medical services. The written plan shall be posted in the immediate area when personnel are entering and working inside fuel cells and tanks. All personnel involved shall be instructed in the proper procedures to be followed in rescue efforts. 32. ‘I’ and ‘O’ level Rescue Plans Activities with access to base or local fire and rescue services, may use those services if identified in the site specific rescue plan. If local services cannot be used, activities shall write their own rescue plan that allows for independent rescue operations. Although more stringent requirements may be added which are appropriate for specific situations, the following requirements shall be incorporated, as a minimum, in the activity's Plan: a. A Safety Observer shall be stationed outside any fuel cell or tank containing an authorized entrant. b. Rescue control points shall be manned with an adequate number of trained and qualified Backup Safety Observers to provide support for active Safety Observers. c. Each Safety Observer shall practice making rescues at least once every 12 months. Simulated rescue operations in which dummies, manikins, or actual persons can be used. It is preferable to schedule training in actual fuel cells while the fuel cell is open and prepared for some maintenance action. It should not be necessary to open and prepare a fuel cell solely for the purpose of rescue training. Repre sentative fuel cells shall, with respect to opening size, configuration, and accessibility, simulate the types of fuel cells from which rescue is to be performed. d. Each Safety Observer shall be trained and current in cardiopulmonary resuscitation (CPR). Training in Basic First Aid is suggested but not mandatory. e. Medical services and treatment shall be readily available for personnel incapacitated or injured in a fuel cell. Information on the location of medical facilities and means of summoning aid (such as equipment to use and the numbers to call) shall be provided and available for immediate reference.

g. Mishap/accident reports associated with the ACS Program. Retain for a minimum of one year from the date of issue.

33. Civilian only Depot ‘D’ level Rescue Plans Civilian activities (DON) shall use local fire department rescue services provided the following conditions are met:

h. Records of rescue drills. Retain for a minimum of one year from date of drill.

a. The posted rescue plan shall specifically prohibit anyone, except fire department rescue personnel, from entering a fuel cell to perform rescue operations.

i.

A current copy of the Rescue Plan.

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b. The fire department is notified of any and all hazards they may confront when called on to perform rescues. c. The fire department is granted access to all space(s) from which rescue may be necessary so they can develop appropriate rescue plans and practice rescue operations. d. In the event of an incident, which requires the attention of the fire department, thus rendering it unable to perform rescue services, all fuel cell entry operations shall cease until such a time as the fire department has specifically advised adequate rescue services are once again available. e. Means of summoning fire department or rescue services shall be provided and the phone numbers posted on the permit. 34. Personal Protective Equipment (PPE). Based on local SOP or conditions, personnel entering fuel cells shall be respirator qualified by the station Occupational Safety and Health Office in the proper use of National Institutes of Occupational Safety and Health (NIOSH) approved respirators. a. Personnel shall be trained in the proper use of safety clothing, and approved explosion-proof, spark-proof or intrinsically safe equipment appropriate to the situation. 35. PERSONNEL 36. This section describes job responsibilities and qualification requirements for personnel who administer and perform the various functions covered by the ACS Program. The complete program consists of the following key personnel: a.

The Commanding Officer (CO)

b. The Aircraft Confined Space Program Manager (ACSPM) c.

Entry Authority (EA)

d.

Management Personnel

e.

Entry Supervisors

f.

Authorized Entrant

g.

Safety Observer

h.

Backup Safety Observer

i.

Fire Watch

j. Naval Air Technical Data and Engineering Service Command (NATEC) Representatives. 37. The Commanding Officer (CO). 38. The Commanding Officer, consistent with the inherent duties and responsibilities of his position, is responsible for the safety and health of personnel, and the protection of property within the Command. Accordingly, the CO is responsible for: a. Establishing and conducting a complete and comprehensive ACS Program which meets the purpose, intent, and specific requirements of this manual. In so doing, the CO shall enforce the mandatory requirements of this manual and be guided by the advisory provisions. b. Initiating procedures and directives, and require inspections necessary to effect compliance with the standards and regulations prescribed herein. c. Require personnel of other agencies, including contractors, while within the purview of the command, to conduct activities and operations per applicable laws, regulations, and standards. SEE IRAC #16 d. The CO or a designated individual shall sign and date letters of certification for Entry Authorities. The CO may delegate endorsement of certification letters. Delegation must be in writing and available for review. Functions, which the individual is qualified to perform (such as Hot Work) shall be stated in the letter. The sample certification letter, Figure 4-1, is an example for content only, and may be altered to fit the command’s requirements. (1) ‘I’ and ‘O’ level: Copies of this letter shall be forwarded to the individual’s training and service record, the individual’s log book, and to the ACSPM. The letter will expire at the end of the calendar month, one year from the date the letter was signed. (2) ‘D’ level: The local ACSPM shall retain copies of certification letters for civilian DON employees for the length of employment at that location. 39. The Aircraft Confined Space Program Manager (ACSPM).

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The following letter is for example only. Each command is given the authority to tailor the letter to the specific needs of the command. From: To: Date: Subj:

Commanding Officer Individual dd Month yyyy AIRCRAFT CONFINED SPACE PROGRAM CERTIFICATION

Ref:

(a) (b)

COMNAVAIRFORINST 4790.2 (Series) NA 0l-lA-35

1. You are hereby certified as an Entry Authority (EA) for this command. This duty and responsibility is assigned because of your successful completion of the requirements and prerequisites of an EA as outlined in references (a) and (b). You are responsible for complying with the Aircraft Confined Space Program for this command as prescribed in reference (b). 2. As the command Aircraft Confined Space Program Manager (ACSPM), you shall comply with the requirements of references (a) and (b). (Applies only to Depot level personnel, when assigned.) 3. You are authorized to certify hot work because of successful completion of training by the command/station Confined Space Program Manager (CSPM). (When authorized.) 4. This certification shall remain in effect for a period of one year from the above date. Annual certification will be based on requirements outlined in reference (b). (Annual certification is not required for Depot level personnel) Signature Copy to: Individual's Training Record Individual's Service Record ACSPM GFE/CSPM

Figure 4-1. Sample Certification Letter a. ‘I’ and ‘O’ level Aircraft Confined Space Program Manager shall meet the following qualifications: (1) Complete NAMTG C-600-3000A. This training shall include hands-on instruction on the operation and calibration of gas detecting equipment. (2) Must be a Quality Assurance Representative (QAR) or a Collateral Duty Quality Assurance Representative (CDQAR). The prospective ACSPM shall be assigned to the Quality Assurance Officer (QAO). (3) Be designated in writing by the CO or designee. b. ‘D’ level Aircraft Confined Space Program Manager shall meet the following requirements: (1) Complete NAMTG C-600-3000A or the more comprehensive CNATTU A-493-0030. This training shall include hands-on instruction on the operation and calibration of gas detecting equipment.

(2) The civilian ACSPM is ordinarily associated with the activity's Occupational Safety and Health (OSH) Office, and shall have direct access to the CO. (3) Be designated in writing by the CO or designee. c. Duties and responsibilities. The Aircraft Confined Space Program Manager shall: (1) Establish and administer the ACS Program as required by this manual. (2) Monitor the Program within the organization, ensuring all safety requirements within the scope of this Program are followed. (3) Ensure necessary support equipment is available, maintained, and calibrated. (4) Ensure assigned personnel are properly trained and certified.

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(5) Ensure all appropriate personnel are familiar with potential hazards and established procedures related to the Program.

(4) Certification Renewal Requirements. The EA shall be certified in writing by the CO annually. Prior to certification, each EA shall:

(6) Provide for the evaluation and testing of fuel cells, preparations and issuing of Permits.

audit.

(7) Maintain and perform an annual review of program administrative records and EA personal logbooks.

year:

(8) Be trained to perform the duties of an EA when required. Familiarization or training of T/M/S aircraft systems shall be obtained prior to any potential service rendered as an EA.

mits.

(9) Prepare, update, post and assure that all appropriate personnel are familiar with the local Rescue Plan. (10) Recommend Entry Authorities to the CO or the CO’s designee for certification. 40. Entry Authority (EA) a. ‘I’ and ‘O’ level EA shall meet the following qualifications: (1) The prospective EA shall be a QAR or a CDQAR to gain initial certification. However, once certified as an EA, they may retain certification in the same command even if they no longer work in QA. (2) Successfully complete the NAMTG course C600-3000A. This training shall include hands-on instruction on the operation and calibration of gas detecting equipment (3) OJT training shall be completed to acquaint the EA with the different characteristics of each individual fuel cell on each Type/Model/Series (T/M/S) aircraft for which they are to be qualified. If a Series change for a particular aircraft T/M results in no change to the fuel cell configuration of the aircraft, then familiarization with one member of the Series, qualifies the EA on all members of the Series. For example, if an EA has OJT'd on a FA-18C then they are automatically qualified to certify FA-18A, B, and D aircraft fuel cells as well because the configuration of their cells are identical. However, that person is not qualified to certify the FA-18E/F because the E/F has a different configuration of cells. Training shall involve: (a) A thorough review of technical publications concerning the specific aircraft's fuel cells. (b) In a one-on-one situation, a knowledgeable fuel system maintenance person for that T/M/S aircraft or an EA who is qualified to certify that T/M/S aircraft, shall point out the different characteristics of the fuel cells with respect to the confined space testing. (Although there is no strict requirement that the aircraft's cells be open for this familiarization, the training will be most effective if it can be scheduled at a time when the aircraft's cells are open and the trainee can actually view what the trainer is discussing.)

(a) Submit EA personal logbook to ACSPM for (b) Complete one of the following within the last 1

Demonstrate that they have issued five Per-

2 Complete an oral or written examination that sufficiently demonstrates the desired skills. 3 Successfully complete the NAMTG course C-600-3000A (5) Each military EA must maintain a personal logbook as specified in paragraph 29a. b. tions:

‘D’ level EA shall meet the following qualifica-

(1) The prospective civilian EA may be any employee designated by Management who is trained and certified. (2) Complete NAMTG C-600-3000A or the more comprehensive A-493-0030. This training shall include hands-on instruction on the operation and calibration of gas detecting equipment. (3) Installations shall acquaint personnel with the fuel cells associated with each T/M/S aircraft or fuel cell configuration on which they will be providing aircraft confined space services. (a) A thorough review of technical publications concerning the specific aircraft's fuel cells. (b) In a one-on-one situation, a knowledgeable fuel system maintenance person for that T/M/S aircraft or an EA who is qualified to certify that T/M/S aircraft, shall point out the different characteristics of the fuel cells with respect to the confined space testing. (Although there is no strict requirement that the aircraft's cells be open for this familiarization, the training will be most effective if it can be scheduled at a time when the aircraft's cells are open and the trainee can actually view what the trainer is discussing.) (4) Yearly renewal certification letters of civilian Entry Authorities are not required provided EA maintains proficiency deemed appropriate by the local ACSPM. (5) Personal logbooks are not required for civilian employees. Work specific logbooks and /or a file of issued permits shall be maintained by the issuing activity. Copies of Permits shall be maintained on file for 12 months after issue.

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c. EA Duties and Responsibilities. The EA has primary responsibility for determining if a fuel cell has safe levels of oxygen, explosive and toxic vapor. The EA shall: (1) Conduct tests of fuel cells as required by this manual. (2) Issue, maintain, post, and update Permits. (3) Stop work and evacuate personnel from a fuel cell when an unsafe condition is detected or suspected. Immediately notify the Entry Supervisor and the Confined Space Program Manager or QAO of the problem. Ensure all test equipment is calibrated, as required. (4) Ensure the Rescue Plan is posted and emergency personnel and equipment are in place. Ensure that all personnel are familiar with applicable procedures for summoning aid prior to authorizing entry or work. (5) Report up the chain of command any conditions detrimental to continued safe conduct of Fuel Cell related maintenance. (6) Certify Hot Work if trained by the local command/station CSPM and be designated in writing by the CO. Completion of Confined Space Safety Course A-4930030 is recommended. (7) Perform the duties of the Aircraft Confined Space Program Manager (when assigned). 41. Management Personnel. 42. Department Heads and Division Officers, who have under their control, spaces, operations or personnel falling under the provisions of this manual shall: a. Ensure the provisions, procedures, and requirements of this manual are fully met. b. Ensure ACSP personnel perform all prescribed testing, apply all required controls and ascertain that fuel cells have been certified safe for the prescribed operations prior to commencement of such operations. 43. Entry Supervisors.

b. Know the hazards that may be faced during entry, including information on the mode, signs or symptoms, and consequences of exposure to fuel vapor. Instruct all personnel regarding the nature of the hazards associated with operations and precautions required to control such hazards. List all authorized hazardous materials on the Permit. c. Take effective measures, such as posting signs and cordoning off the area, to warn personnel of the existence of an open fuel cell. Keep unauthorized personnel out of the area. d. Notify Maintenance Control before beginning fuel cell maintenance procedures (‘O’ level only). e. Ensure all energy sources (batteries and ground power receptacles) will be disconnected and identified as such. f. Verify, by checking that appropriate entries have been made on the Permit. Ensure all tests specified by the Permit have been conducted. Ensure all procedures and equipment specified by the Permit are in place before endorsing the Permit. Post the Permit at the opening of the tank or cell. g. Terminate the entry and notify the EA if conditions are deemed unsafe. h. Verify emergency medical services are available, the means for summoning them are in place, and ensure emergency evacuation procedures are posted. i. Prevent unauthorized personnel from entering the fuel cell during entry operations. j. When the duties of the entry supervisor are relinquished to another supervisor, the original and all copies of the Permits shall be changed to denote when this occurs or the original Permit shall be canceled and a new Permit issued and posted. k.

Enforce all safety and health requirements.

l. Be familiar with the provisions of this manual as they relate to personnel or operations under their supervisory control. m. Ensure no person enters or works in a fuel cell without a safety observer, with the exception of cells discussed in paragraph 72.

44. An Entry Supervisor is the individual who has direct supervisory responsibility over the area in which fuel cell maintenance is to be conducted. An Entry Supervisor may also serve as a Safety Observer or as an Authorized Entrant as long as they are trained and equipped as required for each role they fill. Also, the duties of Entry Supervisor may be passed from one individual to another during the course of an entry operation. The Entry Supervisor shall comply with the following:

45. Authorized Entrant.

a. By signing the Permit, the Entry Supervisor is verifying that the Authorized Entrant and Observer is qualified to do their task.

46. An Authorized Entrant (hereinafter referred to as Entrant) is any individual who is authorized to enter a fuel cell for any purpose. All Entrant(s) shall:

n. Coordinate corrections of any situation affecting the safety of personnel or equipment. When warranted by the severity of such conditions, cease all operations and cancel the Permit. Notify the EA.

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a. Be trained in the proper use of respirators and Cardio Pulmonary Resuscitation (CPR) (‘O’ level only).

d. Maintain an accurate count of Entrant(s) in the fuel cell and ensure all the Entrant(s) are listed on the Permit.

b. Be trained in the proper use of personal protection equipment (PPE) and hazards associated with improper oxygen, flammable, and toxic vapor limits.

e. Communicate with the Entrant(s), by the means specified on the Permit.

c. Know the hazards that may be faced during entry, which includes information from MSDS on materials being used and consequences of exposure to fuel vapor. d.

Properly use all maintenance specific equipment.

e. Properly use all required personal protective equipment. Communicate with the Safety Observer using un-amplified voice communication. This enables the Safety Observer to monitor Entrant status, and alerts the observer of the need to evacuate the fuel cell. f.

Alert the Safety Observer whenever:

(1) Any dangerous situation such as symptoms of fuel exposure, injury, or evidence of impaired health, which may affect the safe performance of duties, is detected.

f. Monitor activities inside and outside the fuel cell to determine if it is safe for Entrant(s) to remain in the fuel cell. g. Order Entrant(s) to evacuate the fuel cell if any of the following is detected: (1) Any condition in the fuel cell that is not addressed specifically on the Permit. (2) Adverse effects of fuel exposure to an Entrant. (3) A situation outside the fuel cell that could endanger the Entrant. h. Take the following actions when unauthorized persons attempt to enter or do enter a fuel cell: (1) Warn them they must stay away.

(2) Any condition in the fuel cell that invalidates the Permit is detected.

(2) Advise them they must exit immediately.

g. Exit from the fuel cell as quickly as possible whenever:

(3) Inform Entrant(s) and the Entry Supervisor if unauthorized persons enter the fuel cell.

(1) An order to evacuate is given by the Safety Observer or the Entry Supervisor.

i. Perform no duties that might interfere with primary duty to monitor and protect Entrant(s).

(2) Any dangerous situation such as symptoms of fuel exposure, injury, or evidence of impaired health that may affect the safe performance of duties is detected. (3) Any condition in the fuel cell that invalidates the Permit is detected. (4) An evacuation alarm is sounded. h. Report to the Entry Supervisor any condition, procedure or equipment that is considered unsafe. i. Warn others who are endangered by their own failure to observe the proper procedures, precautions, or of any unnoticed hazard. 47. Safety Observer. 48. A Safety Observer is an individual stationed outside a fuel cell who monitors the Entrant(s). Each Safety Observer shall: a. Be trained in the proper use of respirators and Cardio Pulmonary Resuscitation (CPR) (‘O’ level only). b. Be trained in the proper use of personal protection equipment (PPE) and hazards associated with improper oxygen, flammable, and toxic vapor limits. c. Know the hazards that may be faced during entry, which includes information from MSDS on materials being used and consequences of exposure to fuel vapor.

j. ‘O’ level personnel may be required to ensure an air-supplied respirator is ready and available for immediate use. k.

‘O’ level, with rescue capabilities:

(1) Upon determining that an Entrant has collapsed or is incapable of exiting a fuel cell, the Safety Observer shall: (a) Activate the activity rescue plan. (b) Remain outside the fuel cell until Backup Safety Observer arrives to assist. (c) Don approved safety equipment. (d) If authorized by the activities rescue plan, enter the cell and extract the incapacitated Entrant. If not authorized by the activity’s rescue plan, remain on station until rescue services arrive. (e) Check the incapacitated Entrant for breathing and heartbeat and apply appropriate cardiopulmonary resuscitation measures, continuing until relieved by medical personnel. (This action may be completed by the Safety Observer or any properly qualified bystander.)

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l. vices:

For ‘D’ level utilizing Fire Department rescue ser-

(1) Upon determining that an Entrant has collapsed or is incapable of exiting a fuel cell, they shall:

Spaces. Permit Required Confined Spaces shall be tested by a qualified EA or ACSPM prior to any maintenance or hot work on or near the fuel tank or cell and a Permit shall be issued specifying the conditions and classification of the space.

(a) Activate the activity’s rescue plan to summon emergency rescue and medical services per station or facility SOP.

a. Non-maintenance procedures, such as changing of fuel probes, where documented procedures are contained in other manuals, do not require atmospheric testing.

(b) Remain outside the fuel cell until Emergency Rescue and Medical Services arrive.

b. Fuel cells and tanks may be reclassified as NonPermit Required Confined Spaces after appropriate testing and after hazards have been eliminated.

(c) Ensure that Rescue Services are aware of the location and possible condition of the Entrant. Provide any information possible to the rescue team that is requested. 49. Backup Safety Observer

NOTE Only activities that perform independent rescue operations as part of their written safety plan and do not use base or local rescue services are required to maintain Backup Safety Observers. 50. In accordance with the activity rescue plan, the BackUp Safety Observer is an individual who will be summoned to assume the duties of the Safety Observer during rescue operations. Therefore, they must be able to perform all the duties of a Safety Observer. 51. Fire Watch. 52. A Fire Watch is an individual stationed outside a fuel cell who is equipped with and trained in the use of fire extinguishing equipment appropriate to the expected hazard. A fire watch is required to be posted whenever hot work is to be performed. The duties of Fire Watch may be performed by the Safety Observer.

NOTE A fire watch shall be maintained for at least a half hour after completion of cutting or welding operation to detect and extinguish smoldering fires 53. Naval Air Technical Data and Engineering Service Command (NATEC) Representatives. a. NATEC representatives may provide ACS training when there is no local Naval Air Maintenance Training Detachment (NAM-TRADET). They shall teach Naval Air Maintenance Training Group (NAMTG) course C-6003000A. 54. TESTING PROCEDURES 55. General. As a matter of policy, all fuel cells on Naval aircraft are initially considered Permit Required Confined

56. Instrumentation. a. 'I' and 'O' Level: Only the Naval Air Systems Command (NAVAIRSYSCOM) (PMA 260) approved gas detectors shall be used to obtain required test readings of the atmosphere in a fuel cell. (Table 2-5, Item 7.a.) b. 'D' Level: Civilian activities shall use equipment that meets all OSHA standards for the testing of confined spaces. The equipment shall be approved by the depot Aircraft Confined Space Program Manager. c. Contractors: Contractors supplying their own equipment must meet all OSHA standards for testing of confined spaces. d. Gas detection equipment is authorized for below deck operation only while aboard ship. e. Instruments shall be maintained in good operating condition. Instruments that require calibration shall be calibrated in accordance with manufacturer’s instructions at least daily. It is recommended that instruments be field calibrated immediately prior to and after each work shift in which the instruments are used. A record shall be maintained of all calibration checks. Where instruments fail to respond or respond incorrectly to known calibrations, the instrument shall be removed from service. 57. Procedure. The testing and examination of a fuel cell will involve certain steps as a matter of established routine. The Permit Flow Chart, Figure 4-2, illustrates the general conditions that may be encountered on initial testing and the steps to be taken when each condition is encountered. It is emphasized that Figure 4-2 addresses only general conditions to illustrate basic atmospheric and permit procedures. It does not attempt to cover special requirements and considerations relating to items such as hot work, handsin/tools-in, cleaning procedures, etc. Hands-in/tool-in is covered in paragraph 70.

NOTE Safety procedures for open fuel cell and aircraft maintenance must comply with the instructions in WP 005.

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58. Initial testing shall be performed from outside the fuel tank or cell. Testing the interior of the tank or cell may be performed by inserting sample probes and hoses into the cell.

If readings of oxygen are not within the range of 19.5% to 22.0%, testing shall be discontinued. Subsequent tests for combustible vapors and for toxics may be in error. a. Test for oxygen content first. Normal oxygen content of ambient air is approximately 21 percent. Oxygen levels less than 19.5 percent or greater than 22.0 percent represent potentially dangerous situations. The explosive readings will not be accurate if oxygen reading is not near normal.

NOTE Some instruments may have a programmed alarm at 23.5%, set by the manufacturer. The Navy requires the oxygen to not exceed 22.0% for safe entry. b. Test for combustible vapors next. The Lower Explosive Limit (LEL) reading shall be below 10% for personnel entry. A LEL of 0% is required for any Hot Work. c. Test for toxic air contaminants next. Personnel exposure to toxic materials shall not exceed permissible exposure limits (PELs) established by the Occupational Safety and Health Administration (OSHA). The Material Safety Data Sheet (MSDS) PEL for Aircraft fuels (JP-4, JP-5, JP8) is 200 PPM. Navy has established the limit for safe entry at 50 PPM or less.

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Start

Test For O2 Levels

Between 19.5 – 22.0%?

No

Stop testing immediately purge cell

Yes Test for Flammables Test for Toxics

No

Were the results within limits?

Is depuddling necessary?

Yes

Issue provisional Permit for depuddling.

depuddle

Yes

Retest

Issue Permit

Yes

Figure 4-2. Permit Flow Chart

No

Purge

No

Within limits?

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Table 4-1. Classifications of Fuel Cell Permits Oxygen Levels

Permit Classification

% LEL

Toxicity ppm

Notes

For the following, if any of the three properties are as specified, the space is considered dangerous Class 1: Not Safe For Personnel – Not Safe For Hot Work

<16.5%

> 10%

> PEL

>22.0%

(>200 ppm)

Emergency entry only

For the following: All three properties have to be within specified limits Class 2: Not Safe For Personnel Without Protection – Not Safe For Hot Work

16.5% 22.0%

<10%

<200 ppm

Class 3: Safe For Personnel – Not Safe For Hot Work

19.5% 22.0%

<10%

<50 ppm

Class 4: Safe For Personnel – Safe For Hot Work

19.5% 22.0%

0%

<50 ppm

Class 5: Hands-In/Tool-In Maintenance

SEE IRAC #15

Class 6: Reclassified Non-Permit Required Confined Space

…… Refer to paragraphs 70 / 71 .…….

Provisional Permit with respirator

JP-4 or AVGAS requires Permit

Only for rubber fuel cells, drop tanks, or extended range tanks that have had hazards eliminated

** This table is for quick reference only. Refer to specific paragraphs for actual values to be measured ** 59. Hazard Mitigation. Refer to Work Package 005 00 for procedures on Defueling, Depuddling, and Purging and personnel entry protection.

last three fuelings) Aviation Gas or JP-4. The Entry Authority must make a careful evaluation prior to authorizing entry. 60. PERMITTING OF FUEL CELLS AND TANKS

Personnel shall not enter fuel cells that contain flammable atmospheres above 10 percent of the LEL. or which are Immediately Dangerous to Life and Health (IDLH) per paragraph 62 except in case of extreme emergency such as a rescue effort. Do not perform any maintenance on the aircraft during hazardous cleaning operations. Certain types of fuel cells shall not be entered when the Aircraft discrepancy book (ADB) indicates a fuel cell contains, or previously contained (within the

61. Classifications of Permits. The following categories should be used on Permits to indicate the conditions found at the time tests are conducted. This information is compiled in Table 4-1. a. Class 1: Not Safe For Personnel – Not Safe For Hot Work b. Class 2: Not Safe For Personnel Without Protection - Not Safe For Hot Work (Provisional Permit) c. Work

Class 3: Safe For Personnel - Not Safe For Hot

d.

Class 4: Safe For Personnel - Safe For Hot Work

e.

Class 5: Hands-In/Tool-In Maintenance

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f. Class 6: Reclassified Non-Permit Required Confined Space

NOTE See Work Package 003, paragraph 7 for protective clothing and Work Package 003 00, paragraph 9 for protective equipment required when entering and working on fuel cells and tanks. An oxygen deficient atmosphere means an atmosphere containing less than 19.5% (by volume) oxygen. An oxygen enriched atmosphere means an atmosphere containing more than 22.0% (by volume) oxygen Instruments may have alarms pre-set by the manufacturer at 23.5%. The Navy requires oxygen levels to be below 22.0% prior to safe entry of confined spaces. 62. Class 1: Not Safe For Personnel - Not Safe For Hot Work. Immediately Dangerous to Life and Health (IDLH)

NOTE Entry into a cell in this condition (Class 1) is authorized only for emergency rescue. A NIOSH approved air-supplied respirator or SCBA shall be worn when entering the fuel cell. No concurrent maintenance is allowed on the aircraft when open fuel cells are in this condition (Class 1). 63. This class shall be noted on the Permit when: a. Oxygen content is less than 16.5% or greater than 22.0%. There is a danger of asphyxiation due to an oxygen deficiency or of explosion with an oxygen-enriched atmosphere. b. LEL is greater than 10%. There is a danger of fire or explosion if the reading is above 10% of the LEL

e. Work may be performed on the exterior areas of this class cell, from outside the cell provided that the work performed does not generate heat or other ignition sources, which may cause ignition of atmosphere within the cell. 64. Class 2: Not Safe For Personnel Without Protection Not Safe For Hot Work (Provisional Permit).

NOTE A NIOSH approved air-supplied respirator or SCBA shall be worn when entering the fuel cell. No concurrent maintenance is allowed on the aircraft when open fuel cells are in this condition (Class 2). 65. This class shall be noted on the Permit when entry is required for cleaning, foam removal, etc., including conditions as follows: a. Oxygen content is greater than 16.5% but less than 22.0%. b. Flammable vapors may be present or may be evolved but at levels less than 10 percent of the LEL, or controls can be installed to maintain levels below 10 percent of the LEL. c. Toxic fuel vapors may be present in the cell or may be evolved, but at levels less than the PEL (less than 200 ppm for fuels). It is also within the level of protection offered by prescribed respiratory protective devices and other PPE. d. Hot work in areas surrounding the fuel cell for which a Provisional Permit is issued is prohibited. e. Contamination in this class cell shall be identified and removed to the maximum degree possible by ventilating prior to entry for subsequent cleaning operations. f. Personnel entering the fuel cell shall be equipped with an air-supplied respirator or SCBA. 66. Class 3: Safe For Personnel - Not Safe For Hot Work.

NOTE

c. Toxic vapors present at greater than 200 ppm for most fuels. If the toxic vapor is above it’s PEL, there is danger from exposure that could cause harm to the body. d. Entry into and work in this class cells shall not be permitted under normal operations and is authorized only in cases of extreme emergency such as rescue efforts. In the event of any such emergencies, personnel entering the fuel cell shall be equipped with an air-supplied respirator, a harness and lifeline for retrieval (unless the retrieval equipment would increase the overall risk of entry or would not contribute to the rescue of the Entrant), and other necessary PPE suitable to the conditions and exposure.

Concurrent maintenance, excluding hot work, is allowed on the aircraft when open fuel cells are in this condition (Class 3). 67. This class shall be noted on the Permit when: a. Oxygen content is sufficient (19.5% to 22.0%) and suitable for personnel. b. Explosive vapor LEL is less than 10%. The space may have the potential for producing a flammable vapor atmosphere and is Not Safe for Hot Work. c.

Toxic vapor shall be less than 50 ppm.

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d. Respirators may be required based on local Industrial Hygienist sampling. 68. Class 4: Safe For Personnel - Safe For Hot Work.

NOTE Concurrent maintenance is allowed on the aircraft when open fuel cells are in this condition (Class 4).

(1) Disconnect aircraft electrical power and batteries. (2) Do not perform Hot Work. (3) Do not perform concurrent maintenance. (4) Post fire watch.

69. This category shall be noted on the Permit when:

(5) Comply with all electrostatic discharge requirements in accordance with procedures within this manual.

a. Oxygen levels are sufficient (19.5% to 22.0%) and suitable for personnel.

72. Class 6: Reclassified Non-Permit Required Confined Space

b. Explosive vapor LEL is 0%. Flammable materials, vapors, or gases have been removed, are not likely to be evolved, and/or are controllable by ventilation.

73. Discussion. All fuel cells and fuel tanks shall be issued a Permit to document the initial conditions of the space and the means by which the space was tested. Certain types of fuel cells or tanks may be reclassified as Non-Permit Required Confined Space per OSHA classifications. This classification is valid over an indefinite period of time without the requirement for periodic retesting. These types of fuel cells and tanks have a very low chance for causing injury and have negligible risk of creating a combustible atmosphere. Fuel Cells, Drop Tanks, Internal Extended Range Tanks etc. may be reclassified Non-Permit Required Confined Space (as long as current conditions do not change) using the following procedures:

c. Toxic vapor shall be controlled by proper ventilation to be maintained at or below 50 ppm. d.

Surrounding areas have been protected as required.

e. Respirator is not required except if significant changes occurring within the fuel cell such as detection of hazards or new operations or materials being introduced into the space or actual hot work in progress 70. Class 5: Hands-In/Tool-In Maintenance

SEE IRAC #15

NOTE JP-4 and AVGAS have lower flash points than other fuels and pose a significant fire and explosion risk. Confined Space testing and an Permit shall be issued prior to hands-in/tool-in maintenance of a fuel cell previously containing either JP-4 or AVGAS in the last three fuelings. LEL must be less than 10% for all hands-in/tool-in procedures. 71. Hands-in/tool-in maintenance procedures do not require bodily entry and a person cannot become trapped, asphyxiated, or injured from electrical or mechanical hazards. a. The EA may reclassify specific Hands-in/Tool-in maintenance procedures as Non-Permit Required Confined Spaces. b. Safety procedures, including specifying the PPE, explosion proof equipment, etc, shall be specified in a written maintenance procedure for the T/M/S aircraft. The maintenance procedure shall be approved by the ACSPM. c. Prior to Hands-in/Tool-in maintenance, the level of the fuel shall be lower than the area of maintenance. d. All other safety procedures for open fuel cell maintenance must be followed to include:

Control of atmospheric hazards through forced air ventilation does not constitute elimination of the hazards. Concurrent maintenance is allowed on the aircraft when open fuel cells are in this condition. a. If testing and inspection demonstrate that recognized hazards within the fuel cell have been eliminated, the fuel cell may be reclassified a Non-Permit Required Confined Space. (1) Oxygen levels are between 19.5% and 22.0% (2) LEL is 0% (3) Toxic vapors are less than 50 ppm b. Document the basis for determining that recognized hazards have been eliminated by issuing a Permit, designating the space as a Non-Permit Required Confined Space. c. Reclassified Non-Permit Required Confined Space need not be re-tested unless hazards arise or conditions change to warrant a re-test. d. If recognized hazards arise within a reclassified Non-Permit Required Confined Space, persons in the cell shall exit the cell. The Permit will be cancelled.

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e. Once previously removed fuel cells have been reinstalled on the aircraft, the EA will be summoned to determine proper classification and issue a new Permit. 74. Purged Tanks. A drop tank, external fuel tank (such as a “Buddy Store”), or internal range extension tank which has been removed from the aircraft, purged, and will be stored in or adjacent to a building until reinstallation on/in the aircraft may be reclassified as requiring no Permit using the following procedures: a. If testing and inspection demonstrate that the flammability hazards within the tank have been eliminated (less than 10 % LEL), the tank may be considered as not requiring a Permit for as long as the hazards remain eliminated. Flammability hazards may be reduced by following the procedures documented in WP 005. b. Document the fact that all flammability hazards have been eliminated by issuing a permit that contains date, part number and serial number of the tank, and signature of the person making the determination. Annotate the Permit as follows: “This tank contains no flammability hazards (less than 10% LEL) and requires no further testing.” The Permit shall be prominently posted on the tank. c. If hazards arise within a tank that has been reclassified as “Non-Permit Required Confined Space”, or if it is determined that work must be performed on the tank, the tank shall then be reevaluated to determine whether it must be reclassified as requiring a Permit. 75. Un-Purged Tanks. A drop tank, external fuel tank, or internal range extension tank which has been removed from the aircraft, not purged, and will only be stored until it is reinstalled does not need atmospheric testing, or have a Permit attached. Such tanks must be stored away from buildings, in a non-smoking area, and according to base fire regulations. If it is determined that work must be performed on a tank stored in this manner, the tank must be atmospheric tested and have a Permit attached.

b.

Date and time Permit expires.

c. Date and time of retesting and update of Permit (if continuous or periodic testing is to be performed). d. Percentage of oxygen, percentage of LEL and PEL (in ppm). e. Signature of Entry Authority performing tests or re-tests. f.

Name of ship, unit, or activity.

g. Aircraft Bureau Number and equipment serial number. h. Physical location of fuel cell for which the Permit is being issued. i. Type of operation for which the Permit was requested (such as hot work). j. Classification of conditions found to exist within the space (e.g., "Class 3: Safe for Personnel - Not Safe for Hot Work"). k. Requirements for conditions or operations within the fuel cell (ventilation, PPE, explosion-proof equipment, etc.). l. Special conditions shall be noted under remarks (such as hazardous materials authorized to be used in the cell during maintenance and repair). m. List all Entrants and Observers (may be an attachment since personnel may change during the life of the Permit). n. Means of Communications between Entrant(s) and Safety Observers. o. Instrument used (type, serial number) and calibration/ function check dates. p.

Signature of Entry Supervisor.

76. THE PERMIT

79. The Permit Process.

77. Permits may be issued only after completion of testing, inspection, evaluation, and/or ventilation is appropriate or required. Provisional Permits (for example: Class 2 Permits) may be issued to describe further ventilation or cleaning requirements necessary to earn a Permit for entry (Class 3 or higher).

80. Initial Permit. The initial Permit shall be accomplished by the EA as follows:

78. The Permit shall indicate the conditions found to exist at the time the testing was performed, any requirements necessary to maintain the conditions within the fuel cell, and any requirements associated with the operations that are to be conducted within the fuel cell. Activities may prepare Permits tailored to their needs, however, the following information must appear on all Permits; a.

Date and time of tests.

a. Issue initial Permit for entry. Aviation detachments deployed aboard non-aviation ships shall use the services of the ship's Gas Free Engineer or Confined Space Manager in the absence of their own Entry Authority. b.

Certify hot work if authorized by the CO.

c. Issue initial Permit for a period of time not to exceed 12 hours. Permits may be maintained by continuous or periodic testing. d. Opportunity shall be made available for authorized Entrant(s) or their representatives to observe the testing of the space during pre-entry and entry.

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81. Continuous or Periodic Testing and Maintaining Permits. The following provisions apply: a. The period for which Permits are valid and the requirements for testing and maintaining validity of the Permit shall be specified by the EA, not to exceed 12 hours. A change in personnel due to shift change requires updating of the Permit (and all copies) or the issuing of a new Permit. b. Periodic testing shall be performed when, in the professional judgment of the Entry Authority, safe conditions within the fuel cell may deteriorate or the limitations of the Permit may be exceeded. Periodic testing shall be performed during any operation that possesses the potential for producing or releasing toxic, flammable, or asphyxiating atmospheres or materials into the fuel cell. The overriding concern is that safe conditions are maintained within the cell during operations and after interruptions in operations. Therefore, retesting, recertifying conditions, and updating of Permits is required when work interruptions occur which could result in deterioration of safe conditions within the cell. 82. Retesting Fuel Cells. 83. Fuel cells shall be retested in the same manner as an initial Permit whenever events have occurred which could result in a significant change in the conditions within the cell. The previous Permit shall be cancelled and a new Permit issued. Such events include, but are not necessarily limited to the following: a. Expiration of the time limit of the Permit without any periodic testing or Permit updating being performed. b. Significant changes occurring within the cell such as detection of hazards sufficient to warrant stopping operations and removing personnel or new operations or materials being introduced into the space which were not noted on the Permit. 84. Permit Distribution. 85. When Permits are issued, distribution shall be as follows: a. The original copy shall be placed in a protective cover (if needed) and posted at the main entrance or most commonly used access to the fuel cell. b. One legible copy shall be posted at all other access areas that are open and readily accessible to personnel. Each copy may be placed in a protective cover if needed. c. One legible copy shall be retained in the EA personal logbook (‘I’ and ‘O’ level). d. One legible copy shall be provided to the Aircraft Confined Space Program Manager. e. One legible copy shall be provided to the Maintenance Control requesting the service (‘O’ level only).

f. Other legible copies shall be distributed as required by the administrative or operational requirements peculiar to the activity. 86. Cancellation of Permits. 87. Entry may be terminated by anyone listed to work under the Permit. The EA or the Entry Supervisor may cancel the Permit. Examples of when Permits shall be cancelled are: a. The job for which the Permit was written has been completed. b. The time period for which the Permit was written has expired without subsequent testing being performed. c. Periodic or continuous testing shows that the conditions within the cell have changed from the original conditions to unsafe conditions. d. Hazardous materials (which were not authorized on the Permit) are introduced into the space. e. An Entrant has collapsed and has been extracted from the cell. 88. ENTRY AND WORK RESTRICTIONS 89. All fuel cells shall be considered hazardous and entry into, or work in or on them shall be restricted. The following restrictions apply to entry and work in or on fuel cells or tanks. 90. General Requirements a. When, upon initial testing, it is determined purging is required to provide adequate oxygen levels and/or to remove detected contaminants, the cell shall be purged and retested. Test results shall be satisfactory before a Permit for entry or work is issued. b. When, upon initial testing, it is determined that cleaning is required to remove contaminants from a fuel cell, a provisional Permit for cleaning shall be issued. The provisional Permit shall specify any conditions that must be observed. c. Permits issued for entry into or work in or on fuel cells shall be valid for the period of time specified by the EA for a period of time not to exceed 12 hours or until completion of task, whichever occurs first. Fuel cells may be continuously or periodically tested as determined by the EA and the Permit updated to maintain safe conditions within the fuel cell. d. When significant work interruptions occur, and operations or conditions are such that a deterioration of safe conditions could occur, then the cell shall be retested after the interruption and prior to resuming entry or work in the cell.

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e. Where toxic or flammable materials are or may be introduced into the cell, one or a combination of the following must be employed:

(3) NIOSH approved respiratory protective equipment suitable to the exposure.

(1) General ventilation with one complete air change within the cell every three minutes. A Station CSPM or ship Gas Free Engineer can make calculations for air changes.

f. Communications between personnel outside the fuel cell and personnel entering or working in a fuel cell shall be established and maintained. The type of communication (voice, signal line, etc.) and the frequency of contact (continuous, periodic check, etc.) shall be determined by the EA based on the configuration of the fuel cell, the nature of the operations being conducted, and the degree of hazard.

(2) Local exhaust ventilation where the air intake is positioned close to the point of work where contaminants are generated.

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AIRCRAFT FUEL SYSTEMS MAINTENANCE FACILITIES AND AREAS

Reference Material None

Alphabetical Index Subject

Page

Enclosed Fuel Cell Maintenance .......................................................................................................................................... 1 Fuel System Repair Area Checklist...................................................................................................................................... 2 Open Fuel Cell Maintenance ................................................................................................................................................ 1

1.

FUEL CELL MAINTENANCE AREA

2. The defueling, depuddling, purging, and inerting procedures described in WP 006 shall only be performed on aircraft when parked in an area specifically authorized for such operations. Fuel cell maintenance areas shall be approved by the Maintenance Officer, Fire Marshall, and Safety Officer. In addition, the following shall be closely observed: 3. OPEN FUEL CELL MAINTENANCE. (See Figure 5-1) An open fuel cell maintenance area is any outside area. a. Open area approval and identification. The Maintenance Officer, with coordination of the safety and fire personnel must approve the fuel cell maintenance area. This area shall be identified with warnings posted as shown in Figure 5-1. An additional 50-foot requirement may apply if exhaust purge is used. Rope off and clearly mark the fuel cell maintenance area with warning signs reading “DANGER OPEN FUEL TANKS, UNAUTHORIZED PERSONNEL KEEP OUT”. b. Authorized portable equipment. The fuel system work done in an open area is highly dependent on weather conditions and available authorized portable equipment. All portable electrical equipment and connections shall meet the requirements of the National Electrical Code for Class 1, Division 1, and Group D Hazardous Locations. All open areas shall be equipped with at least two fully charged fire extinguishers. Additional extinguishers shall be provided as required by the Station Fire Marshal. c. Safety requirements. Adjacent aircraft shall not be allowed to operate under their own power within 100 feet of their operating area. They shall also be limited from operations where jet blast or rotor downwash could affect the safety as outlined in applicable aircraft manuals.

4. ENCLOSED FUEL CELL MAINTENANCE AREA. Aircraft hangers or nose docks used for aircraft fuel system repairs are considered enclosed maintenance areas. Exhaust purging within an enclosed maintenance area is permissible provided the exhaust outlet is vented to the outdoors and the vapors cannot reenter the enclosed maintenance area. a. Enclosed area approval and identification. The Commanding Officer or Maintenance Officer with the coordination of safety and fire department personnel shall approve these fuel cell maintenance areas. Rope off and clearly mark the fuel cell maintenance area with warning signs reading “DANGER OPEN FUEL TANKS, UNAUTHORIZED PERSONNEL KEEP OUT.” b. Authorized portable equipment. All portable electrical equipment and connections shall meet the requirements of the National Electrical Code for Class1, Division1, Group D Hazardous Locations.

Do not defuel aircraft in the vicinity of an electrical storm. Do not perform other maintenance on aircraft during defueling, depuddling, purging, or inerting operations. Aircraft radar shall not be operated within 100 feet of fuel cell maintenance areas or as specified by the applicable aircraft Maintenance Instruction Manual (MIM), and the site location shall be at least 300 feet from Ground Radar Installations. High frequency radars or ground installation radars are capable of producing sufficient energy to ignite fuel vapors.

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Do not operate aircraft engines, auxiliary power units or ground support equipment gas turbine engines within 100 feet of a fuel cell maintenance area. 5. FUEL SYSTEM REPAIR AREA CHECKLIST. Each designated repair area shall have a checklist, work sheet, or job guide available for use. The following check list is provided to cover general procedures that are required to position an aircraft in a fuel cell maintenance area. This checklist is general in nature and is not intended to cover peculiarities of individual aircraft or facilities. Therefore, a specific aircraft or fuel system check list should be developed by the Aircraft Confined Space Program Manager (ACSPM) using the following guide.

f. Check that the aircraft is properly grounded in accordance with WP 006 paragraph 4 and the applicable technical manuals. g.

Check that all explosive materials are made safe.

h. Check that aircraft batteries are disconnected and made safe in accordance with the system peculiar technical manuals. i. Check that the aircraft external power receptacles and fuel control panels are tagged. j. Check that fuel cell maintenance areas are clearly identified and roped off. k. Check (if required) that the inert gas cart has proper marking, and is grounded and bonded prior to use.

Fuel cells containing mixtures of JP-4 or AVGAS require initial certification by an Entry Authority prior to entry or work. a. Review last three fueling records to determine if a mixture of JP-4 or AVGAS has been used. b.

Review aircraft VIDS/MAF and brief personnel.

l.

Check that required fire extinguishers are ready for

use. m. Check that the work area is clear of all nonapproved equipment. n.

Check that the fire department has been notified.

c. Check personnel for proper clothing, equipment, and removal of jewelry and spark/flame producing devices prior to entry into fuel cell maintenance area.

o. Check that no other maintenance is accomplished on the aircraft while depuddling, purging, and inerting operations are being accomplished.

d. Ensure aircraft is positioned in an approved fuel cell maintenance area.

p. Check that emergency communication procedures are available.

e. Check that the aircraft is chocked and tied down per applicable aircraft technical manuals.

q. Ensure approved emergency eyewash is available for immediate use.

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Figure 5-1. Out-of-Doors Exhaust or Blow Purge Safety Zone (Typical)

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MAINTENANCE INSTRUCTIONS DEFUELING, DEPUDDLING, PURGING, HOT WORK, AND INERTING

Reference Material Aeronautical Equipment Welding .......................................................................................................... NAVAIR 01-1A-34 NATOPS Aircraft Refueling ...............................................................................................................NAVAIR 00-80T-109 Preservation of Naval Aircraft .............................................................................................................. NAVAIR 15-01-500

Alphabetical Index Subject

Page

Basic Definitions .................................................................................................................................................................. 2 Defueling ................................................................................................................................................................... 2 Depuddling ................................................................................................................................................................ 2 Hot Work ................................................................................................................................................................... 2 Inert Atmosphere ....................................................................................................................................................... 2 Inert Gas .................................................................................................................................................................... 2 Inerting ...................................................................................................................................................................... 2 Purging ...................................................................................................................................................................... 2 Bonding and Grounding ....................................................................................................................................................... 2 Bonding ..................................................................................................................................................................... 2 Grounding.................................................................................................................................................................. 2 The Bonding and Grounding Process ........................................................................................................................ 2 Defueling.............................................................................................................................................................................. 3 Aircraft Defueling...................................................................................................................................................... 3 Fuel Cell Repair Aboard Ship.................................................................................................................................... 3 Depuddling........................................................................................................................................................................... 4 Fuel Cell Entry .......................................................................................................................................................... 6 Fuel Cell Entry Preparations...................................................................................................................................... 5 Procedures ................................................................................................................................................................. 4 Removing Fuel Puddles............................................................................................................................................. 6 Removing Fuel Puddles From Thin Wing Aircraft ................................................................................................... 6 Safety Observer ......................................................................................................................................................... 6 Hot Work............................................................................................................................................................................ 14 Boundary Space....................................................................................................................................................... 15 Cleaning................................................................................................................................................................... 15 Compressed Gas Cylinders...................................................................................................................................... 16 Electric Arc Units or Machines ............................................................................................................................... 16 Electrode Holders .................................................................................................................................................... 17 Fire Extinguishing Equipment................................................................................................................................. 15 Fire Prevention ........................................................................................................................................................ 15 Gas Supplies ............................................................................................................................................................ 16 Gas Welding and Cutting Equipment ...................................................................................................................... 16 Hazardous Byproducts............................................................................................................................................. 17 Hot Work in the Presence of Flammable Coatings.................................................................................................. 15 Hot Work in the Presence of Pressurized Systems .................................................................................................. 16 Hot Work on Closed Containers and Structures ...................................................................................................... 17 Hot Work on Pipes, Tubes, or Coils ........................................................................................................................ 16 Hot Work Operations............................................................................................................................................... 14 On-Aircraft Welding............................................................................................................................................... 17 Inerting ............................................................................................................................................................................... 17 Permit ...................................................................................................................................................................... 18

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Pressure Inerting of Fuel Systems ............................................................................................................................19 Siphon Inerting of Fuel Systems ..............................................................................................................................18 Purging..................................................................................................................................................................................8 Air Blow Purging ....................................................................................................................................................11 Air Exhaust Purging...................................................................................................................................................8 Detergent Cleaning and Purging of Auxiliary Fuel Cells ........................................................................................14 JP-5/JP-8 Fuel Purging ............................................................................................................................................13 Oil Dilution Purging.................................................................................................................................................12 1.

GENERAL

2. This section provides definitions and general instructions for defueling, depuddling, purging, hot work and inerting, of fuel cells for inspection, repair, or entry by maintenance personnel. These operations require strict compliance with the safety instructions in this manual.

potential difference is minimized and a static electrical discharge between these objects is, therefore, minimized. Bonding is as essential as grounding, and shall be used together with grounding. Although bonding can equalize the charge between connected objects, the objects themselves may still be highly charged. By connecting a ground wire to the bonded objects, this charge can be drained off.

3. BASIC DEFINITIONS. Basic definitions applicable to this Section are provided in the following paragraphs. 4. Defueling. Defueling is the process of removing fuel from the aircraft. 5. Depuddling. Depuddling is the process of removing residual fuel from the aircraft fuel cell after defueling and low-point draining. 6. Purging. Purging is the process of removing fuel vapors capable of producing a combustible or toxic atmosphere. 7. Hot work. Hot work is any work which produces a temperature equal to or greater than 400oF (204oC). Such as soldiering, heat shrink operations, welding, cutting, brazing, grinding, flame-spray/metal-spray, etc. 8. Inerting. Inerting is the process of attaining an oxygendeficient, noncombustible atmosphere in a fuel cell. It is achieved by introducing an inert gas (usually dry nitrogen) to reduce the percentage of oxygen in the atmosphere to less than one percent. 9.

Bonding and grounding wires must be attached to clean, unpainted, conductive surfaces to be effective. Connect all grounding and bonding wires (cables) prior to removing fuel tank filler cap. Do not disconnect any grounding or bonding wire until fuel tank filler cap is reinstalled. 13. Grounding. Grounding is the process of electrically connecting a conductive object to the ground. It provides a path through low resistance conductive wires over which static charges can flow to the ground harmlessly. Proper grounding minimizes the differential in electrical charge potential between the object and the ground. a. The Grounding and Bonding Process. Attach all required grounding and bonding cables before opening the aircraft or defueler tanks. Do not allow the grounding or bonding cables to drag on the ground. Attach grounding wires to the applicable Maintenance Instruction Manual's designated aircraft approved grounding point.

Inert gas. Inert gas is any gas that is nonflammable.

10. Inert atmosphere. Inert atmosphere is any atmosphere that will not support combustion or life. 11. BONDING AND GROUNDING. Bonding is done to minimize electrical charge potential differences between two or more conductive objects. Grounding is done to minimize electrical charge potential differences between objects and the ground. 12. Bonding. Bonding is the process of electrically connecting two conductive objects. By connecting the two objects together with a conductive wire, any electrical charge

Bonding and grounding wires must be attached to a clean, unpainted, conductive surface to be effective. Connect all grounding and bonding wires (cables) prior to removing fuel tank filler cap. Do not disconnect any grounding or bonding wire until fuel tank filler cap is reinstalled. b. Grounding and bonding prior to defueling. (See Figure 6-1.)

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(1) Attach one end of a ground cable to an approved grounding point. (2) Attach second end of the ground cable to the aircraft. (3) Attach one end of a bonding cable to the defueler.

Locate fuel cell maintenance areas at least 100 feet from aircraft radar or at least 300 feet from ground installation radar. High frequency aircraft radars or ground installation radars is capable of producing sufficient energy to ignite fuel vapors. Do not operate aircraft engines, auxiliary power units or ground support equipment gas turbine engines within 100 feet of a fuel cell maintenance area.

Do not allow the defueling hose nozzle to drag on the ground. (4) Attach the second end of the bonding cable to the aircraft. (5) Contact the defueling hose nozzle with a metal part of the aircraft as far away from fuel cell as practicable. (6) Attach nozzle bonding cable to the aircraft. c.

Connect defueling nozzle to aircraft.

14. DEFUELING 15. Defuel in accordance with the applicable aircraft Maintenance Instruction Manual (MIM). Additionally, apply the safety precautions described in the following paragraphs. 16. Aircraft Defueling Ashore and Afloat. To defuel, position aircraft ashore at least 100 feet from any buildings or smoking area. Position aircraft afloat in the safest possible position, as directed by aircraft handling officer. a. Fire extinguishers. Equip the fuel cell maintenance areas with approved fire extinguishers. b. Communications. To ensure the safety of personnel and equipment, establish and maintain communications between members of the defueling team. c. Defueler. Park the defueler as far from the aircraft as possible and position it so it can be moved quickly in an emergency. d. Personnel positioning. Before starting defueling operations, ensure personnel are positioned as follows:

(1) Position one person at each fire extinguisher. Ensure that at least one person has a clear view of the defueling operation. (2) One person shall operate the defueler. This person shall be an authorized operator. (3) Position one person to operate the aircraft defueling panel. (4) If applicable, position one person to operate the aircraft fuel system control panel. e. Defueler removal. When the defueler is filled to capacity, or defueling is completed, disconnect and remove the defueler in the following sequence: (1) With bonding wires still connected, remove defueling nozzle from aircraft. (2) Install fuel cell filler caps. (3) Disconnect defueling nozzle bonding wire from aircraft. (4) Reel up defueling hose. (5) Disconnect bonding cable from aircraft, and then from defueler. (6) The defueler can now be moved from the area. f. Low-point drain. (pencil drain). Drain remaining fuel as outlined in Applicable Aircraft MIMs, into safety containers, RR-S-30 (Table 2-5, Item 3a). Bond the safety containers to the aircraft. 17. Fuel Cell Repair Aboard Ship. When conducting fuel cell maintenance aboard ship, defuel at designated defueling station and spot for maintenance in the area assigned by Hangar Deck Control.

Do not defuel aircraft in the vicinity of an electrical storm.

a. Area identification. Rope off and clearly mark the fuel cell maintenance area with warning signs reading "DANGER, OPEN FUEL TANKS, UNAUTHORIZED PERSONNEL KEEP OUT."

Do not perform other maintenance on aircraft during defueling, depuddling, purging, or inerting operations.

b. Tank purging. Use the air exhaust purging method described in paragraph 23 with the outlet duct extended outside the ship.

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Figure 6-1. Sequence of Connecting Static Cables (Defueling Aircraft) 18. DEPUDDLING. 19. Depuddling is required to remove residual fuel remaining after defueling and low-point draining. Depuddling is a necessary step prior to air purging when a non-toxic and non-combustible atmospheric state is required in a fuel cell or tank. 20. Depuddling Hazards. Depuddling can be hazardous to personnel as it requires entry or partial entry into a cell to remove residual fuel. To minimize depuddling hazards, personnel must work in pairs. One person must remain outside the cell while the other is inside. 21. Depuddling Procedures. To depuddle, proceed as follows:

Do not air blow purge fuel cells during depuddling, cleaning or when flammables or toxics are introduced into fuel cells. Failure to comply will result in introducing hazardous toxic/flammable vapors into closed maintenance areas. Do not defuel aircraft in the vicinity of an electrical storm.

Do not perform other maintenance on aircraft during defueling, depuddling, purging, or inerting operations. a. Disconnect the aircraft batteries (so that fuel valves will not actuate allowing fuel to enter cell being depuddled). b. Tag aircraft battery connector with warning "Do not reconnect battery." c. Tag aircraft external power receptacle with warning "Do not apply external power to aircraft."

Only qualified personnel shall start and operate ground powered equipment and aircraft auxiliary power units. All rolling equipment used in fuel cell maintenance areas shall be equipped with rubber tires or wheels. Position non-explosion-proof equip-ment upwind from aircraft and outside of the fuel cell maintenance area.

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Bonding and grounding wires must be attached to clean, unpainted, conductive surfaces to be effective. Connect all grounding and bonding wires (cables) prior to removing fuel tank filler cap. Do not disconnect any grounding or bonding wire until fuel tank filler cap is reinstalled. d. Position and ground the following equipment as applicable: Air blower, MIL-B-7619 (Table 2-5, Item 1a(1) Pneumatic driven fan, APV-12 (Table 2-5, Item 1a(2)

e.

NOTE In cold weather warm air for purging may be obtained with the use of a hot air blower assembly, MMEP12B. f. Start air blower and position the outlet duct at a 45 degree angle to the access panel that will later be removed for purging (See Figure 6-2). g. Attach a bonding cable to the wire reinforcement of the air blower duct outlet end. h. Attach bonding cable located at outlet end of duct to the aircraft structure. i.

Remove access panel to initiate purging.

Hot air blower assembly, MMEP12B (Table 25, Item 1b)

j. Notify EA and proceed with approved Aviation Confined Space procedures (refer to Work Package 004).

Explosion-proof vacuum cleaner (Table 2-6, Item 2b)

22. Fuel Cell Entry Preparations. (See Figure 6-3) After the air in the cell has been certified "Safe for Personnel", and the appropriate information indicated on the Permit, the safety observer and the person to enter the fuel cell to depuddle shall proceed as follows:

Seal base of air eductor to ensure an air-tight fit.

Start air blower or hot air blower before connecting air ducts to the aircraft. Do not shut down air blower or hot air blower when air duct is connected to the aircraft.

Testing of fuel cells for SAFE conditions shall be performed by an Entry Authority (EA). A permit shall be issued before work begins and/or as work progresses as directed by the EA.

If air blower or hot air blower fails during operation, remove air duct from aircraft immediately and move the duct, air blower, or hot air blower to an area upwind free from fuel vapors.

Do not remove any garment while in an open fuel cell or area adjacent to an open fuel cell. Normal activity can generate electrical charges on clothing.

Compressed air shall not be used under any circumstances to clean dirt or dust from clothing or blow chips or shavings from work surfaces.

Do not wear clothing made of materials such as nylon, orlon, dacron, wool, or silk while working on an open fuel system component.

Failure to comply with these warnings could result in injury or death to personnel and damage to or destruction of the aircraft.

A NIOSH approved respirator or a SCBA, shall be worn when entering a fuel cell with the exception of entering a fuel cell defined in Work Package 004, paragraph 66 as Safe For Personnel–Not Safe For Hot Work or as defined in Work Package 004, paragraph 68 as Safe For Personnel–Safe For Hot Work. Ensure continuous ventilation when working inside a fuel cell.

If heated air is used for purging, the outlet temperature shall not exceed 100ºF (38ºC).

a. Remove non-cotton clothing and put on coveralls, MIL-C-14610 (Table 2-6, Item 6f).

NAVAIR 01-1A-35

006 00 Page 6 g. The person entering the fuel cell shall put on rubber gloves, MIL-DTL-32066 (Table 2-6, Item 6j) or appropriate barrier cream for depuddling.

Safety shoes shall be worn in fuel cell maintenance areas. Shoes with exposed tacks or metal shall not be worn.

23. Fuel Cell Entry. To enter fuel cell, proceed as follows: a. Perform fuel cell entry preparation procedures (Refer to paragraph 6-3c). b. Remove necessary access covers, as required, to gain entry.

Shoes shall not be worn inside of bladder or self-sealing fuel cells.

c. Immediately after entry into cell, cap or seal all openings leading from other sources of fuel or fuel vapors.

Socks shall be free of oil, grit, and dirt. Only clean socks shall be worn.

24. Safety Observer. (See Figure 6-4) The safety observer shall perform the following:

NOTE

a. Ensure an air-supplied respirator is readily available for immediate use.

If coveralls are not equipped with wrist and ankle bands, place rubber bands around ankles and wrists. b. Remove shoes and non-cotton socks and put on white cotton socks and rubber overshoes, MIL-O-82295.

NOTE

b. Position himself outside the cell to detect any signs of distress from the person inside the cell. 25. Removing Fuel Puddles. To remove fuel puddles, proceed as follows: a. Ground and bond explosion-proof vacuum cleaner to the aircraft.

Safety shoes may be worn inside integral fuel cells provided footwear covers are worn over the shoes

Do not modify vacuum cleaner hose with metal extensions.

c. Apply protective skin compound, P-S-411, to skin surfaces that may be wetted by fuel.

NOTE

d. Inspect and test air-supplied respirator as described in the respirator’s operating guide.

If vacuum cleaner is not available, remove puddled fuel with a cellulose sponge, L-S-0026, and/or cheesecloth, CCC-C-440, Type 1, Class 1. Wring out the sponge and/or cheesecloth into an approved safety can, RR-P-125.

e. Start air blower. Ensure air blower inlet is inserted into fuel cell access and blower outlet is directed outside the enclosed maintenance area. f. Ensure proper communication is established prior to entering the fuel cell. The person entering the cell and the safety observer may obtain and use headset, 79091.

b. Remove fuel puddles with explosion-proof vacuum cleaner, if available. 26. Removing Fuel Puddle From Thin Wing Aircraft. It is impossible for personnel to enter thin wing aircraft fuel cells. To remove fuel puddles from thin wing aircraft, proceed as follows:

A NIOSH approved respirator or a SCBA, shall be worn when entering a fuel cell with the exception of entering a fuel cell defined in Work Package 004 paragraph 66 as Safe For Personnel–Not Safe For Hot Work or as defined in Work Package 004 paragraph 68 as Safe For Personnel–Safe For Hot Work. Ensure continuous ventilation when working inside a fuel cell.

a. Ground and bond explosion-proof vacuum cleaner, (Table 2-5, Item 2b) to the aircraft.

Testing of fuel cells for SAFE conditions shall be performed by an Entry Authority (EA). A permit shall be issued before work begins and/or work progresses as directed by the EA.

Do not modify vacuum cleaner hose with metal extensions. b.

Depuddle with explosion-proof vacuum cleaner.

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Figure 6-2. Connection of Blower Duct

Figure 6-3. Air Supply Respirators

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c. If vacuum cleaner is unavailable, construct a wooden-handled mop with a cheesecloth, CCC-C-440, or a cellulose sponge, L-S-00646, attached to a wooden handle. (1) Wring out the fuel-soaked mop into an approved safety container. (2) Discard fuel wetted sponges and cheesecloth in accordance with local (HMIS) hazardous waste instructions.

before work begins and as work progresses as directed by an EA. 30. AIR EXHAUST PURGING 31. The air exhaust purging method allows controlled capture and discharge of fuel vapors from the fuel cell by using an air blower and ducting to draw outside fresh air through the cell. To air-exhaust purge a fuel cell proceed as follows:

27. PURGING 28. Purging is the process required to obtain, where possible, a "Safe for Personnel-Safe for Hot Work" atmospheric condition in a fuel cell after depuddling. The four approved purging methods are: a.

air exhaust

b.

air blow

c.

oil dilution

d.

JP-5/JP-8 rinse

29. Air should not be blown into a space, which contains a flammable material. Blowing air into the space will agitate and evaporate the contaminant, and disperse them throughout the space. Blowing air into a space also results in an uncontrolled explosion of the hazardous atmosphere from the space through any openings. Drawing air from the space, with the air exhaust method, may be less efficient from an air movement standpoint, but produces a controlled capture and removal process. Air may be blown into the space only when no flammable materials are present or are being generated by the work process, and ventilation is required only to provide clean air for breathing and general comfort.

Air exhaust purge fuel cells during depuddling, cleaning, or when flammables or toxic products are used in fuel cell. The ducts used for air exhaust shall extend to the outside of the enclosed fuel cell maintenance area. Failure to comply will result in introducing hazardous toxic/flammable vapors to enclosed maintenance areas. Do not perform hot work without specific authorization of the Entry Authority (EA) or hot work certificate from the EA. Testing of fuel cells for safe conditions shall be performed by an EA. A permit shall be issued

Bonding and grounding wires must be attached to clean, unpainted, conductive surfaces to be effective. Connect all grounding and bonding wires (cables) prior to removing fuel tank filler cap. Do not disconnect any grounding or bonding wire until fuel tank filler cap is reinstalled. Air exhaust purge fuel cells during depuddling, cleaning, or when flammables or toxic products are used in the fuel cell. The ducts used for air exhaust shall extend to the outside of the enclosed fuel cell maintenance area. Failure to comply will result in introducing toxic/flammable vapors to the enclosed maintenance areas. a. Position and ground the following equipment as applicable: (1)

Air blower, MIL-B-7619

(2)

Pneumatic driven fan, APV-1 or equivalent

(3)

Hot air MMEP12B

(4)

Air-supplied respirator

(5)

Explosion-proof vacuum cleaner

blower

assembly,

b. Ground the air eductor, DP32119 (Table 2-6 Item 1c), and attach a bonding cable from air eductor to aircraft (See Figure 6-5). c. Place air eductor over the vent fitting or, after removing filler cap, over the filler cap opening of cell to be purged. d.

Seal base of air eductor to ensure an air-tight fit.

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WHEN AN EXTERNAL AIR SOURCE IS BEING USED FOR PURGING, POSITION DUCT OUTLET IN THE SAME COMPARTMENT WITH THE MAINTENANCE PERSONNEL. THE FLOW OF AIR SHALL NOT BE DIRECTED TOWARD PUDDLED FUEL AND INTO REPAIR AREA .

Figure 6-4. Fuel Tank Depuddling

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Figure 6-5. Air Eductor Installation (Typical)

If heated air is used for purging, the outlet temperature shall not exceed 100oF (38oC).

Start air blower or hot air blower before connecting air ducts to the aircraft.

NOTE

Do not shut down air blower or hot air blower when air duct is connected to the aircraft. If air blower or hot air blower fails during operation, remove air duct from aircraft immediately and move the duct, air blower, or hot air blower to an area upwind free from fuel vapors. Compressed air shall not be used under any circumstances to clean dirt or dust from clothing or blow chips or shavings from work surfaces.

In cold weather, warm air for purging may be obtained with the use of a hot air blower assembly, MMEP12B. e. Connect air supply hose to air eductor and then to a compressed air source. f. Attach a bonding cable to the wire reinforcement of the air blower duct outlet end. g.

Failure to comply with these warnings could result in injury or death to personnel and damage to or destruction of the aircraft.

Commence airflow to the air eductor.

h. Start air blower and attach bonding cable located at outlet end of duct to aircraft structure.

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i. Place outlet end of duct into fuel cell opening and purge fuel cell. j.

Remove air blower duct from fuel cell opening.

k.

Stop the flow of air to the air eductor.

tinuously vents the air outside. To air blow purge a fuel cell after depuddling, proceed as follows:

Bonding and grounding wires must be attached to clean, unpainted, conductive surfaces to be effective. Connect all grounding and bonding wires (cables) prior to removing fuel tank filler cap. Do not disconnect any grounding or bonding wire until fuel tank filler cap is reinstalled.

Do not perform hot work without specific authorization of a hot work certified Entry Authority (EA). Testing of fuel cells for SAFE conditions shall be performed by an EA. A permit shall be issued before work begins and/or as work progresses as directed by the EA.

a. Position and ground the following equipment as follows:

When air-exhaust purging, position duct inlet in the same compartment with the maintenance personnel. The flow of air shall be directed as much as practical to prevent contaminants from passing over the maintenance personnel. l. Have a hot work certified EA test the air in the cell to ensure that a "Safe for Personnel - Safe for Hot Work" condition is maintained during this procedure.

NOTE Refer to NAVAIR 01-1A-34, Aeronautical and Support Equipment Welding for hot work that includes welding, soldering, brazing, and flame spraying. m. Comply with requirements for fuel cell entry contained in paragraphs 15, 17 and 18 in this Work Package.

When an external air source is being used for Purging, position duct outlet in the same compartment with the maintenance personnel. The flow of air shall not be directed toward puddled fuel and into repair area. n. Continue to purge while personnel are inside or partially inside fuel cells. 32. AIR BLOW PURGING 33. (See Figure 6-4) The air blow purging method uses an air blower and ducting to force fresh, outside air into the fuel cell. An air eductor (Venturi air mover), in the fuel cell con-

(1)

Air blower, MIL-B-7619

(2)

Pneumatic driven fan, APV-1 or equivalent

(3)

Hot air MMEP12B

(4)

Air-supplied respirator

(5)

Explosion-proof vacuum (Table 2-6, Item 2b)

blower

assembly,

cleaner

b. Connect air blower ducting to inlet connection of the air blower. c. Attach a bonding cable to the wire reinforcement of the air blower inlet duct. d.

Connect ducting to outlet connection of air blower.

Position the outlet end of the exhaust duct a minimum of 50 feet downwind from the aircraft for outdoor operations. Extend exhaust duct outlet to the exterior of an enclosed maintenance area. e. Position the outlet end of the ducting to exhaust vapors.

NOTE A grounded maintenance stand may be used to raise ducting to desired height.

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f. Extend outlet duct end into the air to a height sufficient to allow dissipation of fuel vapors before they drift to the ground. g. Open all vents and filler caps for the cell being purged. h.

Bond inlet ducting to aircraft then start the blower.

i. Remove fuel cell access panel and place the inlet duct inside. j. Continue purging until "SAFE for Personnel - Not Safe for Hot Work" condition is obtained. k. Remove air blower duct from the fuel cell or cell opening.

Do not perform hot work without specific authorization of a hot work certified Entry Authority (EA). Testing of fuel cells for SAFE conditions shall be performed by an EA. A permit shall be issued before work begins and/or as work progresses as directed by the EA. l. Have a hot work certified EA test the air in the cell to ensure that a "Safe for Personnel - Not Safe for Hot Work" condition is maintained during this procedure.

NOTE Refer to NAVAIR 01-1A-34, Aeronautical and Support Equipment Welding for hot work that includes welding, soldering, brazing, and flame spraying. m. Comply with requirements for cell entry contained in paragraphs 15, 17 and 18 in this Work Package.

Lubricating Oil MIL-PRF-6081

5

34. OIL DILUTION PURGING 35. The oil dilution purging method uses lubricating oil MIL-PRF-6081, grade 1010, to dilute the fuel vapor in a defueled fuel cell to a safe condition. To oil dilution purge a fuel cell, proceed as follows:

NOTE This method is also used for preservation of auxiliary tanks prior to storage or shipment. It may be desirable to use the Oil Dilution Purging method when it is necessary to perform extensive repair to the aircraft other than to the fuel system. When purging with this method, opening of access doors or fittings is not required. The flash point of the purging fluid shall be 150oF (65oC) or higher to provide reasonable assurance that the cell will be at a "SAFE for Personnel - NOT Safe for Hot Work" level after purging. Testing of the condition shall be performed by an EA. To obtain a “SAFE for Personnel-Safe for Hot Work” atmospheric condition in a fuel cell that has been purged by the oil dilution purging method, remove residual oil and air purge the cell. a. After the aircraft has been defueled, connect a hose to the low-point pencil drains and drain the remaining fuel into a grounded and bonded safety container, RR-S-30 (Table 2-5, Item 3a).

NOTE The purging fluid shall remain in the fuel cell for a minimum of 10 minutes before removal or transfer to another fuel cell.

When air-exhaust purging, position duct inlet in the same compartment with the maintenance personnel. The flow of air shall be directed as much as practical to prevent contaminants from passing over the maintenance personnel. n. Continue to purge while personnel are inside or partially inside fuel cells

b. Connect the purging fluid supply to the aircraft and service the fuel system in accordance with the applicable aircraft MIM.

NOTE The entire fuel system may be filled, or one cell can be filled and the fluid then transferred to the other cells using the aircraft fuel system transfer pumps.

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In the event only one cell is filled with purging fluid, which is then transferred to other cells, any fuel remaining in the cells will dilute the purging fluid as it is transferred from cell to cell. This can reduce the effectiveness of the fluid as a purging medium. c. After the purging fluid has remained in the fuel system for the required time, normally 10-minutes, drain the cells. d.

Have an EA test the air inside the cell.

36. JP-5/JP-8 FUEL PURGING The JP-5/JP-8 fuel purging method uses JP-5 or JP-8 fuel to dilute and help remove all residues from low flash point fuels including JP-4 and AVGAS. These purge fuels must maintain a minimum 120°F flash point. Aircraft serviced with JP-8 may require purging using another approved method if the required flashpoint cannot be maintained. This minimum flashpoint is critical for maintaining a less than 10% LEL making the cell firesafe. To JP-5/JP-8 purge a fuel cell, proceed as follows:

a.

Level aircraft.

b. Defuel aircraft completely, including draining through low-point drains. Refer to applicable aircraft MIMfor location. c. sible).

Drain engine feed systems and manifolds (if pos-

d. Drain residual fuel into grounded and bonded safety containers, RR-S-30 (Table 2-5, Item 3a). e. Fill the entire fuel system to maximum capacity with JP-5/JP-8 fuel in accordance with the procedures of the applicable aircraft MIM. f. Allow the JP-5/JP-8 fuel to remain in the system for a minimum soak period of 12 hours before purging the engine and engine feed system. 37. Purge jet aircraft as follows: (1) Perform 2-3 minute engine ground runs including, where applicable, two momentary afterburner runs. (2) To assure mixing of fuel, actuate fuel transfer systems during engine runs.

Testing of fuel cells for SAFE conditions shall be performed by an Entry Authority (EA). A permit shall be issued before work begins and/or as work progresses as directed by the EA. If the ambient temperature is expected to exceed 75°F the tank should not be purged with JP-8.

Lubricating Oil MIL-PRF-6081

5

(3) If engines are inoperable, purge the engine fuel system by preserving with lubricating oil MIL-PRF-6081, grade 1010 in accordance with the applicable aircraft manual (NAVAIR 02B-XXX-6X) . Because of the tendency of aircraft fuel systems to gravity crossfeed, purging of individual cells or parts of systems by this method should not be attempted.

NOTE The purging fuel can be treated as mixed fuel and used for non-shipboard operations subject to the limitations of NAVAIR 00-80T-109. When using the JP-5/JP-8 fuel purging method, aircraft should be considered safe for extensive repairs except for work on the fuel systems such as opening and drilling into fuel cells or breaking of fuel lines. When any work on the fuel system is involved, comply with the requirements for defueling, depuddling, and air purging.

38. Purge reciprocating engine aircraft as follows: a. Drain fuel from engine feed systems and preserve with lubricating oil MIL-L-6081, grade 1010 in accordance with the applicable aircraft manual or NAVAIR 15-01-500. b. After engine fuel system is purged, ensure aircraft is level and completely defuel aircraft including drainage through low-point drains and engine feed systems.

Lubricating Oil MIL-PRF-6081

5

c. If aircraft is to be out of service long enough to require preservation, preserve fuel system with lubricating oil MIL-PRF-6081, grade 1010 in accordance with NAVAIR 15-01-500.

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d. Before performing any work on the fuel system, the fuel cells shall be tested to obtain a SAFE certificate by an EA. If the proper condition is not obtained, depuddle and exhaust ventilate or take other corrective action as directed by the EA. 39. DETERGENT CLEANING AND PURGING OF AUXILIARY FUEL CELLS 40. The detergent cleaning and purging method uses a solution of detergent and water to remove residual fuel and vapors from auxiliary fuel cells. Detergent cleaning is the most effective method of purging flammable vapor from auxiliary fuel tanks. To detergent clean and purge a fuel cell, proceed as follows:

h. A certified EA shall test the interior atmosphere of the call for a "SAFE for Personnel - NOT Safe for Hot Work" Condition. i. If the required reading is not obtained repeat cleaning and retest.

Start air blower or hot air blower before connecting air ducts to the aircraft Do not shut down air blower or hot air blower when air duct is connected to the aircraft.

Only tanks that have been detergent cleaned and purged shall be inducted or stored in a repair shop due to the presence of welding, grinding, or other operations that generate heat, sparks, or other ignition inducing conditions. Soaps and detergents may cause eye and skin irritation. Use personal protective equipment.

Check applicable fuel tank Maintenance Instruction Manuals before detergent clean. In some fuel tanks, fuel quantity probes could be damaged by detergent cleaning. a. Prepare the detergent mixture so that the solution will be one part by volume of detergent (Table 2-5, Item 4a or 4b), to one part water (warm water preferred). b. Using a high pressure portable foam generator, Model 20, with a fan-type nozzle on the end of the wand, adjust the mixing valve to deliver cleaner in the ratio of 1 part of the 1-to-1 solution to 8 parts water. c. Thoroughly coat all interior surfaces of tank. Then remove wand from interior of tank and spray all exterior surfaces of cell. d.

Allow the solution to set for 5 minutes.

e.

Adjust the wash equipment to deliver water only.

f. Rinse exterior of cell and thoroughly rinse the interior surface of cell until rinse water is free of foam. g.

Allow to drain.

If air blower or hot air blower fails during operation, remove air duct from aircraft immediately and move the duct, air blower, or hot air blower to an area upwind free from fuel vapors. j. To eliminate or minimize residual moisture in the cell, use the air blower. MMEP-12B, to air dry the interior of the cell. The temperature at the end of the outlet duct shall not exceed 120ºF (49ºC). k. If the cell is going to be stored or shipped, preserve the cell using MIL-PRF-6081, 1010 Oil in accordance with NAVAIR 15-01-500. Preservation of Naval Aircraft for Organizational, Intermediate and Depot Maintenance Levels. 41. HOT WORK 42. The following paragraphs apply to all hot work performed in confined or enclosed spaces, or hot work performed on closed structures such as pipes, fuel cells, ducts, tubes, jacketed vessels and similar items.

NOTE Refer to NAVAIR 01-1A-34, Aeronautical and Support Equipment Welding for hot work that includes welding, soldering, brazing, and flame spraying. a. Hot Work Operations. Hot work for the purpose of gas free engineering, includes any work that produces heat by any means, of a temperature of 400ºF (204ºC) or more, in the presence of flammables or flammable atmospheres, such as: Flame heating Welding Torch cutting Brazing

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Carbon arc gouging Arc producing tools or equipment Friction Impact Open flames or embers

fire watch shall be trained in the nature of any fire that may occur, and be proficient in the proper use of fire extinguishing equipment. Where hot work may create temperature increases in a wall, bulkhead, or other separating structure, an additional Fire watch shall be posted on the side opposite the worksite. A system of communication shall be established to permit the fireguard to convey the development of hazardous conditions on the opposite side of separating structures, and to signal the necessity to stop work.

Non-explosion-proof lights, fixtures, motors or equipment b. Cleaning. Prior to commencing hot work in a confined or enclosed space, the space shall be tested, inspected, cleaned and ventilated as required by the provisions of this manual and the applicable aircraft MIM. Testing of the space will be accomplished by the activity Aircraft Confined Space Program Manager (ACSPM) or hot work certified Entry Authority (EA) authorized to issue hot work certificates. The Permit shall state "Safe for Hot Work." To clean space proceed as follows: (1) Remove extraneous materials from the space. (2) Clean or remove flammable material from the space to the degree sufficient to eliminate significant fire hazard.

NOTE Additional Fire watch shall be trained in the nature of any fire that may occur, and be proficient in the proper use of fire extinguishing equipment. e. Fire Extinguishing Equipment. Suitable fire extinguishing equipment shall be provided based on the nature and extent of the flammables or combustibles present and the type of fire that may occur. Water extinguishers or water hoses equipped with fog nozzles or applicators are most suitable for hot work in the presence of ordinary Class A, combustible material or flammable residues or coatings. Fire extinguishing equipment shall be selected based on the following:

(3) Combustible material that cannot be removed shall be adequately protected.

Do not perform hot work without specific authorization of activity Aircraft Confined Space Program Manager (EA) or hot work certified Entry Authority (EA) authorized to issue hot work certificate. Inerting shall not normally be used as a means to permit hot work on any component of a fuel system that contains aviation gasoline or Jet Petroleum (JP) fuels. c. Boundary Space. Spaces adjacent to the space in which hot work is to be performed (above, below, and on all sides) shall be inspected, tested, cleaned, and ventilated or inerted as appropriate. These spaces shall be certified by the ACSPM or hot work certified EA authorized to issue hot work certificates. The Permit shall state "SAFE for Hot Work." The ACSPM/EA shall issue a checklist/procedure for each type of welding operation conducted on an aircraft or aircraft component. d. Fire Prevention. A Fire watch shall be posted at the worksite when hot work is to be conducted in the presence of combustible materials or flammable residues. The

Vaporizing liquid fire extinguishers such as CO2 and Halon shall not be used in confined or enclosed spaces. (1) Extinguishing agent’s ability to suppress the fire. (2) Any hazard that may be created by the discharge of the agent into the space. (3) The capacity of the equipment in relationship to the size and intensity of the potential fire.

NOTE Exceptions may be made in selection of fire extinguishing equipment where restrictions exist due to the nature of the space. f. Hot Work in the Presence of Flammable Coatings. The flammability of coatings shall be determined prior to starting hot work. If flammability of coating is unknown, tests shall be conducted to determine flammability, or worse case conditions must be assumed to exist. Coatings known or found by testing to be combustible shall be removed from the location of the hot work, to a distance sufficient to prevent ignition or outgassing from temperature increase of coating

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materials in the unstripped areas. The distance required for stripping of coating material will vary according to the material involved and the nature of the hot work, but in no case shall be less than 4 inches on all sides from the outermost limits of the hot work. To conduct hot work, proceed as follows:

NOTE Suitable fire extinguishing equipment shall be immediately available, charged and ready for instant use. (1) Periodic or continuous testing shall be conducted from start of hot work to ensure flammable atmospheres are not being produced. (2) Where significant outgassing is detected, hot work shall be stopped and further stripping conducted, artificial cooling methods employed, or other means applied to prevent temperature increases in the unstripped areas. (3) Flame or uncontrolled heat shall not be used for stripping flammable coatings. (4) Methods shall be employed to prevent hot slag or sparks from falling onto flammable coatings in the area of the hot work. (5) The wetting down of surrounding areas to reduce ignition potential may also be used to minimize ignition, consistent with the nature of the coating operation. g. Soft, Greasy Preservative Coatings. Soft greasy coatings may present hazards more serious than those presented by hard surface coatings. Some soft coatings may have much lower flash points, produce outgassing at lower temperatures, and may ignite more easily from hot slag or sparks. Some materials may, under certain conditions, "surface flash," which would involve the entire coated area. The above problems are often further complicated by difficulty in walking, standing, and maneuvering on slippery surfaces, increasing the possibility of falls, dropping lighted torches on unstripped material, etc. Therefore, accomplish the following prior to start of hot work in a confined or enclosed space coated with soft, greasy preservatives:

h. Hot Work on Pipes, Tubes, or Coils. Pipes, tubes, coils, or similar items, which service or enter and exit a confined or enclosed space shall be flushed, blown. purged, or otherwise cleaned and certified "SAFE for Hot Work" prior to the start of hot work. Where they are not cleaned and certified, they shall be prominently tagged "NOT Safe For Hot Work." The Permit for the space shall also contain a notation to that effect.

NOTE Valves to pipes, tubes, and similar items shall be closed and tagged, the pipes blanked off, where possible, to prevent inadvertent discharge or backflow of materials into the space. i. Hot Work in the Presence of Pressurized Systems. Prior to start of hot work in areas that contain pressurized systems (such as fuel, hydraulic, liquid oxygen, etc.), the systems shall be depressurized if there is a possibility that these systems could be affected by the hot work. Piping, fittings, valves, and other system components shall be protected from damage resulting from contact with flames, arcs, hot slag, or sparks. Care shall be taken to ensure that all contamination within the space, such as leaking hydraulic fluid, is cleaned and removed prior to start of hot work. Hydraulic fluid in the presence of high temperatures can decompose and produce highly toxic byproducts. j. Compressed Gas Cylinders. Compressed gas cylinders shall be transported, handled, and stored in accordance with NAVOSH standards. Compressed gas cylinders or gas manifolds used in welding and cutting operations shall not be taken into a confined or enclosed space. Compressed gas cylinders or gas manifolds shall be placed outside the space, in open air, in an area not subject to any fire, explosion, or emergency that may occur within the space. k. Gas Welding and Cutting Equipment. Gas welding and cutting equipment such as hoses, connections, torches, etc., shall be inspected, tested, operated, and maintained in accordance with current NAVOSH standards.

(1) Strip, clean, or otherwise remove the preservative from the area of the hot work a distance sufficient to prevent outgassing and to prevent ignition from heat, sparks, slag, etc.

l. Gas Supplies. Gas supplies shall be turned off at the cylinder or manifold outside the space when equipment is unattended or unused for substantial periods of time, such as breaks or lunch periods. Turn off gas supplies and remove torches and hoses from the space during shift changes or if the equipment is to be idle overnight. Open-ended hoses shall be immediately removed from the space when torches or other devices are removed from the hose.

(2) The space shall be tested and certified "SAFE for Hot Work" by the activity ACSPM or hot work certified EA authorized to issue hot work certificates.

m. Electric Arc Units or Machines. Electric arc units or machines shall not be taken into a confined or enclosed space. Electric arc equipment shall be inspected, tested,

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n. operated, and maintained in accordance with current NAVOSH standards. o. Electrode Holders. When electrode holders are to be left unattended or unused for substantial periods of time, such as breaks or lunch periods, the electrodes shall be removed from the holders. The holders shall be placed in a safe location and protected, and the power switch to the equipment shall be turned off. If unattended for extended periods or the equipment is to be idle overnight, electrode holders, cables, and other equipment shall be removed from the space and the power supply to the equipment disconnected.

Do not perform hot work without specific authorization of activity ACSPM or hot work certified EA authorized to issue hot work certificates. A tailored Hot Work and On-Aircraft Welding Checklist shall be followed for each On-Aircraft welding operation. Failure to comply could cause death or injury to personnel. p. On-Aircraft Welding. Gas shielded arc welding is the only method authorized for on-aircraft welding. OnAircraft welding operations shall normally be accomplished outdoors. On-aircraft welding operations shall be established by the activity ACSPM, in coordination with the Fire Marshal and Aircraft Maintenance Officer. The activity ACSPM shall provide a tailored Hot Work and On-Aircraft Welding Checklist for each on-aircraft welding operation. q. Hazardous Byproducts. Welding, cutting or burning in the presence of certain materials such as hydraulic fluids, chlorinated solvents, halogens, etc., or the application of heat to such materials can result in the decomposition of the materials and the production of hazardous byproducts. Procedures shall be established to ensure that hot work is not conducted on or in the vicinity of such materials. Welding or cutting operations, which produce high levels of ultra-violet radiation shall not be conducted within 200 feet of chlorinated solvents. r. Hot Work on Closed Containers or Structures. Drums, containers, or hollow structures that have contained flammable substances shall be treated as follows: (1) Before welding, cutting, or heating, the object should be filled with water or thoroughly cleaned of flammable substances, ventilated, and tested. (2) Before heat is applied to a drum, container, or

hollow structure, a vent or opening shall be provided for the release of any pressure buildup during the application of heat. (3) Before welding, cutting heating, or brazing is begun on structural voids, a ACSMP or EA authorized to issue hot work certificates shall inspect the object and, if necessary, test it for the presence of flammable residue liquids, or vapors.

NOTE If flammable residues, liquids, or vapors are present, the object shall be made safe. Objects such as those listed above shall also be inspected to determine whether water or other nonflammable liquids are present which, when heated, would build up excessive pressure. If such liquids are determined to be present, the object should be vented, cooled, or otherwise made safe during the application of heat. (4) Jacketed vessels shall be vented before and during welding, cutting, or heating operations, in order to release any pressure that may build up during the application of heat. 43. INERTING 44. Inerting is a suitable means of ensuring a noncombustible atmosphere in fuel cells or tanks when it is not necessary to open the cell for inspection or maintenance. Inerting may be desirable to safeguard a fuel cell adjacent to, but not adjoining, another cell about to undergo inspection or maintenance. Siphon inerting methods and the pressure inerting method are described in this paragraph. Siphon inerting, however, is not approved unless it is specified in the applicable aircraft MIM. The following general precautions are to be observed during inerting procedures.

Inerting shall not normally be used as a means to permit hot work on any component of a fuel system that contains aviation gasoline or Jet Petroleum. Inerting shall be certified by the activity Aircraft Confined Space Program Manager (ACSPM) only. Do not use fire extinguishers or other high velocity gas systems to inert fuel cells. High velocity gas streams, especially from CO2 fire extinguishers, can generate static electrical charges

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and create a danger of fire or explosion. Grounding of fuel cell and bonding the fire extinguisher nozzle to the cell will not eliminate this danger. Do not perform other maintenance on aircraft during defueling. depuddling, purging, or inerting operations. 45. Permit. The EA will test the inert condition of a fuel system or cell. When the required inert condition of the fuel system or cell atmosphere has been achieved, the EA will issue a Permit indicating the conditions, "INERTED--NOT Safe for Personnel Inside---SAFE For Personnel and Hot Work OUTSIDE." The EA will conduct periodic checks to assure the continuing maintenance of an inerted atmosphere. See Work Package 004 for more information. 46. Siphon Inerting of Fuel Systems. Siphon Inerting is the process of inerting pressurized fuel systems wherein the air space of a fuel system or individual cell is slightly pressurized by injecting an inert gas (usually dry nitrogen) through a fuel system pressurization valve while the system/cell is being defueled. The process reduces the percentage of oxygen in the air space to a non-combustible condition. a. Siphon inerting applications. Siphon inerting is suitable for inerting pressurized fuel systems in cases where it is not necessary to open the cells to conduct inspection or work inside. Siphon Inerting is the most efficient method for inerting a single cell as well as interconnected cells. There may be times when Siphon inerting would be desirable for safeguarding a cell adjacent to another cell, which is to undergo inspection, repair, or removal. b. Siphon inerting safety. Fuel cells that have been inerted by this method are not safe for personnel entry due to low oxygen content. However, the cell could be made "SAFE for Personnel - SAFE for Hot Work by depuddling (paragraph 11) and air purging (paragraph 25) as described in this Work Package. c. Siphon inerting procedure. To siphon inert a fuel system/cell, proceed as follows: (1) To eliminate as much free air space as possible where explosive vapors may form, fill fuel system to maximum permissible level in accordance with the applicable aircraft MIM.

(2) Ground the Nitrogen Servicing Trailer, NAN3 (Table 2-5, Item 5b), to a static ground. (3) Bond the nitrogen trailer by connecting a bonding cable first to the nitrogen trailer and then to aircraft.

NOTE Comply with defueling requirements of paragraph 7.

Connect all grounding and bonding wires (cables) prior to removing fuel tank filler cap. Do not disconnect any grounding or bonding wire until fuel tank filler cap is reinstalled. (4) After appropriate bonding of the defueler, attach defueling nozzle to aircraft. (5) Open nitrogen trailer servicing valve and pressure regulator to correct pressure for inerting the fuel system. (6) Crack the flow control valve and allow the nitrogen gas to purge the servicing line for approximately 5 seconds, and then close the flow control valve. (7) Connect nitrogen supply line to aircraft fuel system in accordance with the applicable aircraft manual.

Positive pressure must be maintained in the fuel system during siphon inerting to prevent collapsing of fuel cells, particularly for bladder cells. This pressure must not exceed the safe pressure of the fuel cell as specified in the applicable aircraft Maintenance Instruction Manual (MIM). (8) Slowly open the flow control valve and commence Siphon Inerting and defueling in accordance with the applicable aircraft MIM. (9) When defueling is complete, close defueling nozzle. Disconnect defueler bonding cable from aircraft and then move defueler from the area.

Bonding and grounding wires must be attached to clean, unpainted, conductive surfaces to be effective.

(10) Final draining of remaining fuel shall be accomplished using the low-point drains.

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(11) After low-point draining is completed, close nitrogen trailer servicing valves and then close the flow control valve.

NOTE To retain the inert state of the fuel system atmosphere it is often necessary to maintain a continuous positive pressure of nitrogen gas.

Remove all equipment (vent plugs, caps, tags, etc.) used during inerting operation prior to returning the aircraft to service. (12) Plug fuel system vents of fittings, as required, in accordance with the applicable aircraft MIM to prevent loss of nitrogen gas. Disconnect nitrogen-servicing line from aircraft fuel system servicing fitting and cap the fuel system servicing fitting.

Inerting shall be certified by the activity Aircraft Confined Space Program Manager (ACSPM) only. (13) An EA shall certify the condition of the inert atmosphere in accordance with the applicable MIM and indicate the condition; “INERTED - NOT Safe For Personnel Inside - SAFE For Personnel and Hot Work OUTSIDE”. 47. Pressure Inerting of Fuel Systems. Pressure Inerting is the process of inerting unpressurized fuel systems wherein the air space of a fuel system or individual cell is slightly pressurized by injecting an inert gas (usually dry nitrogen) through an adapter fitting placed in cell fuel filler opening to reduce the percentage of oxygen in the air space to less than one percent. a. Pressure Inerting application. Pressure Inerting is used when it is not necessary to open the cells to conduct inspection or work inside and defueling of the aircraft is not required. However, if defueling is desired it shall be accomplished prior to inerting. The effectiveness of Pressure Inerting can only be assured when it is possible to test the atmosphere in all vapor spaces of each cell inerted to determine that a minimum 99 percent concentration of inert gas is present. Pressure Inerting is useful for inerting a single cell and can be used for inerting a series of interconnected cells.

c. Pressure Inerting procedures. To pressure inert a fuel system/cell, proceed as follows:

NOTE If defueling is required, defuel the aircraft in accordance with paragraph 7. If defueling is not required, comply with steps 40c(1) through 40c(10). (1) Ground the fuel cell to be inerted by attaching a grounding wire to the cell and then the other end to the same static ground to which the nitrogen trailer is grounded. (2) Connect the nitrogen gas delivery fittings to the nitrogen gas delivery line. (3) Bond the nitrogen service line to the fuel cell to be inerted by attaching a bonding wire to the cell to be inerted and then attaching the other end to the service end of the nitrogen line

Positive pressure must be maintained in the fuel system during Pressure Inerting to prevent collapsing of fuel cells, particularly for bladder cells. This pressure, however, must not exceed the safe pressure of the fuel cell as specified in the applicable aircraft Maintenance Instruction Manual (MIM). (4) Open nitrogen trailer servicing valve and set pressure regulator to correct pressure for inerting the fuel system. (5) Crack the flow control valve and allow the nitrogen gas to purge the servicing line for approximately 5 seconds, and then close the flow control valve. (6) Remove filler caps of cell to be inerted and insert gas delivery fitting in the fuel filler opening. (7) Slowly open the flow control valve and commence inerting. (8) When sufficient inert gas has been injected into the fuel system/cell in accordance with the applicable aircraft MIM, close nitrogen-servicing valve. Then close the flow control valve.

Remove all equipment (vent plugs, caps, tags, etc.) used during inerting operation prior to returning the aircraft to service.

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NOTE To retain the inert state of the fuel system atmosphere it is often necessary to maintain a continuous positive pressure of nitrogen gas. (9) Plug fuel system vents of fittings, as required, in accordance with the applicable aircraft MIM to prevent loss of nitrogen gas. Disconnect nitrogen servicing line from aircraft fuel system servicing fittings and cap the fuel system servicing fitting.

Inerting shall be certified by the activity Aircraft Confined Space Program Manager (ACSPM) only. (10) An EA shall certify the condition of the inert atmosphere in accordance with the applicable MIM and indicate the condition; “INERTED - NOT Safe For Personnel Inside - SAFE For Personnel and Hot Work OUTSIDE.

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Page 1 of 10

MAINTENANCE INSTRUCTIONS

AIRCRAFT FUELS AND FUEL CONTAMINATION

Reference Material Aircraft Refueling NATOPS Manual..................................................................................................NAVAIR 00-80T-109

Alphabetical Index Subject

Page

Aviation Fuels ...................................................................................................................................................................... 2 Knock Value.............................................................................................................................................................. 2 Volatility.................................................................................................................................................................... 2 Characteristics of Aviation Fuels ......................................................................................................................................... 3 Contamination of Aircraft Fuels........................................................................................................................................... 3 Micro-Organisms....................................................................................................................................................... 3 Mixed Fuel................................................................................................................................................................. 3 Particulate Matter ...................................................................................................................................................... 3 Water ......................................................................................................................................................................... 3 Fuel Sampling ...................................................................................................................................................................... 5 Acceptable Fuel ......................................................................................................................................................... 5 Sampling Procedures ................................................................................................................................................. 5 Testing for Salt Water Contamination ....................................................................................................................... 7 Methods of Preventing Contamination................................................................................................................................. 5 Particulate Matter Contamination Prevention............................................................................................................ 5 Water Contamination Prevention .............................................................................................................................. 5 Specific Properties of Aviation Fuels................................................................................................................................... 2 Colors of Aviation Gasolines..................................................................................................................................... 2 Grades of Aviation Gasolines.................................................................................................................................... 2 Grades and Colors of Jet Engine Fuels...................................................................................................................... 2 JP-4 Jet Engine Fuel .................................................................................................................................................. 2 JP-5 Jet Engine Fuel .................................................................................................................................................. 2 JP-8 Jet Engine Fuel .................................................................................................................................................. 3 Solvent Properties of Aviation Gasolines .................................................................................................................. 2 Volotility and Solvent Properties of Jet Engine Fuels ............................................................................................... 2

1.

GENERAL.

2. The following paragraphs describe aircraft fuels used in Navy and Marine air activities. Knowledge of the important basic characteristics of these fuels is necessary to understand the importance of delivering the proper fuel to the aircraft. Such knowledge is also valuable in understanding the need for safety and caution in handling these fuels. This section includes the basic characteristics of aviation gasolines and jet engine fuels which fuel handling personnel should know. The following should be understood when handling fuel:

Fuel must be handled with caution Fuel is classified as a flammable liquid Fuel vapors can explode under proper conditions Fuel vapors can cause death or injury in confined areas Fuel can cause skin irritation Fuel vapors are heavier than air.

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Fuel is lighter than water (in liquid form) 3. Specific safety precautions necessary for handling fuel are contained in NAVAIR 00-80T-109, Aircraft Refueling NATOPS Manual. 4.

AVIATION FUELS.

5. Aviation fuels can be divided into two types: aviation gasolines and jet engine fuels. The knock value and the volatility are the two major differences between these fuels. 6. Knock Value. From a performance standpoint, one of the most important differences between aviation gasoline and jet engine fuels is in the tendency of the fuels to produce a knock, or detonation, when used in piston type engines. The continuing occurrence of knocking can damage an aircraft engine to such an extent that a complete engine failure results. For this reason, knocking in aircraft engines must be strictly avoided. 7. Volatility. The tendency of fuels to evaporate, or vaporize, is known as volatility, and is a very important factor in the proper operation of piston-type engines. In a pistontype engine, the fuel must vaporize and be mixed with air in order to burn and deliver power. Aviation gasolines are more volatile than jet engine fuels and consequently they vaporize more readily. This high volatility is necessary to assure that all the gasoline will be burned in a piston engine. 8.

SPECIFIC PROPERTIES OF AVIATION FUELS.

9. Specific properties of aviation fuels, which are extremely important to fuel handling personnel, are described in the following paragraphs. 10. Grades of Aviation Gasolines. Aviation gasolines are designated by octane and performance numbers. Grade designations of 100 and lower are octane numbers, while those above 100 are performance numbers. Most aviation gasolines are designated by two numbers, for example, Grade 11 5/145. Where two numbers are used in this manner, the first number indicates the knock rating with a lean fuel-air mixture, and the second number indicates the knock rating with a rich fuel-air mixture. Aviation gasolines are available in three grades, which are listed in Table 7-1. 11. Colors of Aviation Gasolines. To aid in ready identification of the three grades of aviation gasolines, each grade is dyed a different color (Refer to Table 7-1). Fuel handling personnel should always know the three grades and corresponding colors of aviation gasolines. This is important in assuring that the proper fuel is delivered to the aircraft. 12. Solvent Properties of Aviation Gasolines. All aviation gasolines are able to dissolve a number of materials. They will dissolve common lubricants, such as oils and greases,

in pumps, valves, packing, and other equipment. Because of this, only special lubricants can be used for aviation gasoline service. Aviation gasolines will also cause serious deterioration of rubber materials, except for those designed especially for gasoline service. It is important, therefore, that only hoses that are specially made and designated for aviation gasoline be used in this service. This also applies to packing, gaskets, and other rubber materials, which must be used in aviation gasoline service. 13. Grades and Colors of Jet Engine Fuels. (Refer to Table 7-2.) The grade designation for jet engine fuels indicates the approximate numerical sequence in which the fuel specifications were accepted by the military organization. Also, no dyes are added to jet fuels to aid in their identification. Their color may vary from a water-clear color to a straw color. 14. Volatility and Solvent Properties of Jet Engine Fuels. The volatility of jet engine fuels varies over a wider range than aviation gasolines. Jet engine fuel JP-4 has both gasoline and kerosene components, and a Reid vapor pressure of 2 to 3 psi. Jet engine fuel JP-5 and JP-8 are kerosene type fuels with a very low vapor pressure and are less likely to ignite. Jet engine fuels have certain solvent properties, which dissolve greases and cause deterioration of some rubber materials. They can also dissolve asphalt. 15. JP-4 Jet Engine Fuel. JP-4 is an alternate fuel for JP-5 for Navy and Marine jet aircraft. However, it is used as such only at shore activities and never aboard ship. It is a wide boiling range petroleum product, including both gasoline and kerosene boiling range components, but contains no tetraethyl lead. Because of its vaporizing characteristic well below freezing temperatures, better engine start and restart capabilities are recorded with JP-4 than with JP-5. 16. JP-5 Jet Engine Fuel. JP-5 is a middle distillate fuel (kerosene, diesel, Jet A, etc.) with an especially high flash point, which increases safety in handling. It is widely used at Navy and Marine air activities ashore, and is the only fuel that can be used for turbine engine aircraft aboard ships. The properties of JP-5 as compared to JP-4 are as follows: Higher specific gravity Higher flash point Lower volatility Higher heat content on a per gallon basis Higher freezing point Higher viscosity

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NOTE Because its physical properties are similar, JP-5 is accepted as an alternate to diesel fuel. 17. JP-8 Jet Engine Fuel. JP-8 is a kerosene fuel similar to commercial jet fuel ASTM Jet A-1 except JP-8 contains fuel system icing inhibitor as well as other fuel additives. It is also similar to JP-5 with respect to most fuel properties except flash point and freezing point. Since its flash point is not as high as JP-5’s it cannot be used for shipboard operations. The Air Force is currently in the process of converting operations to JP-8 fuel in order to take advantage of its similarity to commercial aviation turbine fuel and improved safety (lower volatility). 18. CHARACTERISTICS OF AVIATION FUELS. 19. It is important that fuel handling personnel remember the following characteristics of aviation fuels: From the standpoint of fire, explosion, and health, aviation gasolines and jet engine fuels are extremely hazardous and must be handled with equal caution. Aviation gasolines and jet engine fuels are designed for entirely different types of engines; therefore, only the proper fuel must be used for each type aircraft. Aviation gasolines and jet engine fuels are divided into a number of different grades, and the proper grade of fuel shall be used for each aircraft. 20. CONTAMINATION OF AIRCRAFT FUELS. 21. Aircraft fuel systems are complex and will not function if contaminated with particulate matter, water, mixed fuel or micro-organisms. These types of contamination are described in the following paragraphs. a. Particulate Matter. (See Figures 7-1 and 7-2.) Particulate matter contamination is usually caused by the following:

silting and plugging fuel control units and nozzles, and scoring and wear of fuel system components by abrasion. Particulate matter settles much slower in jet fuels than in aviation gasolines. b. Water. Water is a common contaminant of fuels and refueling personnel will be concerned with it in two forms: entrained water and water slugs. (1) Entrained water. Entrained water is found in fuels in the form of very small droplets, fog, or mist, and may or may not be visible. Water usually becomes entrained in the fuel when it is broken up into small droplets and thoroughly mixed with the fuel in equipment such as pumps or meters. (2) Water slugs. Water slugs are quantities of water, which do not mix with the fuel but are carded with the fuel as liquid water. This water enters cells or pipelines through fill lines, vents, cell openings, condensation, etc., and accumulates in cells or equipment, where it is picked up by pumps and carded as water slugs c. Mixed Fuel. The mixing of fuels is usually caused by poor or careless operation of the fuel handling equipment and facilities. All personnel must know and remember that small quantities of one fuel can seriously contaminate and render unusable another aircraft fuel. d. Micro-Organisms. Bacteria and fungi are present in most jet engine fuels. These are common microorganisms that find their way into fuel storage tanks and aircraft fuel systems because of dirt and water contamination. Micro-organism contamination usually appears as a brown slime-like deposit which adheres to the inner surfaces of fuel cells. This results in corrosion of fuel cells, clogging filters, and erratic operation of fuel quantity indicating systems. Generally, microbiological contamination of jet fuels is most severe in tropical climates where temperatures and humidities are high. Some of the most common sources of such fuel supply contamination are: Fuel storage tanks, which contain water bottoms that cannot be completely drained Floating roof tanks that allow the entry of rainwater and airborne dust

Iron-rust and scale Sand

Contaminated water let into storage tanks from pipeline water slugs that are used to separate products

Airborne dirt Foam baffle degradation The presence of large amounts of particulate matter in fuel results in restricting or clogging filter/coalescer elements,

Fuel contaminated during transport in tankers and barges ballasted with water Previously contaminated fuel being defueled from aircraft into storage tanks

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Table 7-1. Grades of Aviation Gasolines Grade

Primary use

NATO symbol

Color

115/145

Combat

F-22

Purple

100/130

Cargo and Transport

F-18

Blue or Green

80/87

Primary Training and Liaison

F-12

Red

Table 7-2. Grades of Jet Engine Fuels Grade

Primary use

NATO symbol

Flash Point

Freeze Point

Jet A

Commercial Aircraft

--

100oF

-40oF

Jet A-1

Commercial Aircraft

F-35

100oF

-58oF

JP-4

US Air Force and Navy training activities

F-40

below 0oF

-72oF

JP-5

Navy shipboard and fleet support shore Activities

F-44

140oF (min.)

-51oF

JP-8

Replace JP-4

F-34

100°F (min.)

-53°F

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Figure 7-1. Comparison of Particle Rate of Settling in Three Types of Fuel 22. METHODS OF PREVENTING CONTAMINATION. 23. Contamination of aircraft fuel can be prevented by the use of proper equipment and by careful and proper operating procedures. a. Particulate Matter Contamination Prevention. The following procedures are used to prevent particulate matter contamination of aircraft fuels: (1) Prevent entry of particulate matter by using dust-tight covers for all openings, connections, and fueling nozzles. These covers shall remain in place except when refueling. (2) Filter fuel by using a filter/separator during fueling operations per NAVAIR 00-80T-109 (See Figure 73). b. Water Contamination Prevention. (See Figure 7-3) Filter/Separators are used to prevent and detect water contamination in aircraft fuels. Filter/Separators are equipped with a number of coalescing-filter elements, which break fuel water emulsions by coalescing filters.

24. FUEL SAMPLING. 25. (Refer to Table 7-3) Fuel samples shall be taken from the fuel cell low point drains as specified in the applicable Maintenance Requirement Card (MRC) deck. a. Acceptable Fuel. As a general rule, acceptable fuel must be clear, bright, and contain no free water. The terms clear and bright are independent of the normal color of fuel. Clear means highly transparent and refers to the absence of any cloud, emulsion, or readily visual particulate matter Bright refers to the shiny appearance of clean dry fuels. A cloud, haze, specks of particulate matter, or unusual color indicates that the fuel is unsuitable and a possible breakdown in fuel handling equipment and/or procedures. Refer to Table 7-3 for acceptable limits. b. Sampling Procedures. Sampling procedures are as follows:

NOTE Obtain fuel samples from the fuel truck prior to refueling.

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Only trained and experienced personnel shall take samples.

NOTE

Improper containers and poorly drawn or handled samples can result in meaningless or misleading results.

If dark colored stringy or fibrous material that tends to float in the fuel is noted in any sample, immediately forward the sample(s) to the nearest Navy Petroleum Laboratory for microbiological growth determination.

Personnel taking samples shall have clean hands; clean gloves may be worn in cold weather. (1) Ensure exterior of low point drain is cleaned prior to taking sample. (2) Drain off one pint from low point drain using a one-quart, clear, clean glass container. (3) Inspect sample for loose drops of water puddled under the fuel.

(4) If water is detected, discard sample and repeat step (1) and (2) until no water is found. (5) Swirl the sample by briskly rotating the container. (6) If water is visible under the swirling vortex, draw another sample and reinspect.

Figure 7-2. Enlargement of Small Particles and Comparison to Human Hair

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Figure 7-3. Filter/Separators (7) Inspect fuel sample for any discoloration, cloudiness, and loose sediment under the swirling vortex.

NOTE A small amount is described as a spot of silt, which would be no more than a slight smudge if picked up on a finger tip. Ensure container is thoroughly cleaned and rinsed before retesting. (8) If small amounts of particulate material are noted, the sample shall be discarded and another drawn and re-inspected. (9) If relatively large quantities of water or foreign matter are noted, or small amounts persist from one or more cell drains, perform the following: (a) Ground the aircraft. (b) Retain the fuel samples. (c) Defuel the aircraft. (d) Immediately investigate the aircraft fuel system and components to determine the source of contamination. (e) If the source of contamination is not isolated to the aircraft, notify the cognizant fuel handling activity. The source of contamination shall be identified.

(f) Forward samples to the nearest Navy Petroleum Laboratory for analysis. NAVAIR 00-80T-109, Aircraft Refueling NATOPS Manual, identifies these laboratories and the approved shipping containers. c. Testing for Salt Water Contamination. If the fuel sample is suspected of being contaminated with salt water, save initial samples of fuel containing water and immediately ground the affected aircraft. Conduct a salt water test as follows: (1) Drain off one pint into clear, clean, one-quart glass or polyethylene container. (2) Obtain 0.1 normal solution of Silver Nitrate in a laboratory type dropping bottle.

NOTE For comparison purposes, it is recommended that this test be conducted on known samples of natural seawater as well as on fresh (tap) water. The addition of the silver nitrate solution to tap water also will result in a white precipitate, but it will be different from the precipitate formed in seawater. (3) Add one drop at a time (not to exceed three drops per pint) of silver nitrate solution to the fuel/water mixture. If the water or water layer contains dissolved sea water salts, the first drop of silver nitrate

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solution will pass through the fuel layer and penetrate the water layer. Here it will produce a while precipitate (silver chloride) which is indicative, of saltwater contamination.

(6) If the contamination is not isolated to the aircraft, notify the cognizant activity. The source of contamination shall be identified.

(4) If salt water is detected, perform decontamination procedures in accordance with Work Package 008.

26. Send the contaminated samples to the nearest Navy Petroleum Testing Laboratory for testing. NAVAIR 0080T-109 identifies these laboratories and the approved shipping container.

(5) Repeat steps (2) through (4) twice.

Table 7-3. Visual Contamination Contaminant 1.

Appearance

Characteristics

Effects on aircraft

Acceptable limits

a. Dissolved water

Not visible.

Fresh water only. Precipitates out as cloud when fuel is cooled.

None unless precipitated out by cooling of fuel. Can then cause ice to form on low pressure fuel filters if fuel temperature is below freezing.

Any amount up to saturation.

b. Free water

A light or heavy cloud; droplets adhering to sides of bottle; gross amounts settled in bottom.

Free water may be saline water or fresh water. Cloud usually indicates water-in-fuel emulsion.

Icing of fuel system; usually low pressure fuel filters. Erratic fuel gauge readings. Gross amounts of water can cause flame-outs. Seawater will cause corrosion of fuel system components.

Fuel must contain no visually detectable free water.

a. Rust

Red or black powder, rouge, or grains. May appear as dye-like material in fuel

Red rust (Fe203) or black rust (Fe304); rust generally comprises major constituent of particulate matter.

Will cause sticking, and sluggish or general malfunction of fuel controls, flow dividers, pumps, nozzles, etc.

Fuel must be clean within limits of paragraph 3-7a.

b. Sand or dust

Crystalline, granular, or glass-like.

Usually present and occasionally constitutes major constituent.

Will cause sticking, and sluggish or malfunction of fuel controls, flow dividers, pumps, nozzles, etc.

Fuel must be clean within limits of paragraph 3-7a.

c. Aluminum or Magnesium compounds

White or gray powder or paste.

Sometimes very sticky or gelatinous when wet with water. Usually present and occasionally represents major constituent.

Will cause sticking and sluggish or general malfunction of fuel controls, flow dividers, pumps, nozzles, etc.

None

Water

2. Particulate Matter

NAVAIR 01-1A-35

007 00 Page 9 Table 7-3. Visual Contamination - Continued

Contaminant

Appearance

Characteristics

Effects on aircraft

Acceptable limits

3. Microbiological Growth

Brown, gray, green, or black; stringy or fibrous.

Usually found with other contaminants in the fuel. Very light weight; floats in fuel longer than water droplets or solid particles. Develops only when free water is present.

Fouls fuel quantity probes, sticks flow dividers, makes fuel controls sluggish.

None visible.

a. Water-in-fuel

Light cloud or heavy cloud.

Finely divided drops of water in fuel. Same as free water cloud. Will settle to bottom in minutes, hours, or weeks depending upon nature of emulsion.

Same as free water.

Fuel must contain no visuallydetectable free water.

b. Fuel and water stabilized

Reddish, brownish, grayish, or blackish; sticky material variously described as gelatinous, gummy, or like catsup or mayonnaise.

Finely divided drops of fuel in water. Contains rust or microbiological growth which stabilizes or "firms" the emulsion. Will adhereto many materials normally in contact with fuels. Usually present as "globules" or stringy, fibrous-like material in clear or cloudy fuel. Will stand from days to months without separating. This material contains half to threefourths water, a small amount of fine rust or microbiological growth, and is one-third to one-half fuel.

Same as free water and sediment, only more drastic. Will cause filter plugging and erratic readings in fuel quantity probes

None visible.

4. Emulsions

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007 00 Page 10 Table 7-3. Visual Contamination - Continued

Contaminant

Appearance

Characteristics

Effects on aircraft

Acceptable limits

a. Interface material

Lacy bubbles or scum at interface between fuel and water; sometimes resembles jellyfish.

Extremely complicated, chemically. Occurs only when emulsion and free water are present.

Same as microbiological growth.

There should be no free water.

b. Air Bubbles

Cloud in Fuel

Disperses upward within a few seconds.

None

Any amount.

5. Miscellaneous

NAVAIR 01-1A-35

008 00

31 August 2005

Page 1 of 6

MAINTENANCE INSTRUCTIONS

DECONTAMINATION PROCEDURES

Reference Material Organizational, Intermediate and Depot Maintenance Preservation of Naval Aircraft ......................... NAVAIR 15-01-500 Aircraft Weapons Systems Cleaning and Corrosion Control ............................................................... NAVAIR 01-1A-509

Alphabetical Index Subject

Page

General ................................................................................................................................................................................. 1 General Decontamination Procedures ....................................................................................................................... 1 Salt Water Contamination Isolation........................................................................................................................... 1 Microbiological Growth Decontamination Procedures ........................................................................................................ 3 Cleaning Fuel Cells ................................................................................................................................................... 4 Component Cleaning ................................................................................................................................................. 3 Component Removal and Inspection......................................................................................................................... 3 Defueling ................................................................................................................................................................... 3 Intricate Component Cleaning................................................................................................................................... 3 Rinsing, Draining, and Drying Components.............................................................................................................. 4 Salt Water Decontamination Procedures.............................................................................................................................. 2 Decontamination of Intermediate and Depot Level Repairable Fuel System Components....................................... 2 Decontamination of Organizational Level Repairable Fuel System Components......................................................... 2 Defueling ................................................................................................................................................................... 2 Flushing the Fuel System .......................................................................................................................................... 2

1.

GENERAL.

2. General decontamination procedures, salt water contamination isolation, and decontamination procedures required for salt water contamination and for microbiological growth are described separately in this section. a. General Decontamination Procedures. General decontamination procedures are as follows:

(2) Remove components, which require decontamination.

NOTE Ultrasonic cleaning equipment can shorten soaking time considerably. (3) Soak components in a hot cleaning solution. (4) Scrub components to remove residual salt deposits and/or for microbiological growth.

Saltwater in particular will rapidly corrode metallic components. Initiate decontamination procedures immediately after contamination is located and isolated. (1) Defuel, depuddle, and purge the fuel system in accordance with WP 006 and the general safety procedures described in WP 004 and 003.

NOTE Residues from the water emulsion cleaning compounds feed microbiological growth. (5) Rinse components thoroughly after cleaning. b. Salt Water Contamination Isolation. To isolate salt water contamination, proceed as follows:

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008 00 Page 2

NOTE Saltwater contamination does not necessarily progress immediately to the engine fuel system.

Ensure that cellulose sponges are in good condition when inside a fuel cell or tank. To prevent a fire hazard, cellulose sponges and cheesecloth used for cleaning fuel cells or tanks shall be disposed of in accordance with local safety instructions.

(1) Fuel sampling procedures. (a) Take fuel samples from the engine fuel system. Begin with the main filters. (b) Continue to sample upstream in the fuel system until contamination is found. (2) Fuel testing. Test fuel samples for saltwater contamination in accordance with WP 007.

(6) Remove residual fuel using an explosion-proof vacuum cleaner, or cellulose sponges, L-S-00626, and cheesecloth, CCC-C-440.

NOTE Disconnect the engine fuel system to prevent contamination of engine fuel system components prior to fuel cell and aircraft plumbing decontamination procedures.

Use an explosion-proof vacuum cleaner or attach cellulose sponge or cheesecloth to a wooden handle to reach remote areas.

3. SALT WATER DECONTAMINATION PROCEDURES.

(7) Inspect fuel cells for leaks, corrosion, scum from seawater, residues, and microbiological growth as described in WP 007. If any of these conditions are present, treat in accordance with 6b through 6f of this work package.

4. The following paragraphs provide procedures for decontaminating the fuel system of salt water.

(8) If none of these conditions are present, comply with paragraph 4-3f, steps (11) through (27).

a. Defueling. Defuel the aircraft in accordance with WP 006 and proceed as follows:

c. Decontamination of Organizational Level Repairable Fuel System Components. To decontaminate fuel system components repairable at the organizational level, proceed as follows:

(1) Drain remaining fuel using low point drains. (2) If contaminated, drain engine fuel system. b. Flushing the Fuel System. To flush the system, proceed as follows:

(1) Remove components, which cannot be inspected in place. (2) Disassemble only enough to allow inspection. (3) Inspect for corrosion. (4) Correct any damage.

Comply with general safety instructions in WP 003, and fuel cell entry preparations in WP 004 and WP 006.

d. Decontamination of Intermediate and Depot Level Repairable Fuel System Components. To decontaminate fuel system components repairable at the intermediate and depot level, proceed as follows:

(1) Remove fuel cell access plates. (2) Remove only those components necessary to provide maximum access.

(1) Remove metering devices and other components. (2) Flush with fresh water, drain, and dry.

(3) Rinse thoroughly with fresh water to ensure all salt water contamination is removed. (4) Open all cells as soon as possible after flushing. (5) Remove access plates, probes, pumps, and fittings for maximum visual inspection of interior areas.

Corrosion Preventive Compound MIL-DTL-81309

1

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008 00 Page 3 NOTE

(3) Preserve with water displacing corrosion preventive compound, MIL-DTL-81309.

Except for fuel quantity indicator probes, which, shall always be removed and cleaned, the extent of further component removal shall be determined by evidence of a need for a more in depth inspection of a component.

(4) Tag with notation, "Contaminated internally with sea water." (5) Forward to the designated rework facility for rework.

NOTE To ensure prompt treatment at the rework facility, install water-crash/fire-damage label on outer shipping container in accordance with NAVAIR 15-01-500, Preservation of Naval Aircraft. 5. MICROBIOLOGICAL GROWTH AND PARTICULATE DECONTAMINATION PROCEDURES. 6. The following paragraphs provide procedures for decontaminating the fuel system of microbiological growth, as described in Work Package 007. This procedure may also be used for removal of particulate contamination, for example fuel cell foam debris, from the fuel system. a. Defueling. Defuel, depuddle, and purge fuel system in accordance with Work Package 006 and the safety procedures described in Work Package 004. b. Component Removal and Inspection. Remove and inspect components as follows:

Comply with general safety instructions in WP 003, and fuel cell entry preparations in WP 004 and WP 006. (1) Remove only those components as required to gain access to all areas, which may have collected microbiological growth. (2) Inspect for saltwater deposits, microbiological growth, or hidden corrosion. (3) Inspect capacitance-type fuel quantity indicator probes. (4) Inspect internal plumbing. (5) Inspect valves. (6) Inspect electrical wiring. (7) Inspect float switches.

c.

Component Cleaning.

Cleaning Compound MIL-PRF-85570

2

(1) Prepare water emulsion cleaning solution by adding one part by volume of cleaning compound, MILPRF-85570, Type II, to nine parts of fresh water.

To prevent possible damage to fuel system nonmetallic components, solution temperature shall not exceed 120oF (49oC). (2) Scrub components with hogbristle brush, H-B420 (Table 2-5, Item 3c), in hot solution. d. Intricate Component Cleaning. For electrical wiring, fuel quantity indicator probes, fittings. plumbing lines, and any intricate components which cannot be effectively cleaned as above, proceed as follows:

Organic solvents are flammable. Avoid breathing of vapors or prolonged skin contact. Use personal protective equipment.

NOTE If possible solution should be heated and maintained at 120oF (49oC) temperature. (1) Immerse in solution for approximately 10 minutes to 3 hours.

NOTE Ultrasonic cleaning equipment can shorten soaking time considerably.

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008 00 Page 4

(2) If ultrasonic equipment is available, proceed as follows: (a) Fill cleaning tank with the solution. (b) Immerse components in solution. (c) Operate ultrasonic equipment until all surfaces are clean. e.

Rinsing, Draining, and Drying Components.

(1) When all residues have been loosened, rinse thoroughly with water until all components are clean. (2) Drain; rotating components for complete draining. (3) Place components in drying ovens at 120oF (49 C) maximum for 12 hours. o

(4) If ovens are not available, proceed as follows:

(2) Inspect bladders and self-sealing cells for cell liner porosity, deterioration, punctures and tears. (3) If leaks are suspected, inspect airframe cavity liners and cavities when cell is removed for repair or replacement. (4) If authorized repair does not require cell removal, disassemble and loosen cell sufficiently to examine for liquid entrapment and corrosion damage. (5) If cavity liner or cavity is wet, remove residual fuel or water using an explosion-proof vacuum cleaner, cellulose sponges, L-S-00626 (Table 2-5, Item 3g), and cheesecloth, CCC-C-440 (Table 2-5, Item 3f). (6) Purge cavity in accordance with Work Package 006. (7) Treat corrosion in accordance with the applicable aircraft MIM and NAVAIR 01-1A-509, Aircraft Weapons Systems Cleaning and Corrosion Control. (8) Open fuel cells low point drains to permit free drainage.

Isopropyl Alcohol TT-I-735

3

(a) Immerse components in undiluted Isopropyl Alcohol, TT-I-735, for approximately 1 minute. (b) Blow dry with clean compressed air at low pressure not to exceed 30 psi. (5) Test fuel quantity probes electrically in accordance with the applicable Maintenance Instruction Manual (MIM). If failed, install new fuel quantity probes. f. Cleaning Fuel Cells. To clean fuel cells, proceed as follows:

(9) Flush and rinse interior of fuel cells with fresh warm water, if available. (10) Continue flushing and rinsing until all foreign matter and cleaning compound residues are removed, or until discharge is clear.

Isopropl Alcohol TT-I-735

3

NOTE A pump and an extension hose may be used to apply the water/alcohol solution. (11) Flush fuel cells with a mixture of one part Isopropyl Alcohol, TT-1-735, and one part tap water.

NOTE Organic solvents are flammable. Avoid breathing of vapors or prolonged skin contact. Use personal protective equipment.

NOTE Efficient scrub brushes may be prepared by trimming bristles of 4-inch hog bristle paint brushes, H-B-420 to approximately one-half the normal length. Brushes may be attached to wooden handles for reaching remote areas. (1) Scrub contaminated areas and all interior areas thoroughly with water-emulsion cleaning solution until all residues have been loosened.

To allow removal of solution from hidden or inaccessible areas formed by bulkheads, baffles, stiffeners, etc.; alter attitude of aircraft by inflating and deflating gear struts, or using jacks in accordance with the applicable MIM. (12) Remove residual solution using explosion-proof vacuum cleaner, cellulose sponges, and cheesecloth.

NOTE Warm air drying can be accomplished using the Blow Purge method in accordance with Work Package 006.

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008 00 Page 5/(6 Blank)

(13) Remove all visible traces of solution by passing warm, dry air 120oF (49oC) maximum through fuel cells for approximately 8 to 12 hours. To ensure adequate drying of fuel cell, perform the following procedures.

NOTE Exit opening should be large enough to allow for ready escape of water/alcohol vapors and prevent pressure buildup in the fuel cells. (a) Close cell, except for two openings located as far apart as possible, one for the entry, and one for the exit of hot air. (b) When possible during the last part of the drying operation, close off the exit. (c) Ensure fuel boost and transfer pump ports are adequately dried by directing air through them.

NOTE Unless the deposits are so extensive that reflushing with water is required, additional forced air drying is not necessary. (14) Inspect fuel cells for evidence of salt crystals.

(15) Remove this residue by swabbing with sponges dampened with the 50 percent water/alcohol solution. (16) Inspect for corrosion. (17) Treat all corroded areas in accordance with the applicable MIM and NAVAIR 01-1A-509, Aircraft Weapons Systems Cleaning and Corrosion Control. (18) Inspect condition of sealant on integral fuel cell. (19) Repair or replace, as necessary, all sealant coatings in accordance with the applicable MIM. (20) Functionally check all electrical equipment before installation, in accordance with the applicable MIM. (21) Reassemble fuel system as soon as possible after cleaning, drying, and sealant replacement. (22) Change all fuel filters. (23) Close all low point drains. (24) Refuel aircraft to normal operating capacity in accordance with the applicable MIM. (25) Wait a minimum of 4 hours. (26) Take fuel samples from the low point drains. (27) Inspect fuel samples in accordance with Work Package 007.

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MAINTENANCE INSTRUCTIONS FUEL CELL FOAM BAFFLES

Reference Material None

Alphabetical Index Subject

Page

Foam Baffle Maintenance Procedures.................................................................................................................................. 1 Foam Baffle Drying................................................................................................................................................... 3 Foam Baffle Extended Storage .................................................................................................................................. 3 Foam Baffle Inspection ............................................................................................................................................. 2 Foam Baffle Installation ............................................................................................................................................ 3 Foam Baffle Preliminary Removal Procedures ......................................................................................................... 1 Foam Baffle Removal................................................................................................................................................ 1 General ................................................................................................................................................................................. 1 1. GENERAL The fuel cell foam baffles are constructed of polyurethane reticulated foam. Reticulated foam is used in fuel cells to reduce the probability of fire or explosion in the event of damage from combat or crash. 2. FOAM BAFFLE MAINTENANCE PROCEDURES. The following paragraphs provide maintenance procedures for foam baffles. a. FOAM BAFFLE PRELIMINARY REMOVAL PROCEDURES. Preliminary removal procedures for foam baffles are as follows: (1) Defuel, depuddle and air purge in accordance with Work Package 006, and comply with general safety instructions in Work Package 003 and 004, and the applicable aircraft Maintenance Instruction Manual (MIM).

(2) After the EA has classified the fuel cell Condition is in "SAFE For Personnel - NOT Safe For Hot Work" condition in accordance with general safety procedures in Work Package 004, remove or install foam baffles.

NOTE A provisional certificate may be issued for removal of foam from cells that cannot be purged below safe limits. The Entry Authority shall recommend safe entry instructions in this condition including mandating respiratory equipment and PPE.

Comply with general safety instructions in Work Packages 003 and 004, and fuel cell entry preparations in Work Package 006.

The vapor concentration test of atmosphere in the fuel cell, taken to certify appropriate safe condition, must be performed by an Entry Authority (EA), as described in Work Package 004

(3) Initiate air purging in accordance with Work Package 006. Continue to purge while personnel are inside or partially inside fuel cells.

The air-supplied respirator shall be worn when removing foam baffles from fuel cells.

b. FOAM BAFFLE REMOVAL. General removal procedures for foam baffles are as follows:

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009 00 Page 2 NOTE

Comply with general safety instructions in Work Packages 003 and 004, and fuel cell entry preparations in Work Package 006.

NOTE Refer to applicable aircraft Maintenance Instruction Manual (MIM) for procedures unique to a particular aircraft fuel cell.

Discoloration of the foam material is not necessarily cause for rejection, since normal aging and exposure to fuel will cause the foam to darken. The foam baffles, which are located in low areas of a fuel cell will be more susceptible to contamination than those in other areas. (1) Inspect the foam material for foreign particles or contamination.

(1) Perform preliminary procedures (Refer to paragraph 2a).

The use of cotton gloves shall be avoided because they can contaminate the foam with lint. Rubber gloves shall be worn for removal, handling, and installation of foam material. Use of barrier creams is also recommended. Cotton coveralls must be worn inside fuel cells. Coveralls and clothing may get soaked with fuel or purging oil. Protect skin with barrier creams and PPE (gloves, knee pads, etc) (2) Use rubber gloves, MIL-DTL-32066 (Table 2-6, Item 6j), to remove foam baffles. (3) Remove baffles from fuel cell; compress as necessary. (4) Inspect identification markings on baffles for legibility.

NOTE Baffles should be dry before marking (Refer to paragraph 2e). (5) If identification markings are not legible, remark using felt-tip marker, GG-M-00114, as specified in applicable MIM.

Do not modify vacuum cleaner hose with metal extensions. (2) Remove foreign particles by hand or with explosion-proof vacuum cleaner, (Table 2-5, Item 2b). (3) Replace foam baffle if it cannot be easily cleaned. (4) Replace foam baffle if evidence of loose strands of foam material are found in open network.

NOTE A small piece of unused baffle material may be used for comparison. (5) Pull or tear a few strands of the baffle using fingers. If foam strands tear easily, replace baffle. (6) Repeat step (e) at various points on the surface of the baffle. (7) Store the baffles in flexible electrostatic-free waterproof/Vaporproof barrier material, MIL-PRF-81705 (Table 2-5, Item 10c). (8) Seal barrier material with tape, PPP-T-60.

c. FOAM BAFFLE INSPECTION. General inspection procedures for foam baffles are as shown:

Do not wash foam baffles with water or emulsion cleaners.

Store fuel cell foam baffles in accordance with sound fire prevention practices, coordinated with the station Fire Department. Fire or explosion may otherwise result.

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009 00 Page 3

Drying of fuel cell foam baffles shall be accomplished in clean well-ventilated areas. Fire or explosion may otherwise result. Do not use electric knives in fuel cell maintenance areas. Fire or explosion may otherwise result.

Drying of fuel cell foam baffles shall be accomplished in clean well-ventilated areas. Fire or explosion may otherwise result.

(9) Remove baffles from fuel cell maintenance area until ready for installation.

f. FOAM BAFFLE-LOCAL MANUFACTURING. Replacement foam baffles can be manufactured locally. Replace damaged, contaminated, and deteriorated baffles. To manufacture replacement baffles, proceed as follows:

d. FOAM BAFFLE EXTENDED STORAGE. General procedures for extended storage of foam baffles are as follows:

Store fuel cell foam baffles in accordance with sound fire prevention practices, coordinated with the station Fire Department. Fire or explosion may otherwise result.

Do not use electric knives in fuel cell maintenance areas. Fire or explosion may otherwise result.

NOTE

Drying of fuel cell foam baffles shall be accomplished in clean well-ventilated areas. Fire or explosion may otherwise result.

It is essential that original cutout design in the damaged baffle be followed in making the replacement baffle.

Do not use electric knives in fuel cell maintenance areas. Fire or explosion may otherwise result.

(1) Make a replacement baffle from polyurethane foam, MIL-DTL-83054 (Table 2-5, Item 12e), using an electric carving knife.

(1) Perform drying procedures (Refer to paragraph 2e). (2) Store baffles in flexible electrostatic-free waterproof/vaporproof barrier material, MIL-PRF-81705 (Table 2-5, Item 10c). (3) Seal barrier material with tape, PPP-T-60. (4) Store baffles in accordance with sound fire prevention practices and coordinated with Station Fire Department. e. FOAM BAFFLE DRYING. Drying may be achieved by static exposure to air or by blowing air through the baffles using one of the following blowers: Hot-Air Blower Assembly, MMEP12B Air Blower, MIL-B-7619 Pneumatic Driven Fan, APV-12

(2) Mark replacement baffle with same identification as the damaged baffle using felt-tip marker, GG-M00114. (3) Verify correct identification number on the baffle (Refer to the applicable MIM). g. FOAM BAFFLE INSTALLATION. General installation procedures for foam baffles are as follows:

The vapor concentration test of atmosphere in the fuel cell, taken to certify appropriate safe condition, must be performed by an Aviation Confined Space Program Manager (ACSPM) or Entry Authority (EA), as described in Work Package 004.

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009 00 Page 4

The air-supplied respirator shall be worn when removing foam baffles from fuel cells. Comply with general safety instructions in Work Packages 003 and 004, and fuel cell entry preparations in Work Package 006.

Rubber gloves shall be worn for removal, handling, and installation of foam material. (4) Use rubber gloves, MIL-DTL-32066 (Table 2-6, Item 6j), to install foam baffles. (5) Install baffles in accordance with specific instructions in the applicable MIM.

NOTE Refer to applicable aircraft MIM for procedures unique to a particular aircraft fuel cell. (1) Perform preliminary procedures (Refer to paragraph 2a). (2) Inspect interior of the fuel cell for foreign material. (3) Verify all lines, fittings, and components inside fuel cell are properly installed.

(6) Inspect fuel cell for contamination or foreign matter.

If new baffles are installed or 25 percent or more of the baffling material has been removed, the fuel system should be flushed. (7) Remove foam particles from fuel cell by wiping with lint free cloth and/or by explosion proof vacuum. Flush fuel cell in accordance with decontamination procedures in Work Package 008, paragraph 5. (8) Fill fuel cell with clean fuel. (9) Take a low-point drain sample for solid contamination analysis.

Correct positioning of foam baffles in the fuel cell is extremely important. Some foam baffles have slots and holes to accommodate lines and components. Ensure these blocks are property installed. The use of cotton gloves shall be avoided because they can contaminate the foam with lint.

NOTE Maximum acceptable increase in solid contamination is 0.52 mg per liter over that serviced to the aircraft during fueling. (10) Perform fuel sample analysis to determine if contamination exists in accordance with Work Package 007.

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31 August 2005

Page 1 of 14

MAINTENANCE INSTRUCTIONS FUEL CELL REMOVAL, INSTALLATION, PRESERVATION, AND PACKAGING FOR SHIPMENT AND STORAGE

Reference Material None

Alphabetical Index Subject

Page

Fuel Cell Installation.............................................................................................................................................................6 Fuel Cell Maintenance Procedures .......................................................................................................................................1 Fuel Cell Fitting Torque Requirements......................................................................................................................2 Fuel Cell Handling Precautions .................................................................................................................................1 Fuel Cell Restoring ....................................................................................................................................................2 Fuel Cell Safety-Wiring Procedures ..........................................................................................................................2 Fuel Cell Uncrating....................................................................................................................................................2 Fuel Cell Packaging For Shipment and Storage ...................................................................................................................7 Bladder Fuel Cell Packaging For Shipment and Storage .........................................................................................11 Damaged Bladder-Type Fuel Cell Packaging For Delivery to Supply ......................................................................7 Self-Sealing Fuel Cell Packaging For Delivery to Supply.........................................................................................8 Self-Sealing Fuel Cell Packaging For Shipment and Storage ..................................................................................12 Fuel Cell Preservation...........................................................................................................................................................7 Fuel Cell Removal ................................................................................................................................................................4 Fuel Cell Storage ................................................................................................................................................................12 General..................................................................................................................................................................................1 Shipping Container Markings.............................................................................................................................................12

1. GENERAL These general procedures should be used during the removal, installation, preservation, and packaging for shipment and storage of self-sealing and bladder fuel cells. Refer to the applicable aircraft Maintenance Instruction Manual (MIM) for specific maintenance instructions. 2. FUEL CELL MAINTENANCE PROCEDURES. The following paragraphs provide general fuel cell maintenance procedures. a. Fuel Cell Handling Precautions. Damage to fuel cells most often occurs during handling. Observe the following precautions during removal, installation, packaging, and shipment: Transport cell on a well-padded truck or dolly, or carry by hand. Do not use fuel cell fittings for hand holds.

Do not drag or tumble a fuel cell. During cold weather warm fuel cell and aircraft cavity to at least 60oF (16oC) before working with the fuel cell. Avoid using unnecessary pressure to collapse cell into a smaller package. Do not fold cell across or beside any of its fittings. Do not leave a self-sealing fuel cell in a collapsed condition for more than one hour. Do not rest a cell on sharp objects, on table corners, on edges of a cavity, or on it's own fitting. Install protector caps on cell fittings when cell is removed.

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010 00 Page 2

When working on a cell, cover worktable or floor with barrier material, MIL-B-121 (Table 2-5, Item 10a), or polyethylene film, L-P-378 (Table 2-5, Item 10l).

(3) Inspect threaded inserts for corrosion preventive compounds or dirt. (4) Install all bolts in place fingertight. (5) Torque bolts to 3/4 of final torque value.

NOTE Shipping containers may be stored and reused. b. Fuel Cell Uncrating. Refer to the crate opening instructions attached to the shipping container. c. Fuel Cell Restoring. The following procedures will restore fuel cells that have shrunk or become distorted in storage. (1) Perform uncrating procedures, if needed.

Do not overtorque, or damage to equipment may result. (6) Re-torque to final torque value, using the following values:

NOTE

(a) Bolts installed in molded fittings with metal inserts should be torqued to 20 to 30 inch-pounds for selfsealing fuel cells.

Soaking time can be reduced by placing cell in an air circulating oven at a maximum of 120oF (49oC) for 4 hours, maintaining a high humidity.

(b) Lightweight fittings (fabric and rubber cured on the nut ring or compression ring) on bladder fuel cells should have bolts torqued to 40 to 50 inch-pounds.

(2) Soak cell for 48 to 72 hours in water at 70oF o (21 C) minimum. d. Fuel Cell Fitting Torque Requirements. Refer to the applicable aircraft MIM for specific instructions. The following general torquing procedures may be used if no specific instructions are given.

Use proper torque sequence throughout procedure or fuel leaks may result. (1) Mark the sequence pattern by each hole using white marking pencil, SS-P-196 or A-A-87 (See Figure 10-1). (2) Inspect attaching hardware for defects and correct length.

(c) O-Ring fittings have a metal surface that has an O-ring groove and a flat area which mates with an attaching cover. The O-ring is compressed and the metal surfaces are drawn together by the securing bolts. Bolts used on O-ring type fittings should be torqued to 50 to 70 inch-pounds. (d) Safety-wire bolts as required (Refer paragraph 2e and Figure 10-2). e. Fuel Cell Safety-Wiring Procedures. Refer to the applicable aircraft MIM for specific instructions. Wire shall conform to MS20995. If specific instructions are not provided, use the following general instructions: (1) Double twist wiring two or more bolts at a time (See Figure 10-2). (2) Where it is difficult to double twist wire, single strand wiring is permissible. Single strand wiring requires the bolt holes to be aligned so that the single-strand wire may be passed through the holes without becoming kinked.

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Figure 10-1. Torque Pattern for Bolts

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010 00 Page 4

3. FUEL CELL REMOVAL. moval procedures are as follows:

General fuel cell re-

Comply with general safety instructions in Work Package 004, and fuel cell entry preparations in Work Package 006. The air-supplied respirator shall be worn when entering a fuel cell. Ensure continuous ventilation when working inside a fuel cell.

Lubricating oils may cause eye, skin, and respiratory irritation. Use personal protective equipment.

Keep external surface of cells free of oil, grease, fuel, or solvent.

NOTE For specific instructions for a particular fuel cell and cavity, refer to the applicable aircraft MIM.

j. If a defueled cell will not contain fuel for at least 72 hours, perform preservation procedures (Refer to paragraph 5).

Upon removal of fuel cells, inspect fuel cell cavity condition and prep per aircraft MIM. Ensure Fuel Cell support foam is in good condition and replace if necessary per aircraft MIM. a. Defuel, depuddle, and purge the fuel cell in accordance with Work Package 004 and 006, and the applicable aircraft MIM. b. Continuous air purge shall be initiated and maintained while personnel are working inside or partially inside fuel cell (Refer to Work Package 006). c. Remove all interior components, lines, clamps, fittings, and plates from cell.

Fuel cells are easily damaged. Use caution when cutting nylon lacing cord. k. Untie and remove lacing cord. If cord is cut during removal, retain old cord to determine length of replacement cord. l. Disengage hangers and install lifting device, if necessary. m. Cover any sharp edges of airframe access opening with anti-chafing tape, SJ-8561 (Table 2-5, Item 11a).

d. Cap or plug all lines, fittings, and components removed from the cell to prevent contamination. e. Place removed items in a separate container for each cell, and identify with serial number of the cell and aircraft bureau number. f. If possible, locate and mark with a yellow crayon, A-A-2360 (Table 2-5, Item 7a), any damaged areas that show evidence of leakage. g. If the sealant layer is exposed, cover with tape, MIL-T-22085 or AMS-T-22085 (Table 2-5, Item 11c). h.

Disconnect cell fittings and interconnects.

i. Verify that all hardware is removed and cell is ready for removal.

Do not allow a self-sealing fuel cell to remain in collapsed or folded condition for longer than one hour without changing the position of the folds.

NOTE Different cells require different ways of folding. Refer to the applicable aircraft MIM for specific folding techniques. n. Fold as necessary for ease of removal. Avoid unnecessary folding.

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Figure 10-2. Securing Screws, Nuts, Bolts, and Snap Rings

Do not force the fuel cell out of the cavity, or damage to fuel cell may result. o.

Ease the cell out of the aircraft cavity.

p. If cell needs to be collapsed completely, use these general procedures and refer to the applicable aircraft MIM for specific instructions:

Do not modify vacuum cleaner hose with metal extensions. (1) Use explosion-proof vacuum cleaner (Table 25, Item 2b) to collapse the cell. (2) Remove cell from cavity. (3) Remove vacuum as soon as possible to prevent cracking in the nylon barrier.

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010 00 Page 6

NOTE If appropriate dollies are not available, brace fuel cell as per packing procedures (Refer to paragraph 6). q. Transfer the self-sealing or combination bladder/self-sealing fuel cell to a special dolly that conforms to the cell shape. r. Bladder fuel cells shall be placed bottom down on a sheet of polyethylene film, L-P-378 (Table 2-5, Item 10.l). s. rally. t.

Do not use cell fittings for hand holds or for lifting. Use of fittings for lifting purposes could distort fittings, and render the cell unserviceable. k.

Attach lifting device to cell, if required.

l. Cover all sharp edges of airframe access opening with anti-chafing tape.

Unfold the fuel cell and allow it to collapse natu-

m. Fold cell, if required, so that it may be inserted in cavity and can be unfolded in the correct position.

Straighten folds to prevent creasing the fuel cell.

n. Insert cell in cavity and assure proper position so that excess pulling and strain will not be required.

4. FUEL CELL INSTALLATION. General fuel cell installation procedures are as follows:

NOTE

NOTE

Ensure hangers and fittings are positioned properly for installation.

For specific instructions for a particular fuel cell, refer to the applicable aircraft MIM.

o.

a. Visually inspect the aircraft cell cavity for foreign matter, burrs, sharp edges, cracks, and corrosion. b. jects.

p. Hang cell in cavity and complete installation of cell and components in accordance with the procedures given in the applicable aircraft MIM.

Vacuum cell cavity for small pieces of foreign ob-

c. Apply anti-chafing tape, SJ-8560 (Table 2-5, Item 11a), as required to protect fuel cell from protruding objects.

Comply with general safety instructions in Work Package 004, and fuel cell entry preparations in Work Package 006.

d. Place fuel cell on barrier material, MIL-B-121, or 6 mil. polyethylene film, L-P-378. e. Carefully unfold cell and smooth any folds or creases. f. Inspect cell inner liner and outer surface for defects, especially in folded areas. g. Remove protective covers or plastic coating from metal cell fittings.

Dry Cleaning Solvent MIL-PRF-680

4

h. Clean fittings with dry cleaning solvent, MILPRF-680 Type II or III. i. Inspect fitting for cracks, burrs, corrosion, and warpage before installation. j.

Unfold cell in correct position.

Install hardware using new gaskets and seals.

The air-supplied respirator shall be worn when entering a fuel cell. Ensure continuous ventilation when working inside a fuel cell. q. Inspect the interior and accessible exterior of the cell for damage that may have occurred during installation. r.

Remove all foreign material.

s. Wipe interior of cell with cheesecloth, CCC-C440 (Table 2-5, Item 3f), dampened with water to remove any residual dirt and lint. t. Perform a thorough inspection of the cell for damage or foreign matter. u. Remove tape used to cover sharp edges of airframe access opening. v. Unless required to be left open for the fuel cell leak check, install cavity access plates or covers.

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010 00 Page 7 6. FUEL CELL PACKAGING FOR SHIPMENT AND STORAGE. Packaging procedures for fuel cell shipment and storage are provided in the following paragraphs.

Cold repair fuel cells shall not be fueled until at least 72 hours after completion of repair.

a. Damaged Bladder-Type Fuel Cell Packaging For Delivery to Supply. To package damaged bladder-type fuel cells for delivery to supply, proceed as follows:

w. Fuel the cell and check for leaks in accordance with the applicable aircraft MIM.

(1) Perform preservation procedures (Refer to paragraph 5).

x. Install cavity access plates or covers if not previously installed.

(2) Cover openings of the cell with barrier material, MIL-B-121.

5. FUEL CELL PRESERVATION. Preservation procedures used to protect empty cells from cracking and checking. Preservation procedures for self-sealing and bladder cells are as follows:

T-60.

a. On self-sealing cells, cover exposed sealant with tape, MIL-T-22085 (Table 2-5. Item 11c).

(3) Tape barrier material in place using tape, PPP-

Corrosion Preventive Compound MIL-DTL-85054

6

(4) Preserve metal fittings by coating with preservation compound, MIL-DTL-85054. (5) Place a sheet of barrier material on a clear, swept area. (6) Place the cell bottom down on barrier material.

The air-supplied respirator shall be worn when entering a fuel cell. Ensure continuous ventilation when working inside a fuel cell.

(7) Unfold the cell and allow to collapse naturally. (8) Straighten the folds to prevent creasing.

Lubricating oils may cause eye, skin, and respiratory irritation. Use personal protective equipment. Do not apply pressure to fold as this could result in sharp creases that will damage the cell structure.

Lubricating Oil MIL-PRF-6081

5

NOTE Do not allow oil to puddle. Remove excess with cheesecloth, CCC-C-440. b. Using cheesecloth, brush, or spray, apply a thin uniform coat of lubricating oil, MIL-PRF-6081, Grade 1010, to the interior of the cell. c.

Remove any excess oil using cheesecloth.

(9) Lightly fold the cell according to instructions in the applicable aircraft MIM. (10) Wrap the cell in barrier material and place in fiberboard container, ASTM D5168, or equivalent. (11) Ensure bottom of cell is placed on the bottom of container. (12) Close top of container and mark to indicate "This Side Up". (13) Attach necessary documents to container with tape (do not staple

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010 00 Page 8

(14) Forward cell in container to Supply. b. Self-Sealing Fuel Cell Packaging For Delivery to Supply. To package self-sealing fuel cells for delivery to Supply, proceed as follows:

NOTE

Keep external surface of cells free of oil, grease, fuel, or solvent. (9) Touch up preservation coating as required with lubricating oil, MIL-PRF-6081, Grade 1010.

Use fuel cell shipping containers, if available, as they are designed to provide the support required.

(10) Cover small openings with barrier material. (11) Tape barrier material in place.

(1) Locally manufacture adjustable braces for the fuel cell (See Figures 10-3 and 10-4).

NOTE

(2) If facilities are not available to manufacture the adjustable brace, a substitute can be fabricated from wood as follows (See Figure 10-5):

Insulate fiberboard or plywood, NN-P-530, with barrier material.

(a) Cut a 2" by 2" brace to desired length.

(12) Cover large openings using double-faced corrugated fiberboard or plywood.

(b) Cut two 6 to 8 inch diameter discs from 1/2inch plywood.

Ensure wire does not rub or bear directly on cell outer surface. Wood glue may cause skin irritation. Use either barrier cream or personal protective equipment.

(13) Attach cover using wire or bolts (See Figure 10-6).

(c) Secure a disc at each end of the brace with wood glue, MMM-A-125, and six-penny common nails. (3) Cover the face of the disc that will contact the fuel cell with double-faced corrugated fiberboard, PPP-F320 (See figure 8-4). (4) Wrap disc in barrier material, MIL-B-121. (5) Tape barrier material in place using tape, PPPT-60.

(14) Leave a small vent hole in one opening for atmospheric equalization.

Dry Cleaning Solvent MIL-PRF-680

4

(15) Clean fuel cell metal fittings by wiping with cheesecloth, CCC-C-440, dampened in solvent, MIL-PRF680 Type II or III.

(6) Position a brace every 18 inches vertically and horizontally on each face of the cell (See Figure 10-5 for typical placement). (7) Tie cross braces together for mutual support (See Figure 10-5).

Corrosion Preventive Compound MIL-DTL-85054

6

(16) Preserve metal fittings by coating with corrosion preventive compound, MIL-DTL-85054.

(8) Clean cell interior of all debris.

(17) Wrap cell in barrier material or polyethylene film, L-P-378. Lubricating Oil MIL-PRF-6081

5

(18) Attach necessary document to container with tape and forward cell to Supply.

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010 00 Page 9

Figure 10-3. Adjustable Brace Details

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Figure 10-4. Brace Installation

Figure 10-5. Brace Placement Patterns

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010 00 Page 11

Figure 10-6. Tank Cover Assembly

c. Bladder Fuel Cell Packaging For Shipment and Storage. Packaging procedures for shipment and storage of bladder fuel cells are as follows:

NOTE Mechanical damage to cells is usually due to mishandling in the form of dropping, puncturing, crushing, chafing, etc. It is recommended that bladder cells be braced and suspended instead of folded (Refer to paragraph 6b). (1) Fold as smoothly and lightly as possible. Do not fold cell excessively.

NOTE Cushioning material should be wrapped with barrier material. (2) Cushion inside and outside of folds with mailing tubes, PPP-P-495, or rolled, single-faced corrugated paperboard, PPP-P-291. (3) Wrap the cell in barrier material, MIL-B-121, or polyethylene film, L-P-378. (4) Pack wrapped cell in container conforming to MIL-STD-2073-1.

NOTE Mark container to indicate the presence and type of preservation compound, and method of packing.

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010 00 Page 12 Date of Manufacture (month, year)

(5) Mark shipping container in accordance with paragraph 7.

Name of Cell Manufacturer

d. Self-Sealing Fuel Cell Packaging for Shipment and Storage. Packaging procedures for shipment and storage of self-sealing fuel cells are as follows:

Navy Gas Free Certificate Number

(1) Brace and/or suspend cells to conform to their installed shape (Refer to paragraph 6b).

NOTE

Activity 8. FUEL CELL STORAGE. Fuel cell storage procedures are as follows:

Container shall be determined by the size and weight of the cell and shall conform to MILSTD-2073-1. Shipping containers shall be provided with a liner using barrier material, PPP-B-1055, or MIL-B-13239, in accordance with MIL-L10547.

Protect fuel cells from exposure to prolonged sunlight and heat, or damage to fuel cells may result. Proper storage is critical to prolonging the life of rubber fuel cells. Maintain temperatures of not less than 45 ºF and not greater than 95 ºF. Do not store in direct sunlight. Protect from severe weather conditions.

Cushioning, blocking, bracing, and bolting shall be in accordance with MIL-STD-1186. (2) Pack in shipping containers meeting one of the specifications listed in Table 10-1. (3) Mark shipping container in, accordance with paragraph 7. 7. SHIPPING CONTAINER MARKINGS. Mark all shipping containers in accordance with MIL-STD-129, Standard Practice for Military Packaging. A typical container marking is as follows: Fuel cell: Self-sealing, aircraft Aircraft model fuel cell is intended for

a. Store cells in an area that is clean, dark, dry, free of constant air circulation or draft, and temperature controlled between 45oF (7oC) and 95oF (35oC). b. Store cells in their original shipping containers, if undamaged. c.

Cell container may be stacked if properly crated.

d. first.

Cells should be stored so that oldest cell is issued

Specification National Stock Number Part Number

Electrical equipment produces ozone, which will cause rubber to crack.

Serial Number Contract Number

e.

Store cells away from electrical equipment.

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Table 10-1. Shipping Container Requirements Specification

Title

PPP-B-576

Boxes, wood, cleated, veneer, paper overlay

PPP-B-585

Boxes, wood, wire-bound

ASTM D6251 PPP-B-621

Boxes, wood, cleated plywood Boxes, wood, nailed and lock corner

NOTE If under 500 pounds and being packed for direct domestic shipment to the using activity, a corrugated triple wall fiberboard box, ASTM D5168, may be used.

This page intentionally left blank.

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Page 1 of 6

MAINTENANCE INSTRUCTIONS LEAK DETECTION OF INSTALLED FUEL CELLS

Reference Material None

Alphabetical Index Subject

Page

General ................................................................................................................................................................................. 1 Integral Fuel Tank Leak Detection....................................................................................................................................... 2 Condition and Action................................................................................................................................................. 3 Integral Fuel Tank Leak Classification...................................................................................................................... 2 Leak Categories ......................................................................................................................................................... 2 Leak Limits................................................................................................................................................................ 2 Location..................................................................................................................................................................... 2 Mating Surface Sealing ............................................................................................................................................. 2 Leak Detection ..................................................................................................................................................................... 1 Locating Leaks in Fuel Cells and Fuel System Plumbing ......................................................................................... 1 Process of Elimination............................................................................................................................................... 1 References for Leak Detection .................................................................................................................................. 1 Use of Dye in JP-Fuel Systems to Detect Fuel System Leaks.............................................................................................. 3 Dye/Fuel Mixing ....................................................................................................................................................... 3 Dye Solution Leak Detection Procedures.................................................................................................................. 3 Preparation for Dye Use ............................................................................................................................................ 3 Recording of Dye Usage............................................................................................................................................ 3

1. GENERAL. Leak detection is a process used to locate the source of a fuel leak. There can be other causes of fuel leaks, but a significant number of fuel leaks are caused by incorrectly applied maintenance procedures. a. Fuel Leak Causes. Fuel leak causes include incorrect installation of fuel cells, components, lines, fittings, seals, and the incorrect sealing of integral cells. b. Procedures Which May Result in Fuel Leaks. Incorrect procedures result in cross-threaded or stripped fittings, loose fittings, improper seating of lines, fittings, seals, gaps, and voids in integral cell sealant grooves, overtorquing and under-torquing of lines, fittings, bolts, etc. 2. LEAK DETECTION. The following paragraphs provide information about the leak detection process. a. REFERENCES FOR LEAK DETECTION. Reference for leak detection include the applicable aircraft Maintenance Instruction Manual (MIM), fuel system schematic diagrams, installation diagrams, troubleshooting charts, and the cavity drain systems path.

b. PROCESS OF ELIMINATION. A methodical process of elimination will isolate the source of a fuel leak. A check of the Aircraft Discrepancy Log Book may save unnecessary man-hours spent looking for a leak. It may reveal maintenance, which resulted in spilled fuel not properly wiped up, or improper installation of a fuel system component, line, fitting, seat, etc.

NOTE Never assume that the leak you locate is the only leak. Test the fuel system in accordance with the applicable aircraft MIM for evidence of further leaks. c. LOCATING LEAKS IN FUEL CELLS AND FUEL SYSTEM PLUMBING. Many variables make it difficult to isolate the source of a leak. These include the interconnecting of fuel cells, attitudes of draining surfaces, location of fuel cell cavity drain passages, and leak severity. Determining when the leak occurred will aid in leak detection. The following information can aid in locating the source of some leaks:

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011 00 Page 2

(1) Severe running leaks. Severe running leaks spill large quantities of fuel into the cavity drain system just below or adjacent to the cell. These leaks are usually caused by a ruptured or cut fuel cell, a loose interconnection fitting, a pinched, cut, or distorted O-ring in a cell fitting, or a missing O-ring. These leaks usually appear immediately after fueling. (2) Dripping leaks. Dripping leaks usually originate at the fuel system plumbing connections. These leaks can be caused by under-torquing or over-torquing of fuel system lines, hoses, or fittings. Under-torquing can result in a loose connection; over-torquing may cause cracked seating surfaces on tubing flares, hose nipples, or attached fittings. Additionally, a chafing hose may start to drip fuel before further chafing causes it to leak severely. Dripping leak sources can usually be identified by pressurizing the fuel system using the fuel transfer pump/boost pumps. (3) Intermittent leaks. Intermittent leaks are usually caused by loose cell fittings, connections, fuel quantity probes, etc., mounted on the top or high side of the fuel cell. They leak only when the cells are full, or when the aircraft is in a climb or descent. These leaks can be found by completely filling the fuel cell. 3. INTEGRAL FUEL TANK LEAK EVALUATION. An integral fuel tank is a part of the aircraft structure, built so that it will hold fuel without leaking after the seams, structural fasteners, and access doors have been properly sealed. The cell area is usually located between two spars and is capped off on the ends by sealed-end ribs. The skin covering may be riveted to the cell structure or be milled from a plate of aluminum alloy. The milled skin is usually bolted in place. The structural members, along with the s kin of the wing, serve as top, bottom, and sides of the cell. a. MATING SURFACE SEALING. The integral cell mating surfaces are built to close tolerances to allow for sealing. The sealing of these mating surfaces is attained by the use of gaskets and sealants. In most cases, the perimeter of the cell is sealed by the use of non-hardening sealant, which is injected into a groove machined in one structural member along the mating surface. Flush head bolts, other than those located within the sealant channel groove, are sealed by O- rings placed under the head of the bolt. Protruding bolt heads are sealed by special seals, which consist of an O-ring embedded in a metal washer. b. INTEGRAL FUEL TANK LEAK CLASSIFICATION. To classify integral fuel tank leaks, proceed as follows:

Mixtures of JP-4 with JP-8 and/or JP-5 shall use JP-4 leak classification criteria.

NOTE When in doubt, classify leak to the higher leak category for repair determination. (1) Check integral fuel cells for external leakage around skin joints, rivets, screws, and bolts. (2) Begin classification by wiping the leak area completely dry with cheesecloth, CCC-C-440 (Table 2-5, Item 3f), or by using forced air in locations difficult to wipe. (3) After drying the leak area, wait 6 minutes and classify the leak according to the criteria in Table 11-1. c. LEAK CATEGORIES. Leak categories are shown on the left column of Table 11-1. They apply to fuels presently in use in Navy aircraft. d. LEAK LIMITS. Leak limits are shown in the middle columns of Table 11-1. They correspond to the fuel type and the leak category column. These limits shall be used with the general leak location in the right column. e. LOCATION. After a leak is located, refer to the following leak location definitions to determine repair condition and actions.

Careful examination must be made to ensure that the leak is not progressing to a critical area of the aircraft and that there is no possibility of fuel being blown into the fuselage area.

NOTE The following definitions are general, and the appropriate aircraft MIM shall be used to identify fuel leak areas. (1) External locations. Areas exposed to air or airflow in flight are considered external. Areas exposed to airflow only when extended (flaps, slats, landing gear, etc.) are not considered external. (2) Vented internal locations. These are areas, which are vented into the atmosphere or onto the ground. Examples include the front and rear spars and the dry bays, which are drained and vented to the atmosphere. (3) Non-vented internal locations. These are areas, which are normally adjacent to fuel cells or fuel lines. These areas have no air circulation even when they are drained.

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f. CONDITION AND ACTION. (Refer to Table 112.) The conditions and actions in Table 11-2 are minimum requirements. Leaks, however, may always be repaired back to a no-leak condition. 4. USE OF DYE IN JP-FUEL SYSTEMS TO DETECT FUEL SYSTEM LEAKS. Adding a dye (MIL-D81298) to JP-fuel systems is one of the most practical means of locating hidden fuel leak sources. Adding a dye is useful for three main reasons:

NOTE The dye color used should be one that will provide the highest visibility in the area where the leakage of fuel is suspected. (1) Add 2 ounces of red or yellow liquid dye, MILD-81298, to each 100 gallons of fuel in the cell.

The leaking dyed fuel will leave a stain, which can be followed back to the source of the leak.

d. DYE SOLUTION LEAK DETECTION PROCEDURES. To locate fuel leaks using the dye solution, different procedures are used for different areas of the aircraft.

The dyed fuel is particularly useful in checking for leakage near the engine hot section area and afterburner pigtail couplings, where high temperatures prevent fuel from leaving a wet spot.

(1) Fuel cells, components, and attaching plumbing. To locate fuel leaks, using the dye solution, perform the following procedures:

When the dyed fuel evaporates from a surface, the dye remains as a visual deposited residue.

(a) Fuel the cell suspected of leaking to 1/3 of known capacity. If the cell is full, either transfer the excess fuel to another cell, or defuel to 1/3 capacity.

a. PREPARATION FOR DYE USE. Before the dye, MIL-D-81298 (Table 2-5, Item 6b), is used to determine the source of fuel leaks, any leaks in the visible portion of the fuel system should be located and repaired.

NOTE Fuel sample analyzers should be informed that fuel color changes result from the use of the dye and should be disregarded in fuel sample analysis. b. RECORDING OF DYE USAGE. When dye, MILD-81298, is added to a fuel system for leak detection, a notation should be made in the Aircraft Log Book Miscellaneous History, OPNAV Form 4790/25A, and in the Aircraft Log Book for aircraft serviced with dyed fuel. c. DYE/FUEL MIXING. To mix dye, MIL-D-81298, and fuel, perform the following procedure:

(b) Add 2 ounces of red or yellow liquid dye, MIL-D-81298, to each 100 gallons of fuel in the cell. (c) Inspect for signs of coloration from the leaking fuel. It may take an hour or more for the color from a small leak to appear. If at the 1/3 level leakage does not appear after a reasonable waiting period, proceed to the following step. (d) Add fuel to, bring the cell to 2/3 capacity and then add two ounces of red liquid dye or yellow liquid dye for each 100 gallons of fuel added. Repeat step (c). (e) If at the 2/3 level leakage still does not appear after a reasonable time, repeat step (d) at full capacity. (f) Transfer the dyed fuel, using the aircraft transfer pumps, from cell to cell following steps (c) through (e) until the leak is found, or it is determined that the fuel cells, attaching fittings, components, lines, etc., are not leaking. (g) When the leak is located, defuel, depuddle, and air purge, if required, in accordance with WP 006.

Fuel dyes contain organic solvents that are flammable. Avoid breathing of vapors or skin contact. Use personal protective equipment.

The addition of unmixed dyes to empty fuel cells can cause deterioration of cell lining. Dyes shall be added to the fuel, rather that fuel to the dye.

Careful examination must be made to ensure that the leak is not progressing to a critical area of the aircraft and that there is no possibility of fuel being blown into the fuselage area.

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011 00 Page 4 (e) Perform engine run-up or test flight in accordance with applicable directives.

Dry Cleaning Solvent MIL-PRF-680

4

(h) Perform required repairs and remove dyed fuel stains using cheesecloth, CCC-C-440 (Table 2-5, Item 3f), dampened with solvent, MIL-PRF-680, Type II or III. Stains on the rubber cell surface should be removed by using cheesecloth dampened with fresh water.

NOTE

(f) Upon completion of engine run-up and/or test flight, inspect engine mounted fuel components, fuel lines, connections, fittings, and afterburner pigtail connections. (g) If fuel leaks are found, repair, remove dye stain, and repeat leak test. (3) Airframe mounted lines and connectors. To locate fuel leaks using the dye solution, perform the following procedures: (a) Comply with paragraph 4d(1), steps (a) and

After completion of the leak test, the dyed fuel can be left in the cell and the aircraft flown without harmful effects. Aircraft fuel systems containing dyes will remain colored until the system has been filled and emptied several times.

(b). (b) Pressurize the airframe mounted lines utilizing the fuel boost pump and inspect fuel cell interconnects, lines, hoses, connection, filter, valve, etc.

Test the cell with dyed fuel to determine whether or not the cell still leaks.

Careful examination must be made to ensure that the leak is not progressing to a critical area of the aircraft and that there is no possibility of fuel being blown into the fuselage area.

(2) Engine mounted fuel lines and connection. To locate fuel leaks using the dye solution, perform the following procedures: (a) Determine quantity of fuel required for static test, engine run-up, or flight test, as applicable. (b) Add red liquid dye or yellow liquid dye in accordance with paragraph 4c. (c) Pressurize engine fuel line utilizing the fuel boost pump and inspect for leaks.

Careful examination must be made to ensure that the leak is not progressing to a critical area of the aircraft and that there is no possibility of fuel being blown into the fuselage area.

Dry Cleaning Solvent MIL-PRF-680

4

(c) If fuel leaks are found, repair and remove the dye stain using cheesecloth, CCC-C-440, dampened with solvent, MIL-PRF-680, Type II or III, and repeat the leak test. (4) Integral fuel cells. To locate fuel leaks using the dye solution, perform the following procedures: (a) Comply with paragraph 4d(1), steps (a) and (b). (b) Allow the dyed fuel to stand in the tanks for 30 minutes and then inspect for obvious leaks. (c) Mark, if necessary, and classify the leak in accordance with Table 11-1.

Dry Cleaning Solvent MIL-PRF-680

4

(d) If leaks are found, repair and remove the dye stain using cheesecloth, CCC-C-440 (Table 2-5, Item 3f), dampened with solvent, MIL-PRF-680, Type II or III, and repeat leak test.

(d) Allow the fuel to stand for approximately one additional hour before performing further leak inspections. (e) Repair fuel leaks in accordance with the applicable MIM. (f) Inspect for leaks.

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011 00 Page 5 (a) Dyed fuel may be left in the aircraft fuel sys tem following leak detection operation and used in normal operations.

Careful examination must be made to ensure that the leak is not progressing to a critical area of the aircraft and that there is no possibility of fuel being blown into the fuselage area.

Dry Cleaning Solvent MIL-PRF-680

4

(g) If fuel leaks are found, repair and remove dye stain using cheese-cloth, CCC-C-440, dampened with solvent, MIL-PRF-680, Type II or III, and repeat steps (a) through (d). e.

Disposition of Dyed Fuel.

(1) Do not return dyed fuel to bulk storage tanks as there is sufficient dye in a 2 ounce can to color 10,000 gallons of fuel. (2) Dyed JP fuel will be disposed of as follows:

NOTE Prior approval of the aircraft reporting custodian must be obtained before fueling an aircraft with dyed fuel. (b) Dyed fuel, which must be removed from the aircraft shall be sampled for contamination in accordance with Work Package 007. (c) If contaminated, it can be used for fire fighting training or disposed of in accordance with local instructions. (d) Provided the fuel is not contaminated, it can be used in other aircraft, engine test cells, or ground equipment. (3) Refer to the applicable aircraft MIM and/or Structural Repair Manual (SRM) for additional leak detection methods for a specific model aircraft.

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Table 11-1. Fuel Leak Classification - Aircraft Integral Fuel Cells 6 minute leak limits by type of fuel

Location - condition/action

Leak categories

AVGAS

JP-4

JP-8, JP-5

External

Class A Slow Seep

0 to 1/4 inch

0 to 1/4 inch

0 to 1/4 inch

1

Class B Seep

greater than 1/4 to ¾ inch

greater than 1/4 to ¾ inch

greater than 1/4 to ¾ inch

1

2 (2 places Max)

3

Class C Heavy Seep

greater than 3/4 to 2-1/2 inches without dripping

greater than 3/4 to 6 inches with-out dripping

greater than 3/4 to 8 inches and/ or 4 drops per minute

2

3

3

Class D Running Leak

greater than 21/2 inches or drips or runs from surface

greater than 6 inches or drips or runs from surface

greater than 8 inches or drips or runs from surface

3

3

3

Internal vented

Internal nonvented 2 (2 places Max)

Table 11-2. Leak Conditions and Actions Condition

Action

1

Document and periodically inspect for leak growth to condition 2 or 3. No repair is necessary; leak may be repaired when cell is opened for inspections or re-pairs.

2

Document and periodically inspect for leak growth to condition 3. No immediate repair is required. Schedule repair when aircraft is down for maintenance, when cell is opened for another inspection or repair, or in accordance with the appropriate aircraft MIM.

3

Document and repair to no leakage or back to condition 1 or 2 in accordance with the appropriate aircraft MIM. If leaks cannot be repaired back to condition 1 or 2, the aircraft shall be grounded until the leaks are repaired.

NOTE Integral cell fuel leaks shall be repaired using the techniques and procedures outlined in the applicable aircraft MIM.

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Page 1 of 10

MAINTENANCE INSTRUCTIONS CLEANING, TESTING, AND CLOSURE REQUIREMENTS OF UNINSTALLED FUEL CELLS

Reference Material Aircraft Weapons Systems Cleaning and Corrosion Control Manual .................................................................. NA 01-1A-509

Alphabetical Index Subject

Page

Fuel Cell Cleaning.........................................................................................................................................................................2 Fuel Cell Final Cleaning ....................................................................................................................................................2 Fuel Cell Initial Cleaning...................................................................................................................................................2 Fuel Cell Testing ...........................................................................................................................................................................3 Alternate Fuel Cell Soap Suds Testing..............................................................................................................................3 Fuel Cell Chemical Testing ...............................................................................................................................................6 Fuel Cell Soap Suds Testing..............................................................................................................................................3 Instrumental Leak Detection Systems ...............................................................................................................................4 Gaskets...........................................................................................................................................................................................9 Gasket Installation..............................................................................................................................................................9 Gasket Removal .................................................................................................................................................................9 General...........................................................................................................................................................................................1 O-Ring Fittings..............................................................................................................................................................................7 O-Ring Fitting Description ................................................................................................................................................7 O-Ring General Work Guidelines .....................................................................................................................................7 O-Ring Installation.............................................................................................................................................................9 Safety Wiring...............................................................................................................................................................................10 Stencils and Decalomanias..........................................................................................................................................................10 Stencil and Decalomania Application .............................................................................................................................10 Stencil and Decalomania General Information ...............................................................................................................10 Torque Requirements ..................................................................................................................................................................10

1. GENERAL. This section contains instructions, procedures, and materials for cleaning and testing uninstalled fuel cells. It includes methods to locate leaks prior to repair, and fuel cell integrity after repairs. Additionally, it includes fuel cell O-ring installation, gasket application, and other closure requirements.

NOTE The following warning appears many times in this chapter:

When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell. The use of the air-supplied respirator or SCBA is required when working inside cells installed in an aircraft. If the cells have been removed from the aircraft and are being worked in a shop

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environment, then the use of a half-face respirator with a cartridge appropriate to the hazard is a suitable alternative to the use of an air supplied respirator. 2. FUEL CELL CLEANING. Cleaning shall be accomplished in a safe working area where solvent vapors can be exhausted and waste residues safely drained. Protective clothing should be worn at all times. Protect exposed skin surfaces with protective skin compound, P-S411 (Table 2-5, Item 12f). a. FUEL CELL INITIAL CLEANING. Fuel cell cleaning may be accomplished in one of two ways, cleaning with MIL-PRF 680 or by steam cleaning. To initially clean the fuel cell, proceed as follows:

(2) Clean the interior of the cell of all fuel residue by one of the two following methods (a) or (b): (a) Clean the interior of uninstalled rubber fuel cells by steam cleaning. Appropriate cleaners are listed in Table 2-5, items 4a or 4b. Follow the instructions presented in the NA 01-1A-509. Do not use high-pressure spray wash systems as damage to the rubber layers may result. (b) Alternate method: clean the interior with MILPRF-680 as follows:

Dry Cleaning Solvent MIL-PRF-680, Type II or III

4

1 Wash the interior of the fuel cell with MILPRF-680 Dry Cleaning Solvent.

NOTE

Comply with general safety instructions in Work Package 004, and fuel cell entry preparations in Work Package 006. The air-supplied respirator shall be worn when entering a fuel cell.

To avoid collapse and possible damage to the fuel cell structure, the fuel cell should be adequately supported during cleaning operations. (1) Support the fuel cell structure (Refer to Work Package 010 and see Figures 10-4 and 10-5).

When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell. Fuel cell cleaning shall be accomplished in a safe working area where solvent vapors can be exhausted and waste residues safely drained. Protective clothing shall be worn. Protect exposed skin surfaces with protective skin compound. Organic solvents or adhesives containing organic solvents are flammable. Avoid breathing of vapors or prolonged skin contact. Use personal protective equipment.

Dusting brush, H-B-00190, may be used for light scrubbing, provided scrubbing action is light enough to avoid damage to the fuel cell. 2 Scrub lightly with cheesecloth, CCC-C-440, or suitable substitute.

Dry Cleaning Solvent MIL-PRF-680, Type II or III

4

3 Rinse the residue from the cell with MILPRF-680 dry cleaning solvent. 4

Wipe dry with cheesecloth.

5 Prepare soap solution, 372, using one cup of soap to each gallon of water. 6

Wash cell interior with soap and water

7

Rinse off soap and water solution with warm

8

Drain fuel cell.

9

Wipe dry with cheesecloth.

solution. water.

b. FUEL CELL FINAL CLEANING. After all repair work has been completed, give the fuel cell a final cleaning as follows: (1) Lightly tap and shake the sides and top of the fuel cell to dislodge buffing dust or other particles on the inside surfaces. (Allow the loose particles to fall to the bottom of the cell).

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(2) Wipe the sides and top of the fuel cell interior with a lint-free cloth, 9409.

(8) Circle the leaking area with a white marking pencil, SS-P-00196.

(3) Wipe the particles on the cell bottom to one

(9) Rinse off the surface of the cell with clean warm water and wipe dry. (Do not remove any leak source marks.)

side. (4) Remove the collected particles by hand. (5) Using a pneumatic vacuum cleaner, 55-20 (Table 2-6, Item 2b), vacuum all internal surfaces thoroughly. (6) Wrap a 3-inch wide strip of tape, PPP-T-60, around the hand, with the adhesive side out. (7) Tack clean the inside surface to remove any remaining lint or dust. 3. FUEL CELL TESTING. Test fuel cells to determine their adequacy as liquid fuel-carrying containers and to check the integrity of cell repairs. Cells can be tested with soapsuds, instrumentally, or chemically.

(10) If no obvious leaks are found, attach water manometer, type W, model A-786, (or calibrated dial type pressure gauge) to the air inlet attachment and readjust the air pressure to 0.5 psi. For non-self sealing fuel cells, inflate to 0.25 psi, using a water manometer reading of 6.9 inches. (11) Allow the cell to remain pressurized for onehalf hour and check the manometer for loss in pressure. (12) After the test, remove the test equipment and cover plate from the cell. (13) Flush with warm water and wipe dry with cheesecloth.

a. FUEL CELL SOAPSUDS TESTING. To soapsuds test fuel cells for leaks, proceed as follows:

b. ALTERNATE FUEL CELL SOAPSUDS TESTING. An alternate method for soapsuds testing a fuel cell for leaks after repair may be performed as follows:

(1) Locally fabricate and install a plate with an air inlet and manometer fitting to fit any of the fittings on the cell (See Figure 15-1).

(1) Locally fabricate and install a plate with an air inlet and manometer fitting to fit any of the fittings on the cell (See Figure 15-1).

(2) Attach cover plates to all openings.

(2) Attach cover plates to all openings.

(3) Torque cover plates and air inlet attachment fitting using the torque values marked on the cell as a guide (Refer to Work Package 010 and see Figure 10-1).

(3) Torque cover plates and air inlet attachment fitting using the torque values marked on the cell as guide (Refer to Work Package 010 and see figure 10-1).

Soaps and detergents may cause eye and skin irritation. Use personal protective equipment.

(4) After blanking off cell openings, place cell in a test jig of proper contour and pressurize to 0.75 psi for selfsealing fuel cells, and 0.25 psi for non-self sealing (bladder) fuel cells. For self-sealing fuel cells, use a water manometer, type W, model A-786 (or calibrated dial type pressure gauge) reading of 20.8 inches. For non-self sealing (bladder) fuel cells, use a water manometer reading of 6.9 inches.

(4) Make up a soap solution by adding 2 cups of soap, 372, to one gallon of warm water. (5) Using either brush, H-B-00190, or a swab, apply the soap solution to the outside surface of the cell, including all cover plates and fittings (See Figure 15-3). (6) Examine cell and fittings for leaks. (Enlarging soap bubbles indicate air leaking out of the fuel cell at that location.) (7) Check the fuel cell a second time, section by section, re-soaping each section as it is being checked.

Allow cell to stand until pressure and temperature have stabilized, and then readjust to exactly 0.75 psi (20.8 inches of water) for self-sealing fuel cells. For non-self sealing (bladder) fuel cells adjust pressure from 0.25 psi. (5) Allow to stand for a period of 30 minutes. (6) If within 30 minutes pressure does not fall below the prescribed limits, the cell will be considered as having satisfactorily passed the leak test.

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Figure 12-1. Fuel Cell Fitting Leak Test Lower Plate

(7) If pressure falls during test period, recheck all fittings, using bubble test solution to detect leaks. Ensure all fittings are leak-proof and repeat test. (8) If air pressure still drops, reexamine cell for leaks and make necessary repairs. (Bubble test solution may be used on walls to detect leaks if necessary.) (9) After repairing, retest as in steps (4), (5), and (6) above. (10) Upon completion of pressure test, exhaust air to atmospheric pressure and remove cell from test jig. c. INSTRUMENTAL LEAK DETECTION SYSTEMS. Systems designed to detect leaks using gaseous compounds such as helium or hydrogen/nitrogen are allowed. Instrumental leak detection systems are most useful for checking fittings and o-rings. Large area testing is best accomplished by another method. Follow manufacturers instructions for the unit and for recommended concentrations of leak detection gas.

Some leak detection gas systems contain hydrogen gas. Low concentrations of hydrogen gas (less than 5%) in an inert nitrogen gas is safe. However, high concentrations of hydrogen gas can pose a danger of creating an explosion hazard. Heed manufacturer’s recommendations for safe use of leak detection gas. (1) Locally fabricate a plate with an air quickdisconnect fitting to fit any of the fittings on the cell (See Figure 15-1). Connect to pressure test stand or manometer. (2) Attach cover plates to all openings. (3) Torque the cover plates and air inlet attachment fitting using the torque values marked on the cell as a guide (Refer to Work Package 010, and see Figure 10-1).

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Figure 12-2. Fuel Cell Chemical Leak Test

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(4) Connect leak detection gas to pressure test stand and fill cell with leak detection gas. Do not over pressurize cell. (5) Calibrate instrument manufacturer’s instructions.

according

to

(6) Inspect surface of the cell with leak detection wand to locate leaks. Small leaks may require multiple passes to pinpoint the exact location of the leak. (7) Mark any leaks found with white marking pencil, SS-P-00196. (8) Repeat step (6) and (7) until the entire exterior surface of the cell has been covered. (9) At the completion of the testing, ensure all leak detection gas has been removed from the cell prior to entering the cell. This can be accomplished by removing all cover plates and then collapsing the cell and re-expanding the cell. The cell could also be purged by providing forced air ventilation per Work Package 006. Continuous ventilation is not necessary once the leak detection gas has been purged from the cell.

Ethyl Alcohol A-A-51693

24

Phenolphthalein

12

NOTE Add the phenolphthalein crystals, to ethyl alcohol, A-A-51693, mix, and then add water. (7) Prepare a solution of equal parts of ethyl alcohol and water to which 15 grams of phenolphthalein crystals per gallon of solution have been added. (8) Attach the air pressure and manometer lines to the fuel cell fitting (See Figure 15-2).

d. FUEL CELL CHEMICAL TESTING. To chemically test fuel cells for leaks after repair, proceed as follows: (1) Locally fabricate and install a plate with an air inlet and manometer fitting to fit any of the fittings on the cell (See Figure 15-1). (2) Attach cover plates to all openings except the access door. (3) Torque the cover plates and air inlet attachment fitting using the torque values marked on the cell as a guide (Refer to Work Package 010, and See Figure 10-1).

Ammonium Hydroxide A-A-59370

Combination self-sealing and non-self sealing (bladder) cells shall be tested at the pressure specified for non-self sealing cells. (9) For self-sealing fuel cells, inflate to 0.5 psi, using a water manometer reading of 13.8 inches. For nonself sealing fuel cells, inflate cell to 0.25 psi, using a water manometer reading of 6.9 inches. (10) Soak a large piece of cheesecloth, CCC-C-440, in the phenolphthalein solution, wring thoroughly, and spread smoothly on the outer surface of the cell.

23

(4) Place the cell in a well-ventilated area. (5) Pour technical grade ammonium hydroxide, AA-59370 (Table 2-5, Item 6a), on an absorbent cloth at the ratio of 3cc per cubic foot of cell capacity, but never use less than 10cc. (6) Wearing rubber gloves, ZZ-G-381 (Table 2-6, Item 6j), place the saturated cloth inside the cell and install and torque the access door.

(11) Press the cloth down to ensure detection of minute leaks. (12) Check the cloth for red spots, which will indicate a leak. (13) Mark any leaks found with white marking pencil, SS-P-00196, and move the cloth to a new location. (14) Repeat step (13) until the entire exterior surface of the cell has been covered.

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NOTE

(20) Flush the cell with warm water and wipe dry with cheesecloth.

If red spots appear on the cloth, the spots may be removed by resoaking the cloth in the solution.

4. O-RING FITTINGS. Fuel cell openings that have a metal O-ring fitting molded to them, which forms the surface of the cell opening require the installation of an Oring to form a seal.

The solution and test cloth are satisfactory as long as they are clean. (15) Indicator solution that is not in immediate use shall be stored in a closed container to prevent evaporation and deterioration. (16) After the test, remove the test equipment and cover plates from the cell.

Ammonia Hydroxide A-A-59370

23

(17) Clean all metal fittings as soon as possible, because the alcohol and ammonium hydroxide, A-A-59370, will cause corrosion.

When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell. (18) Do not enter the cell immediately; let the cell fully air out.

a. O-RING FITTING DESCRIPTION. Each fitting or its mating surface has a groove for the installation of the rubber O-ring. The O-ring acts as a static gasket type seal. The combination of the rubber O-ring and the grooved fitting eliminates the cold flow difficulties of conventional gasket material and rubber-faced fuel cell fittings. Each fitting generally consists of one or two die-cast metal parts of lightweight alloy bonded to the cell at the opening. One of the two metal parts is so constructed that when joined to the cell there is a metal-to-metal contact at some areas of the fitting. Steel thread inserts are installed in some fittings to secure mounting bolts for the different cell units. To function as a fuel-tight seal, the O-ring must be compressed between two metal surfaces that have a high degree of smoothness. One of these surfaces is at the bottom of the Oring groove, and the other is at the sealing surface in the mating part, such as cell interconnectors, bulkhead fittings and other cell units. b. O-RING GENERAL WORK GUIDELINES. When working with O-rings or installing them, the following precautions should be observed: To prevent leaking, the two mating surfaces must be clean, free of tape, scratches, paint, threads, hair or other foreign material. The O-ring fitting to be used must be free of foreign material, scratches, or sharp irregularities, which would prevent an absolute seal. Do not reuse old O-rings.

When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell.

Be sure there is no paint on the sealing surface of fuel cell O-ring fittings and their mating parts.

(19) After the cell has aired, remove the ammonium hydroxide saturated cloth from the interior of the cell.

Zinc chromate primer can cause wicking of fuel.

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Figure 12-3. Testing Cell for Leaks

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c. O-RING INSTALLATION. Using the following general procedures and guidelines, O-rings may be installed as follows:

(2) If any resistance is experienced, proceed to step (3). (3) Apply a coating of Acetone, ASTM D329 to the gasket.

Misalignment of a fitting can cause cracking of the metal portion and fouling of the bolt or insert threads. This generally results in loose metal particles, which will prevent a fuel-tight seal between the two mating surfaces. (1) Line up all fuel cell fittings with their mating parts without forcing the cell. (2) Check to ensure that the fittings are in alignment and that correct bolt lengths are used. (Do not pinch the O-ring seal.) (3) Make certain the O-ring is the correct size and is in its groove before joining the mating parts.

NOTE Installation of the clamping ring will hold the O-ring in the groove until final installation of plumbing or component equipment. (4) Position the clamping ring over the cell fitting and start the bolts.

(4) Work the gasket loose with a blunt tool.

Acetone ASTM D329

7

(5) Clean the exposed cell area with Acetone, ASTM D329 after removing the gasket. b. GASKET INSTALLATION. New gaskets may be made from such material as cork and rubber composite sheet (MIL-G-6183). To install a new gasket proceed as follows: (1) Locally fabricate a new gasket if a replacement is not readily available.

NOTE To ensure proper sealing, gaskets should be installed at the time the fuel cell is being fitted and mated. (2) Place the gasket on gasket mounting surface.

(5) Press against the clamping ring until the cell fitting is snug against the mating fitting.

(3) If gasket does not remain in position for fitting and mating, proceed to step (4).

(6) Tighten bolts fingertight. (7) Make final component/ plumbing installation. (8) Tighten bolts to specification requirements. 5. GASKETS. Gaskets are required on some fittings to form a seal. Most gaskets used on fuel cells will take on a permanent set after installation and should not be reused after disassembly. a. GASKET REMOVAL. Gaskets may generally be removed using the following procedures:

NOTE Some gaskets may be simply lifted or pulled off. (1) Lift off gasket with fingers.

Sealing Compound AMS-S-4383

11

Sealants, paste, or fluid on fuel cell fitting gasket surfaces should be avoided. These act as a lubricant and accelerate the cold flow of the rubber gasket material. Failure of the seal and leakage at the fitting will occur. (4) Tack the gasket into position using three or four small dabs of sealing compound, AMS-S-4383.

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6. TORQUE REQUIREMENTS. Refer to Work Package 010 for torque requirements and torque sequencing. 7. SAFETY-WIRING. Bolts should be safety-wired in accordance with Work Package 010. 8. STENCILS AND DECALCOMANIAS. Stencils and decalcomania contain important information. To avoid the loss of this information during cell repair it is advisable to copy the information prior to repair for reapplication upon completion of fuel cell repairs. a. STENCIL AND DECALCOMANIA GENERAL INFORMATION. Stencils and decalcomania that have been applied to fuel cells for extended periods of time and have been subjected to solvents and cleaners may have very little protective coating left. Therefore, recording data from all stencils and decalcomania is recommended, even if fuel cell repair work is limited to a small area. b. STENCIL AND DECALCOMANIA APPLICATION. To apply stencil and decalcomania proceed as follows: (1) Ensure information contained in original stencil has been properly recorded in exactly the same order. (2) Locate the correct area to be stenciled.

Paints, lacquers and thinners contain organic solvents and may be hazardous or toxic. They can also cause skin, eye, or respiratory irritation upon prolonged contact. Use personal protective equipment during mixing, thinning, and application of these coatings. (3) Ensure that all lettering is the same size as the original and the following are included as applicable: Name of activity Date of repair/test Torque limits Name of manufacturer Warnings (4) Apply stencils to the fuel cell exterior using white or red paint, A-A-2787, as appropriate. (5) Apply decalcomania in their proper locations.

Enamel A-A-2787

25

(6) Overcoat decalcomania with clear enamel, A-A2787 (Table 2-5, Item 7f).

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Page 1 of 58

MAINTENANCE INSTRUCTIONS INTEGRAL FUEL TANKS LEAK DETECTION, REPAIR, AND SEALING

Reference Material Inspection and Acceptance Standards for Fuel Cells and Fittings ...............................................................MIL-STD-801 series Aircraft Weapons Systems Cleaning and Corrosion Control Manual .................................................................. NA 01-1A-509

Alphabetical Index Subject

Page

Access Door Sealing Methods ......................................................................................................................................................3 Bonded-in-Place-Molded Seals .........................................................................................................................................3 Direct-Seal Doors...............................................................................................................................................................3 Flat Gasket Seals ................................................................................................................................................................3 Formed-in-Place Seals .......................................................................................................................................................3 Molded-in-Place Seals .......................................................................................................................................................3 O-Ring Seals ......................................................................................................................................................................3 Plug Doors..........................................................................................................................................................................3 Causes of Fuel Leaks.....................................................................................................................................................................4 Curing Type Sealing Methods ......................................................................................................................................................2 Curing Type Sealing Repairs ......................................................................................................................................................44 Brush Coat or Overcoat Seals..........................................................................................................................................44 Faying Surface Seals........................................................................................................................................................44 Fillet Seals ........................................................................................................................................................................44 Injection Seals ..................................................................................................................................................................44 Prepacked Seals................................................................................................................................................................44 Determining Which Tank is Leaking..........................................................................................................................................17 Development of Leak Path Analysis ..........................................................................................................................................19 Fastener Sealing Methods .............................................................................................................................................................3 Non-Self-Sealing Fasteners ...............................................................................................................................................4 Self-Sealing Fasteners........................................................................................................................................................3 General...........................................................................................................................................................................................2 Helium or Argon Gas Method ....................................................................................................................................................19 Inspection of Tank Interior..........................................................................................................................................................20 Leak Path Analysis......................................................................................................................................................................13 Locating Leak Exit Points...........................................................................................................................................................13 Red Talcum Powder Method ...........................................................................................................................................13 Torn Paper Method ..........................................................................................................................................................14 Locating Leaks in Integral Tanks................................................................................................................................................13 Locating Leak Sources ................................................................................................................................................................20 Blow Back Method ..........................................................................................................................................................24 Dye Injection Method ......................................................................................................................................................24 Vacuum Methods .............................................................................................................................................................29 Non-Curing Type Sealing Methods..............................................................................................................................................3 Non-Curing Type Sealant Repairs ..............................................................................................................................................43 Permanent Repairs.......................................................................................................................................................................36 Application Life of Sealants ............................................................................................................................................38 Freezing and Thawing Mixed Sealant .............................................................................................................................38 General .............................................................................................................................................................................36

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Mixing of Curing Type Sealant .......................................................................................................................................37 Quality Conformance For Curing Type Sealants............................................................................................................37 Quality Conformance For Field Mixed Sealants.............................................................................................................37 Sealant Cure .....................................................................................................................................................................38 Sealants.............................................................................................................................................................................36 Storage of Sealants...........................................................................................................................................................36 Tack-Free Time................................................................................................................................................................38 Pressure Test................................................................................................................................................................................18 Purpose ..........................................................................................................................................................................................2 Related Equipment and Materials...............................................................................................................................................39 Mixing Kit Sealant ...........................................................................................................................................................39 Sealant Guns.....................................................................................................................................................................40 Repair of Access Doors / Components .......................................................................................................................................58 Repair of Chalking Sealant Procedure (Optional)......................................................................................................................49 Repair of Fasteners......................................................................................................................................................................55 Fasteners Located in Sealant Grooves.............................................................................................................................57 Fasteners Sealed by Brushcoat and Fillet ........................................................................................................................57 Fasteners Sealed with Dome Nuts ...................................................................................................................................57 Fasteners with Sealing Washers or O-Rings ...................................................................................................................57 Self-Sealing Fastener .......................................................................................................................................................55 Wet Installed Fastener......................................................................................................................................................57 Repair of Sealant Top Coating....................................................................................................................................................49 Sealants ........................................................................................................................................................................................39 Curing Type Sealants .......................................................................................................................................................39 Non-Curing Sealants ........................................................................................................................................................39 Sealing Requirements....................................................................................................................................................................2 Structural Adhesive Type Sealing Methods .................................................................................................................................3 Temporary Repairs......................................................................................................................................................................31 Aluminum Foil Patch Bonded With AMS-S-8802/AMS 3276 Sealant.........................................................................33 Comp Air D239 Injector Kit............................................................................................................................................34 Epoxy Tab Type O...........................................................................................................................................................33 Hardman Extra-Fast Setting Epoxy With or Without Aluminum Foil Patch.................................................................32 Non-Foil Sealant/Adhesive Patch....................................................................................................................................34 Oylite Stik.........................................................................................................................................................................36

1. PURPOSE. This section defines integral tanks and describes sealing methods, leaks theory, temporary and permanent repairs, and the use of related materials/equipment. 2. GENERAL. Integral tanks were developed because they offered the capability for greater fuel containment with a decrease in weight over fuel cell type construction. Integral tanks are defined as those compartments of an aircraft's structure designed to contain a liquid, normally fuel. They are manufactured with a liquid-tight boundary, commonly called a seal plane, which has been sealed with gaskets, structural adhesives, elastic films or other sealants. They have been built into both the wing and fuselage sections of the aircraft with the primary structure forming the boundaries of the fuel tanks (See Figure 13-1). 3. SEALING REQUIREMENTS. All integral tanks are similar in design in that all surfaces of the wing or fuselage (such as tank boundary bulkheads, ribs, spars, beams,

longerons, etc.) are required to be sealed fuel tight. The three main areas of an integral fuel tank, which require sealing are the tank boundaries, the access doors, and fasteners. The tank boundaries have been sealed using three basic types of sealants used in integral tanks design. They are curing type, non-curing type and structural adhesives. 4. CURING TYPE SEALING METHODS. Curing type sealants have been used on various types of aircraft to seal tank boundaries. The sealant used in these designs flows during application, normally cures with time and remains flexible after cure. Curing type sealants have been: injected into fittings, grooves, and corners; prepacked during initial assembly; applied between surfaces called faying surface sealing; used to overcoat fasteners and small parts; and as fillets on seams, butt joints, etc. In curing type sealant designs tank access is normally required during initial fabrication and for in service repairs. Leaks through the sealant generally require removal and replacement of the defective sealant (See Figure 13-2).

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5. NON-CURING TYPE SEALING METHODS. Non-curing type sealants have been used to seal tank boundaries on aircraft, which have little or no access into the tank interior. The sealant used does not cure with time or temperature and remains in a semi-fluid/moveable condition. Channels or grooves are machined into one of the surfaces of all fuel tank boundaries and the sealant is injected into the grooves or channel through injection ports. The injected sealant adheres to the groove/channel and is packed between the structural members to form a fuel tight seal (See Figure 13-3). Leaks through the faying surface channel seal are repaired from the outside of the tank by reinjection with new sealant. The groove/channels may be located between fasteners, zigzagged with the fasteners, between rows of fasteners or to one side of the tank fasteners (See Figure 13-4). Proper attention must be given to assembly detail to determine which fasteners and how these fasteners must be sealed to prevent an inadvertent leak path. 6. STRUCTURAL ADHESIVE SEALING METHODS. Structural adhesive for fuel tank sealing has been used on fighter and transport aircraft to seal tank boundaries. This design uses an unusually flexible structural adhesive to bond the structure together and seal the faying surfaces. Since the adhesive is flexible, the fasteners carry most of the structural loading. The structural adhesive is thermo-curing which means it must be heated to cure. One adhesive in tape form is installed between the faying surfaces during tank construction. After the tank is assembled, it is placed in an oven and heated to 325oF to cure the adhesive. Voids and corner fittings are then sealed with a curing type sealant and the integral tank is then fuel tight. If a leak occurs in the faying surface it is repaired with curing type sealant fillets and/or overcoats (See Figure 13-5). 7. ACCESS DOOR SEALING METHODS. Integral fuel tank access doors come in many shapes and sizes; but there are two basic types, plug and direct-seal. All access doors are sealed with a static seal of which there are five main configurations; flat gasket, O-ring, molded-in-place bonded-in-place molded, and formed-in-place seals. a. Plug Doors. This door opens into the fuel tank and because of design the fuel pressure tends to press the door back out which provides a tighter seal (See Figure 13-6).

retightening to provide a continuous fuel seal. They require flat mating surfaces (See Figure 13-8). d. O-Ring Seals. This method requires a matching groove to be machined in the access door and mating surface. When properly installed they exhibit no leakage and are generally maintenance free. They have the disadvantages of being easily installed with the O-ring in the wrong position, they are hard to install around comers, and are generally not reusable (See Figure 13-9). e. Molded-in-Place Seals. These seals are molded in place in the access door during manufacturing of the door. They generally provide a good seal and are reusable. They cost more originally and if damaged the entire door must be replaced (See Figure 13-10). f. Bonded-in-Place-Molded Seals. Same as moldedin-place with the exception that these seals can be removed with a new seal bonded (glued) in place of the old damaged seal.

Compound Silicone AMS-S-8802

15

Adhesive MIL-S-8784

21

Formed-in-Place Seals. This seal is established g. application of sealant (AMS-S-8802 or MIL-S-8784), AMS-S-8802 sealants requires a parting agent such as polyvinyl alcohol (PVA) in the door to frame mating surface, MIL-S-8784 is a low adhesive sealant, therefore does not require a parting agent. The door is then installed prior to cure of the sealant. Subsequent removal of the door frequently destroys the seal. The old sealant needs to be removed, the surfaces need to be cleaned and a new application of sealant needs to be made for each reinstallation of the door.

b. Direct-Seal Door. This door opens to the outside of the fuel/tank and fuel/pressure tends to press on the door which increases loading on the access door fasteners. The door fasteners provide all of the clamping force required to make the door seal fuel tight (See Figure 13-7).

8. FASTENER SEALING METHODS. For detail information of the structural fuel tank fastener combinations refer to your system particular MIM technical manuals. The fasteners used in fuel tanks can be divided into two major types: self-sealing and non-self-sealing.

c. Flat Gasket Seal. This is the oldest method of tank access door sealing. It is simple to manufacture and install but many times are not reusable, wrinkle easily, or requires

a. Self-Sealing Fasteners. The self-sealing type of fasteners seal the hole by either swelling when installed as in the case of rivets or by interference fit which is forcing

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the fastener against the sides of the hole due to the fasteners being larger than the hole by a few thousandths of an inch. Self-sealing fasteners normally do not require additional sealing b. Non-Self-Sealing Fasteners. This type of fastener cannot be installed in a hole and expected to be fuel tight. Examples of non-self sealing fasteners are access door screws or attach bolts which slip into the holes with little or no interference. They are usually seated by other methods such as the following:

Dome nuts, sealing washers, and O-rings (See Figure 13-11). (1)

(2)

Fastener overcoat and fillet (Figure 13-12).

(3) Machine fitting as in some access doors (See Figure 13-13). (4) Sealant grooves as in some non-curing sealant designs (See Figure 13-3). 9. CAUSES OF FUEL LEAKS. Fuel leaks have been caused by a large variety of different reasons all of which have caused considerable expenditures of maintenance repair efforts and availability of the aircraft. Fuel leaks have occurred in integral tanks due to material deficiencies, structural cracks, corrosion, and improper techniques during assembly or repair. The following is a list of some of the common causes of fuel leaks: a. Improper mixing, storage, or preparation of sealant.

e.

Improperly installed, cracked or missing fasteners.

f. Improper application of sealant or omission in critical areas. g. Entrapment of air in sealant leading to leaks as result of joint flexing. h. Incomplete filling of voids, causing sealant to blister and rupture. i. Improper curing of sealant before pressurizing or refueling tanks. j. Improper installation of access doors (faulty gaskets, wrong fastener length or incorrect fastener torque). k. Improper installation of fasteners (poor holes, wrong length, incorrect torque, or failure to compensate for sealant flow in faying surfaces by retightening or using setup bolts). l.

Structural cracks, material failures.

m. Sealant material deficiencies. n.

Corrosion of the metal surfaces.

o.

Defective O-rings, sealing washers, or nut-plates.

p. Improper sealing of fasteners (failing to clean fasteners, failing. to coat all fastener surfaces with sealant, or failing to install static seals correctly).

Improper repair or missing of the true source of a

q. Improper fit of repairs, which form fuel tank boundaries (such as mismatch of adjoining members, interference between adjoining members, or insufficient void widths).

d. Improper cleaning of surfaces before application of sealant thereby preventing adequate adhesion.

r. Connection and fitting (electrical and tubing) that pass through any of the tank boundaries with improper installations, faulty seals, or cracked/broken arts.

b. c. leak.

Use of the wrong sealant for a particular aircraft.

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Figure 13-1. Typical Integral Fuel Tanks

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Figure 13-2. Curing Sealant Design

NOTE: FASTENER A MAY BE SEALED ON EITHER END. FASTENER B MUST BE SEALED ON NUT END AND FASTENER C MUST BE SEALED IN THE COUNTERSINK

Figure 13-3. Non-Curing Sealant Design

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Figure 13-4. Typical Locations of Grooves/Channels (Sheet 1 of 2)

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Figure 13-4. Typical Locations of Grooves/Channels (Sheet 2 of 2)

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Figure 13-5. Structural Adhesive Sealing

Figure 13-7. Direct Seal Door

Figure 13-6. Plug Door Figure 13-8. Flat Gasket Seal

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Figure 13-9. O-Ring Seal

Figure 13-10. Molded-In-Place Seal

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Figure 13-11. Typical Fastener Seals

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Figure 13-12. Typical Fasteners, Overcoat and Fillet

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10. LEAK PATH ANALYSIS. This is one of the most important steps performed in fuel system repair. Leak path analysis is simply the study of how fuel in an integral tank leaks to the outside. The three basic elements of leak path analysis are the initial point where the leak starts called the "leak source", the trail or route that the fuel travels called the "leak path" and the exit on the outside of the tank called the "leak exit." (See Figure 13-14.) In integral tanks, a seal plane or barrier is established during initial assembly of the integral tanks. The seal plane consists of a liquid tight boundary composed of aircraft structure, fasteners, and some type of sealing system. If this seal plane is broken, then a leak path is established which allows fuel to drip or leak from the integral tanks. To repair a leaking integral fuel tank, a leak path analysis of each leak is required. This could be as simple as the short leak path of a single fastener (Figure 13-15), leaks across a non-curing sealing groove (Figure 13-4) or it could involve a leak path which travels many feet through adjoining structure and seals (Figure 1316). These leak paths should be studied to assist in the correct identification of leak sources, paths and exits. Always locate the complete leak path with source and exit before beginning repairs. Do not repair leaks singly as they are found, because this is excessively time consuming and costly. If a leak is found that requires repair, inspect the leak for any other leaks within that tank and complete all repairs prior to tank closure. Figures 13-17, 13-18, 13-19, and 13-20 illustrate various leak paths. Remember, leaks can channel through structure and can exit at points great distances from the leak source making the leak path analysis a most difficult task to perform. 11. LOCATING LEAKS IN INTEGRAL TANKS. Planning is extremely important in locating fuel leak paths. The procedures for locating fuel leaks shall be followed closely and shall include the following sequence of operations:

located. Depending on the complexity of tank structure in the area of the leak use one or more of the internal leak source methods to locate the leak source. g.

Repair the fuel tank to a leak-free condition.

12. LOCATING LEAK EXIT POINT. In order to make the best possible evaluation of a fuel leak both in regard to intensity and location, examine the leak while the tank is fueled and pressurized. There are many methods of locating the leak exit points and the following are approved methods: red talcum powder, torn paper, pressure test, and gas detection methods. The red talcum powder and torn paper methods are used after a visible fuel leak has been detected and before the tanks are defueled. The talcum and paper methods have proven to be two of the most effective and easiest to use.

When using leak detection powder avoid repeated or prolonged breathing of dust. Use only in a well ventilated area. If material other than leak detection powder is used, have the material inspected by a local bioenvironmental engineer. a. Red Talcum Powder Method. After a visible fuel leak has been detected and before the tanks are defueled the following procedure can be accomplished to localize the leak on the exterior surface:

a. Determine the exact leak exit point(s) using one or more of the approved methods for locating exit points. b. If the leak exit point(s) indicates more than one tank could contain the leak source, determine which tank is leaking. c. Using the aircraft technical manual sealing details, analyze possible leak paths through the seal plane. d. For integral tanks, which do not allow access to the interior go to step g. e. For integral tanks, which allow repairman access, have the aircraft defueled and prepare for tank entry. f. Thoroughly inspect the area of the tank where the leak path analysis indicates possible leak sources to be

Red talcum powder is for external use only and shall not be mixed with fuel as a dye. (1) Have a container of red talcum powder (Table 2-5, Item 6f) and a thick-bristled, camel's hairbrush (Table 2-5, Item 3d) for applying the powder on suspected leak sources, or use the aerosol packaged red talcum powder. Have plenty of clean absorbent wiping cloths available. (2) Strip exterior sealants from seams that are in suspected leak areas as required. Some paths may be interconnected and finding that one leak point does not necessarily eliminate others.

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Figure 13-13. Machine Fitted Plug-Type Access Door for Attaching Screws (6) When the fuel leak exit point has been determined, identify it with a marking pencil (Table 2-5, Item 7c). Wipe up remaining talcum, being careful not to remove leak exit point markings. When using air pressure, be extremely careful. Do not blow stream of air toward yourself or any other person. Users of air pressure and personnel within the immediate area shall wear safety glasses, goggles, or face shield. Ear protection may be required. Pressure shall not exceed 30 psig. (3) Wipe off the leak area thoroughly using three or four changes of absorbent wiping cloths. Blow out all seams and corners with compressed air. The area shall be completely dry.

(7) Continue fuel leak path analysis. b. Torn Paper Method. The torn paper method is similar to the talcum powder method in that it is used after a visible fuel leak has been detected and before the tanks are defueled. The following procedure can be used to locate fuel exit points: (1) Strip exterior sealants in seams from suspected leak areas as required.

NOTE Use air hose with a control nozzle and with a 30 psig maximum line pressure, and keep at least 1/2 inch away from sealant or structure to prevent damage to sealant. (4) Dust area with talcum powder immediately. Keep dusted area under constant observation in order to pinpoint the exact point of exit. Note the first sign of change in color. The talcum, which contacts fuel will turn bright red. This change of color will spread rapidly. (5) Continue to observe area for an adequate period of time to determine sequence in which different areas become wetted.

Figure 13-14. Leak Path Analysis

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Figure 13-15. Fastener Leaks

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Figure 13-16. Examples of Long Leak Paths

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Perform fuel transfer and comply with center of gravity limits as specified in applicable aircraft technical manual. a. Transfer/defuel one of the tanks adjacent to the leak, normally the outboard tank. b. Allow an adequate time for residual fuel to drain and check for leakage stoppage. If the leak has stopped, then this is the tank that is leaking. If the leak continues, complete step c.

Figure 13-17. Fastener Movement in Oversize Hole

c. Transfer/defuel the other tank and refuel the first tank emptied. If the leak stops, the defueled tank is leaking. If the leak continues either both tanks are leaking or residual fuel is giving the indication. If residual fuel is suspected of giving the indication, complete step d. d. Transfer/defuel both tanks and drain all residual fuel to stop the leak.

When using air pressure, be extremely careful. Do not blow stream of air toward yourself or any other person. Users of air pressure and personnel within the immediate area shall wear safety glasses, goggles, or face shield. Ear protection may be required. Pressure will not exceed 30 psig. (2) Wipe off leak area thoroughly using three or four changes of absorbent wiping cloths. Blow out all seams and corners with compressed air. The area shall be completely dry. (3) Tear paper to obtain a fuzzy edge. Slowly move fuzzy edge along suspected leak area. Paper will readily absorb fluid and give good visual indication in the presence of any fuel leak. (4) Mark the leak exit point(s) with marking pencil. (5)

Continue fuel leak path analysis.

13. DETERMINING WHICH TANK IS LEAKING. Fuel leaks which appear near the common boundary of two adjacent tanks may originate in either tank. One method to determine which tank is leaking is by defueling the tanks using the following procedures:

e. Fuel the one tank, if no leak indication appears, the other drained tank is the leaker. If a leak indication is obtained, complete step f. f. Transfer/defuel the fueled tank, wait for leak to stop, then fuel the other tank. If a leak indication is obtained both tanks are leaking.

It is absolutely essential for the safety of the airplane structure and the safety of personnel in the area that the pressures be positively limited. Refer to applicable handbook. Injury to personnel and extensive damage to aircraft structure and equipment could result during pressurization and only a qualified fuel system repairer shall accomplish this testing. Compressed air used for cleaning and drying purposes shall be reduced to 30 psi and used then only with adequate chip guarding and personnel protective equipment.

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Figure 13-18. Multiple Leaks Paths From a Single Leak Source

14. PRESSURE TEST. This test may be used to locate the exact leak exit point(s) and confirm repairs. Because of the extensive preparation required for some aircraft and the damage that could result from not complying with instructions, extreme care should be taken when using this test. Before attempting or deciding to use this test, a careful review of the aircraft technical manual must be accomplished. Particular attention must be given to the aircraft's vent system and the specified pressure limits for the applicable tank. This test shall be accomplished using a water manometer (See Figure 13-21). In addition to an entry, a checklist shall be prepared listing all plugs, cover plates and caps installed during the test. This list shall be checked after completion of the test. If previous procedures have failed to identify the location of the exact leak exit, a pressure test should be accomplished when the nature of the leak indicates that other tests would be ineffective or impractical. Some circumstances which might warrant use of the pressure test are as follows: leaks which appear only under stress, inflight leaks, confirmation of leak repairs

before refueling, or when many leaks exist in the same tank. To locate fuel leak point(s), refer to applicable weapon system manual for specific guidance. General procedures are as follows: a. If required, defuel the aircraft and purge the tanks to a fire-safe condition as required by Work Package 006.

Before performing pressure testing of any aircraft tank, careful review of the aircraft technical manual shall be made. b. Comply with the safety and health requirements of Work Package 004.

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c. Install plates/caps/plug as required to all fittings, making sure that cables are attached to the door cover. Check that red safety streamer (Table 2-6, Item 3c) is attached to outer side of door cover.

Be sure the negative pressure attaching connection of the manometer is uncapped when the tank is under positive pressure.

To avoid possible structural or sealant damage, do not relieve the pressure in less than 15 minutes. i. Wash area to which leak detection compound has been applied and remove equipment from aircraft. Leak detection compound should be removed no later than 24 hours after application. j.

Continue with the leak path analysis.

NOTE If a fastener has been newly sealed under the head as a repair measure, the sealant shall be tack-free before retesting. The diameter of the water manometer hose shall be equal to or larger than the fuel tank/cell line used for water manometer connection to prevent any restriction of air movement. d. Attach air supply and manometer (Table 2-6, Item 8b) to connection on door cover. e. Station a man at tank access adapter door and instruct him to carefully observe pressure gage and manometer during the entire procedure. If pressure reaches the maximum limits and relief valves fail to operate, manually bleed off pressure and discontinue operation. Check gages and relief valves for proper and accurate settings. f. Pressurize the tank to a maximum as stated in the aircraft technical manual. g. Additional pressure will not improve or speed the bubble formation employed to detect leaks in this test.

Leak Detection Compound MIL-PRF-25567

13

h. Apply non-corrosive leak detection compound MIL-PRF-25567 (Table 2-5, Item 6g), to the tank exterior. Observe closely for signs of bubbling. Mark all leaks with a marking pencil (Table 2-5, Item 7e).

15. HELIUM OR ARGON GAS METHOD. This method of fuel leak detection uses helium or argon gas that is applied under pressure to a tank or system. It is primarily used to locate fuel leak exit points but can be used to locate internal fuel leak sources. This detector (Table 2-6, Item 7a) is explosive proof in accordance with MIL-STD-801 series, Method 511.1, Procedure II. It is safe for use within areas containing the presence of AVGAS or Jet fuel vapors. Refer to manufacturer’s instructions for the proper operation of the helium or argon leak detector, model 540.

NOTE Gases other than Helium or Argon shall not be used for this test with this test equipment. 16. DEVELOPMENT OF LEAK PATH ANALYSIS. Develop a leak path analysis for each of the fuel leak exit points identified by the preceding methods. Thoroughly analyze the area and structure around the leak for all possible leak paths and leak sources. When investigating the location and the cause of a fuel leak in the fuel tank boundary structure, keep in mind that a leak can be caused by a structural failure. Fuel will leak through an almost invisible crack in the structure. When a leak occurs, structural failure should be considered as a possible cause. Integral tanks too small to permit access by repairer (such as groove injection type) shall be repaired using the fuel leak exit points and the leak path analysis as aids. Integral tanks, which permit access, shall be prepared for tank entry and inspection using the procedures required by Section IV, Aircraft Preparation for Maintenance.

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17. INSPECTION OF TANK INTERIOR. A thorough investigation of the area surrounding the leak exit can help to isolate the leak source. Study the structure in the leak area and the direction from which the leak seems to be flowing. Inspect the interior of the tank in the area determined by the leak path analysis. Entry into the fuel tank requires extreme caution and all personnel shall comply with the safety and health requirements of Section II prior to tank entry. An inspection checklist can be developed using detailed information from the leak path analysis and the tanks sealing system. The following is a list of some common items that should be checked by visual inspections to determine possible leak sources.

NOTE Use mirrors to inspect areas, which are not otherwise completely visible.

(5) Loss luster, discoloration, chalking or loss of topcoat. (6) Loss of elasticity by firmly pressing sealant with a blunt metal punch of not less than 3/16-inch diameter. The sealant is good if it gives and returns to its original position; it is defective if the sealant breaks and holds its pressed position. b.

Inspect for loose, cracked, or missing fasteners.

Leaks caused by structural failure and not by sealant discrepancies cannot be repaired by applying more sealant. Structural leaks shall be subjected to structural repair in accordance with the applicable aircraft manual.

a. Inspect the leak area carefully for defective sealant such as: (1) Previously repaired areas. (2) Cracks, scuffs or nicks. (3) Indications of air bubbles, shrinkage.

When using air pressure, be extremely careful. Do not blow stream of air toward yourself or any other person. Users of air pressure and personnel within the immediate area shall wear safety glasses, goggles, or face shield. Ear protection may be required. Pressure will not exceed 30 psig. (4) Lack of adhesion by applying air at a maximum of 100 psi with an air gun placed approximately 1/2 inch from the sealant. If loose sealant is found, cut through the sealant and strip by pulling away from the structure. Strip sealant until it breaks rather than pulls away from the tank structure. Take extreme care not to damage the structure or the corrosion control coating.

NOTE Visible defects in sealant or the structure are not necessarily the source of a true leak. Continue visual inspection until the entire suspected leak area has been carefully inspected. Mark all defects. 18. LOCATING LEAK SOURCES. Planning is extremely important in locating true leak sources. The procedures for locating fuel leak sources shall be followed closely. Always locate the true source of all leaks before beginning repairs. Do not repair leaks singularly as they are found, because this is excessively time-consuming and costly. If a leak is found that requires repair, inspect the tank for other leaks within that tank and complete all repairs prior to tank closure. There are many approved methods for finding a leak source in an integral fuel tank. The easier and less time-consuming methods are listed first and their use is dependent on the results of the tank inspections and leak path analysis. The following is a list of the approved methods: Blow back method, dye injection method, vacuum (fluid dye or leak detection compound) and gas detection (helium or argon gas or nitrogen gas) method.

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NOTE:

SOME LEAK PATHS CAN BE CREATED THAT ARE ALMOST IMPOSSIBLE TO FIND AND SEAL SUCH AS THE CREATION OF BRIDGES

FROM THE SIDE A BRIDGE OF SEALANT HIDES AN UNSEALED LEAK PATH

Figure 13-19. Sealant Bridging

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Figure 13-20. Fillet Seal Deflection

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Figure 13-21. Pressure Test Method

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a. Blow Back Method. The blow back method is a method to establish the leak path of fuel from an integral tank and requires access inside of the tank. This system requires at least two repairers, an air hose with pressure nozzle, and non-corrosive leak detection compound (Table 2-5, Item 6g). To locate either the internal leak source or external leak exit point use the following procedures: (See Figure 13-22.)

NOTE A system of tapping signals can be arranged for communication between the two repairers to indicate when the air pressure is to be applied, shut off, or reapplied as required.

(1) Prepare the aircraft for entry into the integral tank or tanks as required by Work Package 006, Defueling, Depuddling, Purging, Hot work, and Inerting.

(6) If bubbles are observed, mark the spot and notify the other man to mark the spot where the air was applied. This locates the exit and entrance of the fuel leak path.

(2) Prior to entry into the fuel tank comply with the safety and health requirements of Work Package 004, General Safety Instructions.

(7) Continue the process until all of the suspected area is completely covered. (8) Small leaks, which require air pressures for longer periods of time, may require the use of a pressure box (Table 2-6, Item 7b).

When using air pressure, be extremely careful. Do not blow stream of air toward yourself or any other person. Users of air pressure and personnel within the immediate area will wear safety glasses, goggles or face shield. Ear protection may be required. Compressed air used for cleaning and drying purposes shall be reduced to 30 psi and used then only with adequate chip guarding and personnel protective equipment.

(9) Recheck suspected leak spots by reversing the air hose and applying air pressure to the places where the leak detection compound has been applied. (10) After completion of inspections, wipe up the leak detection compound from the tank surfaces with a damp cloth. (11) Check that the leak points have been properly marked, with marked pencils. (Table 2-5, Item 7c). (12) If this method did not expose the fuel leak source, use one of the other methods as follows:

(3) Position one repairer inside the fuel tank and one repairer outside the tank. (4) One repairer shall apply leak detection compound (Table 2-5, Item 6g) around the suspected leak area.

NOTE Variance of air pressure, not to exceed 100 psig, may be required to locate the leak. (5) The other repairer shall apply air pressure to the leak point or suspected leak point area. The air hose and supply shall be capable of delivering air at approximately 90 to 100 psi. Care shall be taken to keep the air nozzle approximately 1/2 inch from the structure or sealant.

Extensive damage to aircraft structure, tank sealant, personnel and equipment could result from these tests. They shall only be accomplished by qualified fuel system repairers. Fluorescent dye is toxic to skin, eyes, and respiratory tract. Avoid skin and eye contact. Good general ventilation is normally adequate. b. Dye Injection Method. This method identifies the leak source and leak path by injecting a small quantity of dyed fuel through the leak exit point. The dye used can be

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either a red dye, which leaves a visible red stain, or a fluorescent dye, which can be seen with aid of an ultraviolet (black) light. This method consists of a control box, two dye injecting devices (a double cup or hollow bolt), a pressure box and a vacuum cup. The control box requires a portable air compressor or other compressed air device and converts this external air supply to a vacuum source and a pressure injection source with dyed fuel reservoir. The control box may be used with any of the dye injecting devices, pressure box or vacuum cup. The following procedures shall be accomplished prior to test: (1) Prepare the aircraft for entry into the tank or tanks, as required by Work Package 006, Defueling, Depuddling, Purging, Hot work, and Inerting.

(2) Prior to entry into the fuel tank, comply with the safety and health requirements of Work Package 004, General Safety Instructions. (3) Mix dye outside of the aircraft and fill control box reservoir. The dye shall be mixed per the following: (a) For fluorescent detection, mix one part of fluorescent dye red or yellow (Table 2-5, Item 6b) to ten parts of jet fuel. (b) For visual detection mix one ounce of red dye (Table 2-5, Item 6b) to 100 gallons of jet fuel. A stronger solution may be mixed for better leak source identification.

Figure 13-22. Blow Back Method (4) Connect the control box (Table 2-6, Item 7b) to either the double cup assembly, hollow bolt, vacuum cup (Table 2-6, Item 7c) or pressure box.

(b) Attach the double cup assembly to the surface over the leak exit point.

(5) Using Double Cup Assembly. The double cup assembly is used to locate leak sources by forcing dye solution through the leak exit point. To locate leak sources, with the double cup assembly use the following procedures.

NOTE

(a) Connect double cup assembly to the control box (Table 2-6, Item 7b). The hose from the cup outer segment connects to the vacuum source and the inner segment connects to the pressure dye source (See Figure 13-23).

Any irregularities in the attaching surface that could cause leakage around the injection cup should be sealed with sealing compound (MILS-11030). Do not cover leak exit point with sealant.

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The leak tracing device should be as close to the double cup as is practical to minimize pressure errors.

The leakage tracing device should be as close to the double cup as is practical to minimize pressure errors.

Monitor the dye container gage and equipment at all times while pressure is applied.

(c) Apply four psi air pressure, or air pressure specified by the aircraft technical manual, to the dyed-fuel pressure tank. Bleed air from the dyed-fuel tank and hose by opening the clamp on the hollow bolt until dyed fuel is ejected, then close clamp.

(c) Apply four psi air pressure, or as specified by the aircraft technical manual, to the dyed-fuel pressure tank. Bleed air from the dyed-fuel tank and hose by opening the clamp on the double cup assembly until dyed fuel is ejected, then close clamp. (d) Check for dyed-fuel vapor ejection from the air ejector. Any dyed fuel leaking from the cup inner segment will be sucked down the outer segment hose and blown out of the air ejector. No leakage is permissible. (e) After insuring compliance of all tank entry safety precautions, enter tank and observe suspected leak area for indications of dye. When fluorescent dye is used, an explosion-proof ultraviolet light will be required to detect dye in tank.

(d) After insuring compliance of all tank entry safety precautions, enter tank and observe the suspected leak area for indications of dye. When fluorescent dye is used, an explosion-proof ultraviolet light will be required to detect dye in the tank. (e) Continue the dye pressure application as long as required to allow the dyed fuel to travel the leak path. (In some cases this may require 24 hours or more.)

(f) Continue the dye pressure application as long as required to allow the dyed fuel to travel the leak path. (In some cases, this would require 24 hours or more.)

Monitor the dye container gauge and equipment at all times while pressure is applied.

(g) When the dye appears inside the tank, mark the point of appearance and close the flow valve, remove equipment.

(f) When the dye appears inside the tank, mark the point of appearance and close the flow valve. Remove equipment.

(6) Using the Hollow Bolt. The hollow bolt injecting device is used to locate leak sources by forcing dye solution between the mating (faying) surfaces and along the leak, path. It should be used only when the double cup assembly could not identify the leak source. To locate leak source with the hollow bolt device, use the following procedures:

(7) Using the Vacuum Cup. The vacuum cup is a device used to confirm a repair or to identify a leak exit point by pulling air, dyed fuel or bubble solution through the tank structure and into the plastic container. To locate leak exits or confirm repairs use the following procedures:

(a) Remove the leaking fastener or a fastener near the leak and install the hollow bolt (See Figure 13-23.) (b) Connect the hollow bolt with a hose to the pressure dye source of the control box.

(a) Connect the vacuum cup (Table 2-6, Item 7c) with a hose to the vacuum source of the control box (Table 2-6, Item 7b) (See Figure 13-23). (b) Attach the vacuum cup (Table 2-6, Item 7c) to the surface over the repaired area or suspected leak exit point.

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Figure 13-23. Dye Injection Method

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NOTE Any irregularities in the attaching surface that could cause leakage around the injection cup should be sealed with sealing compound (MILS-11030). Do not cover leak exit point with sealant. (c) Apply vacuum and wet inside of tank near leak source with dyed fuel. (d) Check for dyed fuel through the transparent glass.

(8) Use of Pressure Box. The pressure box is used to locate leak sources by pressurizing a large exterior surface area, which in turn forces air back through the leak path into the tank. The pressure box can be used in contoured or flat areas and may be used with bubble solution or dyed fuels (See Figure 13-24). It is useful in pressurizing areas, which contain seep type leaks. To locate leak sources with the pressure box use the following procedures: (a) Steps 1 through 5 describe the method of forcing air through the leak path. Steps 6 through 15 shall be used for forcing dye through the leak path. 1 Install appropriate end plates for covering structure at external leak point.

(e) Continue as long as required to allow dyed fuel to travel leak path. (f) When the dye appears inside the vacuum cup, mark the point of appearance and close the flow valve, remove equipment.

2 Mount pressure box over external leak exit point. For lower wing surfaces support with an air strut. The air strut should have a minimum of 10-inch free piston travel up or down to allow for changes in wing position. For upper surfaces hold in place with shot bags.

Figure 13-24. Use of Pressure Box for Dye Injection

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NOTE When the air strut is used, the air supplied shall be controlled by a pressure regulator. Applying 60 psi air pressure to the strut should be sufficient to seal the unpressurized box to the wing surface. It will be necessary to increase the strut pressure as the box is pressurized

13. Close the tube clamp an injection bottle nozzle and mount bottle containing dyed fuel mixture to nozzle. 14. Release pressure from pressure box, open injection bottle nozzle tube clamp, and inject dyed fuel solution into plastic patch area. 15. Close injection bottle nozzle tube clamp and apply air pressure of four psi (maximum) to pressure box using control box.

3 Connect the pressure box to the control box and pressurize the box to four psi or to the pressure specified in the aircraft manual. If the air strut to 100 psi maximum or to a pressure equivalent force or as specified in the aircraft manual.

16. Inspect the tank interior for any signs of dyed fuel. Mark all sources with marking pencils (Table 2-5, Item 7c).

4 Apply leak detection compound (Table 2-5, Item 6g) to the suspected leak source areas. Mark all areas that bubble with a marking pencil (Table 2-5, Item 7c).

18. To assure an effective repair, the tank may be tested after completion of the repair. A contrasting type dye may also be used to aid in the re-inspection.

5 Remove equipment and repair tank using permanent repair methods.

c. Vacuum Methods. The vacuum dye method and the vacuum bubble method are used to identify fuel leak sources in integral tanks. In both methods a vacuum or negative pressure is applied to the integral tank or tanks. The vacuum dye method uses red dye or fluorescent dye mixed with fuel and applied to the outside of the tank. The dyed fuel is pulled inside the tank through the leak path and thereby identifying the leak source. In the vacuum bubble method a repairer is required inside the tank to apply leak detection compound. This requires extreme caution and alertness of the repairers when this test is being accomplished. As air is pulled inside the tank, the leak detection compound will bubble at any leak sources. The following procedures shall be accomplished prior to either vacuum test method:

6 To utilize the pressure box for dye injection, fill the pressure box with dyed fuel. To reduce the amount of dye required, a plastic sheet supporting a quantity of dyed fuel may be taped to the lower wing surface with the pressure in the box mounted on top of the sheet.

Pressurize the box to force the dye back 7 along the leak path with dye solution in the control box. Air should be removed through one of the bleed screws near the top of the pressure box.

17. Remove equipment and repair tank using permanent repair methods.

8 To use less dye, tape a sheet of plastic material the same size as the pressure box seal over the external leak point with double backed tape.

(1) Prepare the aircraft for entry into the tank or tanks as required by Work Package 006.

Tape the flat nozzle of the dye injector bottle 9 through the plastic patch seal.

(2) Prior to entry into the fuel tank, comply with safety and health requirements of Work Package 004.

10 Mount pressure box over plastic patch, make sure the box seal bears on the plastic patch seal. Support box with air strut and seal around injector bottle nozzle with zinc chromate putty.

(3) Prepare tank for evacuation test as described in aircraft technical manual and determine negative pressure approved for the aircraft.

11 Remove injection bottle from nozzle and loosen tube clamp so the air may be bled from inside the plastic patch area. 12 Apply approximately 1/4-psi air pressure to pressure box from the control box to force all air from inside plastic bag

(4) Check manometer reservoir for proper fluid level and make sure pressure connection on manometer is free of obstruction. Tank test filing shall be equipped with vacuum relief valve. All cover plates, plugs, and caps that require internal installation shall be attached to test door. Make a list of all equipment taken into the tank. The diameter of the water manometer hose shall be equal to or larger than the fuel tank/cell line used for water manometer connection to prevent any restriction of air movement.

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Ethylene Glycol is toxic to skin, eyes, and respiratory tract. Avoid skin and eye contact. Good general ventilation is normally adequate.

to one to two hours. This time is dependent upon leak classification; leaks of the seep type should be kept wet for one-half hour and vacuum on tank for one hour. It may be necessary to lengthen the time in case of very small leaks.

NOTE

(5) Connect manometer to tank test fitting. Only manometers filled with a mixture of fifty percent water and ethylene glycol (Table 2-5, Item 6h) shall be used in testing fuel tank.

The length of the time necessary to keep that area wet depends on the size of the leak. The negative pressure should be applied for twice the time that the area is kept wet. (g) Relieve vacuum from tank and prepare for entry.

It is absolutely essential for the safety of the aircraft structure and personnel in the area that the only, negative pressure used is the pressure specified in the aircraft manual. (6) Use either the vacuum dye method or the vacuum bubble method. (7) Vacuum Dye Method. To accomplish the vacuum dye method use the following procedures:

(h) When using fluorescent dye, inspect the interior of the tank with an ultraviolet (black) light. Mark all leaks with a marking pencil (Table 2-5, Item 7c). (i) If dye has not been drawn into tank repeat steps (b) through (h) allowing a longer period of pressurization. (j) Repair all leaks using permanent repair methods.

(a) Mix dyed fuel per the following: 1 For fluorescent detection, mix one part of fluorescent dye to ten parts of jet fuel. 2 For visual detection, mix one ounce of red dye (Table 2-5, Item 6b) to 100 gallons of jet fuel. A stronger solution may be mixed for better leak source identification. (b) Apply negative pressure to tank as stated in the aircraft technical manual. (c) With camel hair brush (Table 2-5, Item 3d) or syringe, apply dye solution to the external leak point. (d) On the lower wing surface it may be necessary to tape a plastic bag full of dye solution to the surface to keep area constantly covered. (e) On the upper wing surface, wetting may be accomplished by building a circular dam (using sealing compound, MIL-S-11030 or other suitable material) around the leak area and filling with dye solution. (f) Keep leak point wet for minimum of one-half

Before returning the airplane to service, check that all test and repair equipment has been removed. (8) Vacuum Bubble Method. To accomplish the vacuum bubble method use the following procedures:

NOTE The plexiglas door requirements is to provide a person in the tank an escape hatch without the help of other personnel. (a) After the tank has been purged to a fire safe level or lower, place a locally manufactured plexiglas door in the place of the access door. A typical plexiglas door will have a smooth sealing surface and is not drilled for bolt holes. It is equipped with telephone jack plug and a handle on the outside, and air respirator plugs and is held in place by vacuum (negative pressure). One fitting or access door shall be equipped with an inlet and outlet for vacuum lines and water manometer. All other fittings shall be plugged and all plugs shall have red safety streamers.

NAVAIR 01-1A-35

013 00 Page 31 19. TEMPORARY REPAIRS.

(b) Before entering tank, persons shall: 1

Connect respirator and telephone.

water

e. Temporary repairs are designed to downgrade leak classifications to a flyable condition until such time as scheduled permanent repairs can be accomplished. They should be replaced with a permanent type repair when aircraft is grounded for other maintenance, which provides access to the applicable integral tanks.

(c) The vacuum shall be closely observed. Never pull more vacuum than the applicable aircraft manual specifies.

f. Strictly observe fuel leak classification for various fuels described in this manual and the applicable aircraft manual when determining the degree of leakage and the corrective action necessary.

Vacuum pressures other than prescribed by the aircraft technical manual can cause the structure to collapse and costly damage to the aircraft.

g. Temporary repairs accomplished by depot and contractor personnel prior to functional test flight shall be removed and permanent repairs accomplished prior to release of aircraft to the using organization. Only those temporary repairs, (a maximum of one per fuel tank) made during the delivery preparation phase of this aircraft process will be allowed to remain on the aircraft when delivered. Temporary repairs accomplished during the delivery preparation shall be made in accordance with this manual. Temporary repair limitations apply only to Program Depot Maintenance (PDM) aircraft. However, they may be exempted or modified by the contract work specification, or system technical data.

2 Check to ensure that air resupply and communications equipment are working properly. 3 Connect vacuum manometer (Table 2-6, Item 8b).

pump

and

(d) When the vacuum has reached the value stated in the aircraft technical manual, the repairer shall, apply non-corrosion leak detection compound (Table 2-5, Item 6g), to suspected leak areas in cell/tank interior. (e) When a leak is found, mark it with a marking pencil and continue on until the tank has been completely tested. (f) After completing the vacuum test, clean all leak detection compound from the surface of the tank with water-dampened cheesecloth or equivalent. (g) Remove equipment and repair tank using permanent repair methods. d. Gas Detection Method. Refer to paragraph 13-15 for locating leak sources with helium or argon gas. Consult bioenvironmental engineering prior to accomplishing this operation.

h. When performing fuel systems repair on a particular aircraft, the records pertaining to that aircraft shall be consulted. The records of an aircraft shall accompany that aircraft into PDM and upon transfer. i.

The approved temporary repair methods are:

(1) Hardman extra-fast setting epoxy (Table 2-5, Item 2b).

Sealant AMS-S-8802

Sealing Compound AMS 3276 Before returning the aircraft to service, check that all test and repair equipment has been removed.

14

(2) Aluminum foil patch with MIL-S-83318 (Table 2-5, Item 8aa), AMS-S-8802 (Table 2-5, Item 8k), AMS 3276 sealant (Table 2-5, Item 8ab).

NAVAIR 01-1A-35

013 00 Page 32

(3)

Epoxy tabs, Type O (Table 2-5, Item 12.l).

(4)

Click patch (Table 2-5, Item 12m).

(5)

Off pressure seal.

(6)

Comp Air D-236 injector kit (Table 2-6, Item

(4) Mix the Hardman epoxy according to the directions on the package until it has a uniform appearance. (5) Coat the cleaned side of the patch with 0.015 to 0.020 inch of the Hardman epoxy.

7e).

(6) Press the patch into place over fastener head. The adhesive will cure in approximately 15 minutes at 75oF.

(7) Oyltite Stik (Table 2-5, Item 13k). j. Hardman Extra-Fast Setting Epoxy With or Without Aluminum Foil Patch. The aircraft does not need to be defueled to repair leaks. Use the following procedures for proper patch application:

Acetone ASTM D329

7

NOTE

Do not use the heater from the sealant patch kit to cure the adhesive. Heat curing will cause the adhesive to become brittle and fail. (7) Repair Method Limitations. (a) Temperature range within which repair can be made is +40OF to +120OF.

When not using aluminum foil patch to repair leak, follow steps (1) and (4) then apply a thin coat of epoxy to the leak area.

NOTE

(1) Clean area around the fastener with Cleaning Compound A-A-59281, Type I of II and/or Acetone, ASTM D329 .

When the temperature is +40OF to +60OF, the epoxy should be kept at above 60OF until mixing.

(2) Use a patch cut from 0.002-inch thick aluminum foil (Table 2-5, Item 12t) that will cover the head of the fastener and extend 1/2 inch beyond the edge of the fastener.

Acetone ASTM D329

(b) Curing time of repair ranges from 40 minutes at +40OF to 15 minutes at +120OF. (c)

Humidity has little effect on curing time.

(d) Do not remove the coating from around the fastener. The epoxy adheres better to the coating than to bare aluminum.

7

(3) Clean the surface of the patch to which the adhesive will be applied with Acetone, ASTM D329.

(e) Do not use heat to cure the epoxy. The heating device used with the sealant patch will cause the epoxy to become brittle.

(8) Removal of Repair.

Epoxy is flammable and toxic to eyes, skin, and respiratory tract. Skin and eye protection required. Avoid repeated or prolonged contact. Good general ventilation is normally adequate. Keep away from open flames or other sources of ignition.

Handling hot items presents a serious burn potential. Temperature resistant gloves are required.

NAVAIR 01-1A-35

013 00 Page 33

(a) Heat the patch to a temperature of 200OF to 250 F using a heating gun. O

While the patch is hot, use a plastic scraper to pry up part of the patch. Continue to apply heat and use needle-nosed pliers to pull off the patch. (b)

(c)

15

Reheat the area.

While the epoxy is hot, scrape off the epoxy using a plastic scraper. Continue to apply heat and scrape until epoxy is removed. (d)

NOTE If the temperature is under 200OF, the epoxy will not soften. If the temperature is over 250OF, the aircraft paint will be scraped off with the epoxy. Using the correct temperature range will insure removal of epoxy and minimal aircraft coating damage. k. Aluminum Foil Patch Bonded with AMS-S-8802/ AMS 3276 Sealant. The aluminum foil patch method is approved for use as a temporary repair for leaking fasteners. To obtain best results, aircraft should be defueled below leak exit point. Use the following procedures for proper patch application: (1) Clean the area around the fastener with four part cleaner (Table 2-5, Item 4g).

NOTE For illustrated breakdown of aluminum foil patch kit, see Work Package 010. (2) Use an aluminum foil patch from kit (Table 2-5, Item 12m), or cut a patch from 0.0015 inch aluminum foil (Table 2-5, Item 12s), that will cover the head of the fastener and extend 1/2 inch beyond edge of fastener.

Acetone ASTM D329

Sealant AMS-S-8802

7

(3) Clean the surface of the patch to which the sealant will be applied with Acetone, ASTM D329.

Sealing Compound AMS 3276

14

(4) Coat the patch with 0.015 to 0.020 inch of AMS-S-8802 sealant (Table 2-5, Item 8n) or AMS 3276 class B 1/2 sealant (Table 2-5, Item 8ab). (5) Press the patch into place over the fastener head. (6) Apply heat to the patch to cure the sealant using the heat applicator in the kit. Cure for approximately 30 minutes at 140OF. (7) Repair Method Limitations. (a) No temperature limitations apply when the heating device from the repair kit is used.

NOTE At low temperatures (50OF and below), better results will be obtained if the surface around the fastener is preheated for a few minutes before the sealant and patch are applied. (b) Curing time of repair is 30 minutes at 140OF. (The temperature produced by the heating device in the kit.) (c) Refer to tack-free times for effect of humidity on cure time. (8) Removal of Repair. Cut the sealant under the edge of the patch with a plastic scraper using a slicing motion. Pull up on the patch and continue cutting the sealant until the sealant and patch are removed. l. Epoxy Tab Type O. The aircraft does not need to be defueled to repair leaks. Use the following procedures for proper application:

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013 00 Page 34

Acetone ASTM D329

7

leaks are experienced at these repairs for the particular weapon system/repair activity. Also, refer to weapon system technical data for restrictions on use of temporary repairs. (1) Defuel the affected tank. Bottom drain is necessary.

Epoxy is flammable and toxic to eyes skin, and respiratory tract. Skin and eye protection is required. Avoid repeated or prolonged contact. Good general ventilation is normally adequate. Keep away from open flames or other sources of ignition. (1) Clean the area around the fastener with Acetone, ASTM D329. (2) Mix epoxy tab type O (Table 2-5, Item 12.l) according to the directions on the package until it has a uniform appearance. (3) Apply the epoxy tab type O over the fastener using an ample amount of material (approximately 1/8 inch thick). Feather out the edges so that the material extends approximately 1/2 inch beyond the edge of the fastener. (4) Repair Method Limitations. (a) No temperature limitations are applicable. (b) No curing time limitations are applicable. (c) No humidity limitations are applicable. (5) Removal of Repair. Place a plastic scraper at the edge of the repair as you would for scraping. Tap the other end of the scraper with a rubber mallet until the repair pops off. m. Click Patch. Click patch kits (Table 2-5, Item 12m) may be used to make temporary repairs. The electric click patches should not be used. Prepare the surfaces, mix and apply the sealant or epoxy adhesive as applicable and apply the patch in accordance with the enclosed instruction sheet in each kit. When it becomes necessary to remove the patches, remove as for the aluminum foil patches as above and according to whether sealant or epoxy adhesive was used. n. Non-Foil Sealant/Adhesive Patch. The following rapid repair method should be used only on non-pressurized fuel tank surfaces, and should be discontinued if recurring

Acetone ASTM D329

7

(2) Clean area around the leak exit point with Acetone, ASTM D329 and approved wiping cloth (Table 2-5, Item 3h).

Sealant AMS-S-8802

15

(3) Apply a thin coat of Hardman Epoxy, AMS-S8802 or MIL-S-83318 sealant to the leak exit point. (4) Allow sealant or epoxy to cure before fuel servicing and leak check are accomplished.

Sealant MIL-S-22473

16

o. Comp Air D236 Injector Kit. The Comp Air D236 injector kit (Table 2-6, Item 7e) is approved for temporary repair of fuel leaks around flush type fasteners. This repair can be accomplished without defueling aircraft. This injector forces MIL-S-22473 sealant (Table 2-5, Item 8ad) into the leaks around the fastener at a pressure of approximately 900 psi. After the sealant is injected, the head of the fastener is covered with aluminum tape and the sealant is heat-cured to stop the leak. Use the following procedure for proper sealant injection:

Acetone ASTM D329

7

When using air pressure, be extremely careful. Do not blow stream of air toward yourself or

NAVAIR 01-1A-35

013 00 Page 35

any other person. Users of air pressure and personnel in the immediate area shall wear safety glasses, goggles, or face shield. Ear protection may be required. Pressure will not exceed 30 psig. (1) Remove paint from area around leaking fastener. Clean surface with clean rags dampened with Acetone, ASTM D329 and wipe dry. (2)

For leaks in lower wing surfaces:

Position locator D236-12-2 overhead of fastener and attach with suction cups. (a)

(b) Attach D236-11 cylinder and D236-10 jack (with extensions if necessary). (c)

Align complete assembly to be perpendicular

to surface. (d)

Attach compressed air source to cylinder.

(e)

Fill injector with sealant.

(f)

Place injector through locator.

(k) Remove tape by peeling.

Sealant MIL-S-22473

16

(3) Sealing fuel leaks at fasteners in wing upper surface: This procedure is similar to that used for lower surfaces except, use D236-3 injector, and D236-12-3 locator and apply MIL-S-22473 sealant as follows: (a)

Place correct foot assembly over leak.

(b)

Position the D236-12-3 locator correctly.

Sealant MIL-S-22473 (c)

16

Insert MIL-S-22473 sealant (Table 2-5, Item

8ad) in foot.

Since deflection of the wing may cause impact with the injector kit stand, and possible damage to underside wing skin panels, the wing should be tied down, or otherwise rigidly restrained per the applicable technical order to prevent movement from wind gusts. (g) Manually extend jack to force the cylinder rod to retract into the cylinder approximately three inches. (h) Observe injector head. When all sealant has been injected, the sleeve will line up with edge of the body.

Acetone ASTM D329

10 minutes to cure sealant. Temperature of heating iron shall not exceed 150oF.

(d)

Install plunger in foot assembly.

(e)

Press down on plunger to inject sealant.

Acetone ASTM D329

7

(f) After sealant has been injected remove injector and immediately wipe surface with rag dampened with Acetone, ASTM D329 to remove excess sealant and immediately apply aluminum foil tape, approximately one inch square, over fastener head. (g) Immediately apply preheated D236-14 heating iron to aluminum tape and hold firmly against tape for 5 to 10 minutes to cure sealant. Temperature of heating iron shall not exceed 150oF.

7

(i) After sealant has been injected, remove injector and immediately wipe surface with rag dampened with Acetone, ASTM D329 to remove excess sealant and immediately apply aluminum foil tape, approximately oneinch square, over fastener head.

(j) Immediately apply preheated D236-14 heating iron to aluminum tape and hold firmly against tape for 5 to

Oyltite Stik is flammable and toxic to eyes, skin and respiratory tract. Skin and eye protection required. Avoid repeated or prolonged contact. Good general ventilation is normally adequate.

NAVAIR 01-1A-35

013 00 Page 36

Keep away from open flames other sources of ignition.

source will be identified for tanks which allow personnel access.

(h) Oyltite Stik. The Oyltite Stik (Table 2-5, Item 13k) is an approved method for the temporary repair of leaking fasteners. Use the following procedure for proper application of Oyltite Stik:

(3) Review the aircraft manual sealing section to identify sealant used and sealing methods employed for structure, fasteners, and access doors/components. (4) Develop a list of items to be worked while tank is open or being worked (such as fuel leaks, corrosion, repair of interior finishes, or structural repairs).

Acetone ASTM D329

7

(i) Clean area around fastener with Acetone, ASTM D329. (j) Soften Oyltite Stik by dipping open end in Acetone, ASTM D329. (k) Firmly apply Oyltite Stik around fastener head. Repeat application until leak stops. (l) Remove excess material.

NOTE Repairs made in areas that are painted may require paint touch-up. 20. PERMANENT REPAIRS. a. General. Permanent leak repairs are those repairs to an integral tank, which do not require further maintenance to the aircraft. The fuel leak classification of this manual and applicable aircraft manuals shall be observed when determining the degree of allowable leakage and corrective action. Those leaks, which require permanent repairs, shall be repaired using the information contained in this manual and the applicable aircraft manuals. Prior to making a permanent repair the following steps must be accomplished:

Careless workmanship or disregard for basic sealing principles can affect the flight worthiness of the aircraft. (1) Identify fuel leaks, which require permanent repairs. (2) Each leak requires a leak path analysis with determination of leak exit point and leak path. The leak

(5) Accomplish repairs. The repair of integral tanks is divided into the following basic parts: (a) Sealants. (b) Related equipment and materials. (c) Non-curing type sealant repairs. (d) Curing type sealant repairs. (e) Repair of fasteners. (f) Repair of access doors/components.

NOTE All or some of these repair methods may be required to correct a fuel tank leak(s) and to accomplish a permanent repair.

Leaks caused by structural failure and not by sealant discrepancies shall not be repaired by applying more sealant. Structural leaks shall be subjected to structural repair in accordance with the applicable aircraft manual. b. Sealants. Sealants used for fuel tank repair are either curing type or non-curing type. Sealants used in the repair of integral tanks require proper storage, packing, mixing, application, and inspections. c. Storage of Sealants. Unmixed sealants shall be stored according to the manufacturer's recommendations. Prior to expiration of the original shelf life, sealants should be examined and tested for updating in accordance with the manufacturer's instructions. The supply activity shall process material in their custody, and the maintenance activity shall test over age sealant in their bench stock.

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013 00 Page 37

Sealants are flammable and toxic to eyes, skin and respiratory tract. Skin and eye protection is required. Avoid repeated or prolonged contact. Good general ventilation is normally adequate. Keep away from open flames or other sources of ignition. d. Mixing of Curing Type Sealant. When two-part curing type sealant (those with an accelerator and base compound) is prepared for use, the accelerator shall be mixed as appropriate to obtain a thorough and complete mixture. Do not attempt to partially mix a kit unless accurate scales are available for weighing. Any sealant or accelerator found to be hard or lumpy shall be discarded. Filleting type sealants should be machine mixed to avoid entrapment of air. Hand mixing is permitted provided manufacturer’s instructions are followed. Brushable type sealants may be hand mixed for fuel tank repairs but should also be machine mixed if large quantities are to be applied. Hand mixing may be accomplished on a flat plate, folding the material so as not to trap air. For small hand-mixed batches of brush-type, Class A application sealants, mixing may be accomplished inside the "base" container if care is taken not to trap air in the mixture during mixing, and insure all of the base component in the bottom, corners and sides is thoroughly mixed. e. Quality Conformance for Curing Type Sealants. This paragraph describes the procedures to be applied when large amounts of curing type sealant are used. A large amount is defined as more than 5-gallon base material, mixed and/or applied to aircraft fuel tanks in a five-day period. Mixed sealants shall be tested to assure proper quality before being released for production application to aircraft fuel tanks. This quality assurance shall include the following steps (1) Sampling. (a) Frequency. Representative samples from each newly opened container or as requested by the sealant mixing facility. 1

One sample from each hand mixed run

2 Representative samples from each machine mixed run (i.e., one sample from at least beginning, middle, and end of run). (b) Label each sample of sealant as follows: 1

Type and class of sealant

2

Manufacturer

3

Manufacture's lot number

4

Date mixed

5

Run number

(2) Laboratory Testing. (a) An accelerated cure mechanism is acceptable for evaluating laboratory samples provided that the accelerated cure temperature does not exceed 130oF and the accelerated cure relative humidity does not exceed 50 percent. Shore A hardness evaluations for lab samples should be based on standard curves for hardness versus cure time developed at temperature and humidity selected for accelerated cure and for each individual type and class of sealant used. (b) The following tests should be conducted: 1

Condition of container and contents

2

Application time

3

Tack-free time

4

Curing time

5

Shore A hardness

6 Peel strength (Use two aluminum panels coated with SAE AMS-C-27725 which have been aged in jet reference fluid seven days at 140oF.) The bell strength test is necessary only if other tests indicate a problem with the sealant. (c) Refer to the applicable specification for requirements for application time, tack-free time, and cure time after nine months storage. The material can be extended 1/2 of the original shelf life. (3) Each sealant run (or portion thereof) must pass all laboratory tests prior to being issued for use on aircraft. (4) Machine mixers that meter the two-sealant components for mixing and dispensing shall be on a definite schedule for inspection of proper mixing ratio. Testing shall also be accomplished after maintenance or adjustment to the machine. f. Quality Conformance For Field Mixed Sealants. For small mixing of two-part curing type sealants (less than five gallons) use the following instructions: (1) Spread thin layer of mixed sealant on a strip of aluminum and visually examine the sealant for small particles of accelerator.

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(2) If particles of accelerator remain after five minutes of mixing, dispose of the corresponding mixed batch of sealant. After mixing, sealants shall have a minimum application time as specified by its dash number. Sealants that will not wet the surface or spread smooth shall be discarded. g.

Freezing and Thawing Mixed Sealant.

Isopropyl Alcohol TT-I-735

3

Dry Ice CGA-G-602

17

(a) Warm water bath. 1

Bath temperature not to exceed 170oF.

2 Immersion time not to exceed 15 minutes for A2, B2, B6 or C sealants. (b) Cartridges are to be capped at large end with a plastic cover and at small end with a plastic cap and a rubber cap prior to either quick thawing method. Excess water is to be wiped from surface of sealant prior to issue. Exterior of cartridge is to be checked for hot spots. That is, spots where temperature is higher than that of the rest of the cartridge and cannot be held comfortably for 30 seconds in the bare hand. When hot spots are found, check the temperature of the sealant by inserting a thermometer into the sealant through the nozzle end. Temperature of the thawed sealant should be 60oF to 80oF. If the temperature of the thawed sealant exceeds 95oF the cartridge should be discarded. (c) Stamp each cartridge prior to issue with:

Temperature resistant gloves and apron required. Carbon Dioxide (CO2) displaces oxygen, which can cause asphyxiation. Use only in well ventilated area. (1) Freezing. Two-part curing type sealants may be premixed and frozen for use at a later time. Mixed sealant may be placed in clean, airtight cartridge that has both ends closed with seal caps to prevent fluid entry. A container of dry ice and isobutyl or isopropyl alcohol may be used to quick freeze sealant. A temperature of minus 100o F shall be maintained in the container. The cartridge shall be immersed nozzle end first to a depth that will cover all of the cartridge except one inch of the large end. Allow a minimum of five minutes for freezing, then place the cartridge in a freezer and store at a temperature of minus 20oF or less. (Refer to Table 13-1.) (2) Thawing. The time consumed by freezing, storing and thawing operations reduces total application life. Cartridges may be quick thawed in a warm water bath. Table 13-1. Mixed Sealant Storage Time Frozen Sealant Storage AMS-S-8802 & AMS 3276

-20oF 14-Day Storage

-40oF 30-Day Storage

1

Time of thaw.

2

Application time.

h. Application Life of Sealants. Non-curing type of sealants have an unlimited application life, however curing type sealants do have an application life, or time during which the sealant remains suitable for use. Application life of two-part curing type sealants is the time that the mixed compound remains suitable for application with a brush, injection or extrusion gun. Application life is always based on standard conditions of 75oF and 50 percent relative humidity. For every rise in temperature, application life is reduced, and for every drop it is increased. Sealant shall not be used, regardless of time, when it will no longer spread smoothly or when it no longer readily wets the metal to which it is being applied. Sealant shall not be used beyond its application time. i. Tack-Free Time. The tack-free time of the sealant is that time at which the outer surface of the sealant will not stick to a plastic film. The tack-free time can be determined by lightly touching a clean nozzle or cartridge to the surface of the sealant. If material does not transfer to the nozzle or cartridge, the sealant is tack-free. j. Sealant Cure. Curing type sealants require that applied materials cure during specified times at standard conditions of 77oF and 50 percent relative humidity. Proper conditions for curing of sealants are dependent on both temperature and humidity. When temperature increases (and humidity stays the same), tack-free time decreases. When humidity increases (and temperature stays the same), tack-free time decreases. When temperature and humidity

NAVAIR 01-1A-35

013 00 Page 39

both increase, tack-free greatly decreases. Curing of sealant may be accelerated by applying heat not to exceed 120oF. Fuel tanks shall not be fueled until sealant is tack-free. 21. SEALANTS. The following types of sealants are the primary items used to seal integral fuel tanks and are divided into two classifications – curing sealants and noncuring sealants: a.

Curing Type Sealants:

Sealant AMS-S-8802

15

AMS-S-8802 (PR-1440) is a polysulfide fuel tank sealant. Most aircraft integral fuel tanks are sealed with this material. The sealant is cured by the addition of an accelerator to a base compound in appropriate proportions. Class A material is for brush application, Class B for filleting, and Class C for faying surfaces. It is available with varying application lives, such as 1/2 hour and two hours. (1)

Sealing Compound AMS 3276

14

AMS 3276 (PR-1750) is similar to AMS-S8802 except it has better high temperature performance, and is designed for limited service life at temperatures up to 360oF. AMS 3276 may be used as a substitute for AMS-S8802 to make repairs but the reverse is not true without system manager approval. (2)

Seal/Coat Compound Corrosion Inhibitive MIL-PRF-81733

20

(3) MIL-PRF-81733 (PS-870) is similar to AMS-S8802 with added chromates for corrosion inhibition. This sealant shall not be used fuel tanks. It is used in faying surfaces and for installation of fasteners.

Sealant AMS-3277

19

Primer

22

(4) AMS-3277 (PR-1826) is a two part chemically curing polythioether polymer based sealant characterized by

rapid cure at low temperature to a fuel resistant elastomer. This material has application temperatures as low as 20oF. When used with primer, the sealant adheres to A1clad, MIL-A-8625, MIL-C-5541, Titanium, Stainless Steel SAE AMS-C-27725, coated surfaces and AMS-S-8802 sealants. Primer must be used to adhere polysulfides to polythioether sealants. Primer will promote adhesion of AMS-3277 to itself and to materials and treatments commonly used for aircraft fasteners.

Sealant AMS-3284

21

(5) AMS-3284 (PR-1428) is a two-part, low adhesion sealant for use on some faying surfaces, and gasket type seals for access doors and accessories. The sealant is colored red to distinguish it from AMS-S-8802 material. AMS-3284 is available in two dash numbers indicating -1/2 and -2 hours work-life. The sealant is also supplied in two viscosities, Class A (suitable for brush application) and Class B (suitable for application by spatula or filleting gun).

Sealant PR-2200

18

(6) PR-2200 is a two part, high adhesion fuel resistant, electrically conductive, corrosion inhibitive sealing compound for access doors. b.

Non-Curing Sealants:

(1) Q94-011 and Q94-031 are non-curing one part fluorosilicone based sealants which do not harden and remain flexible. Q94-031 is the same as 94-011 but contains plastic beads, which pile up at leakage points and tends to be better for sealing leaks. Color is white or light gray and is a "semi-fluid" material. These sealants are used for channel sealing only. 22. RELATED EQUIPMENT AND MATERIALS. For a list of approved sealing and repair equipment refer to Table 2-5 or B. a. Mixing Kit Sealant. The cartridge is a compact unit designed for easy mixing and proper application at two part curing type sealants in small quantities. The base sealant is packaged in standard 2-1/2 and 6-ounce cartridges, which can be placed in the filleting gun, or injection gun, for application. The handle or dasher contains pre-measured catalyst. The catalyst is retained until the ramrod is placed in position in the center of the dasher handle and pressure is applied to release the seal at the

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bottom of the dasher. The kit may be hand mixed (Figure 13-25), but to obtain the best mixing of the sealant, it should be mixed by mixing machine (See Figure 13-26). b. Sealant guns. Sealant guns are air operated and require different air pressures for filleting and injection sealing. Refer to the appropriate aircraft handbook for these guns and associated operating pressures and instructions. To prolong the life of the sealant guns they shall be cleaned after each use. (1) Filleting Gun. The accomplished after each use:

following

shall

(2) Injection Gun. The following shall be accomplished after each use. (a) Immediately after use disassemble the gun for cleaning. (b) Remove nozzle and then remove sealant with a cleaning rod. (c) Remove barrel cap. (d) Remove barrel.

be

(e) Remove ram.

(a) Loosen hand knob and remove retainer.

(f) Remove empty cartridge.

(b) Remove cartridge and nozzle from retainer.

(g) Remove plunger from push rod.

Acetone ASTM D329

7

(c) Wipe gun and retainer with clean rag dampened in Acetone, ASTM D329).

Acetone ASTM D329

(h) Wipe all components of the gun with clean rag that has been dampened in Acetone, ASTM D329 (Table 25, Item 4g).

(d) Wipe dry, with clean rag. (e) Reassemble finger-tight and place in safe place to prevent damage.

7

(i) Wipe all components with clean dry rag. (j) Reassemble and place in safe place to prevent damage.

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Figure 13-25. Machine Mixing of Sealant Kit

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013 00 Page 42

1. PLACE SELECTOR SWITCH IN “MIX” POSITION.

2. AFTER THE CARTRIDGE HAS BEEN PREPARED AS REQUIRED IN FIGURE 13-26. OPERATIONS 1 THROUGH 4, REMOVE RAM ROD AND PLACE THE WHOLE OF THE DASHER ROD DOWN OVER THE PILOT OF THE ROTATING SPINDLE.

3. GRIP THE HANDLE OF THE DASHER ROD AND HOLD FIRMLY UNTIL IT IS ENGAGED WITH THE SELF-TAPPING SCREW.

5. REMOVE CARTRIDGE FROM THE MIXER BY PLACING THE SELECTOR SWITCH IN “REVERSE” POSITION. GRIP DASHER ROD HANDLE FIRMLY AND LIFT CARTRIDGE FROM MIXER.

4. SET BELL TIMER TO THE REQUIRED TIME CYCLE.

6. REMOVE SEAL CAP AND DASHER ROD. CARTRIDGE IS NOW READY FOR USE IN EITHER THE FILLETING GUN OR THE INJECTION GUN. THE INJECTION GUN USES 650 CARTRIDGE ONLY.

Figure 13-26. Machine Mixing of Cartridges

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013 00 Page 43

23. NON-CURING TYPE SEALANT REPAIRS. a. Non-curing type sealant designs consist of a variety of grooves/channels filled with a continuous bead of non-curing sealant, which seals the mating structure faying surfaces. In some designs the fasteners are sealed by this groove (See Figure 13-4). If this sealant develops a void or gap, a fuel leak will appear (See Figure 13-27). Non-curing designs allow little or no internal access and are repaired from the outside by re-injecting new sealant. The new sealant is injected through a series of injection holes provided through one side of the groove, which allows the non-curing sealant to flow into the channel. There, injection holes are spaced along the sealant groove at regular intervals (normally from 3 to 6 inches) and when not in use are plugged with small flush screws. After the location of the leak source has been determined, two or more of these screws will be removed; one on each side of the leak path. The new fresh non-curing sealant is injected through one hole and pushes the old sealant out the other hole. b. In the past, proper sealant injection techniques were not always accomplished for a variety of reasons. Improper techniques result from the extreme difficulty in holding the injection gun over head for long periods of time without support during injection of sealant in lower wing structures. Corrective action is to construct a support stand using such locally-available equipment as a work stand, a jack and easily-manufactured adapters to support the sealant gun during overhead injection.

normally prevent adequate sealant injection and flushing of the sealant channel. If two or more adjacent sealant injection screws are damaged, they shall be replaced to allow proper reinjection of new sealant. d. Other problems have resulted in poor sealant procedures such as using the wrong type of sealant. Curing type sealant injected in non-curing channels may initially stop leaks but destroys channels by preventing further resealing with non-curing sealant. Some non-curing sealants when cold become stiff and resist flow. Local heating of the structure in the vicinity of the groove with an approved heater may aid in flushing out of the cold sealant. Also some leaks may require defueling below the leak source before they can be successfully reinjected with new sealant. e. With the leak path analysis, review of the sealing system structure and corrosion repair completed, use the following non-curing type sealant repair procedures: (1) Identify the correct non-curing sealant to be injected. Refer to the applicable aircraft technical order.

NOTE Non-curing sealant substitutes are not authorized by this technical order. Curing type sealants can block sealant grooves and shall not be used. (2) Use the injection gun, injection nozzle and air pressure as described in the system peculiar technical manual.

Sealant in injection guns shall be free of air pockets/voids. Air pockets/voids will result in fuel leak paths when injected into sealant grooves.

Figure 13-27. Void in Non-Curing Sealant Groove

(3) Load the injection gun with non-curing type sealant using either a prepacked cartridge or sealant packed into injection gun by hand. Be careful to eliminate air pockets and voids. (4) Set air pressure and connect injection gun to air

c. Another problem arises from using the wrong tools to remove injection screws. Sometimes these screws are damaged to the point that normal removal is impossible. However, one damaged sealant injection port will not

source. (5) Extrude some sealants to remove any air trapped in the nozzle.

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013 00 Page 44

(6) Remove two injection screws, one on each side of the leak.

NOTE Local heating of the structure in the vicinity of the groove with an approved heater may aid in flushing out the cold sealant.

manual. Repair of failed sealant is normally not a speedy operation. Adequate time shall be allowed to complete all repairs and proper cure of the sealants. Less manhours will be spent in the long run if ample time is allowed. Effective original inspection and repairs will stop repetitive fuel leaks, a major contributor to extensive fuel leak difficulties. Extreme caution for safety and health hazards shall be observed during repair inside integral tanks. The types of seals or application of sealant used in curing type designs are the following:

(7) Insert gun nozzle into the injection port and reinject sealant. New sealant shall be injected until a string of sealant approximately twice as long as the distance between the holes is extruded. This assures that voids in the old sealant are flushed from the channel and allows the fresh sealant to adhere to the walls of the channel.

a. Prepacked Seals. Prepacked seals are areas or voids in the tank structure that are filled or packed with curing type sealant during assembly. Prepacked seals are not accessible without disassembly and are usually repaired with a fillet seal when disassembly is not practical (See Figure 13-2).

(8) For the repair of long leak paths or hard to identify leak exit points, remove additional screws as necessary. Start at one end of the leak path and remove two injection screws. Repeat step g. Working toward the other end of the leak path, remove one additional screw and replace screw in the previous port. Inject new sealant and continue process until leak is repaired.

b. Injection Seals. Injection seals are areas, voids, holes, fittings, joggles or channels, which are filled with sealant injected under high pressure. Injection seals may or may not be repaired without disassembly (See Figure 13-2).

(9) Replace screws. (10) Non-curing sealants do not harden and remain flexible. Therefore, after injection of the new sealant has been accomplished and has stopped the fuel leak, the aircraft can be serviced with fuel.

Leaks caused by structural failure and not by sealant discrepancies shall not be repaired by applying more sealant. Structural leaks shall be subjected to structural repair procedures in accordance with the applicable aircraft manual. 24. CURING TYPE SEALANT REPAIR. Leaks in curing type sealing systems generally require removal and replacement of defective sealant. However, some curing type seals can be repaired using high-pressure injection guns. Curing type sealing systems utilize a relatively small amount of materials applied to all potential fuel leak paths. Extensive application of repair sealants can add excessive weight to the aircraft. For curing type repairs, the sealant shall be properly mixed (two-part type), the repair surfaces carefully cleaned and the sealant applied using the procedures outlined in this manual and the aircraft technical

c. Faying Surface Seals. Faying surface seals are seals between mating surfaces and are generally used as secondary or isolation seals to prevent fuel from traveling along or through mating surfaces. Faying surface seals normally require disassembly for repair (See Figure 13-2). d. Fillet Seals. Fillet seals are seals applied along the edges of faying surfaces, over parts, between parts, and along the edges of parts. Fillet seals are repaired by removal of defective seal and replacement with fresh sealant (See Figure 13-2). e. Brush Coat or Overcoat Seals. Brush coat or overcoat seals are the application of a thin brushable curing type sealant to seal or overcoat small openings prior to the application of a fillet seal. The brush coat is a secondary seat and shall not be used over fillet seals as a leak repair. The following steps shall be used to repair curing type sealants: (1) Prepare for Entry. Prior to entry into the fuel tank follow the safety and health requirements of Section II. (2) Repair Damaged Structure/Corrosion. All structural repair shall be accomplished in accordance with aircraft structural repair manual prior to application of sealant. Removal and treatment of corrosion shall be accomplished in accordance with NAVAIR 01-1A-509 Aircraft Weapons Systems Cleaning and Corrosion Control Manual and the applicable aircraft maintenance manual. Application or repair to coating SAE AMS-C-27725 shall be in accordance with manufacturer's instructions.

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013 00 Page 45

Steel, copper and brass scrapers or knives shall not be used to remove sealant. These tools can cause damage or corrosion to the aircraft structures. (3) Removal of Damaged Seal(s). After all leak sources have been located and marked, areas adjacent to the leak and the bottom of the tank may be covered with heavy paper or wiping cloths to protect the coating from dirt, tools and foreign materials. Carefully remove any defective/damaged sealant using hardwood, phenolic, or 2024-T3 aluminum scrapers or spatulas (See Figure 13-30). As damaged sealant is removed, place it in a container to avoid contamination and reduce time spent in cleaning. Sealant from faying surfaces and some short prepacked or long injection seals may be removed with a hooked wire and small cutting tool made from any material no harder than 2024-T3 aluminum. The entire seal shall be clear to permit complete filling with new sealant and prevent any trapped air pockets. Sealant from faying surfaces and some prepacked or long injection seals cannot be removed without structural disassembly. If structural disassembly is required, consult the aircraft structural repair manual or prime CFA. Defective fillet seals shall be removed and the remaining ends of fillets cut or tapered to approximately 45 degree angle. Abrade at least 1/2 inch on each end of the fillet to prepare surface for now fillet seal (See Figure 13-28 and 13-29).

Acetone ASTM D329

7

(4) Cleaning of Surfaces to be Sealed. Remove all chips and foreign materials from the tank structure. Thoroughly clean all surfaces to be sealed and all adjacent areas at least twice with Acetone, ASTM D329 and lint-free cheesecloth, (Table 2-5, Item 3f) or gauze pads (Table 2-5, Item 3.l). Acid brushes (Table 2-5, Item 3a) may be used to agitate the cleaning solvent. Beginning at the top of the areas to be repaired and working downward, use a clean, lint-free cheesecloth pad saturated with cleaning solvent. The solvent will cause oil residual fuel, grease, dirt, etc., to float to the surface and make it easy to remove by wiping with a dry, lint-free cheesecloth. The solvent shall not be allowed to evaporate from the surface before wiping, because oil, dirt, etc., will be redeposited on the surface where it cannot be removed with a dry cloth. To avoid contamination of the solvent with oil

or dirt, never dip the pad into a fresh supply of solvent. Always pour the solution onto the cheesecloth. Use a stiff bristle brush (Table 2-5, Item 3e) to assist in cleaning around bolts, rivets, etc. Change cheesecloth as often as necessary to insure proper cleaning. Wipe the area dry with clean cheesecloth and repeat at least one additional time or until clean. A clean surface is the most important step in the repair of a curing type sealant. Once the surface is clean do not touch with bare hands, as oil or dirt will contaminate surface and sealant will not adhere (See Figure 13-30).

Sealant AMS-S-8802

15

Sealing Compound AMS 3276

14

Seal/Coat Compound Corrosion Inhibitive MIL-PRF-81733

20

NOTE Exposed cadmium plated parts (fasteners, dome nuts, fitting, etc.) which are to be sealed with curing type sealants (AMS-S-8802, AMS 3276, MIL-PRF-81733, or MIL-S-83318) should be isolated with an appropriate topcoating (EC1945, or SAE AMS-C-27725). This topcoat should be fully dried before application of adhesion promoter and final sealing material. (5) Application of Adhesion Promoter. After the surface has been thoroughly cleaned, a light film of adhesion promoter (Table 2-5, Item 8d) shall be applied to all surfaces that require faying surface seals, fillet seals or pre-packed seals. The promoter may be applied by using clean cheesecloth or a fine bristle brush. Excess promoter shall be removed by blotting with cheesecloth (Table 2-5, Item 3f). The promoter shall be allowed to dry for 30 minutes before applying sealant. If more than 24 hours has elapsed or if the surface has become contaminated since application of the promoter, the surface shall be recleaned and promoter reapplied. When applying a pre-coat sealant followed by a filet sealant the adhesion promoter can be applied to the tack-free surface of the pre-coat sealant.

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013 00 Page 46

1.

INTERNAL SOURCE OF LEAK.

2.

CUT COMPLETELY THROUGH FILLET APPROXIMATELY IN CENTER OF DEFECTIVE AREA WITH SHARP CUTTING TOOL.

3.

GRASP CUT ENDS OF SEALANT AND PULL AWAY UNTIL SEALANT FAILS WITHIN ITSELF RATHER THAN PULLS AWAY FROM STRUCTURE.

4.

SCARF EDGES OF REMAINING FILLET TO INSURE A GOOD BOND BETWEEN OLD AND NEW SEALANT. IT IS NOT NECESSARY TO REMOVE BITS OF SEALANT THAT ADHERE FIRMLY TO THE STRUCTURE.

Figure 13-28. Typical Removal of Defective Fillet

NAVAIR 01-1A-35

013 00 Page 47 NOTE Adhesion Promoter (Table 2-5, Item 8d) should be discarded when it becomes cloudy. Keep container closed when not being used.

(6) Selecting Sealant and Application Time. Select the proper curing type of sealant(s) as recommended by your system peculiar technical manuals. Two-part curing type sealants shall be mixed in accordance with paragraph 20d, and application time noted. Sealant shall not be used beyond its application time. Sealant will not be used, regardless of time, when it no longer spreads smoothly or when it no longer readily wets the surface to which it is being applied.

Figure 13-29. Removal of Damaged Sealant for Fillet Repair

DO NOT ALLOW CLEANER TO DRY ON SURFACE. WIPE OFF IMMEDIATELY. DO NOT TOUCH AREA WITH FINGERS AS OIL FROM THE SKIN WILL FORM A FILM ON THE METAL TO WHICH SEALANT WILL NOT ADHERE.

Do not apply sealant to metal if temperature of metal surface is below 60oF. This should be checked with a bimetallic dial thermometer (Table 2-6, Item 8c).

NOTE A combination of the seals may be required at a single leak location. (7) Application of Brush Coat Seal. The brush coat may be used for fillets and is applied 0.10 inch wider than the fillet on either side of the seam (See Figure 13-31). Using a brush, apply a seal of brushable curing type sealant on top of the clean adhesion promoter prepared surface. The brush coat seal is worked into and around crevices, holes, seams, fasteners and on surfaces to be sealed. Allow the surface to become tack-free before application of final seals. Brush coats shall not be used over any primary seals. (8) Application of Fillet Seals. To repair damaged fillet seals or to add new isolation seals use the following procedures:

Figure 13-30. Final Cleaning

(9) Insert properly mixed fillet type curing sealant into filleting gun (See Figure 13-32).

NAVAIR 01-1A-35

013 00 Page 48 (b) Apply a bead of sealant (See Figure 13-33) along the parts. For large repairs/seals, apply the bead in approximately three-foot lengths. (c) Work the bead with a sealant spatula (Table 26, Item 8d) to fill all voids in the seam and to remove air bubbles (See Figure 13-34). Thoroughness and care used in working out air bubbles is extremely important in obtaining a leak-free service life of the sealant. (d) For small fillets, a single bead is all that is required. Shape the fillets to conform to the dimensions shown in Figure 13-35, or per the applicable aircraft handbook. After sealant is tack-free, examine fillets for air bubbles and repeat repair for any air pockets found. (e) For large fillets, a double bead should be applied (Figure 13-31). Apply a small bead as in step (d). Allow to cure tack-free and examine first bead for any air bubbles. Any air bubble cavities found shall be enlarged to permit easy filling during final full-bodied fillet installation.

Figure 13-31. Two Bead Fillet

Sealant AMS-S-8802

15

Sealing Compound AMS 3276

14

Seal/Coat Compound Corrosion Inhibitive MIL-PRF-81733

20

NOTE Exposed cadmium plated parts (fasteners, dome nuts, fitting, etc.) which are to be sealed with curing type sealants (AMS-S-8802, AMS 3276, MIL- PRF-81733, or MIL-S-83318 should be isolated with an appropriate top coating (EC1945 or SAE AMS-C-27725). This topcoat should be fully dried before application of adhesion promoter and final sealing material. (a) Select nozzle(s) for size of fillet to be applied. If a small fillet is to be laid, use a small orifice nozzle; a large fillet requires large nozzle (Refer to Figure 13-39 for nozzle sizes available). It is advisable to set up a locally fabricated condition to simulate components to be filleted. This can usually be done very quickly with cardboard and saves guesswork in selecting proper nozzle sizes.

(f) Apply final full-bodied fillet and shape to conform to dimensions shown in (See Figure 13-35) or per the applicable aircraft handbook. After sealant is tack-free examine for air bubble cavities and repeat repair methods for any found.

Do not use brush-coat type curing sealant for injection, pre-packed or faying surface seals because solvents contained in the brush-coat type sealants will be trapped and leave air bubble cavities/leak paths. (10) Application of Injection Seals. To repair a failed injection seal requires one of the following repairs: Removing damaged seal (short seals only), disassembly to remove sealant or applying a fillet (isolation) seal to separate the faulty seal from the fuel. (a) To apply an isolation seal, use the procedures outlined in step (8). (b) To apply an injection seal, the entire channel or groove shall be clear of old sealant all the way through, since trapped air will prevent complete filling with sealant. If disassembly is required it shall be accomplished per the structural repair manual. (c) Insert properly mixed filleting type curing sealant into the injection gun and follow the operating instruction as outlined on Figure 13-36.

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013 00 Page 49 NOTE

(d) For open void, inject sealant until it extrudes from the opposite end and then slowly remove injection tip while continuing to inject sealant. Wipe off excess sealant. (e) For closed voids, a long injection tip is required to reach bottom of the voids. Inject sealant and slowly remove injection tip. Completely fill void with sealant.

NOTE

Fillet type sealant shall be tack-free before fuel tank is closed. 25. REPAIR OF SEALANT TOP COATING. Some aircraft fuel cells/tanks use a coating over the top of fuel exposed surface of the sealant for protection from surface deterioration. Check the applicable aircraft Maintenance Instruction Manuals (MIMs) for this requirement. When this top coating is to be replaced use the following steps:

Closed voids are extremely difficult to fill completely due to the possibility of trapped air. (11) Pre-Pack and Faying Surface Seals. The repair of pre-packed or faying surface seals requires the removal of structure/ fasteners and shall be made as directed by the aircraft technical manual. A damaged pre-packed or faying surface seal may be in some cases repaired by adding a fillet or isolation seal completely around the leak part/seal. This fillet (isolation) seal adds weight to the airplane and any major fillet (isolation) sealing shall be approved by the prime CFA. When installing pre-packed or faying surface seals, use the following procedures: (a) Insert properly mixed filleting type curing sealant into filleting gun (See Figure 13-32). (b) Apply sealant to faying surfaces before assembly on top of adhesion promoter prepared surfaces, using filleting gun. Filleting tip should be large enough to apply a bead that can be spread over the whole surface and allow some sealant to squeeze out when parts are assembled. (c) Spread evenly over the entire mating surface (Figure 13-37). (d) Assemble part and clamp together with set up bolts, wing type Cleco fasteners, or other temporary fasteners (See Figure 13-38).

NOTE

(f) Remove excess extruded sealant.

(Refer

7

Clean the sealant surface with lint free cheesecloth a. (Table 2-5, Item 3f) dampened with Acetone, ASTM D329. After rinsing and while still wet, wipe the surface dry with clean lint free cloth.

Sealing Compound MIL-S-4383

11

Apply a coating of topcoat, MIL-S-4383 (Table 2b. 5, Item 13h) or MIL-C-83012, to the cleaned sealant surface with a soft bristle paint brush. Overlay the coating 1/4 to 1/2 inch onto adjacent surface. The finished coat should be approximately 1 to 3 mils thick. Allow the coating to cure until it is tackfree c. (approximately four hours) before refueling tank. 26. REPAIR OF CHALKING SEALANT PROCEDURE (OPTIONAL). As the age of the fuel tank sealant increases, it may develop areas of chalking. These will appear as light colored powdery areas on the sealant, and will probably be detected during maintenance or inspection of the tanks or components. Repair the sealant according to the following procedure: Clean the chalky areas by scrubbing vigorously a. with a dry stiff bristle brush. Hold a vacuum cleaner hose near the work area to pick up the chalk dust.

Permanent fasteners must be installed and retightened twice within 30 minutes before the sealant in the faying surface reaches the end of its application time. (e) Install permanent fasteners paragraph 13-26) for fastener sealing.

Acetone ASTM D329

to

Acetone ASTM D329

7

b.

Clean affected areas with Acetone, ASTM D329.

c.

Apply sealant topcoat.

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013 00 Page 50

1. READY FOR ASSEMBLY. 4. ENGAGE RETAINER STUDS INTO GUN BAYONET LOCK.

2. SELECT PROPER NOZZLE FOR APPLICATION AND SCREW INTO MIXED CARTIDGE.

5. SEAL SECURELY BY ROTATION HAND KNOB.

3. INSERT CARTRIDGE INTO RETAINER.

Figure 13-32. Inserting Cartridge Into Filleting Gun

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013 00 Page 51

Figure 13-33. Application of Fillet Seals

Figure 13-34. Typical Fillet Seals

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013 00 Page 52

Figure 13-35. Typical Fillet Dimensions (Sheet 1 of 2)

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013 00 Page 53 C-140 (LOCKHEED) W = 3/16" TO 1/4" A = 1/16" TO 1/8" D = LESS THAN 1/4"

F-8 (VOUGHT) W = 0.12" TO 0.25" A = 0.06" TO 0.12" B = LESS THAN 0.15"

C-5A (LOCKHEED) W = 1/2" NOMINAL, 3/8" = MIN A = 1/4" NOMINAL, 3/16"= MIN D = 1/4" = MAX B = 1/4" = MAX

L-1011 (LOCKHEED) W = 3/16" TO 1/4" A = 1/16" TO 1/8" D = 1/8" MIN B = 1/3" MAX

B-1 ((ROCKWELL) W = 0.25" MIN, 0.35" AVERAGE A = 0.12" MIN D = 0.12" MIN B = LESS THAN 0.15"

DOUGLAS (ALL MODELS) W = 1/4" MIN A = 1/4" MIN

C-140 (LOCKHEED)

F-8 (VOUGHT)

W = 3/8" TO 1/2"

W = 0.12" TO 0.25"

B = 1/4" TO 1/2"

B = 0.15" MIN

D = 3/16" MIN C-5A (LOCKHEED)

L-1011 (LOCKHEED)

W = 1/2" = NOMINAL, 3/8" = MIN

W = 1/4" TO 3/8"

B = 1/4" = MIN

B = 1/8' MIN

D = 1/4" MIN

D = 1/8" MIN DOUGLAS (ALL MODELS) W = 1/4" MIN

C-130 (LOCKHEED)

B = 1/4" MIN

W - 1/4" MIN, 3/8" = AVERAGE D = 1/8" = MIN C-140 (LOCKHEED)

L-1011 (LOCKHEED) W = 1/4" TO 5/8"

W = 3/8" TO 1/2" D = 3/16" MIN

D = 1/8" MIN

C-5A (LOCKHEED)

DOUGLAS (ALL MODELS)

W = 1/2" = NOMINAL, 3/8" = MIN

W = 1/4" MIN

D = 1/4"= MIN F-8 (VOUGHT) W = 0.12" TO 0.25"

Figure 13-35. Typical Fillet Dimensions (Sheet 2 of 2)

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013 00 Page 54

OPERATION OF SEALANT INJECTION GUN.

8. ATTACH THE GUN BARREL TO THE COUPLING AND ATTACH THE GUN NOZZLE TO THE GUN BARREL.

1. DETERMINE MATERIAL TO BE USED IN ACCORDANCE WITH INSTRUCTIONS FOR REPAIR BEING PERFORMED, AND PREPARE MIXTURE AS REQUIRED. 2. DETACH THE GUN NOZZLE FROM THE GUN BARREL AND DETACH THE GUN BARREL FROM THE COUPLING. 3. REMOVE CARTRIDGE PLUNGER AND DRILL A 3/8-INCH DIAMETER HOLE THROUGH ITS CENTER.

9. ATTACH THE UNIT TO THE AIR MOTOR AND HAND-TIGHTEN ALL PARTS OF THE GUN. 10. IF REQUIRED, ATTACH INJECTION TIP TO GUN NOZZLE. 11. ATTACH GUN TO AIR SOURCE OF 100- TO 120- POUND AIR PRESSURE. 12. DEPRESS TRIGGER TO OPERATE GUN.

4. IF ATTACHED, REMOVE THE NOZZLE OF THE CARTRIDGE. 5. SLIP GUN PLUNGER CARTRIDGE PLUNGER.

THROUGH

DRILLED

HOLE

IN

6. POUR MIXTURE INTO CARTRIDGE. 7. CAREFULLY EXTEND GUN PLUNGER THROUGH FILM CARTRIDGE, MAKING SURE GUN PLUNGER EXTENDS COMPLETELY THROUGH CARTRIDGE AND CARTRIDGE PLUNGER IS PROPERLY SEATED AGAINST MIXTURE IN CARTRIDGE.

THE GUN PLUNGER IS APT TO BECOME DAMAGED DURING OPERATION IF NOT EXTENDED COMPLETELY THROUGH THE CARTRIDGE.

NOTE A SMALL AMOUNT OF MIXTURE (APPROXIMATELY 6 GRAMS OF AMS-S-8802 SEALING COMPOUND) IS EJECTED WITH EACH DEPRESSION OF THE TRIGGER, AND THE GUN MUST BE OPERATED SLOWLY TO ALLOW THE GUN NOZZLE TO REFILL AFTER EACH EJECTION. 13. AFTER INJECTING MIXTURE. IMMEDIATELY DISASSEMBLE THE GUN, REMOVE THE CARTRIDGE AND CLEAN THE GUN PARTS. NOTE IF CLEANING PROCEEDS IMMEDIATELY AFTER USE, THE MIXTURE REMAINING IN THE GUN CAN BE RELOADED EASILY WITH COMPRESSED AIR. DRIED MIXTURE CAN BE RELOADED BY CAREFULLY SCRAPING THE GUN PARTS.

NOTE THE CARTRIDGE PLUNGER MUST BE FIRMLY SEATED AGAINST THE MIXTURE TO INSURE REMOVAL OF TRAPPED AIR IN THE MIXTURE.

Figure 13-36. Injection Gun

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013 00 Page 55 27. REPAIRS OF FASTENERS. Fasteners used in integral tanks are sealed in a variety of ways, which are described in paragraph 8 and illustrated in Figures 13-11 through 13-13. A combination of these sealing methods may be used on a single fastener. Consult your system peculiar technical order to identify the fastener type and sealing system used in your aircraft. The following are approved repair methods utilized in the sealing of leaking or replacement fasteners:

Figure 13-37. Application of Faying Surface Sealant

Sealant AMS-S-8802

15

Sealing Compound AMS 3276

14

Seal/Coat Compound Corrosion Inhibitive MIL-PRF-81733

20

Leaks caused by structural failure and not by sealant discrepancies shall not be repaired by applying more sealant. Structural leaks shall be subjected to structural repair in accordance with the applicable aircraft manual.

NOTE Exposed cadmium plated parts (fasteners, dome nuts, fitting, etc.) which are to be sealed with curing type sealants (AMS-S-8802, AMS 3276, MIL-PRF-81733, or MIL-S-83318) should be isolated with an appropriate topcoating (EC1945, or SAE AMS-C-27725). This topcoat should be fully dried before application of adhesion promoter and final sealing material.

Figure 13-38. Faying Surface Seal Assembly

a. Self-Sealing Fastener. Fasteners, which are designed to seal the hole into which they were installed, either by interference fit or by swelling to fit the hole, shall be repaired by a brush-overcoat-fillet or replaced in accordance with system peculiar technical order.

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013 00 Page 56

Figure 13-39. Nozzle Filleting

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013 00 Page 57

b. Fasteners with Sealing Washers or O-Rings (Figure 13-11). Leaking fasteners incorporating a sealing washer or O-ring can often be repaired by tightening fastener to proper torque specifications given in system peculiar technical order. Loosen leaking fastener a turn or two to prevent false torque readings, then tighten to proper torque value. If this action does not stop leak, repair the fastener using the following method: (1) Remove the fastener(s). (2) Inspect the sealing washer/O-ring for nicks, cuts, tears, abrasions, deterioration or deformation. If sealing washer/O-ring is found to be defective due to any of these conditions, replace with a new sealing washer/O-ring. (3) Replace fastener(s). (4) Torque fastener(s) to specifications according to system peculiar technical order. c. Fasteners Located in Sealant Grooves. Some aircraft incorporate a non-curing sealant injected into a sealing groove to seal the fasteners located in the sealing groove. Leaking fasteners located in sealing grooves shall be resealed by reinjection of non-curing sealant. For proper procedures on reinjection, refer to paragraph 22.

NOTE Make certain that all chalk dust is removed. If any dust remains, it will act as a parting agent between the sealant and the new coatings. d. Fasteners Sealed by Brushcoat and Fillet (See Figure 13-12). The following step shall be followed in repairing a leaking fastener sealed with the brushcoat-andfillet method. For detailed procedure of steps outlined below, refer to paragraph 23. (1) Remove existing brushcoat and fillet from leaking fastener with approved scraper.

(3) Clean fastener and surrounding area with Acetone, ASTM D329, using lint-free cheesecloth (Table 25, Item 3f). Acid brushes may be used to agitate the solvent.

Top coating compounds are flammable and toxic to eyes, skin, and respiratory tract. Skin and eye protection required. Avoid repeated or prolonged contact. Good general ventilation is normally adequate. Keep away from open flames or other sources of ignition. (4) Apply adhesion promoter (Table 2-5, Item 8d) to fastener end and surrounding area. Allow to dry for 30 minutes. (5) Apply properly mixed brushable sealant to the fastener and surrounding area using a stiff brush (Table 2-5, Item 3e). Work the thin coat into all crevices and surfaces around the fastener. (6) Using a filleting gun or spatula apply a fillet of the properly mixed sealant over the fastener. (7) Work sealant to final shape with a spatula. Be careful to remove all trapped air bubbles in the seal.

NOTE When forming a fillet seal around closelyspaced fasteners or structure, avoid forming a bridge of sealant. This bridge of sealant provides a hidden leak path, which is extremely difficult to locate (See Figure 13-19).

(2) After removing old sealant, all fasteners in the area to be sealed shall be tightened to their proper torque values. Retightening shall not be permitted after sealant operations have begun.

e. Fasteners Sealed with Dome Nuts. To repair leaking fasteners sealed with dome nuts, follow the procedure for "Fasteners Sealed by Brushcoat and Fillet" with one additional step. After removing old sealant, inspect the dome nut for damage and replace with dome nut if damaged.

Acetone ASTM D329

f. Wet Installed Fastener. Fasteners which were wet installed shall be replaced using the following steps:

7

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Acetone ASTM D329

7

(1) Clean hole and surrounding area with Acetone, ASTM D329). Small holes may be cleaned using cottontipped swabs and four part cleaner. (2) Clean fastener with Acetone, ASTM D329. Acid brushes may be used to agitate the solvent.

a. The following are general steps to replace the compression type seals such as flat gaskets, O-rings, and bonded-in-place molded seals. Refer to system peculiar technical order for detailed information. (1) Remove the seal from access door. (2) Clean the sealing surface of the door with Acetone, ASTM D329 and cheesecloth (Table 2-5, Item 3f).

(3) Apply adhesion promoter (Table 2-5, Item 8d) per instructions in paragraph 23.

(3) Replace with the same type seal, using adhesive as required.

(4) Apply a small bead of curing type filleting sealant around the shoulder of the fastener (See Figure 1312.).

(4) Install the door, and tighten fasteners to the required torque value.

(5) Install fastener(s) and tighten to proper torque value. Final torque shall be completed before the end of the sealant work-life.

b. For the repair of accessory components such as booster pumps, cover plates, etc., sealed with curing type sealant, use the following procedures:

28. REPAIR OF ACCESS DOORS / COMPONENTS. Access doors and accessory components probable leak sources are fasteners and seals. If the leak path analysis has indicated fasteners as the leak source refer to paragraph 26. The four main configurations of static seals used to seal access doors are: flat gasket, O-ring, mold-in-place, and bonded-in-place molded seals. Three of these four seals can be repaired. If a gasket type seal is used the first check before repair is retightening the attaching fasteners. Leaking screws and bolts on access doors may be repaired, sometimes, without draining the tank. Remove the leaking screw of bolt, clean it with solvent to remove old sealant and soil. After drying, apply a small bead of class A sealant to the shank under the head of the screw or bolt. Install the screw or bolt and tighten to the required torque value. Remove excess sealant. This may be all that is necessary, however, if access doors or components still leak they shall be removed and inspected.

(1) Remove old sealant using an approved nonmetallic scraper. (2) Clean part with Acetone, ASTM D329, and cheesecloth (Table 2-5, Item 3f). (3) Select the proper sealant. A low adhesion curing type sealant is preferred, however, if this type is not available or authorized, a standard curing type-filleting sealant may be used. (4) If a standard curing type sealant is used, a thin coat of parting agent shall be applied to one of the mating surfaces. (5) Apply the sealant to the other faying surface and install component. (6) Tighten attaching hardware to required torque value to remove excess faying surface sealant.

Care shall be taken when removing access doors and components to prevent structure or seal damage.

(7) Apply a fillet seal to the fasteners and edges as required to accomplish final sealing.

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MAINTENANCE INSTRUCTIONS INSPECTION AND ASSESSMENT OF SELF SEALING, SELF SEALING CRASH RESITANT, AND NON SELF SEALING CRASH RESISTANT FUEL CELLS

Reference Material None

Alphabetical Index Subject

Page

Self-Sealing Fuel Cells......................................................................................................................................................... 1 Inner Liner ................................................................................................................................................................. 1 Nylon Fuel Barrier..................................................................................................................................................... 1 Retainer ..................................................................................................................................................................... 1 Sealant ....................................................................................................................................................................... 1 Self-Sealing Fuel Cell Damage/Defect Repair Procedures – General.................................................................................. 1 Self-Sealing Fuel Cell Damage/Defect Repair Requirements.............................................................................................. 1 Self-Sealing Fuel Cell Defects and Acceptable Limitations ................................................................................................ 1 Types of Fuel Cells .............................................................................................................................................................. 1 1. TYPES OF FUEL CELLS There are three major types of fuel cells used in Naval Aircraft: a. Self-Sealing, which can be further divided into Crash Resistant or Non-Crash Resistant. (Work Packages 014 through 017) b.

Urethane (Work Packages 018 and 019)

c. Non-self Sealing or Bladder Cells (Work Packages 020 through 022) 2. SELF SEALING FUEL CELLS. (See figure 14-1.) The self-sealing fuel cell is constructed in four primary layers: inner liner nylon fuel barrier sealant retainer a. Inner Liner. The inner liner is fuelresistant solid synthetic rubber or nitrile (BUNAN)-coated nylon fabric. b. Nylon Fuel Barrier. The nylon fuel barrier is an unbroken nylon film, which prevents fuel diffusion. The fuel barrier thickness ranges from 0.001 to 0.003 inches.

c. Sealant. The purpose of the sealant is to immediately close punctures in the fuel cell, thereby preventing the loss of fuel (See Figures 14-2 and 14-3). The sealant layer is natural gum rubber. Fuel penetrating the fuel barrier causes the sealant to swell many times its normal size, sealing the opening. The sealant is constructed in two layers with a fabric separator. d. Retainer. The retainer is laminated plies of nylon cord and fabric impregnated with fuel-resistant synthetic rubber nitrile (BUNA-N). The retainer has an outside coating of buna vinylite lacquer to seal the surface. 3. SELF-SEALING FUEL CELL DEFECTS AND ACCEPTABLE LIMITATIONS. (Refer to Tables 14-1 and 142.) Self-sealing fuel cell defects that are within established tolerances will not be cause for removal and/or repair. 4. SELF-SEALING FUEL CELL DAMAGE/ DEFECT REPAIR REQUIREMENTS. (Refer to Tables 15-1 and 152) Self-sealing fuel cell damage/defect repair may require a combination of repair procedures dependent upon the type and severity of damage/defect. 5. SELF-SEALING FUEL CELL DAMAGE/ DEFECT REPAIR PROCEDURES-GENERAL. Refer to Work Package 0015 for repair instructions for Self Sealing Fuel Cells. Refer to Work Package 0016 for repair instructions of Self Sealing Fuel Cell Fittings.

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Figure 14-1. Variations in Multi-layer Self-Sealing Fuel Cell Construction

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Figure 14-2. Penetration of Fuel Cell

Figure 14-3. Sealing Action

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Table 14-1. Uninstalled Fuel Cell Defects and Acceptable Limitations Defect

Limitation

NOTE Inspection procedures are the same for crash-resistant (ARM) self-sealing fuel cells and lightweight or standard construction self-sealing fuel cells. 1.

Cell Interior a.

Vertical Edge Looseness. Separation of Rubber Material (Fillet) from the vertical surface of the metal fitting.

Around the entire metal fitting is an acceptable condition for Urethane Fuel Cell (See Figure 18-1). Unacceptable for Nitrile Fuel Cells. Not acceptable on Crash-Resistant Construction

b.

Loose liner at throat of fitting Edge looseness at liner lap.

1/2-inch looseness in width around entire circumference at edge of fitting (See Figure 14-4). Acceptable up to 1/4-inch width maximum length of liner lap, provided 1-inch bond is maintained. If fitting fabric flange is less than 1-inch in size, 100% bond must be maintained. Crash Resistant AmFuel cells need to maintain a 2-inch bond.

c.

Edge looseness on liner reinforcements, corner patches, and chafing patches.

Acceptable up to 1/4-inch width for complete length of liner lap if 1-inch bond is maintained on fabric liner and 1/4-inch on rubber liner. 1/2-inch maximum looseness, provided loose area does not exceed 15 percent of total area. Blisters or separations in other than the edge area allowable up to 15 percent of total area.

d.

Looseness under cemented components such as attaching straps, baffle shoes, etc.

15 percent of individual area, provided 1/4-inch bond is maintained around the edge (See Figure 14-5).

e.

Blisters between liner and fitting flange.

1/4-inch maximum dimension; maximum one per lineal foot and two per fitting, provided 1-inch bond is maintained (See Figure 14-4). Crash Resistant AmFuel cells need to maintain a 2-inch bond.

f.

Damaged grommets in accessories.

Acceptable, provided serviceability is not affected.

g.

Damaged coating on accessories (metal, wood or rubber.

Acceptable, provided corrosion or other deterioration is not present.

h.

Checking due to weather, ozone, dry cracking, or surface imperfections.

Acceptable, provided there is no penetration beyond 50 percent of the inner liner material thickness (See Figure 14-6).

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Table 14-1. Uninstalled Fuel Cell Defects and Acceptable Limitations - Continued Defect 1.

2.

Limitation

Cell Interior - Continued i.

Blisters in liner laps.

1/4-inch maximum dimension; average one per lineal foot of splice with a maximum of five in any one 5-foot length of splice (See Figure 14-7).

j.

Blisters, delaminations, or ply separations.

1-inch maximum dimension, provided there is a 6-inch bond between blisters and no more than one per square foot of total cell area.

k.

Channels in inner liner laps.

1/8-inch by 3-inch maximum dimension with a maximum of one in any 5 lineal feet of splice (See Figure 14-7).

l.

Channels around entire outer edge of fitting flange.

1/4-inch maximum width (See Figure 14-4).

m. Channels at tapered construction step-off area, or edge of lap splices of any ply.

1/4-inch maximum width entire length of lap (See Figure 14-7).

n.

Open end channels in three-ply liner overlaps or tailored comers.

1/8-inch by 3-inch maximum dimension, provided 1-inch minimum bond is maintained between end of channel and sealant (See Figure 14-7).

o.

Cuts or holes in inner liner.

Not acceptable.

p.

Buffing through inner liner.

Not acceptable.

q.

Activated areas.

Not acceptable.

Cell Exterior a.

Blisters or ply separation between any plies except liner and sealant.

1-inch maximum dimension.

b.

Skim coat blisters.

Acceptable.

c.

Loose hanger straps or hanger attaching points.

Acceptable up to 15 percent of total area provided 1/4-inch bond is maintained around the edge.

d.

Loose or damaged tapes, corner patches and other outside accessories.

1/2-inch maximum allowable looseness, provided this looseness does not exceed 15 percent of the total area.

e.

Checking due to weather, ozone, dry cracking or surface imperfections (See Figure 14-1).

Acceptable up to 50 percent of material thickness.

f.

Damaged grommets in accessories.

Acceptable, provided serviceability is not affected.

g.

Damage through outer cord or fabric ply.

Not acceptable.

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Table 14-1. Uninstalled Fuel Cell Defects and Acceptable Limitations – Continued Defect 2.

Limitation

Cell Exterior - Continued h.

Channels or bridging of outer plies at cord or fabric splice.

1/2-inch maximum width full length of splice (See Figure 14-8). Crash Resistant AmFuel cells need to maintain a 2-inch bond.

i.

Outer ply cuts or splits parallel to cords where cords are not damaged.

Not acceptable; may result in outside activation.

Table 14-2. Installed Fuel Cell Defects and Acceptable Limitations Defect

Limitation

NOTE Inspection procedures are the same for crash-resistant (ARM) self-sealing fuel cells and lightweight or standard construction self-sealing fuel cells. 1.

Cell Interior a.

Vertical Edge Looseness. Separation of Rubber Material (Fillet) from the vertical surface of the metal fitting.

Rubber Material (Fillet) around the entire metal fitting is an acceptable condition (See Figure 18-1). Not acceptable on Crash-Resistant Construction.

b.

Loose liner at throat of fitting Edge looseness at liner lap.

1/2-inch looseness in width around entire circumference at edge of fitting (See Figure 14-4). Acceptable up to 1/4-inch width maximum length of liner lap, provided 1-inch bond is maintained. If fitting fabric flange is less than 1-inch in size, 100% bond must be maintained. Crash Resistant AmFuel cells need to maintain a 2-inch bond.

c.

Edge looseness on liner reinforcements, corner patches, and chafing patches.

1/2-inch maximum looseness, provided loose area does not exceed 20 percent of total area. Blisters or separations in other than the edge area allowable up to 20 percent of total area.

d.

Looseness under cemented components such as attaching straps, baffle shoes, etc.

20 percent of individual area, provided 1/4-inch bond is maintained around the edge (See Figure 14-4).

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Table 14-2. Installed Fuel Cell Defects and Acceptable Limitations - Continued Defect 1.

Limitation

Cell Interior - Continued e.

Blisters between liner and fitting flange.

1/2-inch maximum dimension, maximum two per lineal foot and three per fitting, provided 1-inch bond is maintained (See Figure 14-4). Crash Resistant AmFuel cells need to maintain a 2-inch bond.

f.

Damaged grommets in accessories.

Acceptable, provided serviceability is not affected.

g.

Damaged coating on accessories (rubber, metal or wood).

Acceptable, provided corrosion or other deterioration is not present.

h.

Checking due to weather, ozone, dry cracking, or surface imperfections.

Acceptable, provided there is no penetration beyond 50 percent of the inner liner material thickness (See Figure 146).

i.

Blisters in liner laps.

1/2-inch maximum dimension; maximum of five in any 5 lineal feet of splice (seam) With a minimum of 6-inch bond between blisters (See Figure 14-7).

j.

Blisters, delaminations, or ply separations.

1 1/2-inches maximum, provided there is a 6-inch bond between blisters and no more than one per square foot of total cell area.

k.

Channels in inner liner laps.

1/4-inch by 3-inch maximum dimension with maximum of one in any 5 lineal feet of splice (See Figure 14-7).

l.

Channels around entire outer edge of fitting flange.

1/2-inch maximum width (See Figure 14-4).

m. Channels at tapered construction step-off area, or edge of lap splices of any ply.

1/2-inch maximum width entire length of lap (See Figure 14-9). Crash Resistant AmFuel cells need to maintain a 2-inch bond.

n.

Open end channels in three-ply liner overlaps or tailored corners.

1/4-inch by 3-inch maximum dimension, provided 1-inch minimum bond is maintained between end of channel and sealant (See Figure 14-7).

o.

Cuts or holes in inner liner.

Not acceptable.

p.

Buffing through inner liner.

Not acceptable.

q.

Activated areas.

Not acceptable.

r.

Broken stiffeners or supports.

Not acceptable.

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Table 14-2. Installed Fuel Cell Defects and Acceptable Limitations - Continued Defect

Limitation

NOTE Only accessible portions of the fuel cells will be inspected. 2.

NOTE Fuel cells need not be removed from aircraft for inspection.

Fuel Cell Exterior a.

Blisters or ply separations between any plies except liner and sealant.

1 1/2 inches maximum dimension.

b.

Skim coat blisters.

Acceptable.

c.

Loose hanger straps or hanger attaching points.

Acceptable up to 20 percent of total area.

d.

Loose or damaged tapes, corner patches, or other outside accessories.

Acceptable, provided sealant is not activated.

e.

Checking due to ozone, weather, or dry cracking.

Acceptable.

f.

Damaged grommets in accessories.

Acceptable, provided serviceability is not affected.

g.

Damage through outer cord or one fabric ply.

1-inch maximum dimension.

h.

Channels or bridging of outer plies at cord or fabric splice.

1/2-inch width maximum full length of splice (See Figure 14-8). Crash Resistant AmFuel cells need to maintain a 2-inch bond.

i.

Outer ply cuts or splits parallel to cords where cords are not damaged.

Acceptable, provided activation of sealant is not evident.

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Figure 14-4. Channel Blisters and Loose Areas

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Figure 14-5. Loose Baffles

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Figure 14-6. Rubber Inner Liner Imperfections

Figure 14-7. Blisters and Channels in Liner Laps

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Figure 14-8. Lap Channels

Figure 14-9. Channels at Lap Steps

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MAINTENANCE INSTRUCTIONS SELF SEALING FUEL CELL REPAIRS Reference Material None

Alphabetical Index Subject

Page

Combination Self-Sealing and Non-Self-Sealing Fuel Cell Damage / Defect Repair Procedures ..................................... 53 Crash Resistant Self Sealing Fuel Cell (ARM) Damage / Defect Repair Procedures ........................................................ 45 Exterior Repair Patch............................................................................................................................................... 47 Exterior Retainer Scuff and Abrasion Repair .......................................................................................................... 51 Exterior Seam Repair............................................................................................................................................... 53 Inner Liner Blister Repair........................................................................................................................................ 49 Inner Liner Repair Patch.......................................................................................................................................... 46 Inner Liner Scuff and Abrasion Repair.................................................................................................................... 49 Interior Seam Repair................................................................................................................................................ 52 Internal Cell Support ............................................................................................................................................... 45 Repair Patches ......................................................................................................................................................... 45 Self-Sealing Fuel Cell Loose Fitting Flange Surface Repair ................................................................................... 53 Rigid, Non-Metallic, Self-Sealing Fuel Cell Damage / Defect Repair Procedures ............................................................ 54 Rigid Non-Metallic Outer Shell Repairs ................................................................................................................. 54 Self-Sealing Inner Shell Repairs.............................................................................................................................. 54 Self Sealing Fuel Cell / Defect Repair Procedures – Lightweight and Standard Construction ........................................... 5 Aeration and Adhesive Injection Repair.................................................................................................................. 44 Blister Repair........................................................................................................................................................... 41 Built-up Repair Plug................................................................................................................................................ 31 Closed Blister Repair............................................................................................................................................... 42 Cut and Paste Repair................................................................................................................................................ 44 Double Inside Repair Patch ..................................................................................................................................... 15 Double Outside Repair Patch................................................................................................................................... 19 Heat and Pressure Repairs ....................................................................................................................................... 44 Inside Corner Repair Patch...................................................................................................................................... 21 Internal Cell Support ................................................................................................................................................. 5 Loose Lap Seam or Loose Lap Patch Repair........................................................................................................... 42 Ply Separation Repairs............................................................................................................................................. 43 Open Blister Repair ................................................................................................................................................. 41 Outside Corner Repair Patch ................................................................................................................................... 24 Repair Plugs............................................................................................................................................................. 27 Repair Patches – General........................................................................................................................................... 5 Salvage Repair Plugs ............................................................................................................................................... 27 Sealant Repairs ........................................................................................................................................................ 43 Single Inside Repair Patch....................................................................................................................................... 14 Single Outside Repair Patch .................................................................................................................................... 18 Step-Back Repair Plug............................................................................................................................................. 35 Self Sealing Fuel Cell Repairs and Procedures – General.................................................................................................... 2 Adhesives .................................................................................................................................................................. 3 Alternate Environmental Controls ............................................................................................................................. 2 Buffing and Grinding................................................................................................................................................. 4 Bonding ..................................................................................................................................................................... 4

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Environmental Requirements .....................................................................................................................................2 Nitrile (Buna-N) Adhesive .........................................................................................................................................3 Organic Solvents and Adhesives................................................................................................................................2 Polyurethane Based Adhesives ..................................................................................................................................3

1. SELF SEALING FUEL CELL REPAIRS AND PROCEDURES - GENERAL. General self-sealing fuel cell repair procedures are provided in the following paragraphs: a. ORGANIC SOLVENTS AND ADHESIVES. Self-sealing fuel cell repair procedures make extensive use of organic solvents, adhesives containing organic solvents, and polyurethane adhesives capable of producing isocyanate vapors. These materials are both toxic and flammable. However, when used properly and with due caution, adverse reactions can be avoided. Refer to Work Package 003 and 004 for health and safety details. The use of the airsupplied respirator or SCBA is required when working inside cells installed in an aircraft. If the cells have been removed from the aircraft and are being worked in a shop environment, then the use of a half-face respirator with a cartridge appropriate to the hazard is a suitable alternative to the use of an air supplied respirator.

NOTE The following warning appears many times in this chapter:

(1) Use air blower MIL-B-7619, to provide a con tinuous airflow across the repair area. (2) Prepare the repair materials in a warm, dry area (adjacent to a heater).

Acetone ASTM D329

7

When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell. Organic solvents or adhesives containing organic solvents are flammable. Avoid breathing of vapors or prolonged skin contact. Use personal protective equipment. Wear disposable polyethylene gloves, MR-100, when applying solvents by hand.

When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell. b. ENVIRONMENTAL REQUIREMENTS. High humidity in combination with low temperature can cause condensation to form on fuel cell surfaces and prevent proper bonding of repair patches. The desired temperature and humidity ranges are as follows: Temperature-- 65°F (18°C) to 90°F (32°C) Relative Humidity-- 65% maximum c. ALTERNATIVE ENVIRONMENTAL CONTROLS. If the desired environmental requirements cannot be met, repairs can be made using the repair techniques outlined in this Work Package, and the following procedures:

NOTE Combining Acetone, ASTM D329, with water droplets on a surface will cause dissipation and rapid evaporation of the water. Dissipation and evaporation of water droplets from condensation is accomplished by wiping the repair area with cheesecloth, CCC-C-440, moistened with Acetone, ASTM D329. Perform repair procedures as soon as vapors have dissipated. (3) Prior to applying adhesives, dissipate condensation from area to be bonded. (4) Prior to bonding the repair patch or plug, dissipate condensation from the repair area. (5) Delay repair procedures if conditions are such that dissipation of condensation cannot be accomplished.

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d. ADHESIVES. There are two basic types of adhesives used in self-sealing fuel cell repair, each with distinct application requirements. The types of adhesives are nitrile base (BUNA-N), and polyurethane base.

(c) Allow the first and second coats to dry completely before applying the next coat.

Acetone ASTM D329 Each fuel cell manufacturer compounds the natural gum rubber used-in the fuel cells with different ingredients. The reactions to fuel, solvents and adhesives varies. For this reason, it is desirable to use sealant manufactured by each rubber company for repairs on their specific fuel cells. e. NITRILE BASE (BUNA-N) ADHESIVE. The nitrile base adhesive is used primarily in lightweight and standard "A" and "B" self-sealing fuel cell repair. Nitrile base adhesive is used in both hot-cure (vulcanization) and air-cure procedures. (1) Application procedures. Procedures for the application of nitrile base adhesives are as follows:

Acetone ASTM D329

7

7

NOTE Care should be taken not to apply the patch before the adhesive has reached the proper stage of tackiness, as air bubbles or blisters may form under the patch in the drying process. If the adhesive becomes tacky before the patch is applied, there will be no skidding or sliding of the patch immediately after application. Sliding should not be evident in any area of the patch. If the adhesive on the cell and patch dry before the patch is applied, both coated surfaces must be activated by wiping with clean cheesecloth moistened with solvent Acetone, ASTM D329 to effect a tacky condition of the coated areas. To determine if the adhesive is tacky, test it by pressing a knuckle gently against the cemented surface and withdrawing it. This is known as the "knuckle test" (See Figure 15-1). If a few threads of adhesive stick to the knuckle, the adhesive is ready for the patch.

When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell. Organic solvents or adhesives containing organic solvents are flammable. Avoid breathing of vapors or prolonged skin contact. Use personal protective equipment. Wear disposable polyethylene gloves, MR-100, when applying solvents by hand. (a) Wipe off the surface of the bonding areas and clean with cheesecloth, CCC-C-440, moistened with Acetone, ASTM D329. Do not soak the bonding areas, but clean lightly until all grit, dust and other contaminates are removed. (b) Unless repair procedures specifically instruct otherwise, apply three coats of nitrile base adhesive to each of the bonding surfaces.

Figure 15-1. Knuckle Test f. POLYURETHANE BASED ADHESIVE. The polyurethane base adhesive is used on Crash-Resistant SelfSealing Fuel Cells (ARM) only. (1) Polyurethane base adhesive application procedures. Procedures for the application of polyurethane base adhesives are as follows:

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015 00 Page 4 assure that the nylon barrier is not damaged during the buffing operation.

Acetone ASTM D329

Only experienced personnel should use power buffers. Power buffing may produce a polished surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand.

7

NOTE Isocyanate exposure may produce severe allergic reaction and permanent sensitization. Persons with history of allergies or previous sensitization shall not be assigned tasks involving isocyanates. Personal protective equipment for skin and eyes and proper respiratory protection (BUMEDINST 6260.16) shall be required when polyurethane coatings of adhesives are used for fuel cell repairs. When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell. (a) Wipe off the surface of the bonding area and clean with cheesecloth, CCC-C-440, moistened with Acetone, ASTM D329. Do not soak the bonding areas, but clean lightly until all grit, dust and other contaminants are removed. (b) Mix and apply the proper polyurethane base adhesive as required for a specific type damage repair procedure. g. BUFFING AND GRINDING. Buffing and grinding procedures are as follows:

Buffing and grinding should be accomplished in exhaust ventilated booths having a minimum face velocity of 200 linear feet per minute. An air drill may be used as a buffer by inserting a sand or emery wheel in the chuck. When buffing with an air drill, do not buff in one spot too long to avoid burning the surface of the material If power buffing produces a surface that is too smooth for proper adhesion, the surface should be buffed by hand. (1) Buff the area to be repaired in all directions from the damage with 120 grit abrasive cloth or buffing tool. Area to be buffed is dependent on the size and type of repair to be made. h.

BONDING. Bonding procedures are as follows:

(1) Prior to any bonding procedure, buffed areas must be cleaned with cheesecloth, CCC-C-440, dampened with Acetone, ASTM D329. (2) Apply adhesive. For application procedures, see paragraphs 1d through 1f in this work package. (3) Stitch each patch with a 1/4-inch hand roller, starting from the center and working to the outer edge of the patch to eliminate trapped air and ensure a good seal. (4) Apply pressure to the patch during the cure cycle by one of the following methods:

When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations.

Do not buff the nylon barrier side of the inner liner material. Fuel diffusion will occur if barrier is broken. Buffing must be heavy enough to remove all gloss, leaving the surface covered with fine scratches. However, care must be exercised to

(a) Clamping: Place a metal (for heated repairs) or wooden (for unheated repairs) platten over the patch and apply pressure by clamping the platten in place using regular shop C-clamps. (b) Weighting: When the configuration of the cell, or the location of the patch make it difficult or impossible to use clamps, weight may be applied to the patch area using bags of shot. This method is only useful when performing unheated repairs. (c) Vacuum Bagging. After the adhesive has been applied and the patch is positioned and properly stitched down, lay a piece of porous release fabric (Table 25, Item 12u) over the patch and extending 1 to 2 inches in all directions beyond the edge of the patch. If a heated cure is being used, place a heat blanket over the peel ply with a thermocouple underneath the peel ply and near the center of

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015 00 Page 5

the patch. If heat is not required, omit the use of the heat blanket and thermocouple. Next, place 2 or 3 layers of breather material (Table 2-5, Item 12v) over the repair area. Surround the area with vacuum bagging tape (Table 2-5, Item 11d), cover the area with vacuum bagging film (Table 2-5, Item 12w) and attach vacuum hose connections (Table 2-5, Item12x) Obtain a vacuum of at least 25 inches Hg and cure according to adhesive specifications.

NOTE The cell must be supported in the area around the damage so the edges will be lined up properly in their natural position. Wooden blocks or boards used inside fuel cells should be padded or covered with cloth to protect the liner from damage. b. REPAIR PATCHES - GENERAL. There are six basic types of repair patches:

If a heated repair technique is used, do not remove pressure from the repair site until the patch cools to room temperature. If pressure is removed prior to the time it returns to room temperature, the patch will not cure flat, but will assume a permanent set conforming to the shape in its relaxed position. 2. SELF-SEALING FUEL CELL DAMAGE/ DEFECT REPAIR PROCEDURES-LIGHTWEIGHT AND STANDARD CONSTRUCTION. The damage / defect repair procedures for standard and lightweight construction self-sealing fuel cells are provided in the following paragraphs. Refer to Table 15-1 for repair requirements and references for specific procedures.

single inside repair patch double inside repair patch single outside repair patch double outside repair patch inside corner repair patch outside corner repair patch

NOTES Repair patches must have a smoothly-rounded outline and the edges skived or cut at an angle by tilting the edges instead of cutting straight (See Figure 15-3).

The repair procedures for lightweight and standard construction self-sealing fuel cells (ARM) are applicable only to this type of fuel cell. They shall not be used to repair any other type of self-sealing fuel cell.

Single patches are cut to extend 1 1/2 inches from the edge of the damage area.

a. INTERNAL CELL SUPPORT. (See Figure 15-2.) Build a trestle or other support inside the cell.

Extend the second patch 2 ½ inches from the edge of the damage area.

Extend the first patch of a double patch 1 ½ inches from the edge of the damage area.

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Table 15-1. Repair Requirements for MIL-T-5578 Self-Sealing Fuel Cells (Lightweight and Standard Construction) Damage/Defeat 1.

2.

3.

4.

5.

Repair requirement

Cuts, Not Through Cell Wall, No Displacement of Material, Not in Corner a.

Under 2 inches-interior.

Single inside repair patch (Refer to paragraph 2c).

b.

Under 2 inches-exterior.

Single outside repair patch (Refer to paragraph 2e).

c.

2 to 4 inches-interior.

Double inside repair patch (Refer to paragraph 2d).

d.

2 to 4 inches-exterior.

Double outside repair patch (Refer to paragraph 2f).

e.

4 to 6 inches-interior.

Step-back repair plug (Refer to paragraph 2l).

f.

4 to 6 inches-exterior.

Salvage repair plug (Refer to paragraph 2j).

g.

Over 6 inches-interior.

Built-up repair plug (Refer to paragraph 2k).

h.

Over 6 inches-exterior.

Built-up repair plug (Refer to paragraph 2k).

Cuts, Into Corner, Not Through Cell Wall, No Displacement, Not More Than 4 Inches Long a.

Interior.

Inside corner repair patch (Refer to paragraph 2g).

b.

Exterior.

Outside corner repair patch (Refer to paragraph 2h).

Tears, Snags or Any Damage Involving Displacement of Cell Wall Materials a.

Under 6 inches-interior.

Salvage repair plug (Refer to paragraph 2j).

b.

Under 6 inches-exterior.

Salvage repair plug (Refer to paragraph 2j).

c.

Over 6 inches-interior.

Built-up repair plug (Refer to paragraph 2k).

d.

Over 6 inches-exterior.

Built-up repair plug (Refer to paragraph 2k).

Holes Through Cell Walls a.

Under 6 inches-interior.

Built-up repair plug (Refer to paragraph 2k).

b.

Under 6 inches-exterior.

Built-up repair plug (Refer to paragraph 2k).

Blister a.

Inner liner.

See footnotes at the end of table.

Blister repair (Refer to paragraph 2m).

NAVAIR 01-1A-35

015 00 Page 7

Table 15-1. Repair Requirements for MIL-T-5578 Self-Sealing Fuel Cells (Lightweight and Standard Construction) - Continued Damage/Defect 5.

Blisters-continued b.

6.

Repair requirement

Under 6 inches-exterior.

Built-up repair plug (Refer to paragraph 2k).

Loose Lap Seam or Loose Patches a.

Inner liner.

Loose lap seam or loose patch repair (Refer to paragraph 2p).

7.

Activated Sealant

Sealant repair (Refer to paragraph 2q).

8.

Separations

Ply separation repair (Refer to paragraph 2r).

A built-up repair plug may be used in lieu of a salvage repair plug (Refer to paragraph 2k). A step-back repair plug shall be used if structural integrity is questionable due to size or location of damage (Refer to paragraph 2l).

Table 15-2. Repair Requirements for MIL-DTL-27422C Self-Sealing Fuel Cells Crash-Resistant (ARM) Construction Damage/Defect 1.

2.

3.

Cuts, Snags, Tears, Abrasions, Not Over 4 Inches, Not Extending Through Reinforcing Plies a.

Interior.

Inner liner scuff and abrasion repair (Refer to paragraph 3f).

b.

Exterior.

Exterior retainer scuff and abrasion repair (Refer to paragraph 3g).

Cuts, Snags, Tears, Abrasions, Not Over 4 Inches, Extending Through Reinforcing Plies a.

Interior.

b.

Exterior.

Inner liner repair patch (Refer to paragraph 3c). This repair will seal the tank, but may not return the tank to its original crash resistant capability. Exterior repair patch (Refer to paragraph 3d). This repair will seal the tank, but may not return the tank to its original crash resistant capability.

Inner Liner Blisters, Not Over 4 Inches a.

4.

Repair requirement

All areas.

Inner liner blister repair (Refer to paragraph 3c).

Loose Seams a.

Interior.

Interior loose seam repair (Refer to paragraph 3h).

b.

Exterior.

Exterior loose seam repair (Refer to paragraph 3i).

NAVAIR 01-1A-35

015 00 Page 8 Table 15-3. Sheet Materials

Item Number

Nomenclature

Commercial Code

Manufacturer

Total Gauge

Source

NOTE The materials listed are those commonly used for repair of fuel cells. Additionally, materials authorized by the fuel cell manufacturer and approved by the Cognizant Field Activity (CFA) may be used. 1.

HIGH STRENGTH BUNA-N COATED NYLON FABRIC

FT-229

ENGINEERED FABRICS

.031

COMMERCIAL

2.

HIGH STRENGTH BUNA-N COATED NYLON FABRIC

FT-231

ENGINEERED FABRICS

.058

COMMERCIAL

3.

SANDWICHED NYLON SHEET-BUNAN WITH BARRIER

FR-47

ENGINEERED FABRICS

.062

COMMERCIAL

4.

SANDWICHED NYLON SHEET-BUNAN WITH BARRIER

FT-82

ENGINEERED FABRICS

.041

COMMERCIAL

5.

BUNA-N COATED NYLON FABRIC WITH BARRIER

FT-240

ENGINEERED FABRICS

.028

COMMERCIAL

6.

NYLON COATED POLYURETHANE FABRIC

FT-227

ENGINEERED FABRICS

.025

COMMERCIAL

7.

NYLON FABRIC (QUICK CURE METHOD) CURED BUNA-N COATED NYLON FABRIC UNCURED NATURAL RUBBER COATED NYLON FABRIC

3604N (491 alternate) PS-359

ENGINEERED FABRICS AMFUEL

.012

8135-01-242-3515

.018

COMMERCIAL

PS-335

AMFUEL

.022

COMMERCIAL

PS384

AMFUEL

.030

COMMERCIAL

PS-252

AMFUEL

.020

COMMERCIAL

PS-296

AMFUEL

.012

COMMERCIAL

13.

CURED SANDWICHED NYLON SHEETBUNA-N UNCURED BUNA-N COATED NYLON FABRIC UNCURED BUNA-N COATED NYLON FABRIC REINFORCED NYLON FABRIC 12 OZ.

3603N

14.

REINFORCED NYLON FABRIC 24 OZ.

3629N

15.

CURED BUNA-N COATED NYLON FABRIC WITH BARRIER

PS-625

ENGINEERED FABRICS ENGINEERED FABRICS AMFUEL

.029

COMMERCIAL

16.

UNCURED BUNA-N COATED NYLON FABRIC CURED BUNA-N SHEET (SPECIFY CURED WHEN ORDERING) UNCURED BUNA-N SHEET

U5218A

AMFUEL

.020

COMMERCIAL

SA110-1

AMFUEL

.030

COMMERCIAL

8. 9. 10. 11. 12.

17. 18.

19. 20.

UNCURED HIGH STRENGTH BUNA-N COATED NYLON FABRIC 26 OZ. UNCURED HIGH STRENGTH BUNA-N COATED NYLON FABRIC 12 OZ.

COMMERCIAL COMMERCIAL

NITRILE RAW STOCK MIL-R-6855 Class 1, Grade 60 U5397 AMFUEL

AS LOCAL REQUIRE COMPOUNDING D .026 COMMERCIAL

U5485

.041

AMFUEL

COMMERCIAL

Crash-resistant cells selfsealing inner liner Self-sealing outside plies Inner liner with damaged barrier – self-sealing and bladder cells Outside plies polyurethane bladder cells Inner liner polyurethane bladder cells Fabric between sealant plies self-sealing cells Outside plies – bladder cells

1 2 3 X 4 5 6 7 8

X

X

I

X X

X

X

X 9

Sealant plies – AMFUEL selfsealing cells

11 12 13

X

X

X

X

X

X 14 X 15 OVER 400 OVER 400

148

X

X

X

X

X

OVER 400 OVER 400

Item 10, Column 4, when used on fabric inner liner, should be covered with patch of Buna-N Coated Nylon Fabric item 8, PS359.

Item number

Fabric tensile strength on relative scale

Sealant plies – self-sealing except AMFUEL

Non-fabric inner liner with undamaged barrier – self-sealing and bladder cells

10

Solid rubber and for fill-in around fittings – hot process

Fabric inner liner with damaged barrier – self-sealing and bladder cells Solid rubber and for fill-in around fittings – cold process

Crash-resistant cells self sealing outside plies

NAVAIR 01-1A-35 015 00 Page 9

Table 15-3. Sheet Materials - Continued Usage Columns - For Repair of

1.

2.

X 3.

X 4.

5.

X X 6.

X X 7.

152 8.

204 9.

10.

X 191 11.

X 121 12. 13.

14.

155 15.

211

16.

17.

18.

19.

20.

NAVAIR 01-1A-35

015 00 Page 10 Table 15-3. Sheet Materials - Continued

Item Number

Nomenclature

Commercial Code

Manufacture

Total Gauge

Source

NOTE The materials listed are those commonly used for repair of fuel cells. Additionally, materials authorized by the fuel cell manufacturer and approved by the Cognizant Field Activity (CFA) may be used. 21.

UNCURED NATURAL RUBBER COATED NYLON HIGH STRENGTH NYLON FABRIC UNCURED HIGH STRENGTH BUNA-N COATED NYLON WITHOUT BARRIER

U5004

AMFUEL

.070

COMMERCIAL

U5241A

AMFUEL

.045

COMMERCIAL

23.

CURED BUNA-N SHEET (SPECIFY GAUGE AND CURED WHEN ORDERING

LN368 AMFUEL COMPOUND

AS COMMERCIAL REQUIRED

24.

UNCURED BUNA-N SHEET (SPECIFY GAUGE & UNCURED WHEN ORDERING)

LN368 AMFUEL COMPOUND

AS COMMERCIAL REQUIRED

25.

SEALANT UNCURED (SPECIFY GAUGE & UNCURED WHEN ORDERING)

LN878 AMFUEL COMPOUND

.058/.110

COMMERCIAL

26.

SEALANT

26950

ENGINEERED FABRICS

.040/.050

COMMERCIAL

27.

SEALANT CURED

U3024A

AMFUEL

.050

COMMERCIAL

28.

SEALANT UNCURED (SPECIFY GAUGE & UNCURED WHEN ORDERING)

U3024 AMFUEL COMPOUND *

29.

CURED BUNA-N SHEET

22.

NITRILE CURED STOCK MIL-R-6855 Class 1, Grade 40

AS COMMERCIAL REQUIRED AS COMMERCIAL REQUIRED

* This is rubber compound used to calander into sheet form. Amfuel has various part numbers depending on gauge (thickness) of material required.

Crash-resistant cells selfsealing inner liner Self-sealing outside plies Inner liner with damaged barrier – self-sealing and bladder cells Outside plies polyurethane Bladder cells Inner liner polyurethane bladder cells Fabric between sealant plies self-sealing cells Outside plies – bladder cells

1 2 X 3 4 5 6 7 8

X 9

X

Sealant plies – AMFUEL selfsealing cells Sealant plies – self-sealing except AMFUEL

11 12 13 14

X X

X X X

X

Item number

Fabric tensile strength on relative scale

Non-fabric inner liner with undamaged barrier – self-sealing and bladder cells

10

Solid rubber and for fill-in around fittings – hot process

Fabric inner liner with damaged barrier – self-sealing and bladder cells Solid rubber and for fill-in around fittings – cold process

Crash-resistant cells self sealing outside plies

NAVAIR 01-1A-35 015 00 Page 11

Table 15-3. Sheet Materials - Continued Usage columns - for repair of

15 OVER 400 21.

OVER 400 22.

23.

24.

25.

26.

27. 28.

29.

NAVAIR 01-1A-35

015 00 Page 12 Table 15-4. Adhesive Cements

Item number

Material

Manufacturer

1.

5071C

ENGINEERED FABRICS

3 DAYS @ ROOM TEMPERATURE 60 MINUTES 290oF

8040-00-390-5606

2.

1895C

ENGINEERED FABRICS

3 DAYS @ ROOM TEMPERATURE 60 MINUTES 290oF

8040-01-028-9866

3.

1457C

3 DAYS @ ROOM TEMPERATURE

COMMERCIAL

4.

EC-678 (MIL-A-9117)

ENGINEERED FABRICS 3M CO.

3 DAYS @ ROOM TEMPERATURE

8040-00-262-9060

5.

039198

6.

LP979

ENGINEERED FABRICS AMFUEL

Source

o

30 MINUTES @ 270 F

COMMERCIAL

60 MINUTES @ 290oF

COMMERCIAL

o

7.

LP729-2

AMFUEL

60 MINUTES @ 290 F

8040-00-200-6415

8.

205/220 or TY-PLY (BN)

VULCANIZE WITH REPAIR VULCANIZE WITH REPAIR

COMMERCIAL 8010-00-693-2616

9.

AIR DRY AIR DRY

8030-00-166-8313 COMMERCIAL

10.

BUNA-VINYLITE LACQUER or BLACK OUT BLACK 80C29

CHEMLOCK HUGHSON VANDERBILT VARIOUS VANDERBILT

82C12

3 DAYS @ 75oF 2 HOURS @ 240oF AIR DRY

COMMERCIAL

11.

COMMERCIAL

12.

82C18

AIR DRY

COMMERCIAL

13.

82C32

AIR DRY 6 HRS @ 70oF

8040-01-243-6624

14.

1681C

15.

U3242RF-1 (QT) (4 PART) U3242RF-2 (PT)

ENGINEERED FABRICS ENGINEERED FABRICS ENGINEERED FABRICS ENGINEERED FABRICS ENGINEERED FABRICS AMFUEL

60 MINUTES @ 288oF

COMMERCIAL

16.

AMFUEL

3 DAYS @ ROOM TEMPERATURE

COMMERCIAL

17.

PU459-1 (QT) (2 PART) PU459-2 (PT) EC-1751-L B/A

3M CO.

24 HOURS @ ROOM TEMPERATURE 8040-00-181-7548

18.

EA 9394

LOCKTITE CORP

24 HOURS @ ROOM TEMPERATURE 8040-01-502-9778

19.

5923C

ENGINEERED FABRICS

3 DAYS @ 75oF 2 HOURS @ 240oF

COMMERCIAL

8040-00-518-3455 COMMERCIAL

1 4 5 X

X

X 6 7

X

X

X Polyurethane – quick cure Polyurethane – regular cure Crash-resistant – room temp. 2-part Crash-resistant – room temp. 1part barrier adhesive Epoxy-base adhesive-filler for repairing damaged fittings

9 10 11 12 13 14 15

X

X X

X X

X X X X X X X

X

X

X

X

X

X

Item number

Exterior fuel cell protective coating

8 X

Metal primer

Room temperature cure – coating for fuel cell and patch – exterior

Room temperature cure sealantto-sealant

Hot cure – 2 part – BUNA-N to BUNA-N

3 Hot cure – prime for barrier nylon

Hot cure – 1 part – BUNA-N to BUNA-N

2 X Room temperature cure and hot cure sealant-to-sealant and sealant primer for BUNA-N cements

Room temperature cure – 2 part to BUNA-N to BUNA-N

Room temperature cure BUNA-N to BUNA-N

NAVAIR 01-1A-35 015 00 Page 13

Table 15-4. Adhesive Cements - Continued Usage columns

1.

2. 3.

4. 5.

6.

7. 8.

9.

10.

11.

12.

13.

14.

15.

16.

X

17.

X

18.

19.

NAVAIR 01-1A-35

015 00 Page 14 c. SINGLE INSIDE REPAIR PATCH. Application procedures for a single inside repair patch are as follows:

Comply with general safety instructions in Work Package 004, and fuel cell entry preparations in Work Package 006. When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell. When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations. Do not buff the nylon barrier side of the inner liner material. Fuel diffusion will occur if barrier is broken. Figure 15-2. Supporting Cell for Repair

Buffing must be heavy enough to remove all gloss, leaving the surface covered with fine scratches. However, care must be exercised to assure that the nylon barrier is not damaged during the buffing operation. Only experienced personnel should use power buffers. Power buffing may produce a polished surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand. (1) Buff the area to be repaired 1 3/4 inches in all directions from the edge of the damage.

NOTE Repair patches must have a smoothly rounded outline and edges skived or cut at an angle by tilting the shears instead of cutting straight (See Figure 15-3).

Figure 15-3. Skiving Patch

(2) Prepare a patch of nylon sandwich material (Refer to Table 15-3, usage column 4) 1 1/2 inches larger than the area of damage.

NAVAIR 01-1A-35

015 00 Page 15 Wear disposable polyethylene gloves, MR-100, when applying solvents by hand.

When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell. When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations. Do not buff the nylon barrier side of the inner liner material. Fuel diffusion will occur if barrier is broken.

Buffing must be heavy enough to remove all gloss, leaving the surface covered with fine scratches. However, care must be exercised to assure that the nylon barrier is not damaged during the buffing operation. Only experienced personnel should use power buffers. Power buffing may produce a polished surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand.

(4) Clean the buffed areas with cheesecloth, CCCC-440, dampened with, Acetone, ASTM D329, and apply adhesive (Refer to Table 15-4, usage columns 1 or 2, for adhesive, and paragraph 1e(1) for application procedures).

NOTE To determine if the adhesive is tacky, test it by pressing a knuckle gently against the cemented surface and withdrawing it. If a few threads on adhesive stick to the knuckle, the adhesive is ready for patch. When applying patches or laminating layers of repair materials, roll down (stitch) each layer with a 1/4-inch hand roller, starting from the center and working to the outer edge to eliminate trapped air and ensure a good seal (See Figure 15-4). (5) When adhesives are tacky, apply patch and stitch down. (6) After two hours, apply two coats of adhesive (Refer to Table 15-4, usage column 1) to skived edge. (7) Allow to dry completely; restitch.

(3) Buff the patch on the large side.

Acetone ASTM D329

7

When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell. Organic solvents or adhesives containing organic solvents are flammable. Avoid breathing of vapors or prolonged skin contact. Use personal protective equipment.

Fuel cell patches should air-cure a minimum of 72 hours prior to installation or being subjected to fuel. Do not flex the repaired area for the first 24-hour period. Do not place a repaired cell in any type of heating chamber to accelerate curing; such action will cause the cell to deteriorate and shrink beyond safe dimensions. If clamps and platens used in the vulcanization process are disassembled from the patches before room temperature is reached, the bonded patch material will not cure flat but will assume a permanent set conforming to the shape in its relaxed position. (8) Test fuel cell for integrity of repair (Refer to Work Package 012). d. DOUBLE INSIDE REPAIR PATCH. Application procedures for a double inside repair patch are as follows:

NAVAIR 01-1A-35

015 00 Page 16 posure. Always wear eye protection when engaged in buffing operations.

Comply with general safety instructions in Work Package 004, and fuel cell entry preparations in Work Package 006.

Buffing must be heavy enough to remove all gloss, leaving the surface covered with fine scratches. However, care must be exercised to assure that the nylon barrier is not damaged during the buffing operation. Only experienced personnel should use power buffers. Power buffing may produce a polished surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand. (1) Buff the area to be repaired 2 3/4 inches in all directions from the edge of the damage.

NOTE Repair patches must have a smoothly rounded outline and the edges skived or cut at an angle by tilting the shears instead of cutting straight (See Figure 15-3). (2) Prepare a patch of nylon sandwich material (Refer to Table 15-2, usage column 4) 1 1/2 inches larger than the area of damage. (3) Prepare a second patch of the same material that is 1 inch larger than the first.

Do not buff the nylon barrier side of the inner liner material. Fuel diffusion will occur if barrier is broken.

Buffing must be heavy enough to remove all gloss, leaving the surface covered with fine scratches. However, care must be exercised to assure that the nylon barrier is not damaged during the buffing operation. Only experienced personnel should use power buffers. Power buffing may produce a polished surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand. (4) Buff both sides of the first patch and the large side of the second patch.

Acetone ASTM D329

7

When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell. Organic solvents or adhesives containing organic solvents are flammable. Avoid breathing of vapors or prolonged skin contact. Use personal protective equipment.

When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell. When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the ex-

Wear disposable polyethylene gloves, MR-100, when applying solvents by hand. (5) Clean the buffed areas with cheesecloth, CCCC-440, dampened with acetone, ASTM D329, and apply adhesive (Refer to Table 15-4, usage columns 1 or 2) to the small side of the first patch and the large side of the second patch (Refer to paragraph 1e(1) for application procedures).

NAVAIR 01-1A-35

015 00 Page 17 Organic solvents or adhesives containing organic solvents are flammable. Avoid breathing of vapors or prolonged skin contact. Use personal protective equipment.

If clamps and platens used in the vulcanization process are disassembled from the patches before room temperature is reached, the bonded patch material will not cure flat, but will assume a permanent set conforming to the shape in its relaxed position.

NOTE If the vulcanization method of bonding is used rather than the room temperature cure method, the techniques are the same except that vulcanizing adhesives are used (Refer to Table 15-4, usage columns 4 or 5). The cure is accomplished by clamping the double patch between plates and heat curing at the temperature and time listed in Table 15-4. Remove clamps when heater and plates return to room temperature.

Wear disposable polyethylene gloves, MR-100, when applying solvents by hand. (8) Clean the buffed areas in the fuel cell and on the double patch with cheesecloth dampened with acetone, ASTM D329 and apply adhesive (Refer to Table 15-4, usage columns 1 or 2, for adhesive, and paragraph 1e(1) for application procedures).

NOTE When applying patches or laminating layers of repair materials, roll down (stitch) each layer with a 1/4-inch hand roller, starting from the center and working to the outer edge to eliminate trapped air and ensure a good seal (See Figure 15-4).

To determine if the adhesive is tacky, test it by pressing a knuckle gently against the cemented surface and withdrawing it. If a few threads of adhesive stick to the knuckle, the adhesive is ready for the patch. When applying patches or laminating layers of repair materials, roll down (stitch) each layer with a 1/4-inch hand roller, starting from the center and working to the outer edge to eliminate trapped air and ensure a good seal (See Figure 15-4). (6) When adhesives are tacky, mate the bonding surfaces and stitch down. (7) Clamp the patch and allow two hours drying time.

Acetone ASTM D329

7

When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell.

Figure 15-4. Stitching Patch in Place (9) When adhesive is tacky, center the patch over the damage area and stitch down.

Adhesive MIL-PRF-9117

8

(10) After two hours, apply adhesive MIL-PRF-9117 (Refer to Table 15-4, usage column 1) to skived edge. Allow to dry completely; re-stitch.

Fuel cell patches should air-cure a minimum of 72 hours prior to installation or being subjected

NAVAIR 01-1A-35

015 00 Page 18

to fuel. Do not flex the repaired area for the first 24-hour period. Do not place a repaired cell in any type of heating chamber to accelerate curing; such action will cause the cell to deteriorate and shrink beyond safe dimensions. (11) Test fuel cell for integrity of repair (Refer to Work Package 012). e. SINGLE OUTSIDE REPAIR PATCH. Application procedures for a single outside repair patch are as follows:

When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations. Do not buff the nylon barrier side of the inner liner material. Fuel diffusion will occur if barrier is broken.

Buffing must be heavy enough to remove all gloss, leaving the surface covered with fine scratches. However, care must be exercised to assure that the nylon barrier is not damaged during the buffing operation. Only experienced personnel should use power buffers. Power buffing may produce a polished surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand. (1) Buff the area to be repaired 1 3/4 inches in all directions from the edge of the damage.

NOTE Repair patches must have a smoothly rounded outline and the edges skived or cut at an angle by tilting the shears instead of cutting straight (See Figure 15-2). (2) Prepare a patch of outside repair material (Refer to Table 15-2, usage column 3) 1 1/2 inches larger than the area of damage.

When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations. Do not buff the nylon barrier side of the inner liner material. Fuel diffusion will occur it barrier is broken.

Buffing must be heavy enough to remove all gloss, leaving the surface covered with fine scratches. However, care must be exercised to assure that the nylon barrier is not damaged during the buffing operation. Only experienced personnel should use power buffers. Power buffing may produce a polished surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand. (3) Buff the patch on the large side.

Acetone ASTM D329

7

Organic solvents or adhesives containing organic solvents are flammable. Avoid breathing of vapors or prolonged skin contact. Use personal protective equipment. Wear disposable polyethylene gloves, MR-100, when applying solvents by hand. (4) Clean the buffed areas with cheesecloth, CCCC-440, dampened with Acetone, ASTM D329, and apply adhesive (Refer to Table 15-4, usage columns 1 or 2, for adhesive and paragraph 1e(1) for application procedures).

NAVAIR 01-1A-35

015 00 Page 19

NOTE To determine if the adhesive is tacky, test it by pressing a knuckle gently against the cemented surface and withdrawing it. If a few threads of adhesive stick to the knuckle, the adhesive is ready for the patch. When applying patches or laminating layers of repair materials, roll down (stitch) each layer with a 1/4-inch hand roller, starting from the center and working to the outer edge to eliminate trapped air and ensure a good seal (See Figure 15-4). (5) When adhesives are tacky, apply patch and stitch down.

f. DOUBLE OUTSIDE REPAIR PATCH. Application procedures for a double outside repair patch are as follows:

When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations. Do not buff the nylon barrier side of the inner liner material. Fuel diffusion will occur if barrier is broken.

(6) After two hours, apply adhesive (Refer to Table 15-4, usage column 1) to skived edge. (7) Allow to dry completely; restitch. Buffing must be heavy enough to remove all gloss, leaving the surface covered with fine scratches. However, care must be exercised to assure that the nylon barrier is not damaged during the buffing operation.

Adhesive MIL-PRF-9117

8

NOTE Allow multiple coats of sealants or adhesives to dry completely between applications. If exterior fuel cell protective coating (Refer to Table 15-4, usage column 10) is not available, adhesive MIL-PRF-9117 (Refer to Table 15-4, usage column 1) may be used. (8) Apply two coats of exterior fuel cell protective coating (Refer to Table 15-4, usage column 10) to patch and buffed area.

Fuel cell patches should air-cure a minimum of 72 hours prior to installation or being subjected to fuel. Do not flex the repaired area for the first 24-hour period. Do not place a repaired cell in any type of heating chamber to accelerate curing; such action will cause the cell to deteriorate and shrink beyond safe dimensions. (9) Test fuel cell for integrity of repair (Refer to Work Package 012).

Only experienced personnel should use power buffers. Power buffing may produce a polished surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand. (1) Buff the area to be repaired 2 3/4 inches in all directions from the edge of the damage.

NOTE Repair patches must have a smoothly rounded outline and the edges skived or cut at an angle by tilting the shears instead of cutting straight (See Figure 15-2). (2) Prepare a patch of outside repair material (Refer to Table 15-2, usage column 3) 1 1/2 inches larger than the area of damage. (3) Prepare a second patch of the same material that is 1 inch larger than the first.

When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the ex-

NAVAIR 01-1A-35

015 00 Page 20

posure. Always wear eye protection when engaged in buffing operations.

a permanent set conforming to the shape in its relaxed position.

Do not buff the nylon barrier side of the inner liner material. Fuel diffusion will occur if barrier is broken.

NOTE If the vulcanization method of bonding is used rather than the room temperature cure method, the techniques are the same except that vulcanizing adhesives are used (Refer to Table 15-4, usage columns 4 or 5). The cure is accomplished by clamping the double patch between plates and heat curing at the temperature and time listed in Table 15-4. Remove clamps when heater and plates return to room temperature.

Buffing must be heavy enough to remove all gloss, leaving the surface covered with fine scratches. However, care must be exercised to assure that the nylon barrier is not damaged during the buffing operation.

To determine if the adhesive is tacky, test it by pressing a knuckle gently against the cemented surface and withdrawing it. If a few threads of adhesive stick to the knuckle, the adhesive is ready for the patch.

Only experienced personnel should use power buffers. Power buffing may produce a polished surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand.

When applying patches or laminating layers of repair materials, roll down (stitch) each layer with a 1/4-inch hand roller, starting from the center and working to the outer edge to eliminate trapped air and ensure a good seal (See Figure 15-4).

(4) Buff both sides of the first patch and the large side of the second patch.

Acetone ASTM D329

7

(6) When adhesives are tacky, mate the bonding surfaces and stitch down. (7) Clamp the patch and allow two hours drying time.

Organic solvents or adhesives containing organic solvents are flammable. Avoid breathing of vapors or prolonged skin contact. Use personal protective equipment. Wear disposable polyethylene gloves, MR-100, when applying solvents by hand. (5) Clean the buffed areas with cheesecloth, CCCC-440, dampened with, Acetone, ASTM D329, and apply adhesive (Refer to Table 15-4, usage columns 1 or 2) to the small side of the first patch and the large side of the second patch (Refer to paragraph 1e(1) for application procedures).

(8) Clean the buffed areas in the fuel cell and on the double patch with cheesecloth moistened with Acetone, ASTM D329 and apply adhesive (Refer to Table 15-4, usage columns 1 or 2 for adhesive, and paragraph 1e(1) for application procedures). (9) When adhesive is tacky, center the patch over the damage area and stitch down.

Adhesive MIL-PRF-9117

8

(10) After two hours, apply adhesive MIL-PRF-9117 (Refer to Table 15-4, usage column 1) to skived edge. (11) Allow to dry completely; re-stitch.

If clamps and platens used in the vulcanization process are disassembled from the patches before room temperature is reached, the bonded patch material will not cure flat but will assume

Fuel cell patches should air-cure a minimum of 72 hours prior to installation or being subjected

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to fuel. Do not flex the repaired area for the first 24-hour period. Do not place a repaired cell in any type of heating chamber to accelerate curing; such action will cause the cell to deteriorate and shrink beyond safe dimensions.

When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations.

(12) Test fuel cell for integrity of repair (Refer to Work Package 012).

Do not buff the nylon barrier side of the inner liner material. Fuel diffusion will occur if barrier is broken.

g. INSIDE CORNER REPAIR PATCH. (See Figure 15-5.) Application procedures for an inside corner repair patch is as follows:

Comply with general safety instructions in Work Package 004, and fuel cell entry preparations in Work Package 006.

Buffing must be heavy enough to remove all gloss, leaving the surface covered with fine scratches. However, care must be exercised to assure that the nylon barrier is not damaged during the buffing operation.

When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell.

Only experienced personnel should use power buffers. Power buffing may produce a polished surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand.

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Figure 15-5. Repairing Inside Corner

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(1) Buff the area to be repaired 2 3/4 inches in all directions from the edge of the damage.

(6) Make a 1/8-inch long slit in the center at right angles to the first slit.

NOTE

(7) Fit the first patch into the corner. Trim to size and place so that a lap forms in a flat area.

Repair patches must have a smoothly-rounded outline and the edges skived or cut at an angle by tilting the shears instead of cutting straight (See Figure 15-2). (2) Prepare a patch of nylon sandwich material (Refer to Table 15-2, usage column 4) 1 1/2 inches larger than the area of damage. (3) Prepare a second patch of the same material that is 1 inch larger than the first.

(8) Mark outline of first patch on fuel cell with a white marking pencil, SS-P-00196. (9) Fit second patch over the first. Trim to size and place so that the lap it forms is in a flat area as far as possible from the lap on the first patch. (10) Mark outline of second patch on fuel cell with a white marking pencil.

Acetone ASTM D329 When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell. When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations. Do not buff the nylon barrier side of the inner liner material. Fuel diffusion will occur if barrier is broken.

Buffing must be heavy enough to remove all gloss, leaving the surface covered with fine scratches. However, care must be exercised to assure that the nylon barrier is not damaged during the buffing operation. Only experienced personnel should use power buffers. Power buffing may produce a polished surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand. (4) Buff both sides of the first patch and the large side of the second patch. Feather the skived edges. (5) Cut a single slit in each patch from the outside edge to the center.

7

(11) Clean the buffed areas with cheesecloth moistened with Acetone, ASTM D329. Apply adhesive (Refer to Table 15-4, usage column 1 or 2) to the fuel cell and the larger side of the first patch (Refer to paragraph 1e(1) for application procedures).

NOTE To determine if the adhesive is tacky, test it by pressing a knuckle gently against the cemented surface and withdrawing it. If a few threads of adhesive stick to the knuckle, the adhesive is ready for the patch. (12) When the adhesives are tacky, align the first patch with the white marks on the fuel cell. Ensure that the inner end of the 1/8-inch slit falls in the apex of the corner.

NOTE When applying patches or laminating layers of repair materials, roll down (stitch) each layer with a 1/4-inch hand roller. If the roller proves to be too awkward, the patch may be stitched with a rolling motion of the finger. Avoid any wrinkles or trapped air. (13) Stitch patch in place. Start from the inner edge of the slit and work around to the outer edge of the slit. Ensure the lap is secure. (14) Apply adhesive to the exposed side of the first patch and the larger side of the second patch (Refer to paragraph 1e(1) for application procedures).

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(15) When the adhesive is tacky, align the second patch with the white marks on the fuel cell. Ensure that the inner end of the 1/8-inch slit falls in the apex of the corner and that the overlap is opposite that of the first patch.

h. OUTSIDE CORNER REPAIR PATCH. Application procedures for an outside corner repair patch is as follows:

NOTE When applying patches or laminating layers of repair materials, roll down (stitch) each layer with a 1/4-inch hand roller. If the roller proves to be too awkward, the patch may be stitched with a rolling motion of the finger. Avoid any wrinkles or trapped air.

When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations.

(16) Stitch patch in place. Start from the inner edge of the slit and work around to the outer edge of the slit. Ensure the lap is secure.

Do not buff the nylon barrier side of the inner liner material. Fuel diffusion will occur if barrier is broken.

If clamps and platens used in the vulcanization process are disassembled from the patches before room temperature is reached, the bonded patch material will not cure flat but will assume a permanent set conforming to the shape in its relaxed position.

Buffing must be heavy enough to remove all gloss, leaving the surface covered with fine scratches. However, care must be exercised to assure that the nylon barrier is not damaged during the buffing operation.

(17) Clamp the patch and allow two hours drying time.

Adhesive MIL-PRF-9117

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(18) Apply adhesive MIL-PRF-9117 (Refer to Table 15-4, usage column 1) to skived edge. Allow to dry completely; re-stitch.

Fuel cell patches should air-cure a minimum of 72 hours prior to installation or being subjected to fuel. Do not flex the repaired area for the first 24-hour period. Do not place repaired cell in any type of heating chamber to accelerate curing; such action will cause the cell to deteriorate and shrink beyond safe dimensions. (19) Test fuel cell for integrity of repair (Refer to Work Package 012).

Only experienced personnel should use power buffers. Power buffing may produce a polished surface that is too smooth for good adhesion. If this occurs, surface should be buffed by hand. (1) Buff the area to be repaired 2 3/4 inches in all directions from the edge of the damage.

NOTE Repair patches must have a smoothly rounded outline and the edges skived or cut at an angle by tilting the shears instead of cutting straight (See Figure 15-2). (2) Prepare a patch of outside repair material (Refer to Table 15-2, usage column 3) 1 1/2 inches larger than the area of damage. (3) Prepare a second patch of the same material that is 1 inch larger than the first.

When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH ap-

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proved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations. Do not buff the nylon barrier side of the inner liner material. Fuel diffusion will occur if barrier is broken.

Buffing must be heavy enough to remove all gloss, leaving the surface covered with fine scratches. However, care must be exercised to assure that the nylon barrier is not damaged during the buffing operation. Only experienced personnel should use power buffers. Power buffing may produce a polished surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand.

posure. Always wear eye protection when engaged in buffing operations. Do not buff the nylon barrier side of the inner liner material. Fuel diffusion will occur if barrier is broken.

Buffing must be heavy enough to remove all gloss, leaving the surface covered with fine scratches. However, care must be exercised to assure that the nylon barrier is not damaged during the buffing operation. Only experienced personnel should use power buffers. Power buffing may produce a polished surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand. (12) Buff the filler patches on the larger sides.

(4) Buff both sides of the first patch and the large side of the second patch. Feather the skived edges. (5) Cut a single slit in each patch from the outside edge to the center.

Acetone ASTM D329

(6) Make a 1/8-inch long slit in the center at right angles to the first slit.

(13) Clean the buffed areas with cheesecloth, CCCC-440, dampened with, Acetone, ASTM D329, and apply adhesive (Refer to Table 15-4, usage column 1 or 2) to the fuel cell and the larger side of the first patch (Refer to paragraph 1e(1) for application procedures).

(7) Fit the first patch onto the corner. Trim to size and place so that the slit forms an opening in a flat area.

7

(8) Mark outline of first patch on fuel cell with a white marking pencil, SS-P-196.

NOTE

(9) Fit second patch over the first. Trim to size and place so that the slit forms an opening in a flat area as far as possible from the first patch opening.

To determine if the adhesive is tacky, test it by pressing a knuckle gently against the cemented surface and withdrawing it. If a few threads of adhesive stick to the knuckle, the adhesive is ready for the patch.

(10) Mark outline of second patch on fuel cell with white marking pencil. (11) Cut two filler patches of the same repair material to fit into the patch openings with the edges slightly overlapping.

(14) When the adhesives are tacky, align the first patch with the white marks on the fuel cell. Ensure that the inner end of the 1/8-inch slit falls in the apex of the corner and that the opening is in a flat area.

NOTE

When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the ex

When applying patches or laminating layers of repair materials, roll down (stitch) each layer with a 1/4-inch hand roller, starting from the center and working to the outer edge to eliminate trapped air and ensure a good seal (See Figure 15-2).

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(15) Stitch first patch in place.

Acetone ASTM D329

(21) When tacky, center second filler patch in opening. Stitch in place.

7

(16) Clean with cheesecloth moistened with Acetone, ASTM D329 and apply adhesive (Refer to Table 15-4, usage column 1 or 2) to first filler patch and opening in first patch. (17) When tacky, center first filler patch in opening and stitch in place. (18) Apply adhesive to exposed side of first patch and to larger side of second patch (Refer to paragraph 1e(1) for application procedures).

NOTE To determine if the adhesive is tacky, test it by pressing a knuckle gently against the cemented surface and withdrawing it. If a few threads of adhesive stick to the knuckle, the adhesive is ready for the patch.

Adhesive MIL-PRF-9117

8

(22) After two hours, apply adhesive MIL-PRF-9117 (Refer to Table 15-4, usage column 1) to skived edge. (23) Allow to dry completely; re-stitch.

Adhesive MIL-PRF-9117

8

NOTE Allow multiple coats of sealants or adhesives to dry completely between applications.

(19) When the adhesives are tacky, align the second patch with the white marks on the fuel cell. Ensure that the inner end of the 1/8-inch slit falls in the apex of the corner, and that the opening is in a flat area as far as possible from the opening on the first patch.

If exterior fuel cell protective coating (Refer to Table 15-4, usage column 10) is not available, adhesive MIL-PRF-9117 (Refer to Table 15-4, usage column 1) may be used.

NOTE

(24) Apply two coats of exterior fuel cell protective coating (Refer to Table 15-4, usage column 10) to patch and buffed area.

When applying patches or laminating layers of repair materials, roll down (stitch) each layer with a 1/4-inch hand roller, starting from the center and working to the outer edge to eliminate trapped air and ensure a good seal (See Figure 15-4).

Acetone ASTM D329

7

(20) Clean with cheesecloth dampened with Acetone, ASTM D329 and apply adhesive (Table 15-4. usage column 1 or 2) to second filler patch and opening in second patch.

Fuel cell patches should air-cure a minimum of 72 hours prior to installation or being subjected to fuel. Do not flex the repaired area for the first 24-hour period. Do not place a repaired cell in any type of heating chamber to accelerate curing; such action will cause the cell to deteriorate and shrink beyond safe dimensions. (25) Test fuel cell for integrity of repair (Refer to Work Package 012).

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Figure 15-6. Plug-Type Repair

i. REPAIR PLUGS. (See Figure 15-6.) There are two basic-types of fuel cell repair plugs: salvage repair plugs, and built-up repair plugs. j. SALVAGE REPAIR PLUG. Application procedures for a salvage repair plug are as follows:

Comply with general safety instructions in Work Package 004, and fuel cell entry preparations in Work Package 006. When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell. (1) Mark two circles with a white marking pencil, SS-P-196, on the interior side of the fuel cell as follows:

When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations. Do not buff the nylon barrier side of the inner liner material. Fuel diffusion will occur if barrier is broken.

Buffing must be heavy enough to remove all gloss, leaving the surface covered with fine scratches. However, care must be exercised to assure that the nylon barrier is not damaged during the buffing operation.

(a) The inside circle should be large enough to include all of the damage area.

Only experienced personnel should use power buffers. Power buffing may produce a polished surface that is too smooth for good adhesion.

(b) The outside circle should be 1/2 inch larger in radius than the inside circle.

(2) Buff the area of the inner liner extending from the outer circle outward 2 3/4 inches.

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Figure 15-7. Cutting Out Damaged Area

Figure 15-8. Cutting Bevel and Buffing

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(3) Re-mark the outside circle.

(6) Buff the outer ply of the retainer 2 3/4 inches beyond the edge of the hole.

(4) Cut away, at right angles to the cell wall, the cell wall area inside the small circle. A template may be used as a guide if desired (See Figure 15-7).

(7) Prepare and install an outside double repair patch (refer to paragraph 2f).

When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell.

Each fuel cell manufacturer compounds the natural gum rubber used in the fuel cells with slightly different ingredients. The reaction to fuel, solvents and adhesives varies. For this reason, it is desirable to use a salvage plug from a fuel cell manufactured by the same rubber company that manufactured the fuel cell under repair.

When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations. Do not buff the nylon barrier side of the inner liner material. Fuel diffusion will occur if barrier is broken.

Buffing must be heavy enough to remove all gloss, leaving the surface covered with fine scratches. However, care must be exercised to assure that the nylon barrier is not damaged during the buffing operation.

(8) From a scrapped fuel cell, cut a plug 1 inch larger than the cutout of the damaged fuel cell area.

NOTE Rotation and careful alignment of the plug is required to assure proper fit.

When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations.

Only experienced personnel should use power buffers. Power buffing may produce a polished surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand.

Do not buff the nylon barrier side of the inner liner material. Fuel diffusion will occur if barrier is broken.

(5) Bevel cut and buff the edge of the hole, using the large circle as one guide and the edge of the hole at the outer retainer as the other (See Figure 15-8).

(9) Hand trim and buff the edge of the plug to fit snugly, and flush with the adjacent fuel cell surface (See Figure 15-9).

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Figure 15-9. Preparing Plug nate trapped air and ensure a good seal (See Figure 15-4). Acetone ASTM D329

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(11) When tacky, install plug and stitch firmly.

NOTE The exterior patches that have been applied to the fuel cell provide a base to support the plug during fitting and installation. (10) Clean with cheesecloth, CCC-C-440, dampened with Acetone, ASTM D329, and apply adhesive (Refer to Table 15-4, usage column 1 or 2) to the edge and base of the plug and the fuel cell cavity (Refer to paragraph 1e(1) for application procedures).

If clamps and platens used in the vulcanization process are disassembled from the patches before room temperature is reached, the bonded patch material will not cure flat but will assume a permanent set conforming to the shape in its relaxed position. (12) Clamp and allow to dry for 8 to 10 hours.

NOTE To determine if the adhesive is tacky, test it by pressing a knuckle gently against the cemented surface and withdrawing it. If a few threads of adhesive stick to the knuckle, the adhesive is ready for the patch or plug. When applying patches or laminating layers of repair materials, roll down (stitch) each layer with a 1/4-inch hand roller, starting from the center and working to the outer edge to elimi-

When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell. When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the ex-

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posure. Always wear eye protection when engaged in buffing operations.

to fuel. Do not flex the repaired area for the first 24-hour period. Do not place a repaired cell in any type of heating chamber to accelerate curing; such action will cause the cell to deteriorate and shrink beyond safe dimensions.

Do not buff the nylon barrier side of the inner liner material. Fuel diffusion will occur if barrier is broken.

(15) Test fuel cell for integrity of repair (Refer to Work Package 012). k. BUILT-UP REPAIR PLUG. Application procedures for a built-up repair plug are as follows: Buffing must be heavy enough to remove all gloss, leaving the surface covered with fine scratches. However, care must be exercised to assure that the nylon barrier is not damaged during the buffing operation. Only experienced personnel should use power buffers. Power buffing may produce a polished surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand. (13) Lightly buff exposed surface of plug to ensure edges are flush with inner liner.

Comply with general safety instructions in Work Package 004, and fuel cell entry preparations in Work Package 006. (1) Mark two circles with a white marking pencil, SS-P-196, on the interior side of the fuel call as follows: (a) The inside circle should be large enough to include all of the damage area. (b) The outside circle should be 1/2 inch larger in radius than the inside circle.

Acetone ASTM D329

7

When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations.

When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell. Organic solvents or adhesives containing organic solvents are flammable. Avoid breathing of vapors or prolonged skin contact. Use personal protective equipment. Wear disposable polyethylene gloves, MR-100, when applying solvents by hand.

Do not buff the nylon barrier side of the inner liner material. Fuel diffusion will occur if barrier is broken. (2) Buff the area of the inner liner extending from the outer circle outward 2 3/4 inches. (3) Re-mark the outside circle with white marking pencil.

(14) Clean with cheesecloth dampened with Acetone, ASTM D329 and apply an inside double repair patch (Refer to paragraph 2d).

(4) Cut away, at right angles to the cell wall, the cell wall area inside the small circle (See Figure 15-7).

Fuel cell patches should air-cure a minimum of 72 hours prior to installation or being subjected

When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection

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015 00 Page 32

suitable to the exposure and ensure continuous ventilation of the cell.

NOTE

Do not buff the nylon barrier side of the inner liner material. Fuel diffusion will occur if barrier is broken.

When laminating layers of repair materials, roll down (stitch) each layer with a 1/4-inch hand roller, starting from the center and working to the outer edge to eliminate trapped air and to ensure a good seal (See Figure 15-4). (9) Laminate the sealant and coated fabric as follows:

Buffing must be heavy enough to remove all gloss, leaving the surface covered with fine scratches. However, care must be exercised to assure that the nylon barrier is not damaged during the buffing operation. Only experienced personnel should use power buffers. Power buffing may produce a polished surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand.

When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell.

(5) Bevel cut and buff the edge of the hole, using the large circle as one guide, and the edge of the hole at the outer retainer as the other (See Figure 15-8).

Organic solvents or adhesives containing organic solvents are flammable. Avoid breathing of vapors or prolonged skin contact. Use personal protective equipment.

(6) Buff the outer ply of the retainer 2 3/4 inches beyond the edge of the hole.

Wear disposable polyethylene gloves, MR-100, when applying solvents by hand.

(7) Prepare and install an outside double repair patch (Refer to paragraph 2f).

NOTE Use adhesive (Refer to Table 15-4, usage column 3) for hot-cure or adhesive (Refer to Table 15-4, usage column 7) for air-cure.

Each fuel cell manufacturer compounds the natural gum rubber used in the fuel cells with slightly different ingredients. The reactions to fuel, solvents, and adhesives varies. For this reason, it is desirable to use sealant manufactured by each rubber company for repairs on their specific fuel cells.

NOTE Use sealant material and coated fabric comparable in thickness to the material in the area of damage. (8) Cut as many patches of sealant (Refer to Table 15-2, usage 13 or 14) and coated fabric (Refer to Table 152, usage column 7) as there are fabric and sealant layers in the damage area.

(a) Apply three coats of adhesive to one side of a patch of coated fabric (Refer to paragraph 1e(1) for procedures). (b) Apply one coat of adhesive to one side of a patch of sealant.

NOTE To determine if the adhesive is tacky, test it by pressing a knuckle gently against the cemented surface and withdrawing it. If a few threads of adhesive stick to the knuckle, the adhesive is ready for the patch. (c) Allow adhesive to become tacky. (d) Fit coated fabric layer over sealant layer; stitch together.

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When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell. Organic solvents or adhesives containing organic solvents are flammable. Avoid breathing of vapors or prolonged skin contact. Use personal protective equipment. Wear disposable polyethylene gloves, MR-100, when applying solvents by hand.

Buffing must be heavy enough to remove all gloss, leaving the surface covered with fine scratches. However, care must be exercised to assure that the nylon barrier is not damaged during the buffing operation. Only experienced personnel should use power buffers. Power buffing may produce a polished surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand. (l) Buff the synthetic rubber or nitrile coat (BUNA-N) side of the inner liner patches.

NOTE If building up a plug for lightweight or standard construction "A" fuel cells (with only one layer of coated fabric between the sealant layers), proceed to step (g). (e) Apply adhesive to the exposed side of the coated fabric layer and to one side of a second patch of coated fabric (Refer to paragraph 1e(1) for procedures). (f) When tacky, fit the two layers of coated fabric together; stitch down. (g) Apply three coats of adhesive to the ex posed side of the coated fabric (Refer to paragraph 1e(1) for application procedures). (h) Apply one coat of adhesive to one side of the second patch of sealant. (i) Allow adhesive to me tacky. (j) Fit sealant layer over coated fabric layer; stitch together. (k) Cut two patches of inner liner repair material (Refer to Table 15-2, usage column 4).

When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations. Do not buff the nylon barrier side of the inner liner material. Fuel diffusion will occur if barrier is broken.

Acetone ASTM D329

7

(m) Clean with cheesecloth, CCC-C-440, dampened with Acetone, ASTM D329, and apply three coats of adhesive to the nylon film barrier side of the first inner liner patch, and one coat of adhesive to the exposed sealant layer (Refer to paragraph 1e(1) for procedures). (n) Allow sealant to become tacky. (o) Fit inner liner patch over sealant layer and stitch in place. (p) Clean with cheesecloth dampened with Acetone, ASTM D329 and apply three coats of adhesive to the nylon barrier side of the second inner liner patch, and to the exposed inner liner on the plug (Refer to 9-4e(1) for application procedures). (q) Allow adhesive to become tacky. (r) Fit second inner liner patch over exposed inner liner patch on plug; stitch in place. (s) Cut two patches of outside repair material (Refer to Table 15-2, usage column 3).

Buffing must be heavy enough to remove all gloss, leaving the surface covered with fine scratches. However, care must be exercised to assure, that the nylon barrier is not damaged during the buffing operation. Only experienced personnel should use power buffers. Power buffing may produce a polished

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surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand. (t) Buff both sides of both patches.

Acetone ASTM D329

7

(u) Clean with cheesecloth dampened with Acetone, ASTM D329 and apply three coats of adhesive to the first patch of outside repair material, and one coat of adhesive to the exposed sealant layer on the plug (Refer to paragraph 1e(1) for application procedures). (v) Allow adhesive to become tacky. (w) Fit first outside repair patch over exposed sealant layer on plug; stitch in place. (x) Clean with cheesecloth dampened with Acetone, ASTM D329 and apply three coats of adhesive to one side of the second outside repair patch, and to the exposed outside repair patch on the plug (Refer to paragraph 1e(1) for application procedures). (y) Allow adhesive to become tacky. (z) Fit second outside repair patch over the exposed outside repair patch on the plug; stitch in place.

NOTE The exterior patches that have been applied to the fuel cell provide a base to support the plug during fitting and installation. (bb) Clean with cheesecloth, CCC-C-440, dampened with Acetone, ASTM D329, and apply adhesive (Refer to Table 15-4, usage columns 1 or 2) to the edge and base of the plug and the fuel cell cavity (Refer to paragraph 1e(1) for application procedures).

NOTE To determine if the adhesive is tacky, test it by pressing a knuckle gently against the cemented surface and withdrawing it. If a few threads of adhesive stick to the knuckle, the adhesive is ready for the patch or plug. When applying patches or laminating layers of repair materials, roll down (stitch) each layer with a 1/4-inch hand roller, starting from the center and working to the outer edge to eliminate trapped air and ensure a good seal (See Figure 15-4). (cc) When tacky, install plug and stitch firmly.

NOTE The exterior patches that have been applied to the fuel cell provide a base to support the plug during fitting and installation. Rotation and careful alignment of the plug is required to assure proper fit. (aa) From the built-up layers, cut a plug 1 inch larger than the cutout of the fuel cell area. Hand trim and buff the edge of the plug to fit snugly and flush with the adjacent fuel cell surface (See Figure 15-8).

When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell. Wear disposable polyethylene gloves, MR-100, when applying solvents by hand.

If clamps and platens used in the vulcanization process are disassembled from the patches before room temperature is reached, the bonded patch material will not cure flat but will assume a permanent set conforming to the shape in its relaxed position. (dd) Clamp and allow to dry for 8 to 10 hours

When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell. When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations.

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015 00 Page 35 l. STEP-BACK REPAIR PLUG. (See Figures 15-10 and 15-11.) Application procedures for a step-back fuel cell repair plug are as follows:

Buffing must be heavy enough to remove all gloss, leaving the surface covered with fine scratches. However, care must be exercised to assure that the nylon, barrier is not damaged during the buffing operation. Only experienced personnel should use power buffers. Power buffing may produce a polished surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand. (ee) Lightly buff exposed surface of plug to ensure edges are flush with inner liner.

Comply with general safety instructions in Work Package 004, and fuel cell entry preparations in Work Package 006. When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell.

NOTE Acetone ASTM D329

7

(ff) Clean with cheesecloth dampened with Acetone, ASTM D329 and apply an inside double repair patch (Refer to paragraph 2d).

Fuel cell patches should air-cure a minimum of 72 hours prior to installation or being subjected to fuel. Do not flex the repaired area for the first 24-hour period. Do not place a repaired cell in any type of heating chamber to accelerate curing; such action will cause the cell to deteriorate and shrink beyond safe dimensions. (gg) Test fuel cell for integrity of repair (Refer to Work Package 012).

Step-back repair cutouts should be smoothlyrounded with step-backs at right angles to the cell wall. The step-back, as shown in Figure 15-10, has the step-back increase toward the interior of the fuel cell. This is necessary in order to provide maximum strength. A convenient way to mark the step-back is to draw the 1-inch step-back lines on the inside of the fuel cell before cutting into the inside body. Then, knowing the ply sequence, it is an easy matter to accurately stepback from the damage. If desired, it is also possible, by proper marking, to cut from the outer marking line on the inside of the fuel cell down to the required ply. Peel and buff off the cut plies, re-mark, and repeat these steps until the first step-back from the damage is reached. It is recommended that the step-back repair method be practiced on scrap material until acceptable repair techniques are developed.

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Figure 15-10. Step-Back Repair, Construction B Completed

Figure 15-11. Step-Back Repair Cutout Construction A

Figure 15-12. Step-Back Repair Cutout, Construction B

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(1) Cut out the damaged area.

(4) Step-back the sealant gum and fabric separator plies 1 inch from the second retainer layer.

NOTE When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell. When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations. Do not buff the nylon barrier side of the inner liner material. Fuel diffusion will occur if barrier is broken.

Buffing must be heavy enough to remove all gloss, leaving the surface covered with fine scratches. However, care must be exercised to assure that the nylon barrier is not damaged during the buffing operation. Only experienced personnel should use power buffers. Power buffing may produce a polished surface that is too smooth for good adhesion. If his occurs, surface should be rebuffed by hand.

For lightweight and standard construction "A" fuel cells, comply with the instructions in step (5), then proceed to step (7). For standard construction "B" fuel cells, omit step (5). The inner liner is cut to the same edge as the second layer of sealant gum. (5) Step-back the second ply of sealant to expose the single layer of fabric separator between the sealant plies.

NOTE The inner liner is cut to the same edge as the second layer of sealant gum. (6) Step-back the second ply of sealant gum and the second ply of fabric separator to expose the first layer of fabric separator.

NOTE Patches that are over 8 inches in diameter can be applied with better control if a polyethylene film, L-P-378, or Holland Cloth, MIL-C-17564, liner is used between the coated patch and the coated area of the fuel cell. This separate sheet is removed as the patch is stitched down.

(2) Working from the inside, step-back the cutout 1 inch to the outer ply of the retainer. Buff as required to remove material, if necessary.

(7) Prepare and install a double outside repair patch (Refer to paragraph 2f).

NOTE

For repair patches, refer to Table 15-2 and use fabrics from usage column 3 for the first two plies, usage column 13 for the sealant plies, usage column 7 for the plies between the sealant plies, and usage column 4 for the inner liner.

In lightweight and standard construction "A" fuel cells, the original construction is not followed due to the necessity of lapping the single fabric ply used between the plies of sealant gum, and the fact that no strength is obtained in lapping sealant gum. The lap of this fabric ply will reduce the thickness of the sealant gum ply next to the inner liner. (3) Continue to step-back the plies of the fuel cell as shown in Figures 15-11 and 15-12.

NOTE

Standard construction "B" fuel cells require three plies of retainer fabric. (8) Cut out the required number of repair patches, and trim to fit the step-backs as required. (9) Install as follows:

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Acetone ASTM D329 When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell. When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations. Do not buff the nylon barrier side of the inner liner material. Fuel diffusion will occur if barrier is broken.

Buffing must be heavy enough to remove all gloss, leaving the surface covered with fine scratches. However, care must be exercised to assure that the nylon barrier is not damaged during the buffing operation. Only experienced personnel should use power buffers. Power buffing may produce a polished surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand.

NOTE

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(b) Clean with cheesecloth, CCC-C-440, moistened with Acetone, ASTM D329, and apply three coats of adhesive (Refer to Table 15-4, usage column 3) to one side of the first layer retainer fabric insert (Refer to paragraph 1e(1) for application procedures). (c) Apply one coat of the same adhesive to the installed double patch exposed surface and the edge of the first layer retainer fabric. (d) Allow adhesive to become tacky. (e) Install first layer insert; stitch down firmly. (f) Lightly buff the exposed surface of the first layer retainer fabric. (g) Clean with cheesecloth moistened with Acetone, ASTM D329 and apply three coats of adhesive (Refer to Table 15-4, usage column 3) to the first layer retainer fabric (Refer to paragraph 1e(1) for application procedures). (h) Clean with cheesecloth moistened with Acetone, ASTM D329 and apply three coats of the same adhesive to one face, and to the edge of the second layer retainer fabric insert patch (Refer to paragraph 1e(1) for application procedures). (i) Allow adhesive to become tacky. (j) Install second layer retainer fabric insert; stitch down firmly.

NOTE Omit step (k) on standard construction "B" fuel cells.

To determine if the adhesive is tacky, test it by pressing a knuckle gently against the cemented surface and withdrawing it. If a few threads of adhesive stick to the knuckle, the adhesive is ready for the patch.

(k) Repeat steps (f) through (j) for the third layer retainer fabric insert.

When applying patches or laminating layers of repair materials, roll down (stitch) each layer with a 1/4-inch hand roller, starting from the center and working to the outer edge to eliminate trapped air and ensure a good seal (See Figure 15-4).

(m) Clean with cheesecloth moistened with Acetone, ASTM D329. Apply three coats of adhesive (Refer to Table 15-4, usage column 3) to the last layer of retainer fabric and the exposed edge of sealant (Refer to paragraph 1e(1) for application procedures).

(a) Buff both faces of the retainer fabric plies.

(l) Lightly buff the last layer of the installed retainer fabric.

(n) Apply one coat of the same adhesive to one face and the edge of the first gum sealant insert.

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(o) Allow adhesive to become tacky. (p) Install first layer of gum sealant; stitch down firmly.

NOTE Omit steps (q) through (t) on lightweight and standard construction "A" fuel cells.

scratches. However, care must be exercised to assure that the nylon barrier is not damaged during the buffing operation. Only experienced personnel should use power buffers. Power buffing may produce a polished surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand. (u) Lightly buff the exposed step-back area of the sealant ply separator.

Acetone ASTM D329

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(q) Apply three coats of adhesive (Refer to Table 15-4. usage column 3) to one side of the first sealant ply separator insert and the edge (Refer to paragraph 1e(1) for application procedures). (r) Apply one coat of the same adhesive to the exposed sealant layer.

(v) Clean and apply three coats of adhesive (Refer to Table 15-4, usage column 3) to the step-back area (Refer to paragraph 1e(1) for application procedures). (w) Apply one coat of the same adhesive to the exposed sealant ply. (x) Apply three coats of the same adhesive to the sealant ply separator insert patch (Refer to paragraph 1e(1) for application procedures). (y) Allow adhesive to become tacky.

(s) Allow adhesive to become tacky. (t) Install first sealant ply separator insert; stitch down firmly.

NOTE Omit steps (u) through (z) on standard construction "B" fuel cells.

When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell. When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations. Do not buff the nylon barrier side of the inner liner material. Fuel diffusion will occur if barrier is broken.

Buffing must be heavy enough to remove all gloss, leaving the surface covered with fine

(z) Install sealant ply separator insert; stitch down firmly.

NOTE Omit steps (aa) through (dd) on lightweight and standard construction "A" fuel cells.

Buffing must be heavy enough to remove all gloss, leaving the surface covered with fine scratches. However, care must be exercised to assure that the nylon barrier is not damaged during the buffing operation. Only experienced personnel should use power buffers. Power buffing may produce a polished surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand. (aa) Lightly buff first layer sealant ply separator step-back and the exposed first layer sealant ply separator insert patch. (bb) Clean with cheesecloth moistened with Acetone, ASTM D329. Apply three coats of adhesive (Refer to Table 15-4, usage column 3) to the step-back area, the exposed sealant ply insert patch, and to one side of the second sealant ply separator insert patch (Refer to paragraph 1e(1) for application procedures). (cc) Allow adhesive to become tacky.

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(dd) Install second sealant ply separator insert patch; stitch down firmly.

When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell.

(ff) Clean with cheesecloth moistened with Acetone, ASTM D329 and apply three coats of adhesive (Refer to Table 15-4, usage column 3) to the exposed sealant ply separator and the exposed sealant edge (Refer to paragraph 1e(1) for application procedures). (gg) Apply one coat of the same adhesive to one side and edge of the second layer of sealant ply. (hh) Allow adhesive to become tacky. (ii) Install second layer sealant ply; stitch down firmly.

When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations. Do not buff the nylon barrier side of the inner liner material. Fuel diffusion will occur if barrier is broken.

(jj) Apply three coats of adhesive (Refer to Table 15-4, usage column 3) to the nylon fuel barrier side of the inner liner insert patch (Refer to paragraph 1e(1) for application procedures). (kk) Apply one coat of the same adhesive to the exposed layer of sealant ply. (ll) Allow adhesive to become tacky. (mm) Install inner liner insert patch; stitch down firmly.

Buffing must be heavy enough to remove all gloss, leaving the surface covered with fine scratches. However, care must be exercised to assure that the nylon barrier is not damaged during the buffing operation. Only experienced personnel should use power buffers. Power buffing may produce a polished surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand. (ee) Lightly buff the last layer of sealant ply separator installed.

Acetone ASTM D329

(nn) Clean with cheesecloth moistened with Acetone, ASTM D329 and apply an inside double repair patch (Refer to paragraph 2d).

If clamps and platens used in the vulcanization process are disassembled from the patches before room temperature is reached, the bonded patch material will not cure flat but will assume a permanent set conforming to the shape in its relaxed position. (oo) Clamp step-back repair and allow to cure 8 to 10 hours.

7

When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell.

Fuel cell patches should air-cure a minimum of 72 hours prior to installation or being subjected to fuel. Do not flex the repaired area for the first 24-hour period. Do not place a repaired cell in any type of heating chamber to accelerate curing; such action will cause the cell to deteriorate and shrink beyond safe dimensions.

Wear disposable polyethylene. gloves, MR-100, when applying solvents by hand.

(pp) Test fuel cell for integrity of repair (Refer to Work Package 012).

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015 00 Page 41 When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations. Do not buff the nylon barrier side of the inner liner material. Fuel diffusion will occur if barrier is broken.

Buffing must be heavy enough to remove all gloss, leaving the surface covered with fine scratches. However, care must be exercised to assure that the nylon barrier is not damaged during the buffing operation. Only experienced personnel should use power buffers. Power buffing may produce a polished surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand.

Figure 15-13. Slitting Blister

m. BLISTER REPAIR. There are two methods of blister repair: open blister repair (air-cure), and closed blister repair (vulcanization).

NOTE To determine if the adhesive is tacky, test it by pressing a knuckle gently against the cemented surface and withdrawing it. If a few threads of adhesive stick to the knuckle, the adhesive is ready for the patch.

(1) Repair method determination. Blisters are generally repaired by the open blister repair method. The only exceptions are when the following considerations are met: The blister is less than two inches in length.

When applying patches or laminating layers of repair materials, roll down (stitch) each layer with a 1/4-inch hand roller, starting from the center and working to the outer edge to eliminate trapped air and ensure a good seal (See Figure 15-4).

It can be positively determined that there is no fuel in the blister. (2) Inner liner and outside retainer blister repair methods. Outside retainer blisters are repaired in the same manner as inner liner blisters, except that outside repair materials are used. n. OPEN BLISTER REPAIR. The open blister method of fuel cell repair is as follows:

(1) Buff the blister surface and an area extending 2 3/4 inches in all directions from its edge. (2) Slit the blister from end to end (See Figure 1513). (3) Buff the underside of the loose edges to remove all fuel barrier material.

Comply with general safety instructions in Work Package 004, and fuel cell entry preparations in Work Package 006.

Acetone ASTM D329

When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell.

(4) Clean with cheesecloth, CCC-C-440, moistened with Acetone, ASTM D329, and apply three coats of adhesive (Refer to Table 15-4, usage column 1 or 2) to the inside surfaces (Refer to paragraph 1e(1) for application procedures.

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(5) Allow adhesive to become tacky.

NOTE The edges of some blisters, after cutting, may overlap when stitched in place. When this occurs, trim the inner liner material so that the edges will butt together. The edges of other blisters, after cutting, may leave a gap when stitched in place. When this occurs, cut a strip of inner liner material to fill in the gap and bond in place. (6) Stitch blister flaps firmly in place. (7) Apply an inside double repair patch to the repaired area (Refer to paragraph 2d).

(5) Remove clamps and apply an inside single repair patch to the repaired area (Refer to paragraph 2c). (6) Test fuel cell for integrity of repair (Refer to Work Package 012). p. LOOSE LAP SEAM OR LOOSE PATCH REPAIR. Repair procedures for loose lap seams and repair procedures for loose patches are identical. To repair loose lap seams or patches, perform the following procedures:

Comply with general safety instructions in Work Package 004, and fuel cell entry preparations in Work Package 006. When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell.

Fuel cell patches should air-cure a minimum of 72 hours prior to installation or being subjected to fuel. Do not flex the repaired area for the first 24-hour period. Do not place a repaired cell in any type of heating chamber to accelerate curing; such action will cause the cell to deteriorate and shrink beyond safe dimensions. (8) Test fuel cell for integrity of repair (Refer to Work Package 012).

When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations. Do not buff the nylon barrier side of the inner liner material. Fuel diffusion will occur if barrier is broken.

o. CLOSED BLISTER REPAIR. The closed blister method of fuel cell repair is as follows: (1) Fill a syringe and hypodermic needle with vulcanizing adhesive (Refer to Table 15-4, usage column 4 or 5). (2) Insert needle in one end of blister and inject adhesive until blister is full. (3) Extract as much adhesive as possible and withdraw the needle.

Buffing must be heavy enough to remove all gloss, leaving the surface covered with fine scratches. However, care must be exercised to assure that the nylon barrier is not damaged during the buffing operation. Only experienced personnel should use power buffers. Power buffing may produce a polished surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand.

If clamps and platens used in the vulcanization process are disassembled from the patches before room temperature is reached, the bonded patch material will not cure flat but will assume a permanent set conforming to the shape in its relaxed position.

Loose lap seams or patches on the inside of the fuel cell should be repaired as soon as they are detected. This is to prevent the separation from spreading to the sealant.

(4) Clamp the blister down flat and vulcanize at 290°F (143°C) ±5°F (3°C) for 30 minutes.

Outside retainer lap seam repair procedures are the same as inside liner lap seam repairs, except

NOTE

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that material comparable to the outside retainer is used. To determine if the adhesive is tacky, test it by pressing a knuckle gently against the cemented surface and withdrawing it. If a few threads of adhesive stick to the knuckle, the adhesive is ready for the patch. When applying patches or laminating layers of repair materials, roll down (stitch) each layer with a 1/4-inch hand roller, starting from the center and working to the outer edge to eliminate trapped air and ensure a good seal (See Figure 15-4).

NOTE As a general practice, it is easier and faster to replace activated sealant. In some cases the activated sealant will break into chunks or wrinkle extensively. A safe practice is to replace activated sealant where any doubt exists concerning the loss of original properties. The following repair is not valid for fuel cells manufactured by Engineered Fabric Corporation (EFC). (1) Remove all fuel and fuel vapors from the fuel cell (Refer to Work Package 006).

(1) Buff both surfaces inside the separation. (2) Buff an area on top of the loose seam extending 1 3/4 inches in all directions from the edge of the separation.

Acetone ASTM D329

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(3) Clean with cheesecloth, CCC-C-440, moistened with Acetone, ASTM D329, and apply three coats of adhesive (Refer to Table 15-4, usage column 1 or 2) to both surfaces inside the separation (Refer to paragraph 1e(1) for application procedures).

Comply with general safety instructions in Work Package 004, and fuel cell entry preparations in Work Package 006. When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell. (2) Cut away the inner liner and fuel barrier to expose the activated sealant. (3) Allow a maximum of 72 hours for fuel and fuel vapors to dissipate from the sealant.

(4) Allow adhesive to become tacky.

NOTE

(5) Stitch down firmly. (6) Apply a single inside repair patch (Refer to paragraph 2c).

If after 72 hours the sealant has not returned to its normal shape and consistency, remove the affected sealant and replace with new repair sealant. (4) Use step-back patch repair procedures to replace the cut-away material (Refer to paragraph 2l (2L)).

Fuel cell patches should air-cure a minimum of 72 hours prior to installation or being subjected to fuel. Do not flex the repaired area for the first 24-hour period. Do not place a repaired cell in any type of heating chamber to accelerate curing; such action will cause the cell to deteriorate and shrink beyond safe dimensions. (7) Test fuel cell for integrity of repair (Refer to Work Package 012). q. SEALANT REPAIRS. Sealant repair procedures are as follows:

(5) Test fuel cell for integrity of repair (Refer to Work Package 012). r. PLY SEPARATION REPAIRS. Ply separations are an aging characteristic of fuel cells caused by adhesives reverting to an uncured state. There are three methods of fuel cell ply separation repair. They are as follows: Heat and pressure Aeration and adhesive injection Cut and paste

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s. HEAT AND PRESSURE REPAIR. Procedures for heat and pressure repair of fuel cell ply separations are as follows:

Acetone ASTM D329

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(4) Extract Acetone, ASTM D329 with syringe. If clamps and platens used in the vulcanization process are disassembled from the patches before room temperature is reached, the bonded patch material will not cure flat but will assume a permanent set conforming to the shape in its relaxed position.

NOTE Only "C" clamp pressure is required. (1) Clamp vulcanization platens on each side of cell over ply separation area. (2) Apply heat at 150°F (65°C) for two hours. (3) Remove clamps and platens. If repair is not satisfactory, use an alternative repair method. t. AERATION AND ADHESIVE INJECTION REPAIR. Procedures for aeration and adhesive injection repair of fuel cell ply separation are as follows: (1) Ensure that fuel or fuel vapors are not present in the ply separation void by proceeding as follows:

NOTE

NOTE For more effective aeration, insert a needle at the opposite end of the void as a bleed vent. (5) Repeat steps (2) through (4) two times, and remove needle. (6) Aerate void by inserting a needle adapted for air application into the void. (7) Blow air at 5 ± 1 psig into cavity for 5 to 10 minutes to remove remaining Acetone, ASTM D329. (8) Remove aeration needles; reinsert flushing needle and syringe. (9) Flush void with primer (Refer to Table 15-4, usage column 3). Remove needle and syringe. (10) Aerate void until dry (Refer to steps (6) and (7)). (11) Remove aeration needles; reinsert flushing needle and syringe. (12) Inject adhesive (Refer to Table 15-4, usage column 2) into void. Draw off excess. (13) Aerate void until dry (refer to steps (7) and (8)).

Be very careful not to penetrate the inner liner barrier.

(14) Repeat steps (11) and (12). When tacky, stitch down and apply pressure with clamp or weights until adhesive cures.

(a) From the outside wall of the fuel cell, insert hypodermic needle, GG-N-196, at an angle, into the void caused by ply separation.

(15) Remove clamps or weights. If repair is not satisfactory, use cut and paste fuel cell ply separation repair method (Refer to paragraph 2u).

(b) With a syringe, GG-S-935, draw a vacuum in the void to determine if fuel or fuel vapor is present.

(16) If repair is satisfactory, apply a single outside repair patch (Refer to paragraph 2e).

NOTE

u. CUT AND PASTE REPAIR. Procedures for cut and paste repair of fuel cell ply separation are as follows:

If fuel or fuel vapors are detected in the ply separation void, use the cut and paste repair procedure (Refer to paragraph 2u). (2) If no fuel vapors are present, use the syringe to fill the void with Acetone, ASTM D329. (3) Work the separated surfaces by hand to reactivate adhesive or loosen any old reverted adhesive.

NOTE To determine if the adhesive is tacky, test it by pressing a knuckle gently against the cemented surface and withdrawing it. If a few threads of adhesive stick to the knuckle, the adhesive is ready for the patch.

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When applying patches or laminating layers of repair materials, roll down (stitch) each layer with a 1/4-inch hand roller, starting from the center and working to the outer edge to eliminate trapped air and ensure a good seal (See Figure 15-4). When more than one ply of the fuel cell has separated, each ply will require cutting, scraping, aerating, and cementing before the next separated ply is repaired. (1) Cut through the outside of the fuel cell to the ply that has separated. (2) Scrape off reverted adhesive.

Acetone ASTM D329

(7) Remove clamps and apply a double out side repair patch.

Fuel cell patches should air-cure a minimum of 72 hours prior to installation or being subjected to fuel. Do not flex the repaired area for the first 24-hour period. Do not place a repaired cell in any type of heating chamber to accelerate curing; such action will cause the cell to deteriorate and shrink beyond safe dimensions. (8) Test fuel cell for integrity of repair (Refer to Work Package 012).

7

(3) Clean with cheesecloth, CCC-440, moistened with Acetone, ASTM D329, and apply adhesive (Refer to Table 15-4, usage column 1 or 2) to both exposed surfaces (Refer to paragraph 1e(1) for adhesive application procedures). (4) Allow adhesive to become tacky. (5) Press surfaces together; stitch down firmly.

If clamps and platens used in the vulcanization process are disassembled from the patches before room temperature is reached, the bonded patch material will not cure flat but will assume a permanent set conforming to the shape in its relaxed position. (6) Clamp repair and allow to air dry 8 to 10 hours.

NOTE If ply separation was between the inner liner nylon barrier and the first sealant layer, an additional single inside repair patch is required (Refer to paragraph 2c).

3. CRASH-RESISTANT SELF-SEALING FUEL CELL (ARM) DAMAGE/DEFECT REPAIR PROCEDURES. The damage/defect repair procedures for crashresistant fuel cells (ARM) are provided in the following paragraphs.

The repair procedures for crash-resistant selfsealing fuel cells (ARM) are applicable only to this type of fuel cell. They shall not be used to repair any other configuration or type of selfsealing fuel cell. a. INTERNAL CELL SUPPORT. (See Figure 15-2.) Build a trestle or other support inside the cell.

NOTE The cell must be supported in the area around the damage so the edges will be lined up properly in their natural position. Wooden blocks or boards used inside fuel cells should be padded or covered with cloth to protect the liner from damage. b. REPAIR PATCHES. There are two basic types of repair patches: inner liner repair patches, and exterior repair patches.

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NOTE Repair patches must have a smoothly rounded outline and the edges skived or cut at an angle by tilting the edges instead of cutting straight (See Figure 15-4). Patches are cut to extend 1 1/2 inches from the edge of the damage area. c. INNER LINER REPAIR PATCH. Inner liner repair patches can only be applied to inner liner cuts not over 4 inches in length, not extending into a corner or steppedoff area and not penetrating the reinforcement ply under the inner liner. Crash resistant (ARM) self-sealing fuel cells with cuts that exceed those limitations must be returned to the manufacturer for repair. Application of an inner liner repair patch is as follows:

Comply with general safety instructions in Work Package 004, and fuel cell entry preparations in Work Package 006. When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell. When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations. Do not buff the nylon barrier side of the inner liner material. Fuel diffusion will occur if barrier is broken.

The following repair may not return a fuel cell to its original Crash Resistant status. Use of this repair procedure is authorized only with the acknowledgement that the cell will be Non-Crash Resistant.

Acetone ASTM D329

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Comply with general safety instructions in Work Package 004, and fuel cell entry preparations in Work Package 006.

Buffing must be heavy enough to remove all gloss, leaving the surface covered with fine scratches to ensure adhesion. However, care must be exercised to assure that the buffing does not result in excessive reduction of the retainer. Only experienced personnel should use power buffers. Power buffing may produce a polished surface that is too smooth for good adhesion. If this occurs, surface should be re-buffed by hand. (2) Buff the area to be repaired 1 3/4 inches in all directions from the edge of the damage.

NOTE

When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell.

Do not soak buffed area, but clean lightly until all grit and buffing dust are removed.

(1) Clean the damage area with cheesecloth, CCCC-440, moistened with Acetone, ASTM D329.

(3) Dust off the surface and clean the buffed area with cheesecloth moistened with Acetone, ASTM D329.

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Adhesive 82C18

(e) Brush a second coat of barrier adhesive over the first at right angles (90°) to the application of the first coat. 9

(f) Repeat steps (c) and (d). (6) Mix and apply repair adhesive 82C18 in accordance with steps (4)(a) through (4)(d).

Isocyanate exposure may produce severe allergic reaction and permanent sensitization. Persons with history of allergies or previous sensitization shall not be assigned tasks involving isocyanates. Personal protective equipment for skin and eyes and proper respiratory protection (BUMEDINST 6260.16) shall be required when polyurethane coatings or adhesives are used for fuel cell repairs. (4) Mix and apply repair adhesive 82C18 (Refer to Table 15-4, usage column 13, item 12) as follows: (a) Pour the entire contents of 82C18 part 2 into 82C18 part 1. (b) Stir thoroughly, making sure components are thoroughly mixed. (c) Apply a thin coat of the mixed adhesive over the buffed area +0 -1/4 inch of buffed edge.

NOTE Repair patches must have a smoothly-rounded outline and the edges skived or cut at an angle by tilting the shears instead of cutting straight (See Figure 15-2). (7) Out fabric reinforcement patch from material (Refer to Table 15-2, usage column 2, item 13) large enough to extend beyond the damage area 1 1/2 inches in all directions. (8) Wet fabric reinforcement patch with Acetone, ASTM D329.

NOTE Patch shall be free of air bubbles and loose edges and should be centered over defect. (9) Press wet patch into the wet repair adhesive. (10) Allow to air-cure for approximately 30 minutes.

Acetone ASTM D329

(11) Apply a uniform coat of repair adhesive 82C18 over patch. 7

(d) Smooth adhesive surface with gloved fingers wet with Acetone, ASTM D329. (e) Remove any excess adhesive from the unbuffed area with cheesecloth moistened with Acetone, ASTM D329. (f) Allow adhesive to air-cure approximately 30 minutes. (5) Mix and apply barrier adhesive 82C12 (Refer to Table 15-4, usage column 14, item 11) as follows: (a) Thoroughly stir one part of the adhesive. (b) Brush a uniform coat of adhesive over the buffed area. (c) Remove any excess barrier adhesive from unbuffed areas with cheesecloth, CCC-C-440, moistened with Acetone, ASTM D329. (d) Allow barrier adhesive to dry to touch.

Fuel cell patches should air-cure a minimum of 72 hours prior to installation or being subjected to fuel. Do not flex the repaired area for the first 24-hour period. Do not place a repaired cell in any type of heating chamber to accelerate curing; such action will cause the cell to deteriorate and shrink beyond safe dimensions. (12) Test fuel cell for integrity of repair (Refer to Work Package 012). d. EXTERIOR REPAIR PATCH. Exterior repair patches can only be applied to retainer cuts not over four inches in length, not extending into a corner area and not penetrating the reinforcement layer under the retainer. Crash resistant (ARM) self-sealing fuel cells that exceed these limitations must be returned to the manufacturer for repair. Application of an exterior repair patch is as follows:

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015 00 Page 48 surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand.

The following repair may not return a fuel cell to its original Crash Resistant status. Use of this repair procedure is authorized only with the acknowledgement that the cell will be Non-Crash Resistant.

Acetone ASTM D329

(2) Buff the area to be repaired 2 1/4 inches in all directions from the edge of the damage.

NOTE Do not soak buffed area, but clean lightly until all grit and buffing dust is removed. (3) Dust off the surface and clean the buffed area with cheesecloth moistened with Acetone, ASTM D329.

7

(1) Clean the damage area with cheesecloth, CCCC-440, moistened with Acetone, ASTM D329.

Comply with general safety instructions in Work Package 004, and fuel cell entry preparations in Work Package 006. When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell.

Adhesive 82C18

9

Isocyanate exposure may produce severe allergic reaction and permanent sensitization. Persons with history of allergies or previous sensitization shall not be assigned tasks involving isocyanates. Personal protective equipment for skin and eyes and proper respiratory protection (BUMEDINST 6262.16) shall be required when polyurethane coatings or adhesives are used for fuel cell repairs.

When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations.

(4) Mix and apply repair adhesive 82C18 (Refer to Table 15-4, column 13, item 12) as follows:

Do not buff the nylon barrier side of the inner liner material. Fuel diffusion will occur if barrier is broken.

(b) Stir thoroughly, making sure components are thoroughly mixed.

(a) Pour the entire contents of 82C18 part 2 into 82C18 part 1.

(c) Apply a thin coat of the mixed adhesive over the buffed area +0 -1/4 inch of buffed edge.

Buffing must be heavy enough to remove all gloss, leaving the surface covered with fine scratches to ensure adhesion. However, care must be exercised to assure that the buffing does not result in excessive reduction of the retainer.

Organic solvents or adhesives containing organic solvents are flammable. Avoid breathing of vapors or prolonged skin contact. Use personal protective equipment.

Only experienced personnel should use power buffers. Power buffing may produce a polished

Wear disposable polyethylene gloves, MR-100, when applying solvents by hand.

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015 00 Page 49

(d) Smooth adhesive surface with gloved fingers .

(9) Apply a uniform coat of repair adhesive over patch.

Acetone ASTM D329

7

(e) Remove any excess adhesive from the unbuffed area with cheesecloth moistened with Acetone, ASTM D329.

NOTE Repair patches must have a smoothly-rounded outline and the edges skived or cut at an angle by tilting the shears instead of cutting straight (See Figure 15-2). (5) Cut fabric reinforcement patch from material (Refer to Table 15-2, usage column 2, item 13) large enough to extend beyond the damage area 1 1/2 inches in all directions. (6) Wet fabric reinforcement patch with Acetone, ASTM D329.

Fuel cell patches should air-cure a minimum of 72 hours prior to installation or being subjected to fuel. Do not flex the repaired area for the first 24-hour period. Do not place a repaired cell in any type of heating chamber to accelerate curing; such action will cause the cell to deteriorate and shrink beyond safe dimensions. (10) Test fuel cell for integrity of repair (Refer to Work Package 012). e. INNER LINER BLISTER REPAIR. Inner liner blisters over 4 inches in length or extending into a corner or stepped-off area cannot be repaired at Naval facilities. Crash-resistant (ARM) self-sealing fuel cell defects exceeding these limitations must be returned to the manufacturer for repair. Inner liner blister repair procedures are as follows:

NOTE Patch shall be free of air bubbles and loose edges, and should be centered over defect.

Adhesive 82C18

9

(7) Press wet patch into the wet repair adhesive. (8) Allow to air-cure for approximately 30 minutes.

Isocyanate exposure may produce severe allergic reaction and permanent sensitization. Persons with history of allergies or previous sensitization shall not be assigned tasks involving isocyanates. Personal protective equipment for skin and eyes and proper respiratory protection (BUMEDINST 6262.16) shall be required when polyurethane coatings or adhesives are used for fuel cell repairs.

Comply with general safety instructions in Work Package 004, and fuel cell entry preparations in Work Package 006. When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell. (1) Trim away blister. (2) Apply an inner liner repair patch to the blister area (Refer to paragraph 3c). f. INNER LINER SCUFF AND ABRASION REPAIR. Inner liner scuff and abrasion repair procedures are used only to repair damage to the inner liner that does not extend into the fabric reinforcing plies. Inner liner scuff and abrasion repair procedures are as follows:

Comply with general safety instructions in Work Package 004, and fuel cell entry preparations in Work Package 006.

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015 00 Page 50

When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell.

Acetone ASTM D329

7

Wear disposable polyethylene gloves, MR-100, when applying solvents by hand. (1) Clean the damage area with cheesecloth, CCCC-440, moistened with Acetone, ASTM D329.

Comply with general safety instructions in Work Package 004, and fuel cell entry preparations in Work Package 006. When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell. When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations.

Organic solvents or adhesives containing organic solvents are flammable. Avoid breathing of vapors or prolonged skin contact. Use personal protective equipment. Wear disposable polyethylene gloves, MR-100, when applying solvents by hand.

NOTE Do not soak buffed area, but clean lightly until all grit and buffing dust are removed. (3) Dust off the surface and clean the buffed area with cheesecloth moistened with Acetone, ASTM D329.

Adhesive 82C18

9

Do not buff the nylon barrier side of the inner liner material. Fuel diffusion will occur if barrier is broken.

Buffing must be heavy enough to remove all gloss, leaving the surface covered with fine scratches to ensure adhesion. However, care must be exercised to assure that the buffing does not result in excessive reduction of the retainer. Only experienced personnel should use power buffers. Power buffing may produce a polished surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand. (2) Buff the area to be repaired 1 3/4 inches in a directions from the edge of the damage.

Isocyanate exposure may produce severe allergic reaction and permanent sensitization. Persons with history of allergies or previous sensitization shall not be assigned to tasks involving isocyanates. Personal protective equipment for skin and eyes and proper respiratory protection (BUMEDINST 6262.16) shall be required when polyurethane coatings or adhesives are used for fuel cell repairs. (4) Mix and apply repair adhesive 82C18 (Refer to Table 15-4, usage column 13, item 12) as follows: (a) Pour the entire contents of 82C18 part 2 into 82C18 part 1. (b) Stir thoroughly, making sure components are thoroughly mixed.

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015 00 Page 51 (d) Barrier adhesive to dry to touch. Brush a second coat of barrier adhesive over the first at right angles (90°) to the application of the first

Wear disposable polyethylene gloves, MR-100, when applying solvents by hand.

(6) Mix and apply repair adhesive 82C18 in accordance with steps (4)(a) through (4)(d).

(c) Apply a thin coat of the mixed adhesive over the buffed area +0 -1/4 inch of buffed edge.

Acetone ASTM D329

7

(d) Smooth adhesive surface with gloved fingers wet with Acetone, ASTM D329. (e) Remove any excess adhesive from the unbuffed area with cheesecloth, CCC-C-440, moistened with Acetone, ASTM D329. (f) Allow adhesive to air-cure approximately 30 minutes.

Adhesive 82C18

Fuel cell patches should air-cure a minimum of 72 hours prior to installation or being subjected to fuel. Do not flex the repaired area for the first 24-hour period. Do not place a repaired cell in any type of heating chamber to accelerate curing; such action will cause the cell to deteriorate and shrink beyond safe dimensions. (7) Test fuel cell for integrity of repair (Refer to Work Package 012). g. EXTERIOR RETAINER SCUFF AND ABRASION REPAIR. Exterior retainer scuff and abrasion repair procedures are used only to repair retainer damage that does not extend into the fabric reinforcing plies. Exterior retainer scuff and abrasion repair procedures are as follows:

9

Isocyanate exposure may produce severe allergic reaction and permanent sensitization. Persons with history of allergies or previous sensitization shall not be assigned tasks involving isocyanates. Personal protective equipment for skin and eyes and proper respiratory protection (BUMEDINST 6262.16) shall be required when polyurethane coatings or adhesives are used for fuel cell repairs. (5) Mix and apply barrier adhesive 82C12 (Refer to Table 15-4, usage column 14, item 11) as follows: (a) Thoroughly stir one part of the adhesive. (b) Brush a uniform coat of adhesive over the buffed area. (c) Remove any excess barrier adhesive from unbuffed areas with cheesecloth moistened with Acetone, ASTM D329.

(1) Clean the damage area with cheesecloth, CCCC-440, moistened with Acetone, ASTM D329.

Comply with general safety instructions in Work Package 004, and fuel cell entry preparations in Work Package 006. When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell. When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations. Do not buff the nylon barrier side of the inner liner material. Fuel diffusion will occur if barrier is broken.

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015 00 Page 52 (b) Stir thoroughly, making sure components are thoroughly mixed.

Buffing must be heavy enough to remove all gloss, leaving the surface covered with fine scratches to ensure adhesion. However, care must be exercised to assure that the buffing does not result in excessive reduction of the retainer. Only experienced personnel should use power buffers. Power buffing may produce a polished surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand. (2) Buff the area to be repaired 2 1/4 inches in all directions from the edge of the damage.

Acetone ASTM D329

7

NOTE Do not soak buffed area, but clean lightly until all grit and buffing dust are removed. (3) Dust off the surface and clean the buffed area with cheesecloth moistened with Acetone, ASTM D329.

Wear disposable polyethylene gloves, MR-100, when applying solvents by hand. (c) Apply a thin coat of the mixed adhesive over the buffed area +0 -1/4 inch of buffed edge. (d) Smooth adhesive surface with gloved fingers (e) Remove any excess adhesive from the unbuffed area with cheesecloth moistened with Acetone, ASTM D329.

Fuel cell patches should air-cure a minimum of 72 hours prior to installation or being subjected to fuel. Do not flex the repaired area for the first 24-hour period. Do not place a repaired cell in any type of heating chamber to accelerate curing; such action will cause the cell to deteriorate and shrink beyond safe dimensions. (5) Test fuel cell for integrity of repair (Refer to Work Package 012). h. INTERIOR SEAM REPAIR. Interior seam repair procedures are as follows:

Adhesive 82C18

9

Isocyanate exposure may produce severe allergic reaction and permanent sensitization. Persons with history of allergies or previous sensitization shall not be assigned tasks involving isocyanates. Personal protective equipment for skin and eyes and proper respiratory protection (BUMEDINST 6262.16) shall be required when polyurethane coatings or adhesives are used for fuel cell repairs.

Comply with general safety instructions in Work Package 004, and fuel cell entry preparations in Work Package 006. When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell.

NOTE

(4) Mix and apply repair adhesive 82C18 (Refer to Table 15-4, usage column 13, item 12) as follows:

If at least 1 inch of bond remains after trimming away loosened seam, no further repair action is necessary.

(a) Pour the entire contents of 82C18 part 2 into 82C18 part 1.

(1) Trim away loose seam strips.

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015 00 Page 53

(2) Apply an inner liner repair patch over the damage area (Refer to paragraph 3c). i. EXTERIOR SEAM REPAIR. Exterior seam repair procedures are as follows:

Buffing must be heavy enough to remove all gloss, leaving the surface covered with fine scratches. However, care must be exercised to assure that the nylon barrier is not damaged during the buffing operation.

(1) Trim away loose seam. (2) Apply an exterior repair patch to the damage area (Refer to paragraph 3d).

Fuel cell patches should air-cure a minimum of 72 hours prior to installation or being subjected to fuel. Do not flex the repaired area for the first 24-hour period. Do not place a repaired cell in any type of heating chamber to accelerate curing; such action will cause the cell to deteriorate and shrink beyond safe dimension. (3) Test fuel cell for integrity of repair (Refer to Work Package 012). j. SELF-SEALING FUEL CELL LOOSE FITTING FLANGE SURFACE REPAIR. To repair loose flange fitting surfaces, proceed as follows:

Only experienced personnel should use power buffers. Power buffing may produce a polished surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand. (1) Clean with cheesecloth, CCC-C-440, moistened with Acetone, ASTM D329, and buff contact surface. (2) Wipe buffed area with cheesecloth, moistened with Acetone, ASTM D329, and allow to dry.

Adhesive 82C18

9

(3) Mix and apply barrier adhesive, 82C18, in accordance with this Work Package paragraph 1d through 1f. (4) Clamp the flange fitting in place and allow to air-cure for 24 hours at 70ºF (21ºC).

Acetone ASTM D329

7

Comply with general safety instructions in Work Package 004, and fuel cell entry preparations in Work Package 006.

(5) After air-cure is complete, remove clamps and apply a uniform coat of barrier adhesive over the flange area and allow finished repair to air-cure for 24 hours at 70ºF (21ºC) minimum. 4. COMBINATION SELF-SEALING AND NONSELF-SEALING FUEL CELL DAMAGE/DEFECT REPAIR PROCEDURES. Repair procedures for combination self-sealing and non-self-sealing fuel cells are as follows:

When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell. When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations. Do not buff the nylon barrier side of the inner liner material. Fuel diffusion will occur if barrier is broken.

NOTE In the transition area between the self-sealing and non-self-sealing construction the repair area should be extended to 2 1/2 inches beyond the damage area. a. repair.

Duplicate the original construction in each area of

b. Follow repair procedures for specific type of defect/damage as required by the type of construction (Refer to Work Package 021 for non-self-sealing fuel cells and this work package for self-sealing fuel cells).

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015 00 Page 54

Fuel cell patches should air-cure a minimum of 72 hours prior to installation or being subjected to fuel. Do not flex the repaired area for the first 24-hour period. Do not place a repaired cell in any type of heating chamber to accelerate curing; such action will cause the cell to deteriorate and shrink beyond safe dimensions. c. Test fuel cell for integrity of repair (Refer to Work Package 012). 5. RIGID, NON-METALLIC, SELF-SEALING FUEL CELL DAMAGE/DEFECT REPAIR PROCEDURES. Repair procedures for this rigid, nonmetallic, selfsealing fuel cell are provided in the following paragraphs.

NOTE The rigid, nonmetallic, self-sealing fuel cell is essentially two separate fuel cells, each complete within itself. The rigid nonmetallic outer shell has a self-sealing fuel cell fabricated internally. a. RIGID NON-METALLIC OUTER SHELL REPAIRS. Repair procedures for the rigid, nonmetallic outer shell are as follows:

Comply with general safety instructions in Work Package 004, and fuel cell entry preparations in Work Package 006.

When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell.

NOTE Any damage to the outer shell must be repaired to prevent activation of the sealant from outside sources. (1) Damage areas of less than 10 square inches not involving displacement of material require a single outside repair patch (Refer to paragraph 2e). (2) Damage areas of 10 to 25 square inches with no displacement of materials require a double outside repair patch (Refer to paragraph 2f).

NOTE Due to the hardness of the rigid outer shell, it is not advisable to try cutting the outer shell hole to a smooth contour. (3) Damage areas, which involve the loss or displacement of materials require a double outside repair patch (Refer to paragraph 2f). b. SELF-SEALING INNER SHELL REPAIRS. Repair procedures for self-sealing inner shells and standard self-sealing fuel cells are identical (Refer to the appropriate paragraphs in this Work Package for the type of repair procedure required).

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31 August 2005

Page 1 of 54

MAINTENANCE INSTRUCTIONS SELF-SEALING FUEL CELL FITTINGS

Reference Material Aircraft Weapons Systems Cleaning and Corrosion Control....................................................................................... 01-1A-509

Alphabetical Index Subject

Page

Fuel Cell Fitting Corrosion Removal..........................................................................................................................................54 Fuel Cell Fitting Corrosion Control Evaluation ..............................................................................................................54 Fuel Cell Fitting Corrosion Treatment ............................................................................................................................54 Fuel Cell Reconfiguration and Fitting Relocation......................................................................................................................31 Cold-Cure Method for Installation of Constructed Fuel Cell Sections...........................................................................38 Constructed Fuel Cell Section Install Preparation ..........................................................................................................36 Existing Fuel Cell Interior Preparation (In Cutout Area)................................................................................................32 Fuel Cell Fitting Relocation.............................................................................................................................................45 Hot-Cure Method for Installation of Constructed Fuel Cell Sections ............................................................................41 Installed Fuel Cell Section Reinforcement......................................................................................................................42 Lamination Method of Fuel Cell Construction ...............................................................................................................34 Scrap Cell Method of Fuel Section Construction............................................................................................................44 General...........................................................................................................................................................................................2 Self-Sealing Fuel Cell Fitting Damage Evaluation ...........................................................................................................2 Self-Sealing Fuel Cell Fitting Damage Protection ............................................................................................................2 Self-Sealing Fuel Cell Fitting General Information..........................................................................................................2 Lockring Threaded Insert (ROSAN) and Fitting Locating Pin Replacement ...........................................................................29 Fitting Locating Pin Replacement ...................................................................................................................................30 Lockring Threaded Insert (ROSAN) Replacement.........................................................................................................29 Non-Molded Self-Sealing Fuel Cell Fitting Repair....................................................................................................................11 Self-Sealing Fuel Cell Cracked Fitting Area Repair.......................................................................................................14 Self-Sealing Fuel Cell Cracked Fitting Flange Area Repair...........................................................................................17 Self-Sealing Fuel Cell Fitting Exterior Patch Repair ......................................................................................................11 O-Ring Groove Area Fitting Repair ...........................................................................................................................................47 Broken O-Ring Groove Flange Repair............................................................................................................................48 Cracked O-Ring Groove Flange Repair ..........................................................................................................................50 O-Ring Groove Area Damage Evaluation.......................................................................................................................47 Scratched O-Ring Groove Flange Repair........................................................................................................................51 Self-Sealing Fuel Cell Fitting Insert Replacement .....................................................................................................................21 Fitting Insert (Cast-In-Place) Replacement .....................................................................................................................26 Self-Sealing Fuel Cell Fitting Insert Damage Evaluation...............................................................................................21 Self-Sealing Fuel Cell Fitting Insert (Non-Cast-In-Place) Replacement........................................................................21 Self-Sealing Fuel Cell Fitting Replacement .................................................................................................................................2 Self-Sealing Fuel Cell Double Flange Fitting Removal ...................................................................................................3 Self-Sealing Fuel Cell Double Flange Fitting Replacement.............................................................................................6 Self-Sealing Fuel Cell Fitting Damage Evaluation for Replacement ...............................................................................3 Self-Sealing Fuel Cell Molded Fitting Face Repair ...................................................................................................................18 Molded Fitting Face Damage Evaluation........................................................................................................................18 Molded Fitting Face Repair .............................................................................................................................................18

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1. GENERAL. This section provides general information as well as instructions for evaluating damage to self-sealing fuel cell fittings. It also contains repair and replacement techniques, list of materials, and procedures.

NOTE The following warning appears many times in this chapter:

When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell. The use of the air-supplied respirator or SCBA is required when working inside cells installed in an aircraft. If the cells have been removed from the aircraft and are being worked in a shop environment, then the use of a half-face respirator with a cartridge appropriate to the hazard is a suitable alternative to the use of an air supplied respirator. a. Self-Sealing Fuel Cell Fitting General Information. Although some fuel cell fittings are interchangeable between manufacturers, a verification of this fact is needed before any repair substitution is made. Each fuel cell manufacturer has fittings designed to fit a specific fuel cell structure and perform an inter-connector function for internal and external components. There are also a variety of different types of fittings and fitting designs that are used in fuel cell construction. On self-sealing fuel cell construction there is rubber molded fitting with single or double flanges. Fittings may be provided with O-ring sealing grooves, exposed metal sealing surfaces, rubber molded sealing surfaces, or some combination of these. b. Self-Sealing Fuel Cell Fitting Damage Protection. To protect self-sealing fuel cell fittings from damage, it is necessary to protect critical surfaces of the fitting when not installed in the aircraft. Damage such as cuts, scratches, dents, cracks or bends on the sealing faces or O-ring grooves may cause fuel leaks. The following protection guidelines should be observed:

Protect fittings with metal, wood, or plastic cover plates when the fuel cell is not installed in the aircraft. Protect sealing surfaces with tape, MIL-T22085 (AMS-T-22085). Protect sealing faces and/or O-ring areas when the attaching fittings are disassembled from the fuel cell. c. Self-Sealing Fuel Cell Fitting Damage Evaluation. (Refer to Table 16-1.) The close inspection of fuel cell fittings is necessary due to the potential fuel leakage resulting from damage to the fitting sealing surfaces and improper installation of connecting plumbing and fuel components. Fuel cell fittings should be evaluated for damage at the same time that the fuel cell structure is being inspected. Fittings and connections should not be disturbed for inspection unless leakage is suspected. However, fittings that are suspect should be inspected separately. 2. SELF-SEALING FUEL CELL FITTING REPLACEMENT. This paragraph provides damage evaluation and removal procedures for self-sealing fuel cell fittings. Replacement procedures for several types of fittings are also given. Though not specifically covered, the replacement of other types of fittings may be accomplished using the same principles. When replacing fuel cell fittings, the following guidelines should be observed:

Comply with general safety instructions in Work Package 004, and fuel cell entry preparations in Work Package 006. When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell.

Relocation of fitting openings requires a great deal of skill and experience. This should not be

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attempted unless a locating template is used or accurate measuring can be achieved by layout method. Whenever possible, a replacement fitting should be of the same type as the fitting that was removed from the cell.Whenever the inspection process has determined that replacement of a fitting is required, the fuel cell shall be cleaned and supported by bracing of the structure internally (See Figure 16-4). a. Self-Sealing Fuel Cell Fitting Damage Evaluation for Replacement. (See Figure 16-1.) The replacement of fittings is required if the-metal reinforcement ring is broken or bent sufficiently to cause a weakening in the structure of the fitting. Inspect for damage as follows:

(5) Inspect for damage to rubber or metal sealing surfaces. b. Self-Sealing Fuel Cell Double Flange Fitting Removal. When cell fittings are damaged or deteriorated, the cell should be removed from the aircraft as soon as possible, and the fitting replaced or another cell installed. Fitting replacement generally is a precision operation. Great care must be taken to ensure accuracy. The materials and tools employed are the same as those used for other repairs, but the techniques are more exacting. To remove a damaged fitting, proceed as follows:

Comply with general safety instructions in Work Package 004, and fuel cell entry preparations in Work Package 006. Comply with general safety instructions in Work Package 004, and fuel cell entry preparations in Work Package 006. When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell. (1) Inspect for very small cracks appearing in reinforcement rings that have been bent and straightened to their original shape. (2) Inspect for residual distortion or fine surface cracks in reinforcement rings. (3) Reject any reinforcement rings found to be defective in step (2).

Locate the old fitting accurately by measuring from selected points of the cell so that the new fitting can be centered exactly in the original position. (If this is not accomplished new fitting may not line up properly when the cell is reinstalled.) (1) Use a sharp white marking pencil, SS-P-00196 (A-A-87), to locate fittings. (Marks from crayon or chalk are too wide for the required accuracy.) (2) Warm the local area of the expected repair with a heat lamp before commencing the repair. (This makes the rubber and adhesives more pliable and less likely to be damaged during the repair).

NOTE Broken or cracked O-ring groove flanges require repair or fitting replacement.

(3) Gently apply the flat side of a knife blade completely around the finishing collar. Work the blade

(4) Inspect for broken or cracked O-ring groove flanges.

NOTE

between the collar edge of the outside fitting flange and the cell. Be careful not to damage the cell undercord by cutting into the cell.

Damage to rubber or metal sealing surfaces that cannot be adequately repaired will require fitting replacement.

(4) Use knife to carefully slice the adhesive interface between the collar and the cell (See Figure 16-2).

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Table 16-1. Self-Sealing Fuel Cell Fittings Defect Evaluation

SEE IRAC #14

Defect

Limitation

Rubber-Face Fittings. a. Gouges, splits, or deep indentations on the sealing surface.

1/16-inch maximum depth by 1/16-inch maximum length.

b. Weather checking of surfaces other than sealing surfaces.

Acceptable.

O-Ring Fittings Sealing Face Without Groove. a. Scratches within the sealing area.

Not acceptable (See Figure 16-1).

b. Burrs on mating surface.

Not acceptable (See Figure 16-1).

c. Damage to protective coating.

Not acceptable.

d. Corrosion.

Not acceptable.

O-Ring Fittings Sealing Face With Groove. a. Minor surface damage outside of O-ring groove other than rust, corrosion or burrs.

Acceptable (See Figure 16-1).

b. Physical damage to O-ring groove.

Not acceptable.

c. Corrosion.

Not acceptable.

d. Adhesive or other foreign matter in O-ring groove.

Not acceptable.

Bent or Broken Fittings.

Not acceptable.

Thread Damage on Fittings.

Acceptable, provided serviceability is not affected.

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Figure 16-1. O-Ring Fitting Inspection

(5) Work the outside fitting flange edge loose with a screwdriver-type dull-pointed tool. Gradually force the tool under the flange and pry upward to loosen flange.

NOTE Peel fabric in the same direction as the cord but never across the cord. (6) Using duckbill pliers, peel back the outside flange from the fuel cell.

When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations. Do not buff the nylon barrier side of the inner liner material. Fuel diffusion will occur if barrier is broken.

(7) Peel the flange back as far as possible to the metal insert ring (See Figure 16-3). (8) Cut the loosened outer flange away from the fitting ring (See Figure 16-4).

Buffing must be heavy enough to remove all gloss, leaving the surface covered with fine

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scratches. However, care must be exercised to assure that the nylon barrier is not damaged during the buffing operation. Only experienced personnel should use power buffers. Power buffing may produce a polished surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand. (9) Remove the inside fitting flange by buffing away the flange and pan of the inner liner overlap. Buff down to the inner liner surface (See Figure 16-5). (10) After all of the excess rubber has been removed, line up the template for location of the inside reinforcement patches.

(16) Self-Sealing Fuel Cell Double Flange Fitting Replacement. To install a new fitting, proceed as follows:

Comply with general safety instructions in Work Package 004, and fuel cell entry preparations in Work Package 006. When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell.

(11) Mark the cell using white marking pencil and lightly buff the inner liner to the mark. (This area should extend approximately 2 3/4 inches beyond the edge of the fitting flange when the new fitting is set in place.)

When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations.

(12) Do not remove the molded-in metal ring of the fitting until after buffing. (The ring supports the cell opening edge during the buffing operation.)

(17) Do not buff the nylon barrier side of the inner liner material. Fuel diffusion will occur if barrier is broken.

Avoid cutting the cell, which would enlarge the original opening.

NOTE Frequently dip the knife blade in water. This will lubricate the blade and make cutting easier. (13) On fittings without a molded-in metal ring, cut the fitting and flange flush with the outside surface of the cell. (14) Cut out the core of the fitting to the edge of the cell wall. (15) Remove the fitting ring by cutting the fitting through with a sharp knife at the edge of the metal insert ring (See Figure 16-6).

Buffing must be heavy enough to remove all gloss, leaving the surface covered with fine scratches. However, care must be exercise to assure that the nylon barrier is not damaged during the buffing operation. Only experienced personnel should use power buffers. Power buffing may produce a polished surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand.

NOTE Before inserting the fitting through the opening, the size and shape should be checked carefully. This can be accomplished with calipers. The cutout opening should conform exactly with the size and shape of the throat of the new fitting.

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Figure 16-2. Cutting Edge of Fitting Loose

Figure 16-3. Peeling Back Fitting Flange

Figure 16-4. Removing Fitting Outer Flange

Figure 16-5. Buffing Off Inside Flange

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016 00 Page 8

(18) Place an outside patch template on the cell, mark the area with white marking pencil, SS-P-00196 (AA-87), and buff to the mark. The mark should extend approximately 1 3/4 inches in all directions from the edge of the new fitting flange.

When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations. Do not buff the nylon barrier side of the inner liner material. Fuel diffusion will occur if barrier is broken.

NOTE Attachment of the required fitting reinforcement patches on the inside of the fuel cell can often be accomplished with better control when bonded to the inside flange of the fitting before the fitting is installed. The first patch shall have the minor diameter cut to fit next to the fitting insert lugs. The major diameter shall extend 1 1/2 inches beyond the edge of the fitting flange mark and skive the major diameter at approximately a 30-degree angle (See Figure 16-10 and 10-11). (20) Evenly buff both sides of the patch and feather the edge of the major diameters (See Figure 16-12).

Acetone ASTM D329

Buffing must be heavy enough to remove all gloss, leaving the surface covered with fine scratches. However, care must be exercised to assure that the nylon barrier is not damaged during the buffing operation. Only experienced personnel should use power buffers. Power buffing may produce a polished surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand.

NOTE Check the new fitting frequently in the cell opening by placing in position. If the opening is too small, buff the cell until the new fitting mates exactly. If the opening is too large, the excess area should be filled with sufficient sealant gum to assure a perfect fit. After making sure that the fit is satisfactory, remove the fitting and prepare it for installation. The buffing should be uniform in texture and depth (See Figure 16-7). (19) Prepare the fuel cell fitting for installation by lightly, but uniformly, buffing the surfaces to be bonded up to the ring of the insert lugs (See Figures 16-8 and 16-9).

7

(21) Clean the buffed surfaces using a lint-free cloth, 9409, moistened with Acetone, ASTM D329 (See Figure 16-13). (22) Apply three coats of adhesive (See Figure 1614, and refer to Table 15-4, usage columns 1 and 2); allow 20 to 30 minutes drying between coats and allow the third coat to dry tacky to the knuckle touch. (23) The second inside patch shall have a minor diameter 1/4 inch greater than the first patch, and a major diameter that will extend one inch beyond the first patch. (24) Mark and skive the edge of the major diameter at approximately a 30-degree angle. (25) Evenly buff one side of the second patch; clean and apply three coats of adhesive as in step (5). (26) Position and stitch both patches together on the work table, and proceed as follows: (a) Work out all entrapped air. (b) Allow the patches to air-cure under clamp pressure for two hours.

NOTE Approximately 2 1/2 inches of the patches will extend beyond the inside flange of the fitting after assembly.

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Figure 16-6. Cutting Out Fitting Ring

Figure 16-7. Buffing Outside of Cell

Figure 16-8. Buffing Inside V of Flanges

Figure 16-9. Buffing Inside Faces of Flange

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016 00 Page 10

Figure 16-10. Marking Outside Edge of Patch

Figure 16-11. Marking Inside Edge of Patch

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016 00 Page 11 for all surfaces to be bonded (See Figures 16-16 and 16-17).

When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations. Do not buff the nylon barrier side of the inner liner material. Fuel diffusion will occur if barrier is broken.

Buffing must be heavy enough to remove all gloss, leaving the surface covered with fine scratches. However, care must be exercised to assure that the nylon barrier is not damaged during the buffing operation.

(30) Carefully insert and adjust the fitting in the fuel cell (See Figures 16-18 and 16-19). (31) Activate the adhesive applied to the inside and outside of the fuel cell and fitting with Acetone, ASTM D329 (See Figure 16-20). (32) Stitch the flange firmly to the cell (See Figure 16-21). (33) After the fuel cell fitting has been located and installed in place, clamp the fitting and cure for 2 hours (See Figure 16-22). 3. NON-MOLDED SELF-SEALING FUEL CELL FITTING REPAIR. This paragraph describes the procedures for fitting exterior patch repair, cracked fitting area repair, cracked fitting flange repair, and loose fitting flange surface-repair.

Only experienced personnel should use power buffers. Power buffing may produce a polished surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand.

Comply with general safety instructions in Work Package 004, and fuel cell entry preparations in Work Package 006.

(27) Evenly buff, clean and apply three coats of adhesive to the fitting flange and patches allow to dry 20 to 30 minutes between coats.

Acetone ASTM D329

7

(28) Activate adhesive with Acetone, ASTM D329, clamp together, and allow 2 hours for curing after assembly. (29) Clean and apply three successive coats of adhesive to the buffed surfaces of the fitting; allow 20 to 30 minutes drying time between coats (See Figures 16-15 and 16-16).

When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell. a. Self-Sealing Fuel Cell Fitting Exterior Patch Repair. To repair fitting exterior patch, proceed as follows: (1) Cut a proper size patch (Refer to Work Package 15.) (2) Skive the outside diameter at a 30-degree angle.

NOTE The coating of the fitting should be accomplished at the same time that the surfaces of the prepared fuel cell are coated. This is required to assure equal bonding characteristics

When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations.

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Figure 16-12. Buffing Patch

Figure 16-13. Cleaning Buffed Patch

Figure 16-14. Applying Adhesive to Buffed Patch

Figure 16-15. Applying Adhesives to Fitting Flanges

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Figure 16-16. Cleaning Buffed Surface

Figure 16-17. Applying Adhesive to Cell

Figure 16-18. Installing New Fitting in Cell

Figure 16-19. Adjusting Fitting in Place

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Do not buff the nylon barrier side of the inner liner material. Fuel diffusion will occur if barrier is broken.

(6) Self-Sealing Fuel Cell Cracked-Fitting Area Repair. To repair cracked fitting areas, proceed as follows:

Comply with general safety instructions in Work Package 004, and fuel cell entry preparations in Work Package 006..

Buffing must be heavy enough to remove all gloss, leaving the surface covered with fine scratches. However, care must be exercised to assure that the nylon barrier is not damaged during the buffing operation. Only experienced personnel should use power buffers. Power buffing may produce a polished surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand. (3) Clean and apply three coats of adhesive (Refer to Table 15-4, columns 1 and 2); allow two coats to dry, and let the last coat become tacky.

When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell. (7) Cutout all of the loose material in the damaged area. (8) Trim to a V-shape allowing 3/8-inch to 1/2-inch cut on the top surface of the break.

(4) Stitch the patch in place, clamp, and allow 8 to 10 hours to cure (See Figures 16-23 and 16-24).

Do not expose patch to fuel for 72 hours. Fittings that are not to be used as a result of a new location shall be blanked off with a cover plate, bolls installed and properly torqued, and safety-wired as applicable. Use the gasket seal method adaptable to the fitting. (5) After the curing time, seal the outside edge of the patch and adjacent areas with one coat of adhesive.

When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations. Do not buff the nylon barrier side of the inner liner material. Fuel diffusion will occur if barrier is broken. (9) Buff the surface and the edges of the break using an air-driven sanding arbor. (10) Buff both sides of the V-shape using a flat, tapered rotary stone, and ensure that the stone does not cut too deeply.

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Figure 16-20. Activating Previously Applied Adhesive

Figure 16-21. Stitching Outside Flange

Figure 16-22. Clamping Installed Fitting

Figure 16-23. Installing Outside Patch

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016 00 Page 16 (17) Apply two coats of vulcanizing adhesive to each side of the vulcanizing stock and allow each coat to dry approximately 20 minutes. (18) Activate the cemented area and the gum strips with Acetone, ASTM D329 and work the strips of gum by stitching firmly into the damaged area. (19) Build up the layers of vulcanizing stock to approximately 1/8-inch above the surface of the V shape.

Figure 16-24. Stitching Patch in Place

Acetone ASTM D329

7

When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations. Do not buff the nylon barrier side of the inner liner material. Fuel diffusion will occur if barrier is broken.

(11) Clean the buffed area using a lint-free cloth, 9409, moistened with Acetone, ASTM D329.

Should any metal primer get on the adjacent rubber, scrape it off carefully with a knife. Metal primer contains organic solvent. (12) When buffing exposes a metal area of fitting, apply one coat of metal primer (Refer to Table 15-4, usage column 8) to the metal only. (13) Allow the metal primer to dry for approximately 2 hours. (14) Apply vulcanizing adhesive to the entire buffed area, being careful not to wipe off or loosen the metal primer from the metal. (15) Let dry 20 to 30 minutes and apply two more coats 20 minutes apart and let dry. (16) Cut pieces of uncured vulcanizing stock (Refer to Table 15-3, usage column 11) slightly larger than the damaged area and clean with Acetone, ASTM D329.

Buffing must be heavy enough to remove all gloss, leaving the surface covered with fine scratches. However, care must be exercised to assure that the nylon barrier is not damaged during the buffing operation. Only experienced personnel should use power buffers. Power buffing may produce a polished surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand. (20) Before positioning the vulcanizing molds and heaters, very lightly buff the inside of the fitting ring to remove any compressed rubber due to previous torquing of bolts. (21) Slide the male section of the fitting mold gently into position without forcing. (22) Position one section of the fitting mold inside of the cell. (23) Position the other section of the mold on the outside of the fitting and press gently into place.

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(24) Insert a large machine bolt through a hole in the inside mold and outside mold. (25) Select and position two vulcanizing heaters at room temperature on the surface of the outside mold. (26) Slide a bar with a center hole over the bolt allowing the bar to position over both heaters. (27) Place a large washer and nut on the bolt and tighten with enough pressure to hold the mold and heaters in position. (28) Check the heaters and mold for alignment, then plug in the heaters and preheat for approximately 15 minutes to allow the heaters to reach a temperature of 285oF (140oC) to 295oF (146oC).

(32) Remove, set up, and buff repaired area until it is blended in with the fitting surface. (33) Check fitting for flatness. b. Self-Sealing Fuel Cell Cracked Fitting Flange Area Repair. Where the crack in the fitting has extended out into the flange area, but not through the flange, the vulcanizing procedure is the same as outlined in paragraph 10-3b. When the depth of the crack is through the fitting flange down to the sealing gum, repair as follows:

Acetone ASTM D329

7

(29) Immediately after the heaters reach maximum temperature, tighten the bolt firmly. (30) Cure for 60 minutes.

Comply with general safety instructions in Work Package 004, and fuel cell entry preparations in Work Package 006.

(31) Shut off current and allow unit to cool touch.

When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations. Do not buff the nylon barrier side of the inner liner material. Fuel diffusion will occur if barrier is broken.

Buffing must be heavy enough to remove all gloss, leaving the surface covered with fine scratches. However, care must be exercised to assure that the nylon barrier is not damaged during the buffing operation. Only experienced personnel should use power buffers. Power buffing may produce a polished surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand.

When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell. (1) Buff and clean out the crack using lint-free cloth, 9409, moistened with Acetone, ASTM D329 being extremely careful not to remove the gum. 100, when applying solvents by hand. (2) Coat the sealing gum with two coats of vulcanizing adhesive. (3) Cut a strip of outside repair material (Refer to Table 15-3, usage column 3) wide enough to fit the bottom of the V shape. (4) Buff and coat both sides of the material with vulcanizing adhesive, and allow each coat to dry 20 minutes. (5) Activate the strip with Acetone, ASTM D329 prior to the application of vulcanizing stock. (6) Complete the repair as described in paragraph 10-3b.

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4. SELF-SEALING FUEL CELL MOLDED FITTING FACE REPAIR. (See Figure 16-25.) approved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations. Comply with general safety instructions in Work Package 004, and fuel cell entry preparations in Work Package 006. When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell. a. Molded Fitting Face Damage Evaluation. The molded fitting face on self-sealing fuel cells is used with or without a gasket for sealing against fuel leaks during use in the aircraft. Cuts, deformations, etc., in the rubber surface of the sealing face of fittings must be repaired to restore the surface to the original condition. b. Molded Fitting Face Repair. To repair molded fitting face proceed as follows:

Do not buff the nylon barrier side of the inner liner material. Fuel diffusion will occur if barrier is broken.

Buffing must be heavy enough to remove all gloss, leaving the surface covered with fine scratches. However, care must be exercised to assure that the nylon barrier is not damaged during the buffing operation. Only experienced personnel should use power buffers. Power buffing may produce a polished surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand.

(1) Plug the threaded holes in the damaged area in the fitting surface with the appropriate sized headless screw to prevent damage to the threads.

Figure 16-25. Damage Fitting Face

Figure 16-26. Buffing Away Damaged Rubber For Fitting Face Replacement When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH

(2) Buff the rubber from the fitting surface until the defects are removed (See Figure 16-26).

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016 00 Page 19 (14) Inspect the repair surface for smoothness and adequacy. (15) Trim off flash.

Should any metal primer get on the adjacent rubber, scrape it off carefully with a knife. Metal primer contains organic solvent. (3) If the metal insert of the fitting is exposed due to the damage or depth of buff, the exposed surface will require a coat of metal primer. Apply vulcanizing adhesive to the metal surface only (See Figure 16-27 and refer to Table 15-4, usage column 9). Allow 30 minutes to dry.

Acetone ASTM D329

7

(4) Brush the buffed surface to remove any buffing dust and clean with Acetone, ASTM D329.

When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations. Do not buff the nylon barrier side of the inner liner material. Fuel diffusion will occur if barrier is broken.

(5) Apply three coats of vulcanizing adhesive; allow 20 to 30 minutes drying time between coats (See Figure 16-28). (6) When the coated surface becomes tacky, stitch in layers of uncured vulcanizing stock (Refer to Table 15-3, usage column 11). (7) Build up the entire surface 1/32-inch higher than the original surface (See Figure 16-29). (8) Apply Holland cloth, MIL-C-17564, to the mold surface to prevent adhesion of the mold to the vulcanizing stock. (9) Apply inside and outside molds to the fitting surface (See Figure 16-30). (10) Apply a heating unit. (11) Clamp or bolt the molds and heating unit firmly against the surface. (12) Cure at 290oF (143oC) for one hour. (13) Allow the mold to return to room temperature before removing.

Figure 16-27. Applying Adhesive to Metal

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Figure 16-28. Applying Vulcanized Adhesive to Buffed Area

Figure 16-29. Stitching inVulcanizing Stock

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Buffing must be heavy enough to remove all gloss, leaving the surface covered with fine scratches. However, care must be exercised to assure that the nylon barrier is not damaged during the buffing operation. Only experienced personnel should use power buffers. Power buffing may produce a polished surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand. (16) Perform light smooth buff if slight irregularities occur in the repaired area. Ensure flatness of the finished face is retained (See Figure 16-31).

Comply with general safety instructions in Work Package 004, and fuel cell entry preparations in Work Package 006. When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell. (1) With a sharpened white marking pencil, SS-P00196, mark the location of the bad insert to avoid the inadvertent removal of a good insert. (2) Obtain an insert identical to the one to be replaced.

NOTE If a new fitting is not available, a salvaged fitting may be used. When a salvaged fitting is used, remove the old rubber from around the head of the insert and that portion of the insert heat flange that comes in contact with the fitting metal assembly ring. Apply one coat of metal primer (Refer to Table 15-4, usage column 9) to the cleaned surfaces and allow 30 minutes drying time.

(3) Using an insert removing tool, remove the damaged insert (See Figures 16-32 and 16-33).

5. SELF-SEALING FUEL CELL FITTING INSERT REPLACEMENT. (See Figure 16-32.) The following paragraphs provide information about the replacement of non-cast-in-place and cast-in-place fitting inserts. a. Self-Sealing Fuel Cell Fitting Insert Damage Evaluation. Damaged fitting inserts require replacement. When possible, it is desirable to replace the insert on the installed fitting rather than remove and replace the fittings. b. Self-Sealing Fuel Cell Fitting Insert (Non-cast-inPlace) Replacement. To perform the insert replacement on the type of fittings shown in Figure 16-33, proceed as follows:

Figure 16-30. Vulcanizing Repair

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Figure 16-31. Lightly Buffing Finished Repair

When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations.

Organic solvents or adhesives containing organic solvents are flammable. Avoid breathing of vapors or prolonged skin contact. Use personal protective equipment.

Do not buff the nylon barrier side of the inner liner material. Fuel diffusion will occur if barrier is broken.

Wear disposable polyethylene gloves, MR-100, when applying solvents by hand.

Buffing must be heavy enough to remove all gloss, leaving the surface covered with fine scratches. However, care must be exercised to assure that the nylon barrier is not damaged during the buffing operation.

Should any metal primer get on the adjacent rubber, scrape it off carefully with a knife. Metal primer contains organic solvent.

Only experienced personnel should use power buffers. Power buffing may produce a polished surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand. (4) Buff the rubber from around the insert hole (See Figure 16-34).

(4) Clean the buffed area with Acetone, ASTM D329 and apply one coat of metal primer (Refer to Table 15-4, usage column 9) to the exposed metal surface; allow the metal primer to dry 30 minutes.

Acetone ASTM D329

(6) Allow the last coat of vulcanizing adhesive to become tacky.

7

(5) Apply three coats of vulcanizing adhesive (Refer to Table 15-4, column 4 and 5) to the buffed surface (See Figure 16-35); allow 20 to 30 minutes drying time between coats.

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Figure 16-32. Insert – Removing Tool

Figure 16-33. Removing Insert

Figure 16-34. Buffing Away Damaged Rubber For Fitting Insert Replacement

Figure 16-35. Applying Adhesive To Rubber

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016 00 Page 24 (18) Apply heat to the area for 15 minutes at 290oF (143 C), then tighten the clamps until the mold plates properly seat. o

Should any metal primer get on the adjacent rubber, scrape it off carefully with a knife. Metal primer contains organic solvent.

(19) Apply heat at 290oF (143oC) for an additional 45 minutes, then shut off current and cool units to touch before removing the mold (See Figure 16-39).

(7) Apply one coat of metal primer to the outside of the new insert (Refer to Table 15-4, usage column 9).

(20) Inspect the area for smoothness and general appearance.

(8) Install as shown in Figures 16-36 and 16-37. (9) While the adhesive is still slightly tacky, stitch in the vulcanizing stock (Refer to Table 15-3, usage column 11).

Acetone ASTM D329

7

NOTE If the adhesive becomes dry, activate with a cloth moistened in Acetone, ASTM D329.

When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations. Do not buff the nylon barrier side of the inner liner material. Fuel diffusion will occur if barrier is broken.

(10) Stitching may be accomplished by using a piece of new, uncured stock. (11) Cut strips approximately 1/16-inch wide. (12) With a small screwdriver, press the strips into the area around the replaced insert until the mass is approximately 1/8-inch above the surface of the adjacent rubber. (13) Complete stitching operation using a 1/4-inch stitching tool (See Figure 16-38). (14) Use outside and inside aluminum alloy or steel molds, which conform to the shape and the contour of the fitting surface. (15) Apply Holland cloth, MIL-C-17564, to the mold contact surfaces to prevent sticking to the fitting surface. (16) Place the molds and heating unit over the area to be cured, and clamp using C-clamps, screw clamps, or bolt clamps. (17) At first, tighten the clamps lightly.

Buffing must be heavy enough to remove all gloss, leaving the surface covered with fine scratches. However, care must be exercised to assure that the nylon barrier is not damaged during the buffing operation. Only experienced personnel should use power buffers. Power buffing may produce a polished surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand. (21) Trim and buff the repair even with adjacent area (See Figure 16-40).

Adhesive MIL-PRF-9117

8

(22) Apply two coats of adhesive, MIL-PRF-9117, to the repaired area.

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Figure 16-36. Installing Insert

Figure 16-37. Drawing Insert in Place

Figure 16-38. Stitching Vulcanizing Stock

Figure 16-39. Vulcanizing Stock in Place

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c. Fitting Insert (Cast-In-Place) Replacement. Fittings with inserts cast-in-place at time of manufacture are often inadvertently damaged. Two main causes of fitting damage are stripping of insert threads and bottoming out of attachment bolts. Bottoming bolts can crack the metal casting sufficiently to develop a fuel leak. If the sealing surface is not damaged or the fitting is not buckled or bent, the damaged insert can be replaced without having to remove and replace the entire fitting. To replace cast-inplace fittings, proceed as follows:

(8) Leave the bolt and washer installed until the repair is completed.

Acetone ASTM D329

7

(9) Clean the ground surfaces of the fitting lug with Acetone, ASTM D329and allow to dry thoroughly. (10) Place a retainer ring made from tubing or rolled sheet metal over the fitting lug.

Comply with general safety instructions in Work Package 004, and fuel cell entry preparations in Work Package 006.

(11) The ring should have an inside diameter 1/4inch larger than the diameter of the lug and extend as high as the adjacent undamaged lugs.

When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell.

Compound Silicone SAE-AS8660

(1) From the inside of the fuel cell, cut off the end cap of the fitting insert lug with a hacksaw or air-driven handsaw (See Figure 16-41). (2) Install a screw or bolt into the damaged insert and drive the insert out (See Figure 16-42).

10

(12) Wipe the ring inside with silicone compound, SAE-AS8660, and secure the ring in position with tape placed around the base. (13) Mix per manufacturer’s instructions and apply aluminum-filled epoxy adhesive (Refer to Table 15-4, column 15) to the cavity remaining in the lug and around the lug to the top of the retainer ring (See Figure 16-47). (14) Allow 8 hours cure at room temperature before removing the retainer ring.

When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations. (3) Grind the outside surface of the insert lug and 1/4 inch around the base (See Figure 16-43). (4) Grind the inside surface of the lug uniformly to the shoulder that locates the insert (See Figure 16-44).

(15) Remove retainer ring and grind the potted lug to the general shape of the adjoining lugs (See Figure 16-48). (16) Inspect for any porosity or lack of adhesion. (17) If porosity is found, apply a surface coat of the epoxy adhesive. (18) If lack of adhesion is observed, grind away that area and reapply epoxy adhesive to the area.

(5) Install a new insert or an undamaged used insert salvaged from a scrapped fitting. (6) Install insert by hand or use a tool similar to the one shown in Figure 16-45 to draw the insert into the lug cavity. (7) Use the correct size bolt and washer to draw the insert tightly against the lug inside the shoulder (See Figure 16-46).

Sealing Compound AMS-S-4383 (19) When the of sealing compound, drying time between solvents. (Extend the repair area.)

11 repair is satisfactory, apply two coats AMS-S-4383; allow 20 to 30 minutes coats. AMS-S-4383 contains organic sealing compound to the edge of the

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Figure 16-40. Lightly Buffing Completed Repair

Figure 16-41. Cutting Off Lug Cap

Figure 16-42. Driving Out Damaged Insert

Figure 16-43. Grinding Fitting Lug

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Figure 16-44. Grinding Inside of Lug

Figure 16-45. Drawing Insert Into Lug

Figure 16-46. Drawing Insert Tightly in Place

Figure 16-47. Applying Epoxy Adhesive To Lug

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6. LOCKRING THREADED INSERT (ROSAN) AND FITTING LOCATING PIN REPLACEMENT. The following paragraphs provide replacement procedure for locking threaded inserts and fitting locating pins.

(1) Use a drill large enough to drill the insert to the edge of the serrations as shown in Figure 16-49. (2) Drill down until the serrated lockring is drilled through. (3) The lockring can generally be removed by tilting the drill slightly and lifting upward.

Comply with general safety instructions in Work Package 004, and fuel cell entry preparations in Work Package 006. When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell. a. Lockring Threaded Insert (ROSAN) Replacement. To remove and replace this type of fining, proceed as follows:

(4) With an easy-out, back the threaded insert out of the fitting (See Figure 16-50). (5) Install a new insert by threading it into the empty holes. (6) Tighten the insert in place and back off the screw and nut (See Figure 16-51). (7) Install a new lockring by carefully driving the ring into the serrated hole (See Figure 16-52). (8) Continue to drive the ring into the cavity until the edge is flush and the driven face of the ring is pressed against the insert.

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Figure 16-48. Grinding Repaired Lug Shape

Figure 16-49. Drilling Out Damaged Fitting Lockring Insert

b. Fitting Locating Pin Replacement. Various molded fittings incorporate locating pins or studs, which are required to properly align attaching fittings to the cell. To replace the pin, proceed as follows:

Do not buff the nylon barrier side of the inner liner material. Fuel diffusion will occur if barrier is broken.

Comply with general safety instructions in Work Package 004, and fuel cell entry preparations in Work Package 006.

Buffing must be heavy enough to remove all gloss, leaving the surface covered with fine scratches. However, care must be exercised to assure that the nylon barrier is not damaged during the buffing operation.

When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell. When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations.

Only experienced personnel should use power buffers. Power buffing may produce a polished surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand. (1) Buff the rubber on the outside of the fitting down to the insert and pin.

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Figure 16-50. Removing Damaged Insert

Figure 16-51. Installing New Insert (6) Complete repair of fitting as outlined in paragraphs 4b(4) through 4b(17).

When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell. (2) Cut the rubber, on the inside, from the pin or

7. FUEL CELL RECONFIGURATION AND FITTING RELOCATION. It may become necessary to modify or convert fuel cells and fittings from one configuration to another. This can be accomplished only by exacting processing techniques. The three generally accepted methods for constructing fuel cell sections are as follows:

stud.

NOTE Do not remove the entire pin by drilling. (3) If necessary, center punch the pin on the outside of the call and remove the head with a countersink drill. (Threaded studs may be screwed out.) (4) Remove remaining portion of the pin with a drift punch. (5) Install a new pin and, with a center punch, stake in three places.

Laminating repair materials to the desired cell construction. Using a section of a scrap cell of the same construction as the cell to be worked. Using a section of a scrap cell of the same construction with the desired fitting installed.

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Comply with general safety instructions in Work Package 004, and fuel cell entry preparations in Work Package 006. When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell. (1) Attach an air mover to provide continuous ventilation, and then enter the fuel cell. (2) Measure 1 1/2 inches back from the edge of the cutout and mark a solid line entirely around the cutout area. (3) Measure 3 1/2 inches back from the edge and mark a broken line entirely around the cutout area.

Figure 16-52. Driving Lockring in Place

(4) Using a very sharp pointed skiving knife, follow the 1 1/2 inch step-back solid line and cut through the inner liner of the cell to the sealing gum.

Extreme care must be used during this operation. This is to be the inside edge of the cell step-back. Relocation of fitting openings requires a great deal of skill and experience. This should not be attempted unless a locating 2 the gasket seal method adaptable to the fitting. Fittings that are not to be used as a result of a new location shall be blanked off with a cover plate, bolts installed and properly torqued, and safely wired as applicable. Use the gasket seal method adapter to the fitting. a. Existing Fuel Cell Interior Preparation (In Cutout Area). To prepare the fuel cell interior, proceed as follows:

(5) Make a cut from the edge of the cutout across to the solid line that has been cut to the gum layer. (6) Using a small screwdriver, break the 1 1/2-inch strip of liner loose. (7) With a pair of duckbill pliers, grip one piece of the broken strip and start to break loose the 1 1/2-inch strip by rolling on the duckbills (this is similar to opening a can and removing the band with a key (See Figure 16-53). (8) Peal back halfway around, and then peel the other half from the starting point.

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016 00 Page 33 Do not buff the nylon barrier side of the inner liner material. Fuel diffusion will occur if barrier is broken.

Buffing must be heavy enough to remove all gloss, leaving the surface covered with fine scratches. However, care must be exercised to assure that the nylon barrier is not damaged during the buffing operation. Only experienced personnel should use power buffers. Power buffing may produce a polished surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand.

NOTE

Figure 16-53. Removal of Inner Liner Strip

Some of the gum will stick to the liner strip. This is normal. The remaining gum must be buffed off to the nylon cord layer. Care must be exercised when buffing to the cord layer. Do not remove the cord layer. This is the reason for the step-back. (9) Refer to Work Package 015 for step-back details sequence. After completing the step-back operation, lightly buff the surface of the inner liner 2 1/2-inches out from the raised edge of the step to the edge of the broken line. (This is prebuffed prior to applying the reinforcing patches.)

Comply with general safety instructions in Work Package 004, and fuel cell entry preparations in Work Package 006.

Acetone ASTM D329

7

When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell. When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations.

Do not use Acetone, ASTM D329 to loosen the flange. (10) On the side where the pump fitting is located, loosen the inside of the fitting flange back to the edge of the fitting ring.

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(11) Pull the flange loose only to the area of the fitting where the buffing lines exist.

b. Lamination Method of Fuel Cell Construction. To use this method, use the basic construction methods listed in Work Package 015 and proceed as follows: (1) Check the laminated plies of the cell to determine the construction.

Comply with general safety instructions in Work Package 004, and fuel cell entry preparations in Work Package 006. When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell.

(2) Obtain the necessary repair materials and cut the pieces in oversize lengths and widths. (3) Start the build-up of the plies with nylon sandwich Buna-N inner liner material, layer of sealing gum, either one layer or two layers of uncured natural gum rubber with nylon open mesh fabric depending on the cell construction, one layer of sealing gum, and two layers of Buna-N coated outside repair fabric (See Figure 16-55).

When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations. Do not buff the nylon barrier side of the inner liner material. Fuel diffusion will occur if barrier is broken.

Buffing must be heavy enough to remove all gloss, leaving the surface covered with fine scratches. However, care must be exercised to assure that the nylon barrier is not damaged during the buffing operation. Figure 16-54. Buffing Sealant from Flange Only experienced personnel should use power buffers. Power buffing may produce a polished surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand.

Acetone ASTM D329

7

NOTE Most of the step-down buffing may be performed from the outside of the cell. With the exception of the fitting area, the steps to be followed are the same for the other end of the fuel cell. (12) Buff out the gum sealant between the flange by using cone-shaped rotary stones (See Figure 16-54).

When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations.

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Do not buff the nylon barrier side of the inner liner material. Fuel diffusion will occur if barrier is broken.

Acetone ASTM D329

7

(6) Clean surfaces with a cheesecloth dampened with Acetone, ASTM D329; do not soak because the sealant gum will swell. Buffing must be heavy enough to remove all gloss, leaving the surface covered with fine scratches. However, care must be exercised to assure that the nylon barrier is not damaged during the buffing operation. Only experienced personnel should use power buffers. Power buffing may produce a polished surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand. (4) Lightly buff the unfinished side of the Buna-N inner-liner sandwich material and clean with cheesecloth, CCC-C-440, dampened with Acetone, ASTM D329.

(7) Remove the backing from either one or two layers, as required, of the uncured natural gum rubber with nylon cord fabric.

NOTE Cleaning, buffing or sanding is not necessary on this material. (8) Should the paper backing stick to the uncured gum rubber, apply water-soaked cheesecloth to the backing and let stand for a few minutes; the backing will then peel off easily. (9) Allow the uncured gum rubber to dry thoroughly. (10) For the next sealing gum layer, repeat the same procedures as step (7).

Acetone ASTM D329

7

(11) Buff the first layer of outside repair material lightly on both sides, and clean with cheesecloth dampened with Acetone, ASTM D329. (12) Buff the outer layer of outside repair material lightly on one side only, and clean with cheesecloth dampened with Acetone, ASTM D329. (13) Follow the bonding procedures in accordance with Work Package 015.

Figure 16-55. Lamination Section Preparation

(14) When the bonding and stitching operations are completed and the layers are laminated into one piece, examine the construction for loose plies and trapped air.

(5) Remove the backing from the sealing gum and lightly buff both sides to remove the glazed surfaces.

(15) Place the lamination on the end of a bench or equivalent flat clean area and place a piece of plywood, padded with polyethylene film, L-P-378, on top of the constructed section.

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(16) Apply pressure by clamping or by placing heavy sandbags or weights on top of the board; maintain the pressure for at least 12 hours.

(3) The mechanic inside of the fuel cell will hold the section in position, and the mechanic outside will secure the section fitting to the jig with four bolts (See Figure 1656).

(17) Remove the pressure and thoroughly examine the entire piece of lamination to be sure that it is solid. (18) Locate the center on the outside of the oversize laminated construction using a straightedge and a sharp knife. (19) Locate the center of the constructed section, drawing vertical and horizontal lines from ends and sides. (20) Place the new fitting on the constructed section and center it exactly in the center cross lines. (21) Mark the inside diameter of the fitting and the cross fitting locating lines on the constructed section and follow the fitting installation instructions in paragraph 102c, with the exception of applying patches to the fitting flanges. (This step is performed after the complete constructed section is installed in the fuel cell). c. Constructed Fuel Cell Section Install Preparation. To prepare to install the constructed fuel cell section, proceed as follows:

Figure 16-56. Fitting Section in Place Comply with general safety instructions in Work Package 004, and fuel cell entry preparations in Work Package 006. When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell.

NOTE Two mechanics are required to prepare installation of constructed fuel cell section. (1) In the prepared area, step-back the individual layers to fit. (2) Secure the fitting locating jig in position and complete the alignment of the section.

(4) The inside mechanic will apply pressure to the upper and lower parts of the section, forcing the parts against the inside wall of the cell. (5) The outside mechanic will mark the section to conform to the cutout in the cell. (6) The outside mechanic will remove the four bolts holding the section, and the mechanic inside will remove the section from the cell. (7) Place the constructed section on a bench. (8) Measure from the existing line 1 1/2-inches to the outside and draw a line to match the existing line (See Figure 16-57). This is to prepare the section for a matching step-back on the cell. (9) Using a skiving knife, cut along the outside line eliminating excess material. This line must be cut perfectly in order to match the cell step-back (See Figure 16-58).

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NOTE It is best to cut to a depth of one ply and remove it, and then follow the same procedure for the second and third layers. This will reduce the danger of cutting into the center cord ply.

approved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations. Do not buff the nylon barrier side of the inner liner material. Fuel diffusion will occur if barrier is broken.

(10) Cut the inner liner along the inside or existing line to a depth of three layers to the center cord ply.

Figure 16-57. Marking Section for Step-Back Cut

Figure 16-58. Step-Back Cut

(11) Cut across each ply from the inside line to the outer edge in one or two places; this will make it easier in starting to remove the plies.

Do not use solvents for this operation. (12) Using a pair of duckbill pliers, carefully peel back the layers.

Buffing must be heavy enough to remove all gloss, leaving the surface covered with fine scratches. However, care must be exercised to assure that the nylon barrier is not damaged during the buffing operation. Only experienced personnel should use power buffers. Power buffing may produce a polished surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand.

When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH

(13) Remove the sealing gum by buffing. (In buffing off the gum layer it is possible to buff the remaining fabric layer at the same time prior to bonding (See Figure 16-59).

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(14) When the section step-back is complete, repeat the same procedure as in paragraph 10-7c to make sure that the cell step-back and the section step-back mate. Make any necessary adjustments before starting the installation procedures. d. Cold-Cure Method for Installation of Constructed Fuel Cell Sections. To install a constructed section using the cold-cure method, proceed as follow:

NOTE Two mechanics are required to install the constructed fuel cell sections. (1) Apply three coats of adhesive to step-back area on the section, and to the fuel cell (See Figures 16-60 and 16-61). Allow 30 minutes drying time between coats. Figure 16-59. Buffing Sealant Gum

Comply with general safety instructions in Work Package 004, and fuel cell entry preparations in Work Package 006. When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell. (2) Station one mechanic inside the cell, and the other outside. (3) Prior to installing the constructed section, it is advisable to apply a tacking coat of adhesive approximately 3 inches down on each side of the top point of the section, and 3 inches up on each side of the low point. (4) Repeat steps (1) through (3) on the fuel cell.

Figure 16-60. Applying Adhesive to Section

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016 00 Page 39 (8) When the surfaces are ready, the inside mechanic will mate the cell step-back and the section stepback starting at the top. (9) The inside mechanic will apply pressure while the outside mechanic stitches down the outside top area. (10) Repeat steps (5) through (9) for the bottom area. (11) Allow the top and bottom points to set approximately 45 to 60 minutes. (The top and bottom points of the step-back are secured first in order to help shape the fitting section to the correct contour of the cell.) (12) Carefully remove the jig from the fitting section. (13) Thoroughly examine each end of the section to be sure that it is mated correctly inside and out; if not, make the necessary adjustments. (14) Use a C-clamp that is long enough to reach the top of the bonded area and insert it through the section fitting hole.

Figure 16-61. Applying Adhesive to Fuel Cell (5) The mechanic inside the cell will hold the section in position, being very careful not to allow the ends to contact the cell (See Figure 16-62).

NOTE Setting the pressure plates top and bottom requires two mechanics.

(6) The mechanic on the outside will then secure the section to the jig with four or six bolts.

(15) The inside mechanic will position a cushioned pressure plate that is shaped to the inside top contour of the cell.

(7) The tacky area on the top and bottom areas will then be checked for adhesion using the knuckle test.

(16) Both mechanics will hold the plates in position, and then attach a C-clamp to both inside and outside plates (See Figure 16-63).

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Figure 16-62. Holding Section in Place

Figure 16-63. Clamping Section Top in Place

(21) Repeat the same procedure for the lower point. (22) Allow pressure to be maintained approximately 8 hours or overnight, if possible. Moderate pressure should be applied with the clamp. Too much pressure may force the mating surfaces out of adjustment.

(23) Remove the clamps and pressure plates, and then proceed to bond the rest of the fitting section to the cell.

(17) When the clamp for the top is secured, place another C-clamp through the fitting and follow the same procedure for the bottom point.

(24) Start at the top point that is bonded and apply a coat of adhesive to the cell and section step-back surfaces extending to the bottom point of the bonded area. (This is performed first on the side where the section fitting is closest to the cell edge.)

(18) After approximately 1 or 1 1/2 hours, loosen the clamp for the top and very carefully ease the inside and outside plates away from the cell. (19) Check the cell for incorrect contour or wrinkles. Secure the plates in position and moderately tighten the clamp. (20) Correct any necessary adjustments.

discrepancy

and

make

any

(25) Follow steps (15) through (20) for bonding the top and bottom points, except use side pressure plates to match the contour of the side of the cell (See Figure 16-64).

NOTE When bonding the other side of the cell, double check the mating surfaces of the step-back.

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(26) Repeat steps (15) through (20) on the other side of the cell, using the pressure plate designed for that side contour.

cold-cure (Refer to paragraph 7d). The few exceptions are described in the following procedural steps. To install a constructed section in the fuel cell, proceed as follows:

(27) There may be a slight sag in the cell that would cause a mis-mating of the stepback surfaces. Rectify this by making a slight adjustment to the interior cell supports. Allow 8 hours for cure. Comply with general safety instructions in Work Package 004, and fuel cell entry preparations in Work Package 006. When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell. Organic solvents or adhesives containing organic solvents are flammable. Avoid breathing of vapors or prolonged skin contact. Use personal protective equipment. Wear disposable polyethylene gloves, MR-100, when applying solvents by hand. NOTE Use vulcanizing adhesive listed in Work Package 015 in place of room temperature curing adhesive. Use contoured vulcanizing plates and spot vulcanizing heaters for curing in lieu of pressure plates.

Figure 16-64. Clamping Section Side in Place

(28) When all clamps and pressure plates have been removed, thoroughly check the entire built-in section to be sure it is mated properly, and there are no trapped air pockets or blisters. (29) Check the fitting lineup with the jig. If there are any voids between the mating edges of the step-back, they must be filled in with the same material of the specific layer prior to applying the reinforcing patches.

(1) Start with the same steps for installation of the section as used for cold-cure, except use three coats of vulcanizing adhesive in lieu of cold-cure adhesive. (2) Using contoured vulcanizing plates in lieu of pressure plates, attach the plates at the top point first. (3) Clamp a vulcanizing spot heater to the inside plate.

(30) When all the cold cure procedures are completed, apply the reinforcing inside and outside patches.

(4) Preheat 5 minutes and allow to cure 20 minutes ad 287oF (141oC). Remove the heater from the inside to the outside plate and cure the outside the same as the inside (See Figure 16-65).

e. Hot-Cure Method for Installation of Constructed Fuel Cell Sections. The procedures used to hot-cure (vulcanize) a section in place are similar to those used for

(5) Repeat steps (1) through (4) for the bottom point. (Allow the heater to cool before removing.)

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(6) When the top and bottom points are completed, remove all plates and vulcanizing heater. (7) Ensure that the step-back edges are mated properly before conducting further vulcanizing. (8) Fill any irregular voids between the butted edges with rubber and vulcanizing adhesive. (9) After all voids are filled, apply three coats of vulcanizing adhesive 1/2-inch on each side of the butted step-back edges, completely around the installed section. (10) Apply a strip of rubber, MIL-R-6855 (Refer to Table 15-3, column 11). 1-inch wide, 0.032-inch thick, to the coated area along the edge and stitch firmly in place. (11) Vulcanize the step-back edge and reinforcing patch; start at the approximate center edge of the fitting on the right-hand side. (12) Lay a piece of Holland cloth, MIL-C-17564, over the section to be vulcanized, and attach a flat contoured plate over the cloth. (13) The outside mechanic will attach a matching plate with a sponge covered surface to the cell.

Figure 16-65. Heat Curing Top of Section in Place

(14) When the plates are in position, put the Cclamps through the fitting hole and lightly tighten in place. (15) Attach a cold vulcanizing heater to the inside plate. (16) Hold in vulcanizing heater position with the Cclamps, and tighten the C-clamps. (17) the heater is in position, turn on the electricity. (18) Allow 5 minutes for the heater to reach maximum temperature of 287oF (141oC). (19) Allow 20 minutes for curing. (20) Turn off the electricity and allow the attached heater to cool before removing from the cell.

(21) After the plates and heater have been removed, repeat steps (14) through (20) on the left side of the cell using plates that are, contoured for that side. (22) When the inside of the cell is finished, repeat steps (lot) through (20) on the outside of the cell (See Figure 16-66). (23) When all of the vulcanizing is complete, apply the reinforcing inside and outside patches. f. Installed Fuel Cell Section Reinforcement. After the new sections and fittings have been installed at each end of the fuel cell, reinforce with patches as follows:

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Buffing must be heavy enough to remove all gloss, leaving the surface covered with fine scratches. However, care must be exercised to assure that the nylon barrier is not damaged during the buffing operation. Only experienced personnel should use power buffers. Power buffing may produce a polished surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand. (1) Lightly buff inside of cell 7/8-inch on each side of the step-back mating edge and completely around the built-in section. (2) Make a paper pattern of the complete buffed area. This is for a one-piece reinforcing patch 1 3/4 inches wide. Figure 16-66. Vulcanizing Side of Fuel Cell Section

(3) Apply this pattern to a piece of 0.015 or 0.025 Buna-N coated nylon fabric (Refer to Work Package 015, Table 15-3). (4) Place the pattern so that the patch will be cut on the bias in order to prevent stretching during application.

Comply with general safety instructions in Work Package 004, and fuel cell entry preparations in Work Package 006. When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell.

When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations. Do not buff the nylon barrier side of the inner liner material. Fuel diffusion will occur if barrier is broken.

When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations.

(5) Feather-edge the patch inside and outside edges and follow standard buffing and bonding procedures for the cell and ring patch.

Do not buff the nylon barrier side of the inner liner material. Fuel diffusion will occur if barrier is broken.

(6) When applying this outside ring patch, start in the center, in line with the fitting, and work up to the top point.

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(7) Repeat steps (1) through (6) on the other side (See Figure 16-67). Complete the bottom half in the same manner as the top half.

Figure 16-67. Applying the Outside Ring Patch

Figure 16-68. Installing Outside Reinforcing Patch

(8) When installing the inside double patch, begin by centering the patch over the fitting, and bond an area approximately 2-inches wide completely around the fitting. (9) Bond a 2-inch wide area from the center of the fitting to the top point of the section build-up and stitch down the patch along the 2-inch strip, being very careful to keep the patch in line at all times. (10) Begin at the center and work the patch out to the sides, following standard bonding and stitching procedures. (11) Repeat steps (9) and (10) for the bottom half, and also when installing the outside patch (See Figure 1668). (12) When all patches are installed, place the inside and outside pressure jig in position and apply C-clamps to hold the jig in place. (13) Allow the jig to remain in approximately 3 to 4 hours and then remove.

position

Organic solvents or adhesives containing organic solvents are flammable. Avoid breathing of vapors or prolonged skin contact. Use personal protective equipment. Wear disposable polyethylene gloves, MR-100, when applying solvents by hand. (14) Seal the edges of the patches with adhesive upon completion of the installation (Refer to Work Package 015). g. Scrap Cell Method of Fuel Section Construction. For the scrap cell method of fuel section construction, proceed as follows:

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016 00 Page 45 When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell.

Comply with general safety instructions in Work Package 004, and fuel cell entry preparations in Work Package 006. When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell. (1) If a section of a scrap fuel cell is used without a fitting installed, follow the steps outlined in paragraphs 7a through 7f. (2) If a section of a scrap fuel cell is used with fitting installed, trim the section, as outlined in paragraphs 7b, step (20) through 7c, step (10) for preparation and installation in the fuel cell.

(1) Select a fuel cell that is in the best condition of those fuel cells available for modification/conversion. (2) Place plywood board supports 5/8-inch or 3/4inch in thickness in each end of the fuel cell. (Be sure the edges of the boards are rounded and padded on one side.) (3) Place the padded sides against the cell and hold in position by using two expandable support rods or equivalent devices (Refer to Work Package 010). (4) Place the cell in a flat position on the deck with the access door face down, and the bottom of the cell in an upward position.

NOTE

NOTE

Be sure there is no sag between the cell bottom and the template.

Following fuel cell fitting repair, apply Chemical Conversion Coating in accordance with NAVAIR 01-1A-509, Aircraft Weapons Systems Cleaning and Corrosion Control.

(5) Place a layout template in position on the supported end of the cell.

This completes the modification/ conversion of the fuel cell. The fuel cell now has a changed contoured area at each end with a different type fitting installed. This fuel cell can now be installed in a differently equipped model or series aircraft.

(7) Repeat steps (5) and (6) on the other end of the cell and remove the template.

h. Fuel Cell Fitting Relocation. To incorporate fuel cell configuration changes, proceed as follows:

(6) Using the template, mark the cutout area on the left- and right-hand sides of the cell with a white marking pencil, SS-P-00196 (See Figure 16-69).

(8) Using a ruler, measure 1/2-inch in from the existing line and mark a parallel line around the cutout area. (This will reduce the size of the cutout 1/2-inch in all directions).

NOTE

Comply with general safety instructions in Work Package 004, and fuel cell entry preparations in Work Package 006.

Cutting the cell 1/2-inch smaller in all directions is to allow for any irregular cutting. The extra 1/2-inch is trimmed off to the exact size later. (9) Repeat step (8) on the other end.

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016 00 Page 46 (12) Before proceeding to cut out the marked area, note the cutout lines on one side may travel across the pump fitting flange, MS29554 (See Figure 16-70). (13) With a skiving knife, lightly cut along the outer edge of the flange from where the outer cutout lines cross the flange (See Figure 16-70).

NOTE Do not peel the flange back beyond the outer lines (See Figure 16-71). (14) Peel the flange back to the accessed edge of the fitting, but only in the lined area.

NOTE

Figure 16-69. Marking Fuel Cell for Fitting Removal

The inside baffle shoe may be removed prior to cutting the cell and reused later when the cell is complete. If the shoe is very difficult to remove, then cut it out and replace it with a manufactured shoe. (15) With a skiving knife, puncture the cell and proceed to cut out a section of the cell along the inner cutout line, being particularly careful at the edge of the pump flange (See Figure 16-72).

Figure 16-70. Cutting Along Fitting Flange (Rear View)

(10) Stand the cell on end with the marked area down. (11) Place the cell in a holding fixture.

Figure 16-71. Peeling Flange

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(16) Remove the cutout section and repeat step (15) on the other end of the cell.

Only experienced personnel should use power buffers. Power buffing may produce a polished surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand. (19) Using an air motor and a 2-inch sanding arbor with a medium grit sanding band, lightly buff a 2-inch band around the outside of the cell cutout area.

When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations. Do not buff the nylon barrier side of the inner liner material. Fuel diffusion will occur if barrier is broken.

Buffing must be heavy enough to remove all gloss, leaving the surface covered with fine scratches. However, care must be exercised to assure that the nylon barrier is not damaged during the buffing operation. Only experienced personnel should use power buffers. Power buffing may produce a polished surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand. (17) Buff the edge of the cutout very lightly in order to level off the cut edge. This is to prepare the edge so that it will mate with the stepback section that is to be installed. (18) On the outside of the cell, measure back from the cut edge two inches, and mark a broken line around the entire cutout area.

Figure 16-72. Removal of Fitting and Cell Section (20) On the pump fitting side, buff very carefully over the fitting flange to avoid damage. (21) Repeat steps (17) through (20) on the other end of the fuel cell. 8. O-RING GROOVE AREA FITTING REPAIR. Fitting damage in some instances is cause for rejection of an entire fuel cell, particularly when replacement fittings are not available. This situation, unfortunately, is most prevalent with fuel cells of limited production, used in aircraft no longer being manufactured. Since there is normally a requirement for this type of equipment, it is necessary to maintain the capability of servicing these fuel cells and replacing or repairing the fittings.

NOTE It is advisable to retain a stockpile of salvaged fittings from scrap fuel cells in order to readily replace damaged fittings without undue delay. Buffing must be heavy enough to remove all gloss, leaving the surface covered with fine scratches. However, care must be exercised to assure that the nylon barrier is not damaged during the buffing operation.

a. O-Ring Groove Area Damage Evaluation. The most commonly occurring fitting damages are cracks of the O-ring groove and flanges. These result from improper disassembly and alignment when connected to adjacent assemblies. The O-ring groove flanges are generally thin in

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cross-section as compared to the body of the fitting, and therefore break more readily. When the damaged fitting cannot be conveniently replaced, or a replacement fitting is not obtainable and the break is confined to the fitting O-ring groove area, a satisfactory repair can be made.

NOTE

conveniently shaped scrapers, which are also used in dressing the completed repair. Figure 16-73 illustrates the tang end of a file being used as a scraper. Note the ground taper. (1) If the fitting is distorted, reshape using the boltring portion of the mating part as a guide.

Fittings should not be repaired if badly distorted, or if the cracks are other than simple straight or slightly curved cracks. Do not repair cracks through O-ring groove area if longer than twice the distance between, adjacent threaded inserts. Do not make more than two repairs on any fitting. Both types of repair are to be at least 90 degrees apart, and in no case closer than 9 inches measured circumferentially between the ends of the repairs. Do not repair broken O-ring flanges if the damaged area is over 1-inch long. Figure 16-73 illustrates a typical crack. b. Broken O-Ring Groove Flange Repair. To repair broken O-ring groove flange, proceed as follows: Figure 16-73. Fitting – Flange Crack

Comply with general safety instructions in Work Package 004, and fuel cell entry preparations in Work Package 006. When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell.

Epoxies may cause skin sensitization or other allergic reactions. Avoid inhalation of vapor and prevent skin contact. Use personal protective equipment. If skin contact occurs, wash immediately with soap and water. Ensure continuous ventilation.

NOTE

(2) Contour the damage area to receive the epoxy adhesive (Refer to Table 15-4, usage column 15).

To restore fitting to its normal shape, use shaped dolly blocks and soft-faced hammers.

(3) Using a rotary file, clean up the jagged edges of the break.

Use suitably shaped rotary files and scrapers for contouring. Old files can be ground to form

(4) Cut a taper in the bottom of the O-ring groove (See Figure 16-73). The taper shall be such that the outer

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diameter of the O-ring groove remains at its original level while the inner diameter of the retainer land base will be ground to within 1/64-inch to 1/32-inch from the inner surface of the fitting. (5) Ensure taper is in the radial direction. The taper shall extend circumferentially from one end of the repair to the other.

Safety goggles, GG-G-531, shall be worn when drilling, scoring, or grinding fuel cell fittings.

NOTE As the grinding tool approaches the end of the damaged area, rotate the tool to maintain the angle of taper on the bottom of the O-ring groove while meeting the inner face of the Oring groove flange at an angle of 30 degrees to the tangent. (6) Holding the tool in this position, grind a 30degree knife edge taper on the inner face of the flange. (7) Fair the tapers into each other at this intersection. (A cone-shaped rotary file is best for grinding the inner face of the flange). (8) Using 180-grit abrasive cloth, P-C-451, sand all ground surfaces thoroughly.

Figure 16-74. Installing Retainer Ring (11) Form the rings so that spring-back will hold them in place. The inner ring should be approximately 1/16inch to 1/8-inch higher than the flange. The outer ring can be adjusted to the same height by sliding it up or down (See Figure 16-74.) (12) Cover the faces of the rings that will be in contact with the patching compound with tape, MIL-T22085 (AMS-T-22085). (13) Clean the damaged fitting with Acetone, ASTM D329, and install the rings in place on the fitting, being sure that they contact the repair area securely.

Acetone ASTM D329

7

(9) Wash all dirt and grit from the repair area with Acetone, ASTM D329.

PRIMER PR1826 B-1

(10) Fabricate two retainer rings from aluminum alloy sheet of convenient thickness to retain the patching compound. (One ring is to fit the inner face of the flange, and the other ring is to fit the outer face.)

(14) Mix the epoxy adhesive per manufacturer's instructions and fill the space between the rings with patching compound, using a thin instrument such as a torque depressor to work the compound (See Figure 16-75).

22

NAVAIR 01-1A-35

016 00 Page 50 (19) Dress the repair to match the contour and surface finish of the fitting. (20) Maintain the dimensions of the O-ring groove accurately (See Figure 16-77). c. Cracked O-Ring Groove Flange Repair. (See Figure 16-78.) Cracks of this type occur on fittings having a wide O-ring retainer land and a relatively thin cross-section through the bottom of the O-ring groove. To repair, proceed as follows:

Comply with general safety instructions in Work Package 004, and fuel cell entry preparations in Work Package 006. When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell. Figure 16-75. Filling Retainer Ring

PRIMER PR1826 B-1

(1) Straighten the fitting if it is bent to avoid further damage to the fitting.

22

NOTE

Safety goggles, GG-G-531, shall be worn when drilling, scoring, or grinding fuel cell fittings.

Avoid entrapment of air pockets. As the space between the rings is filled, the compound oozes under the ring and onto the taper on the bottom of the O-ring groove.

(2) Stop-drill the ends of the crack with a No. 50 drill (See Figure 16-79).

(15) Spread the compound, as necessary, to bring the level slightly higher than the surrounding area. (16) Allow the repair to cure at room temperature 8 to 16 hours, or until it is solid. (17) Remove the retainer rings. (18) Remove any excess epoxy from the O-ring groove with a scraper; also, use a vacuum cleaner to remove the epoxy particles during the scraping operation (See Figure 16-76).

(3) Working from the inside, vee the crack so that the bottom of the vee is approximately one-half way through the work piece. The included angle between the faces of the vee should be approximately 60 degrees (See Figure 16-80). (4) Use 180-grit abrasive cloth, P-C-451, to sand the surrounding area thoroughly (See Figure 16-81). (5) Use a jeweler’s disc to score the insert bosses and land to 1/32-inch depth (See Figure 16-82). (6) Score the fitting along two lines (See Figure 1682).

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016 00 Page 51

NOTE Do not score the fitting in areas, which cannot be reached by the hacksaw blade scraper. (7) Use a hacksaw blade scraper, ground to have a round cutting edge, to remove the sharp corners at the bottom of the jeweler’s saw scores.

(11) plaster, or other convenient materials. Avoid contaminating the bonding surface of the repair area with these materials.) (12) Prepare the epoxy adhesive (Refer to Table 154, usage column 15) and apply to the repair area (See Figure 16-83). Do not trap air bubbles. (13) Arrange the cell so that gravity will assist to hold the repair material in place as it cures.

(8) Vee out the portion of the crack remaining in the O-ring groove.

Acetone ASTM D329

(14) Allow the compound to cure.

7

Safety goggles, GG-G-531, shall be worn when drilling, scoring, or grinding fuel cell fittings.

NOTE Since the cracks usually occur next to the rear vertical face of the groove, it will be necessary to slightly undercut this face in order to clean up the crack. (9) Vacuum clean the repair area, and then wipe the area with Acetone, ASTM D329.

(15) Dress the repaired area in the O-ring groove to conform to the original dimensions and surface finish. (16) Dress the edge of the reinforcement on the inside surface of the fitting, using a powered cone-shaped rotary stone (See Figure 16-84). (17) Ensure that all debris is removed from the cell cavity. (18) Inspect repair to determine that adhesion is complete and that the patching compound is well cured. When well cured, the compound cannot be dented with the fingernail.

The use of Room Temperature Vulcanizers (RTVs) or other silicone base compounds is not authorized due to the possible contamination of the bonding surface by the silicones. (10) Provide a dam for holding the epoxy compound in place. (Use noncuring aircraft sealers, modeling clay,

(19) Inspect for porosity. A small number of pinpoint bubbles are acceptable. d. Scratched O-Ring Groove Flange Repair. Scratches in the fitting seal area may be repaired with epoxy adhesive (Refer to Table 15-4, usage column 15) using the procedures of paragraphs 8b through 8c.

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016 00 Page 52

Figure 16-76. Cleaning Retainer Ring Groove With Vacuum Cleaner

Figure 16-77. Filling Repaired Area

Figure 16-78. Fitting – Body Crack

Figure 16-79. Stop-Drilling Ends of Crack

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016 00 Page 53

Figure 16-80. V-Grooving Crack

Figure 16-81. Fitting Area to be Sanded

Figure 16-82. Scoring Insert Bosses and Land

Figure 16-83. Applying Epoxy Compound

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016 00 Page 54

9. FUEL CELL FITTING CORROSION REMOVAL. This paragraph briefly outlines corrosion control methods. For complete corrosion control, refer to NAVAIR 01-1A509, Aircraft Weapons Systems Cleaning and Corrosion Control. a. Fuel Cell Fitting Corrosion Control Evaluation. Visible corrosion of aluminum fuel cell fittings will appear on the surface as grey-white powdery deposits, pitting, or bumps and blisters. b. Fuel Cell Fitting Corrosion Treatment. To treat the corroded areas, proceed as follows:

(2) After completion of corrosion removal, clean the area with a clean abrasive mat, A-A-58054, saturated with water.

NOTE To protect the fuel cell rubber surface from damage by the chemical conversion coating, the rubber surrounding the fuel cell fitting shall be covered with polyethylene film, LP-378, or equivalent. (3) Following the cleaning of the area, treat it with a chemical conversion coating in accordance with NAVAIR 01-1A-509, Aircraft Weapons Systems Cleaning and Corrosion Control.

Comply with general safety instructions in Work Package 004, and fuel cell entry preparations in Work Package 006. When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell. (1) Remove the visible corrosion by lightly sanding the corroded area with 240-grit, aluminum oxide cloth, P-C451, followed by sanding with 320-grit, aluminum oxide cloth, P-C-451 (A-A-1048).

Figure 16-84. Dressing Edge of Repair

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Page 1 of 8

MAINTENANCE INSTRUCTIONS REINFORCEMENT OF SELF-SEALING FUEL CELLS AND REPAIR OF FUEL CELL COMPONENTS

Reference Material General Composite Repair Manual.......................................................................................................................... NA 01-1A-21 Naval Aviation Maintenance Program ......................................................................... COMNAVAIRFORINST 4970.2 Series

Alphabetical Index Subject

Page

Detection of Weakened Fuel Cell Structure .................................................................................................................................2 Fuel Cell Baffles............................................................................................................................................................................6 Fiberglass Baffle Repair.....................................................................................................................................................6 Metal Baffle Repair............................................................................................................................................................6 Rubber-Coated Fabric Baffle Repair.................................................................................................................................6 Fuel Cell Baffle Retainers .............................................................................................................................................................6 Fuel Cell Baffle Nylon Cord Replacement .......................................................................................................................6 Fuel Cell Baffle Nylon Tube and Rod Repair...................................................................................................................7 Fuel Cell Hangers..........................................................................................................................................................................3 Hanger Button Replacement and Repair ...........................................................................................................................3 Hanger Strap Reinforcement .............................................................................................................................................4 General...........................................................................................................................................................................................1 Reinforcement of Weakened Fuel Cell Structure.........................................................................................................................2 Applying Fuel Cell Structure Exterior Protective Coating ...............................................................................................2 Fuel Cell Structure Patch Application ...............................................................................................................................2 Fuel Cell Structure Patch Material.....................................................................................................................................2

1. GENERAL. This section provides general information and procedures for reinforcement of selfsealing fuel cells and repair of fuel cell components. Reinforcement of self-sealing fuel cells is required when it has been determined that a weakness exists in the cell structure. Some common causes of weakening are as follows: Repeated catapult launchings Arrested landings

Collapse of cell in aircraft cavity or during storage and/or shipment

NOTE Damage to fuel cells occurring in service should be reported to the responsible Fleet Support Team (FST) or In-Service Support Team (ISST) in accordance with COMNAVAIRFORINST 4790.2 Series so that corrective action can be taken to eliminate the problem where possible.

Extreme flight maneuvers Repeated folding to facilitate installation

The following warning appears many times in this chapter:

NAVAIR 01-1A-35

017 00 Page 2 The patch should extend two and one half inches beyond the area of weakness.

When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell. The use of the air-supplied respirator or SCBA is required when working inside cells installed in an aircraft. If the cells have been removed from the aircraft and are being worked in a shop environment, then the use of a half-face respirator with a cartridge appropriate to the hazard is a suitable alternative to the use of an air-supplied respirator. 2. DETECTION OF WEAKENED FUEL CELL STRUCTURE. Periodic inspection of the fuel cell structure in accordance with the applicable aircraft Maintenance Instruction Manual (MIM) and the applicable Maintenance Requirement Card (MRC) deck is recommended. Inspect for the following:

Apply a double patch with increased overlap for normal repairs before accomplishing reinforcement. Use square-woven fabric, if available. Patch fabric should be applied on the bias relative to the line of damage to increase strength. b. Fuel Cell Structure Patch Material. Reinforcing fabric may be selected using the materials list in Work Package 015. c. Applying Fuel Cell Structure Exterior Protective Coating. A careful inspection of the fuel cell will determine if additional protective coating is required to prevent fuel penetration due to spillage or plumbing leaks. If additional exterior protective coating is require proceed as follows:

Ply breaks Inner liner splits Separation along an edge or fabric lap Fitting rubber cracks

Acetone ASTM D329

7

(1) Clean and aerate the exterior surface with Acetone, ASTM D329 to remove surface residues.

Flange cracks Cell wall delaminations Attachment button and hanger strap tears 3. REINFORCEMENT OF WEAKENED FUEL CELL STRUCTURE. Normally required repairs are generally inadequate to restore the fuel cell to its original condition. Reinforcement of the fuel cell structure should be accomplished to prevent recurring problems. a. Fuel Cell Structure Patch Application. Reinforcing patches may be applied in accordance with the procedures in Work Package 015. In addition, the following guidelines should be observed: Both exterior and interior should be patched.

When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations.

Only experienced personnel should use power buffers. Power buffing may produce a polished surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand.

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(2) Lightly buff the exterior surfaces to be coated until surface residues and rubber deterioration are removed and a uniform roughened surface is produced.

Acetone ASTM D329

7

(3) Clean the surface with Acetone, ASTM D329 to remove any loose particles and freshen the surface.

When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations.

(4) Allow the treated surface to dry.

NOTE Allow sufficient drying time between coats. (5) Apply two coats of Buna-Vinylite lacquer (Refer to Table 15-4, usage column 10), or equivalent, to buffed area. 4. FUEL CELL HANGERS. Fuel cell hanger buttons and straps are subject to extreme loading conditions during service operations.

Only experienced personnel should use power buffers. Power buffing may produce a polished surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand. (2) Buff the chafing strip from the hanger button fabric flange and one inch beyond. (3) Remove the fabric flange with duckbill pliers.

a. Hanger Button Replacement and Repair. Hanger buttons are often broken or pulled from the fuel cell during service operations, removal, or adjustment of the fuel cell. Use the following procedures as a guide when repairing or replacing hanger buttons: When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell. Comply with general safety instructions in Work Package 004, and fuel cell entry preparations in Work Package 006. When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell. (1) Remove the hanger button from the fuel cell by cutting around the edge of the metal flange.

When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations. Do not buff the nylon barrier side of the inner liner material. Fuel diffusion will occur if barrier is broken.

NAVAIR 01-1A-35

017 00 Page 4 (8) Apply three coats of adhesive (Refer to Table 15-4) to both interior and exterior surfaces of the fuel cell and all surfaces of the button fabric flanges. (9) Allow adhesive to cure.

Buffing must be heavy enough to remove all gloss, leaving the surface covered with fine scratches. However, care must be exercised to assure that the nylon barrier is not damaged during the buffing operation. (4) Buff the exterior and interior surfaces of the fuel cell in the area of the removed fabric flange and one inch beyond.

Acetone ASTM D329

7

(10) Install the new button assembly in the prepared hole. Use Acetone, ASTM D329, to moisten the mating surfaces previously coated with adhesive. (11) Stitch mating surfaces in place. (12) Apply clamp pressure to mating surfaces and allow two hours to cure. (13) Remove clamps.

When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations.

(14) Inspect for defects. (15) Moisten the exterior fabric surface with Acetone, ASTM D329.

flange-coated

NOTE The reinforcing patches should overlap the fabric flange by a minimum of one inch. Only experienced personnel should use power buffers. Power buffing may produce a polished surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand.

(16) Prepare and buff the exterior reinforcing patch in accordance with Work Package 015. (17) Inspect for defects or loose edges.

(5) Buff and taper the edges of the button hole to closely fit the new hanger buttons. (6) Place the new button with assembled fabric flanges in the buffed and skived hole to check for proper fit. (7) Remove the new button.

When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell.

(18) Allow to cure for a total of seventy-two hours before air testing, installation, or exposure to fuel. b. Hanger Strap Reinforcement. Hanger strap reinforcement is often required when excessive loads have pulled the fabric straps loose during service. Reinforce fabric straps as follows:

Comply with general safety instructions in Work Package 004, and fuel cell entry preparations in Work Package 006.

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017 00 Page 5

When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell. (1) Mark hanger strap locations to allow for correct replacement.

(5) Apply three coats of adhesive (Refer to Table 15-4, usage column 8) to the buffed fuel cell surface and the hanger strap base. (6) Allow adhesive to cure until tacky. (7) Locate and stitch hanger strap and fuel cell mating surfaces in place. (8) Apply clamp pressure and allow two hours to cure.

Acetone ASTM D329

7

NOTE

(9) Apply three coats of adhesive (Refer to Table 15-4, usage column 8) to the previously buffed top surface of the hanger strap base.

NOTE

Acetone, ASTM D329, or heat lamps may be used to weaken hanger strap bond.

The cover patch should be slotted to clear the strap attachment lug or collar.

(2) Remove loosened hanger straps by carefully peeling back fabric base with duckbill pliers or equivalent.

(10) Cut a reinforcing cover patch to extend a minimum of 1 1/2 inches beyond the edge of the hanger strap.

When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations.

(11) Lightly buff the patch and apply three coats of adhesive (Refer to Table 15-4, usage column 8). (12) Allow treated adhesive surfaces to cure until tacky. (13) Stitch hanger strap and reinforcing cover patch into place. (14) If vulcanization is used as a cure method, and the appropriate adhesive has been previously applied, proceed as follows:

Only experienced personnel should use power buffers. Power buffing may produce a polished, surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand.

(a) Place strap and patch under molds or plates and apply clamp pressure. (b) Cure at 290oF (143oC) +5oF for one hour.

(3) Buff fuel cell hanger strap area a minimum of 1 3/4 inches beyond the edge of hanger strap base. (4) Buff the base and top surface of the new or reusable hanger strap. NOTE If vulcanization will be used as a cure method, use adhesive (Refer to Table 15-4, usage column 8).

If clamps and platens used in the vulcanization process are disassembled from the patches before room temperature is reached, the bonded patch material will not cure flat but will assume a permanent set conforming to the shape in its relaxed position.

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(c) Allow heating unit and mold to cool to room temperature before removing from fuel cell. 5. FUEL CELL BAFFLES. Fuel cell baffles support the cell internally and distributes the forces caused by movement of fuel. The materials most frequently used for baffle construction are rubber coated fabric, fiberglass, and metal. a. Rubber-Coated Fabric Baffle Repair. Torn, abraded, or otherwise damaged rubber-coated fabric baffles are repaired using the same basic methods as those for selfsealing cells. However, the repair material for baffles does not require a nylon barrier. Rubber-coated fabric baffles with holes in them may be repaired as follows:

(4) Cut two patches to lap the damaged area by a minimum of 1 1/2 inches (Refer to Table 15-3). (5) Buff one side of each patch.

Acetone ASTM D329

Clean all buffed areas with Acetone, ASTM D329. (6) Apply three coats of adhesive to all buffed areas. Allow each coat to dry before applying next coat. (7) Allow adhesive to dry until tacky. (8) Stitch patches in place.

NOTE The absence of a nylon barrier allows the fuel to wick and diffuse through the fabric baffle material. A 24-hour drying period should elapse between exposure to fuel and repairs to fabric baffles. (1) Cut out the hole using a punch.

NOTE Materials that are of different thicknesses than that of the baffle require buffing or lamination to match baffle thickness.

7.

(9) Apply clamp pressure and allow two hours to cure. (10) Inspect for defects or loose edges. (11) Inspect for loose or damaged grommets and replace, if required. b. Fiberglass Baffle Repair. Fiberglass delaminates and cracks due to usage and can generally be repaired. Fiberglass baffles can be repaired with epoxy resin and fiberglass materials. If repairs are required, consult the NA 01-1A-21 General Composite Repair Manual.

(2) Cut a plug of material that is the same thickness as the baffle. Fiberglass may cause eye, skin, and respiratory irritation. Use personal protective equipment.

When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations. Do not shut down air blower or hot air blower when air duct is connected to the aircraft. (3) Buff a minimum of 1 3/4 inches beyond the damaged area on both sides of the baffle.

c. Metal Baffle Repair. Metal baffles are repaired using standard sheet metal techniques and practices. 6. FUEL CELL BAFFLE RETAINERS. The fabric baffles are generally held in place in the fuel cell by nylon cord, MIL-C-5040, which is laced through the baffle grommets, internal hanger supports, and straps. Some fuel cells retain the baffles using nylon tubes or rods instead of cord. a. Fuel Cell Baffle Nylon Cord Replacement. The nylon cord should be inspected regularly for abrasion. When abrasion causes breaks in the cord fibers, the nylon cord should be replaced as follows:

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017 00 Page 7

New nylon cord will not be coated.

(7) Recoat any knots and cord ends with adhesive mixture. b. Fuel Cell Baffle Nylon Tube and Rod Repair. The nylon tubes or rods may break, causing the fuel cell baffles to hang loose. Broken parts may be repaired as follows:

Acetone ASTM D329

7

(1) Prepare a solution with equal parts of adhesive (Refer to Table 15-4, usage column 8) and Acetone, ASTM D329. (2) Pour adhesive mixture into a vat or tub. (3) Pull cord through adhesive mixture, thoroughly coating all sides (See Figure 17-1). (4) Place cord on a frame to dry before re-spooling. (5) Cut cord to proper length using old cord as a guide, if available.

NOTE Nylon tubing or rods, which show crazing of 1/64 inch or deeper should be replaced. (1) Inspect tubing or rods for breaks. (2) Cut pieces of aluminum sleeve using aluminum tubing, AMS-T-7081. (3) Place sleeve over broken tubing or rods and push broken ends together.

(6) Tie a figure-eight knot in each end of the cord lacing.

(4) Using a crimping tool, or equivalent, crimp the sleeve ends.

NOTE Uncoated knots or cord ends may cause slipping or fraying of cord lacing. Short pieces of cord should be tied together using square knots.

(5) Inspect all repairs for looseness. (6) Inspect all unbroken nylon tubing or rods for crazing of 1/64 inch or deeper. (7) Replace defective tubing.

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Figure 17-1. Coating Nylon Baffle Cord

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Page 1 of 18

INSPECTION AND ASSESSMENT OF URETHANE FUEL CELLS

Reference Material None .......................................................................................................................................................................................

Alphabetical Index Subject

Page

General ................................................................................................................................................................................. 1 Urethane Fuel Cell Damage/Defect Repair Procedures ....................................................................................................... 1 Urethane Fuel Cell Defects and Acceptable Limitations...................................................................................................... 1

1. GENERAL. This Work Package provides procedures for evaluation and inspection of Urethane Fuel Tanks of the following constructions manufactured by Engineered Fabrics Corporation: BTC-85 BTC-86 BTC-99 BTC-101 BTC-101RB BTC-101RB-2 FTL-103 FTL-107 FTL-107RB

2. URETHANE FUEL CELL DEFECTS AND ACCEPTABLE LIMITATIONS. (Refer to Tables 18-1 and 18-2.) Urethane fuel cell defects that are within established tolerances will not be cause for removal and/or repair. 3. URETHANE FUEL CELL DAMAGE/ DEFECT REPAIR PROCEDURES. Refer to Work Package 0019 for repair instructions for Urethane Fuel Cells. Repair procedures in Work Package 019 are for non-self sealing areas of the fuel cells. Refer to Work Package 0016 for repair instructions of Self Sealing Urethane Fuel Cell Fittings. Refer to Work Package 022 for repair instructions of Nonself Sealing (bladder) Urethane Fuel Cell Fittings.

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Table 18-1. Uninstalled Fuel Cell Defects and Acceptable Limitations

Defect/Condition 1.

Limitation

Cell Interior a.

Edge looseness on liner reinforcements, corner patches, and chafing patches.

Acceptable up to 1/4-inch width for complete length of liner lap if 1-inch bond is maintained on fabric liner and 1/4-inch on rubber liner. 1/2-inch maximum looseness, provided loose area does not exceed 15 percent of total area. Blisters or separations in other than the edge area allowable up to 15 percent of total area.

b.

Looseness under cemented components such as attaching straps, baffle shoes, etc.

15 percent of individual area, provided 1/4-inch bond is maintained around the edge (See Figure 14-2).

c.

Blisters between liner and fitting flange.

1/4-inch maximum dimension; maximum one per lineal foot and two per fitting, provided 1-inch bond is maintained (See Figure 14-1).

d.

Damaged grommets in accessories.

Acceptable, provided serviceability is not affected.

e.

Damaged coating on accessories (metal, wood or rubber.

Acceptable, provided corrosion or other deterioration is not present.

f.

Checking due to weather, ozone, dry cracking, or surface imperfections.

Acceptable, provided there is no penetration beyond 50 percent of the inner liner material thickness (See Figure 143).

g.

Blisters, delaminations, or ply separations.

1-inch maximum dimension, provided there is a 6-inch bond between blisters and no more than one per square foot of total cell area.

h.

Channels around entire outer edge of fitting flange.

1/4-inch maximum width (See Figure 14-1).

i.

Channels at tapered construction step-off area, or edge of lap splices of any ply.

1/4-inch maximum width entire length of lap (See Figure 144).

j.

Cuts or holes in inner liner.

Not acceptable.

k.

Buffing through inner liner.

Not acceptable.

l.

Vertical edge looseness in fillet material at edge if fitting metal.

Separations on either side of flange are acceptable around the entire circumference of the fitting provided that when flexed, there is no fabric damage. (See Figure 18-1 and 18-2)

m. Lumps in innerliner surface.

Acceptable. (See Figure 18-3)

n.

Voids in innerliner surface.

Acceptable. (See Figure 18-5)

o.

Cement runs, drips, and/or sags on surface.

Acceptable. (See Figure 18-4)

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Table 18-1. Uninstalled Fuel Cell Defects and Acceptable Limitations - Continued Defect/Condition

2.

Limitation

p.

Uncovered buffed areas in self-sealing areas of tank. Note: This is in addition to item “k”.

Not acceptable.

q.

Translucency (light shines through tank wall). Disbursement of carbon black can result in translucent areas that do not affect strength or sealing integrity.

Acceptable.

Cell Exterior a.

Blisters or ply separation between any plies except liner and sealant.

1-inch maximum dimension.

b.

Skim coat blisters.

Acceptable.

c.

Loose hanger straps or hanger attaching points.

Acceptable up to 15 percent of total area provided 1/4-inch bond is maintained around the edge.

d.

Loose or damaged tapes, corner patches and other outside accessories.

1/2-inch maximum allowable looseness, provided this looseness does not exceed 15 percent of the total area.

e.

Checking due to weather, ozone, dry cracking or surface imperfections (See Figure 9-4).

Acceptable up to 50 percent of material thickness.

f.

Damaged grommets in accessories.

Acceptable, provided serviceability is not affected.

g.

Damage through outer cord or fabric ply.

Not acceptable.

h.

Channels or bridging of outer plies at cord or fabric splice.

1/2-inch maximum width full length of splice (See Figure 98).

i.

Outer ply cuts or splits parallel to cords where cords are not damaged.

Not acceptable; may result in outside activation.

j.

Mold marks and impressions on external surface.

Acceptable. (See Figure 18-7)

k.

Raised areas in external surface.

Acceptable up to 1/8 inch above normal tank surface as long as the area is solid. (See Figure 18-6)

l.

Step-off or mis-match at ferrule caps, fitting flanges, and/or tank join lines.

Acceptable. (See Figures 18-8, 18-9, and 18-10)

m. Vertical Edge Looseness in fillet material at edge of fitting metal.

Separations on either side of flange are acceptable around the entire circumference of the fitting provided that when flexed, there is no fabric damage. (See Figure 18-1 and 18-2)

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Table 18-1. Uninstalled Fuel Cell Defects and Acceptable Limitations - Continued Defect/Condition

Limitation

n.

Loose Lenoweave (Encapsulated and Nonencapsulated) either encapsulated or nonencapsulated is applicable to specific surfaces of tank positions 1C, 1D, 2C/D, 3C/D, and 4C/D. Non-encapsulated Lenoweave is applicable to tank positions 2E/F, 3E/F, and 4E/F. Location of the Lenoweave for each position is defined in Figures 18-13 through 18-20.

Maximum allowable looseness is one (1) square inch in any given loose area with at least three (3) inches of separation between loose areas. NOTE Lenoweave is an open weave cloth cemented to the exterior surface of the tank. See Figure 18-10 for graphical representation of nominal non-encapsulated Lenoweave and Figure 9K for nominal encapsulated Lenoweave.

o.

Dimpling in Lenoweave (Encapsulated).

The exterior surface of encapsulated Lenoweave fabric contains local areas where the textured appearance of the Lenoweave cloth may be observed. This condition may range from slight dimples in the coating to complete Lenoweave cloth definition and is acceptable as long as the area does not exceed nine (9) square inches in any one (1) square foot of area. See Figure 18-12 for graphical representation of dimpling in encapsulated Lenoweave.

p.

Splits and Edge looseness at tank join line. (Tank join line is defined as the seam area where the top and bottom halves of the tank are joined together). The join line areas for each position are illustrated in Figures 18-13 through 18-20.

Acceptable up to 1/8 inch in width on either side of join line gap with no more than 3 inches in total length allowed in any 5 linear feet of seam. (See Figures 18-22 and 18-23)

q.

Uncovered buffed areas in self-sealing areas of tank. Note: This is in addition to item “p”.

Not acceptable.

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Table 18-2. Installed Fuel Cell Defects and Acceptable Limitations

Defect/Condition 1.

Limitation

Cell Interior a.

Edge looseness on liner reinforcements, corner patches, and chafing patches.

1/2-inch maximum looseness, provided loose area does not exceed 20 percent of total area. Blisters or separations in other than the edge area allowable up to 20 percent of total area.

b.

Looseness under cemented components such as attaching straps, baffle shoes, etc.

20 percent of individual area, provided 1/4-inch bond is maintained around the edge (See Figure 14-1).

c.

Blisters between liner and fitting flange.

1/2-inch maximum dimension, maximum two per lineal foot and three per fitting, provided 1 -inch bond is maintained (See Figure 14-1).

d.

Damaged grommets in accessories.

Acceptable, provided serviceability is not affected.

e.

Damaged coating on accessories (rubber, metal or wood).

Acceptable, provided corrosion or other deterioration is not present.

f.

Checking due to weather, ozone, dry cracking, or surface imperfections.

Acceptable, provided there is no penetration beyond 50 percent of the inner liner material thickness (See Figure 143).

g.

Blisters, delaminations, or ply separations.

1 1/2-inches maximum, provided there is a 6-inch bond between blisters and no more than one per square, foot of total cell area.

i.

Channels around entire outer edge of fitting flange.

1/2-inch maximum width (See Figure 14-1).

j.

Channels at tapered construction step-off area, or edge of lap splices of any ply.

1/2-inch maximum width entire length of lap (See Figure 146).

k.

Cuts or holes in inner liner.

Not acceptable.

l.

Buffing through inner liner.

Not acceptable.

m. Activated areas.

Not acceptable.

n.

Broken stiffeners or supports.

Not acceptable.

o.

Vertical Edge Looseness in fillet material at edge if fitting metal.

Separations on either side of flange are acceptable around the entire circumference of the fitting provided, that when flexed, there is no fabric damage. (See Figure 18-1 and 18-2)

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Table 18-2. Installed Fuel Cell Defects and Acceptable Limitations - Continued Defect/Condition

Limitation

p.

Lumps in innerliner surface.

Acceptable. (See Figure 18-3)

q.

Voids in innerliner surface.

Acceptable. (See Figure 18-5)

r.

Cement runs, drips, and/or sags on surface.

Acceptable. (See Figure 18-4)

s.

Uncovered buffed areas in self-sealing areas of tank. Note: This is in addition to item “p”.

Not acceptable.

t.

Translucency (light shines through tank wall). Disbursement of carbon black can result in translucent areas that do not affect strength or sealing integrity.

Acceptable.

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Table 18-2. Installed Fuel Cell Defects and Acceptable Limitations - Continued Defect/Condition

Limitation

NOTE Only accessible portions of the fuel cells will be inspected. NOTE Fuel cells need not be removed from aircraft for inspection. 2.

Cell Exterior a.

Blisters or ply separations between any plies except liner and sealant.

1 1/2 inches maximum dimension.

b.

Skim coat blisters.

Acceptable.

c.

Loose hanger straps or hanger attaching points.

Acceptable up to 20 percent of total area, provided 1/4-inch bond is maintained around edge.

d.

Loose or damaged tapes, corner patches, or other outside accessories.

Acceptable, provided sealant is not activated.

e.

Checking due to ozone, weather, or dry cracking.

Acceptable.

f.

Damaged grommets in accessories.

Acceptable, provided serviceability is not affected.

g.

Damage through outer cord or one fabric ply.

1-inch maximum dimension.

h.

Channels or bridging of outer plies at cord or fabric splice.

1/2-inch width maximum full length of splice (See Figure 14-5).

i.

Outer ply cuts or splits parallel to cords where cords are not damaged.

Acceptable, provided activation of sealant is not evident.

j.

Mold marks and impressions on external surface.

Acceptable. (See Figure 18-7)

k.

Raised areas in external surface.

Acceptable up to 1/8 inch above normal tank surface as long as the area is solid. (See Figure 18-6)

l.

Step-off or mismatch at ferrule caps, fitting flanges, and/or tank join lines.

Acceptable. (See Figures 18-8, 18-9, and 18-10)

m. Vertical Edge Looseness in fillet material at edge of fitting metal.

Separations on either side of flange are acceptable around the entire circumference of the fitting provided that when flexed, there is no fabric damage. (See Figure 18-1 and 18-2)

n.

Acceptable.

Translucency (light shines through tank wall). Disbursement of carbon black can result in translucent areas that do not affect strength or sealing integrity.

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018 00 Page 8

Looseness Not Acceptable In This Area Vertical Edge Looseness Acceptable Either Side of Flange Outer Tank Coating

Fitting Metal

Tank Wall

FITTING CROSS SECTION VERTICAL EDGE LOOSENESS

FIGURE 9A Figure 18-1. Fitting Cross Section Vertical Edge Looseness

Acceptable

Figure 18-2. Acceptable Vertical Edge Looseness

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Figure 18-3. Lumps on Innerliner Surface

Figure 18-4. Runs, Drips, and Sags on Innerliner

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Figure 18-5. Voids in Innerliner Surface

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Figure 18-6. Raised Areas on External Surface

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Figure 18-7. Mold Mark on External Surface

Figure 18-8. Step-off at Fitting Flange

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A

A

INSIDE OF TANK

STEP-OFF AT FERRULE

CROSS SECTION A-A STEP-OFF AT FERRULE

Figure 18-9. Step-off at Ferrule

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Figure 18-10. Step-off at Tank Join Line

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Figure 18-11. Non-Encapsulated Lenoweave

Figure 18-12. Encapsulated Lenoweave

Figure 18-13. Texture and Dimpling on Encapsulated Lenoweave

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Figure 18-14

Figure 18-15

Figure 18-16

Figure 18-17

FIGURES 18-14 THROUGH 18-18: CONFIGURATIONS FOR F-18 C/D FUEL CELLS 1 THROUGH 4, SHOWING TANK JOIN LINES

Figure 18-18

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Figure 18-19

Figure 18-20

Figure 18-21

FIGURES 18-19 THROUGH 18-21: CONFIGURATIONS FOR F-18 E/F FUEL CELLS 1 THROUGH 4, SHOWING TANK JOIN LINES

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Figure 18-22

Figure 18-23

FIGURES 18-22 AND 18-23: ACCEPTABLE GAP AND LOOSENESS AT TANK JOIN LINES

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31 August 2005

Page 1 of 4

MAINTENANCE INSTRUCTIONS REPAIR OF URETHANE FUEL CELLS

Reference Material None.................................................................................................................................................................................................

Alphabetical Index Subject

Page

General...........................................................................................................................................................................................1 Quick Cure Repair Method ...........................................................................................................................................................1 Repair of Abraded or Missing Top Coat ...........................................................................................................................1 Repair of holes, punctures, cuts, and tears.........................................................................................................................2

1. GENERAL. This section provides repair procedures for urethane fuel cells. 2. QUICK CURE AND REGULAR CURE REPAIR METHOD. This repair method is the primary method for repairing polyurethane fuel cells and is intended for repairing cells with minor damage. This repair may be accomplished without removing the cell from the aircraft if the damage is accessible for repairs. This repair may also be accomplished on a fuel cell that has not been installed or has been removed from an aircraft. The fuel cell must be purged and fuel residue cleaned if repairs are required on the inside of the cell. Damage that can be repaired is listed in Table 18-1 and 18-2 of Work Package 018. a. Adhesives. The choice of two adhesives are authorized for this repair. (1) Quick Cure Method: For a quick cure process, where use of heat is not authorized and quick turn around is required, use Engineered Fabrics Corporation 82C32 two part adhesive. Mix the quick cure adhesive 82C32 as follows: Pour part 2 into the container of part 1 and mix thoroughly for 5 minutes. Allow repair to cure for 6 hours at a minimum temperature of 70oF (21oC). The fuel cell may be refueled after adhesive is cured. (2) Regular Cure Method: For a longer working time adhesive, use Engineered Fabrics Corporation 5923C three parts adhesive. Vigorously shake the contents of Part 2 prior to mixing with Part 1. Mix Part 1 and Part 2 by pouring Part 2 into Part 1 and stirring to blend the materials.

Do not shake the mixture as shaking can result in formation of air bubbles. Mixture should be uniform in color with no residual material on the sides or corners of the container. Add Part 3 to the mixture of Part 1 and Part 2. Stir for three (3) to five (5) minutes. Do not "whip" the material, as this will cause air bubbles.

Comply with general safety instructions in Work Packages 003 and 004, and fuel cell entry preparations in Work Package 006. When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell. b. Repair of Abraded or Missing Top Coat. To repair abraded or missing top coat with no fabric ply damage using the quick-cure method, proceed as follows: (1) Abrade surface adjacent to the damaged area.

Acetone ASTM D329

7

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019 00 Page 2 (3) Mix the adhesive (choose one of the following): (a) Quick Cure Method: instructions in paragraph 2a(1)

Organic solvents or adhesives containing organic solvents are flammable. Avoid breathing of vapors or prolonged skin contact. Use personal protective equipment. Wear disposable polyethylene gloves, MR-100, when applying solvents by hand. (2) Clean abraded area with cheesecloth, CCC-C440, moistened with Acetone, ASTM D329.

Mix

82C32

per

(b) Regular Cure Method: Mix 5923C per instructions in paragraph 2a(2) (3) Carefully and uniformly brush two coats of repair adhesive over the buffed area. (4) Apply the second coat 90o to the application of the first coat. (5) Cure time: (a) Quick Cure Method: If 82C18 quick cure adhesive is used, allow the finished repair to air cure for 6 hours at 70ºF.

Isocyanate exposure may produce severe allergic reaction and permanent sensitization. Persons with history of allergies or previous sensitization shall not be assigned tasks involving isocyanates. Personal protective equipment for skin and eyes and proper respiratory protection (BUMEDINST 6260.16) shall be required when polyurethane coatings or adhesives are used for fuel cell repairs.

(b) Regular Cure Method: If 5923C slow cure adhesive is used, allow the adhesive to cure for 72 hours undisturbed at 70ºF. Alternatively 5923C may be cured at 240ºF for 2 hours. c. Repair of holes, punctures, cuts, and tears. To repair holes, punctures, cuts, and tears, using the quick-cure method, proceed as follows:

Acetone ASTM D329

7

Do not apply hot-cure methods on repairs requiring 82C32 adhesive.

NOTE The adhesive, 82C32, has a usable life of 15 to 45 minutes after mixing. Recapping the adhesive between applications aids in extending the usable life. The adhesive, 5923C, has a usable life of 2 hours after mixing. Recapping the adhesive between applications aids in extending the usable life

ADHESIVE 82C18

9

When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell. Organic solvents or adhesives containing organic solvents are flammable. Avoid breathing of vapors or prolonged skin contact. Use personal protective equipment. Wear disposable polyethylene gloves, MR-100, when applying solvents by hand.

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019 00 Page 3

(1) Clean the inside surface of the cell with cheesecloth, CCC-C-440, moistened with acetone, ASTM D329, approximately 12 inches beyond the damage in all directions.

NOTE When the repair is being made with the cell still installed in the aircraft, only an inside patch is required. (2) Determine the size of the patches required. (The inside patch size must extend beyond the damaged area at least 1 inch in all directions.)

Isocyanate exposure may produce severe allergic reaction and permanent sensitization. Persons with history of allergies or previous sensitization shall not be assigned tasks involving isocyanates. Personal protective equipment for skin and eyes and proper respiratory protection (BUMEDINST 6260.16) shall be required when polyurethane coatings or adhesives are used for fuel cell repairs. (6) Mix the adhesive (choose one of the following): (a) Quick Cure Method: instructions in paragraph 2a(1)

Mix

82C32

per

(b) Regular Cure Method: Mix 5923C per instructions in paragraph 2a(2) Only materials specified for use in the following procedures shall be used to repair Goodyear Vithane bladder fuel cells. Substitutions shall not be made. (3) Cut an inside patch from the repair material, 3604N (491 alternate) (Refer to Work Package 015). (The patch must have a rounded outline.) (4) Center the patch over the defect and mark the cell surface 1/2 inch beyond the patch in all directions.

NOTE Due to short work life, fresh adhesive should be mixed when adhesive becomes thick and unbrushable. Recapping the adhesive between the applications will aid in extending the work life of the adhesive. (7) Apply one brush coat of adhesive to the clean abraded areas; let dry for 15 minutes. (8) Apply second brush coat of adhesive and let dry 15 minutes.

Organic solvents or adhesives containing organic solvents are flammable. Avoid breathing of vapors or prolonged skin contact. Use personal protective equipment. Wear disposable polyethylene gloves, MR-100, when applying solvents by hand. (5) Lightly abrade the cell surface surrounding the damage as marked with 120 grit abrasive cloth, P-C-451, moistened with Acetone, ASTM D329.

Acetone ASTM D329

7

Organic solvents or adhesives containing organic solvents are flammable. Avoid breathing of vapors or prolonged skin contact. Use personal protective equipment.

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019 00 Page 4

Wear disposable polyethylene gloves, MR-100, when applying solvents by hand. (9) Apply third coat of adhesive. Dip fabric patch, 3604N, in Acetone, ASTM D329 and shake out the excess solvent.

ADHESIVE 82C18

(10) While the third coat of adhesive is still wet, lay the nylon fabric patch, 3604N (491 alternate), in the wet cement and smooth out with a brush removing all entrapped air.

(a) Quick Cure Method: If 82C18 quick cure adhesive is used, allow the finished repair to air cure for 6 hours at 70ºF.

(11) Apply a final coat of adhesive over the 3604N (491 alternate) cloth patch, extending the adhesive ½ inch past the edge of the patch. (12) Cure time:

9

(b) Regular Cure Method: If 5923C slow cure adhesive is used, allow the adhesive to cure for 72 hours undisturbed at 70ºF. Alternatively 5923C may be cured at 240ºF for 2 hours.

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31 August 2005

Page 1 of 8

MAINTENANCE INSTRUCTIONS INSPECTION AND ASSESSMENT OF NON-SELF SEALING (BLADDER) FUEL CELLS

Reference Material None

Alphabetical Index Subject

Page

Evaluation of Non-self Sealing (Bladder) Fuel Cells for Damage and Defect............................................................................2 Fuel Seepage ......................................................................................................................................................................2 Inner Liner Crazing ............................................................................................................................................................2 Inner Liner Imperfections ..................................................................................................................................................2 Inner Liner Weather or Ozone Cracking ...........................................................................................................................2 General...........................................................................................................................................................................................1 Description .........................................................................................................................................................................1 Non-self Sealing Fuel Cell Construction...........................................................................................................................1

1. GENERAL. This section provides definitions, construction design, and instructions for evaluating damage to nonself-sealing (bladder) fuel cells. Organizational and Intermediate level Maintenance Activities are authorized to repair fuel cell punctures, rips or tears that are 1 inch in length or less provided such damage is not within 2 inches of a fuel cell fitting. Additionally, touchup of abraded exterior protective coating is authorized.

NOTE The following warning appears many times in this chapter:

from the aircraft and are being worked in a shop environment, then the use of a half-face respirator with a cartridge appropriate to the hazard is a suitable alternative to the use of an air supplied respirator. a. Description. A non-self-sealing fuel cell, commonly called a bladder fuel cell, is a fuel container that does not self-seal holes or punctures. The advantage of using a bladder fuel cell results from the saving in weight and the comparative simplicity of repair techniques. The cell is made slightly larger than the aircraft cavity so that the weight and internal pressure of the fuel is supported by the aircraft structure. Different materials and methods are used for repairing the different types of bladder cells. The two basic types of synthetic rubber bladders currently in use are: Cells constructed of a combination of nitrile (Buna-N) synthetic rubber, nylon fuel barrier, and fabric.

When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell. The use of the air-supplied respirator or SCBA is required when working inside cells installed in an aircraft. If the cells have been removed

Cells constructed of a combination of polyurethane synthetic rubber, nylon fuel barrier, and fabric. b. Nonself-Sealing Fuel Cell Construction. The typical bladder fuel cell has three primary layers of

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020 00 Page 2

material: the inner liner, the fuel barrier, and the retainer (See figure 20-1).

NOTE

(1) Fuel cell inner liner. The inner liner consists of nitrile (Buna-N) synthetic rubber coated nylon fabric or polyurethane (VITHANE) synthetic coated nylon fabric. The purpose of the inner liner is to contain the liquid fuel and provide protection for the nylon barrier.

Certain imperfections in the mold or building form or contamination on its surface may cause inner liner blemishes. Minor surface imperfections are allowable because the nylon barrier will prevent fuel leakage.

(2) Fuel cell fuel barrier. The nylon fuel barrier consists of three to four coats of nylon applied hot by brush, roller, or spray. The purpose of the nylon fuel barrier is to prevent the fuel and fuel vapors from diffusing through the cell wall.

The inner and outer liners are only for protection of the nylon barrier, and are not intended to be fuel barriers.

(3) Fuel cell retainer. The retainer consists of nitrile (Buna-N) synthetic rubber coated heavy nylon fabric or polyurethane (VITHANE) synthetic rubber coated heavy nylon fabric. The retainer forms the exterior of the fuel cell and provides strength for the fuel cell. Additionally, it provides the protection for the nylon fuel barrier. 2. EVALUATION OF NONSELF-SEALING (BLADDER) FUEL CELLS FOR DAMAGE AND DEFECT. (Refer to Table 20-1 and 20-2). The correct analysis and determination of possible defects is necessary to determine if a fuel cell is acceptable or if it must be repaired and the extent of repair required. The following descriptions of conditions, defects and damage will assist in the inspections of fuel cells. a. Fuel Seepage. A bladder cell, when being pressure tested, may appear to seep or weep fuel over a general area, creating the illusion that there are numerous small pin holes in the cell or porous liners. Causes for this condition are as follows: The exterior of the fuel cell comes in contact with fuel from leaking fittings, plumbing, interconnectors or accidental spillage. Fuel is trapped in the airframe cavity seeping into the outer ply fabric, which retains the fuel in much the same manner as a sponge. Internal pressure on the cell, which squeezes or forces the fuel to the surface. This condition is correctly called weeping and is not a defect. b. Inner Liner Imperfections. The synthetic rubber coating on the inner liner fabric ply may not be perfectly smooth or may be imbedded with small pieces of foreign matter, causing indentations on the liner surface.

c. Inner Liner Crazing. (See Figure 14-3). Crazing or cracking of the coating (mold release) used on the forms or molds allow the uncured rubber to flow into these cracks during cure.

NOTE Crazing will be raised, whereas weather checking or other detrimental cracking will be depressed. Crazing of the inner liner is not detrimental to serviceability. d. Inner Liner Weather or Ozone Checking. (See Figure 14-3). Weather checking can be very detrimental to fuel cell serviceability and may be cause for rejection. (1) Description. Weather checking is an actual breakdown of the molecular structure of the rubber resulting in cracks or fissures in the surface that can penetrate to the nylon barrier. Since the nylon barrier is bonded to the inner liner, such cracks will eventually penetrate the nylon fuel barrier, destroying the fuel integrity of the cell. (2) Causes. Compounded into the rubber used in the inner liner is an agent called a plasticizer. After exposure to fuel, the fuel extracts the plasticizer and replaces it in the rubber compound. This condition is not harmful unless the fuel is allowed to evaporate. If this occurs, the rubber will weather or crack. To prevent this, once a cell has been exposed to fuel or a test fluid, it must either be kept in a fuel-wet environment or preserved to prevent evaporation.

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020 00 Page 3

Figure 20-1. Bladder Cell Construction (Typical)

Table 20-1. Uninstalled Bladder Fuel Cell Defects and Acceptable Limitations

Defect

Limitation

a. Vertical Edge Looseness. Separation of Rubber Material (Fillet) from the vertical surface of the metal fitting.

Around the entire metal fitting is an acceptable condition for Urethane Fuel Cell (See Figure 18-1). Unacceptable for Nitrile Fuel Cells.

b. Loose liner at throat of fitting Edge looseness at liner lap.

1/2-inch looseness in width around entire circumference at edge of fitting (See Figure 14-4). Acceptable up to 1/4-inch width (depth) maximum length of liner lap, provided 1-inch bond is maintained. If fitting fabric flange is less than 1-inch in size, 100% bond must be maintained.

c. Looseness on liner reinforcements and chafing patches.

Blisters or separations other than in the edge area allowable or up to 15 percent of the total area.

d. Looseness of cemented internal support components such as attaching straps, baffle supports, etc.

Acceptable up to 15 percent of component area provided 1/4-inch solid bond is maintained around the edge (See Figure 14-5).

e. Blisters between fitting flange and adjacent ply.

1/4-inch maximum dimension; maximum one per linear foot and two per fitting provided 1-inch bond is maintained (See Figure 14-4).

f. Damaged grommets in accessories.

Acceptable provided serviceability is not affected.

1. Cell Interior

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020 00 Page 4

Table 20-1. Uninstalled Bladder Fuel Cell Defects and Acceptable Limitations - Continued Defect

Limitation

g. Damaged coating on accessories (rubber, composite or metal).

Acceptable provided no rust, corrosion or deterioration is apparent.

h. Minor surface imperfections in liner ply and reinforce-ments (Refer to paragraphs 12-2c and 12-2d and see figure 9-6).

Acceptable provided serviceability is not affected.

i. Blisters between inner laps.

1/4-inch maximum dimension; average one per 5 linear feet of splice with a maximum of five in any one 5-foot length of splice (See Figure 14-7).

j. Blisters between plies (in cell panels).

1/4-inch maximum dimension; minimum of 6-inch bond between blisters and no more than one per square foot of cell area.

k. Channels in liner laps.

1/8-inch maximum for length of lap splice.

l. Channels around entire outer edge of fitting flange.

1/8-inch maximum width around entire fitting flange (See Figure 14-4).

m. Buffing through inner liner.

Not acceptable.

n. Exposed fabric.

For fabric inner liners, acceptable provided fabric is not damaged. For rubber only inner liners, not acceptable.

o. Delamination between plies.

1-inch maximum dimension; average of one per 5 square feet of area with a maximum of five in any one 5 square feet of area. Minimum 6-inch solid bond between delaminations.

p. Cuts or holes in inner liners.

Not acceptable.

q. Porosity.

Not acceptable.

2. Cell Exterior a. Skim coat blisters.

Acceptable.

b. Lap splice edge looseness.

1/4 by 3 inch maximum dimension provided there are no more than one per linear foot and a one inch wide bond is maintained.

c. Loose or damage hanger straps or hanger attaching points.

Acceptable up to 15 percent of component area provided 1/4 inch solid bond is maintained around the edge.

d. Loose tapes, corner patches or other outside nonload carrying accessories.

1/2 inch maximum allowable looseness provided this looseness does not exceed 15 percent of the total area.

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020 00 Page 5

Table 20-1. Uninstalled Bladder Fuel Cell Defects and Acceptable Limitations - Continued Defect

Limitation

e. Skim coat off outer ply.

Acceptable provided cords or fabrics are not cut or broken.

f. Mislocated, blistered, split or weather checked rubber tape.

Unacceptable; missing or damaged tape shall be replaced.

g. Blisters or looseness between labels or decals and body of cell.

Acceptable.

h. Weather checked or surface imperfections in outer ply or reinforcements.

Acceptable provided fabric is not damaged or broken.

i. Blistered, loose or missing lacquer coating.

Acceptable.

j. Blisters between fitting flange and adjacent ply.

1/4-inch maximum dimension; maximum of one per linear foot and two per fitting provided 1 inch bond is maintained (See Figure 14-4).

k. Delamination between plies.

1-inch maximum dimension; average of one per 5 square feet of area with a maximum of five in any one 5 square foot area. Minimum 6 inch solid bond between delaminations.

l. Damaged grommets in accessories.

Acceptable provided serviceability is not affected.

m. Blisters between outer ply laps.

1/4 inch maximum dimension; average one per 5 linear feet of splice with a maximum of five in any one 5 foot length of splice.

n. Blisters between plies (in cell panels).

1/4 inch maximum dimension; minimum of 6-inch bond between blisters and no more than one per square foot of cell area.

o. Channels in outer ply laps.

1/4 inch width entire length of lap.

p. Channels around entire outer edge of fitting flange.

1/8-inch maximum around entire fitting flange (See Figure 14-4).

q. Damage through any cord or fabric ply.

Not acceptable.

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020 00 Page 6

Table 20-2. Installed Bladder Fuel Cell Defects and Acceptable Limitations Defect

Limitation

1. Cell Interior a. Loose liner at throat of fitting, except sump type and three plane fittings.

1/2 inch looseness in width around entire circumference at throat of fitting (See Figure 14-4).

a. Vertical Edge Looseness. Separation of Rubber Material (Fillet) from the vertical surface of the metal fitting.

Around the entire metal fitting is an acceptable condition for Urethane Fuel Cell (See Figure 18-1). Unacceptable for Nitrile Fuel Cells.

b. Loose liner at throat of fitting Edge looseness at liner lap.

1/2-inch looseness in width around entire circumference at edge of fitting (See Figure 14-4). Acceptable up to 1/4-inch width (depth) maximum length of liner lap, provided 1-inch bond is maintained. If fitting fabric flange is less than 1-inch in size, 100% bond must be maintained.

d. Edge looseness on liner reinforcements and chafing patches.

1/2 inch maximum looseness provided looseness does not exceed 25 percent of total area; blisters or separations other than in the edge are allowable up to 25 percent of the' total area.

e. Looseness of cemented internal support components such as attaching straps, baffle supports, etc.

Acceptable up to 25 percent of component area provided 1/4 inch solid bond is maintained around the edge (See Figure 14-5).

f. Blisters between fitting flange and adjacent ply.

1/2 inch maximum dimension; maximum two per linear foot and three per fitting provided 1-inch bond is maintained (See Figure 14-4).

g. Damaged grommets in accessories.

Acceptable provided serviceability is not affected.

h. Weather checking or minor surface imperfections in liner ply and reinforcements (refer to paragraphs 12-2c and 12-2d and see figure 9-6).

Acceptable provided serviceability is not affected.

i. Blisters between liner laps.

1/2 inch maximum dimension; maximum of five in any 5 linear feet of splice with a minimum of 6-inch bond between blisters (See Figure 14-7).

j. Blisters between plies (in cell panels).

1 inch maximum dimension; minimum of 6 inch bond between blisters and no more than one per square foot of cell area.

k. Channels in inner liner laps.

1/4-inch by 3-inch maximum dimension with a maximum of one in any 5 linear feet of splice (See Figure 14-7).

l. Channels around entire outer edge of fitting flange.

1/4-inch maximum width around entire fitting flange (See Figure 14-4).

m. Damaged coating on accessories (rubber, metal or wood).

Acceptable provided rust, corrosion or other deterioration is not apparent.

n. Exposed fabric.

Acceptable provided cords are not cut or broken.

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020 00 Page 7

Table 20-2. Installed Bladder Fuel Cell Defects and Acceptable Limitations - Continued Defect

Limitation

o. Split or damaged corner reinforcements.

Acceptable.

q. Delamination between plies.

1 1/2 inches maximum dimension; average one per 5 square feet of area with a maximum of five in any 5 square feet of area, minimum of 6-inches between delaminations.

r. Broken stiffeners or supports.

Not acceptable.

NOTE

NOTE

Only accessible portions of the cells will be inspected.

Cells need not be removed from aircraft for inspection.

2. Cell Exterior a. Skin coat blisters.

Acceptable.

b. Loose or damaged hanger straps or hanger attaching points.

Acceptable up to 20 percent of component area.

c. Loose tapes, corner patches, or other outside nonload carrying accessories.

1/2 inch allowable looseness provided this looseness does not exceed 20 percent of the total area.

d. Lap splice edge looseness.

3/8 inch by 3 inch maximum dimension provided there are no more than one per linear foot.

e. Skin coat off outer ply.

Acceptable provided cords or fabric are not broken.

f. Mislocated, blistered, split or weather checked tape.

Acceptable.

g. Blisters or looseness between labels or decals and body cell.

Acceptable.

h. Weather checked or surface imperfections in outer ply or reinforcements.

Acceptable.

i. Blistered, loose or missing lacquer coating.

Acceptable.

j. Damaged grommets in accessories.

Acceptable provided serviceability is not affected.

k. Damage through any cord or fabric ply.

Not acceptable.

l. Delamination between plies.

1 1/2 inches maximum dimension; average one per 5 square feet of area with a maximum of five in any 5 square feet. Minimum of 6-inches between delaminations.

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Table 20-2. Installed Bladder Fuel Cell Defects and Acceptable Limitations - Continued Defect

Limitation

m. Blisters between fitting flange and adjacent ply.

1/2 inch maximum dimension with a maximum of two per linear foot and three per fitting, provided 1-inch bond is maintained (See Figure 14-4).

n. Blisters between outer ply laps.

1/2 inch maximum dimension; average two per 5 linear feet of splice with a maximum of five in any one 5-foot length of splice.

o. Blisters between plies (in cell panels).

1 inch maximum dimension with a minimum of 6-inches between blisters and no more than one per square foot of cell area.

p. Channels in outer ply laps.

1/4 inch by 3-inch maximum dimension with a maximum of one in any 5 linear feet of splice.

q. Channels around entire edge of fitting flange.

1/4 inch maximum width around entire fitting flange (See Figure 14-4).

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Page 1 of 16

MAINTENANCE INSTRUCTIONS REPAIR OF NON-SELF SEALING (BLADDER) FUEL CELLS

Reference Material None

Alphabetical Index Subject

Page

Alternative Repair Methods ..........................................................................................................................................................5 Air-Cure Bonding Method.................................................................................................................................................6 Blister Repair......................................................................................................................................................................9 Corner Patch Repair ...........................................................................................................................................................8 Double Patch Repair ..........................................................................................................................................................7 Excessive Damage Repair................................................................................................................................................14 Filler Plug Repair Limitations ...........................................................................................................................................9 Filler Plug Repair Method .................................................................................................................................................9 Hot-Cure Bonding Method ................................................................................................................................................7 Inside Corner Patch Repair ................................................................................................................................................9 Inside Repair Patch Procedures .........................................................................................................................................5 Loose Seam Patch Repair ..................................................................................................................................................9 Outside Corner Patch Repair .............................................................................................................................................9 Outside Patch Repair..........................................................................................................................................................8 Plug Build-Up Repair Method.........................................................................................................................................12 General...........................................................................................................................................................................................1 Nitrile (BUNA-N) Synthetic Rubber Bladder Fuel Cell Repair ..................................................................................................2 Fuel Cell Repair Preparation..............................................................................................................................................2 Nitrile (Buna-N) Synthetic Rubber Fuel Cell Repair Limitations ....................................................................................2 Quick Cure Repair Method ...........................................................................................................................................................3 Repair of Abraded or Missing Top Coat ...........................................................................................................................3 Repair of Holes, Punctures, Cuts, and Tears .....................................................................................................................3 1. GENERAL. This section provides instructions for the repair of regular construction non-self sealing (bladder) fuel cells. Repair of polyurethane non-self sealing fuel cells is covered in WP 018 and 019. Organizational and Intermediate level Maintenance Activities are authorized to repair fuel cell punctures, rips or tears that are 1 inch in length or less provided such damage is not within 2 inches of a fuel cell fitting. Additionally, touchup of abraded exterior protective coating is authorized.

NOTE The following warning appears many times in this chapter:

When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell. The use of the air-supplied respirator or SCBA is required when working inside cells installed in an aircraft. If the cells have been removed

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from the aircraft and are being worked in a shop environment, then the use of a half-face respirator with a cartridge appropriate to the hazard is a suitable alternative to the use of an air supplied respirator. 2. NITRILE (BUNA-N) SYNTHETIC RUBBER BLADDER FUEL CELL REPAIR. Nitrile (Buna-N) synthetic rubber bladder fuel cell repair procedures are provided in the following paragraphs. a. FUEL CELL REPAIR PREPARATION. Fuel cells shall be drained, cleaned and thoroughly air dried as soon as possible after detection of a leak (refer to Work Package 006). To ensure proper bonding of fuel cell repairs, the repair area should have an ambient temperature of 65oF (18oC) to 90oF (32oC) with a maximum of 65% relative humidity. High humidity, especially in combination with a low temperature, will cause condensation to form on the fuel cell surface and prevent the proper bonding of repair patches. When desired environmental conditions are not available fuel cell repair should be accomplished in existing shop environment. To prepare fuel cells for repair, refer to Work Package 015 and proceed as follows:

Acetone ASTM D329

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(3) Wipe area to be bonded with cheesecloth CCCC-440, moistened with Acetone, ASTM D329.

NOTE Repair materials should be prepared in a warm, heated area (radiators are a good source). (4) Allow vapors to dissipate. (5) Apply adhesive immediately. (6) Dampen adhesive on repair area and adhesive on patch material with Acetone, ASTM D329. (7) Allow vapors to dissipate. (8) Apply patch material immediately. (9) Stitch to ensure proper bond. (10) Inspect for proper bonding following the application of each layer of repair material. (11) Correct discrepancies as required using standard repair procedures (Refer to Work Package 015).

Comply with general safety instructions in Work Package 004, and fuel cell entry preparations in Work Package 006.

(12) Remove bad areas and rework as required. (13) Inspect for proper bonding.

When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell.

b. NITRILE (BUNA-N) SYNTHETIC RUBBER FUEL CELL REPAIR LIMITATIONS. The following is a general list of repair limitations for nitrite (BUNA-N) synthetic rubber bladders:

(1) Inspect for condensation on fuel cell surface.

(1) Inside patches shall be at least 1 1/2 inches larger than damaged area in each direction.

NOTE If conditions are such that condensation is excessive and the reliability of any repair would be questionable, delay adhesive repairs until favorable environmental conditions exist. (2) If condensation exists, use exhaust air ducts or air movers to create a flow of air across the surface of the area to be repaired.

(2) Pin hole leaks require an inside patch only. (3) Outside patches shall be at least 2 inches larger than the damaged area. (4) Damage, such as punctures, cuts or tears, requires both an inside and outside patch. (5) Damage over 2 inches shall require a double patch; the top patch shall overlap the first patch by 1 inch in all directions.

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(6) External damage confined to a single ply in a three ply area requires an outside cover patch only.

(2) Clean abraded area with cheesecloth, CCC-C440, moistened with Acetone, ASTM D329.

(7) A loose lap may be trimmed provided that a 1inch effective bond remains. (8) Hot repair patches can be inspected, air tested, installed and fueled as soon as repair is cooled to ambient temperature. (9) Cold repair patches may be inspected after air curing for 24 hours. (10) Cold repair patches must air cure for 72 hours before exposure to fuel.

Isocyanate exposure may produce severe allergic reaction and permanent sensitization. Persons with history of allergies or previous sensitization shall not be assigned tasks involving isocyanates. Personal protective equipment for skin and eyes and proper respiratory protection (BUMEDINST 6260.16) shall be required when polyurethane coatings or adhesives are used for fuel cell repairs.

(11) Outside patches, when required, are to be applied and cured prior to installing inside patches. 3. QUICK CURE REPAIR METHOD. The quick cure repair method is the primary method for repairing bladder fuel cells and is intended for repairing cells with minor damage. This repair may be accomplished without removing the cell from the aircraft if the damage is accessible for repairs. Damage that can be repaired is listed in Table 20-1 and 20-2 of Work Package 020.

Do not apply hot-cure methods on repairs requiring 82C32 adhesive.

NOTE

Comply with general safety instructions in Work Package 004, and fuel cell entry preparations in Work Package 006. When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell. a. REPAIR OF ABRADED OR MISSING TOP COAT. To repair abraded or missing top coat with no fabric ply damage using the quick-cure method, proceed as follows: (1) Abrade surface adjacent to the damaged area.

Acetone ASTM D329

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The adhesive, 82C32, has a usable life of 15 to 45 minutes after mixing. Recapping the adhesive between applications aids in extending the usable life. (2) Mix the quick cure adhesive (Refer to Work Package 015) as follows: Pour part 2 into the container of part 1 and mix thoroughly for 5 minutes. (3) Carefully and uniformly brush two coats of repair adhesive over the buffed area. (4) Apply the second coat 90o to the application of the first coat. (5) Allow the finished repair to air cure for 6 hours. b. REPAIR OF HOLES, PUNCTURES, CUTS, AND TEARS. To repair holes, punctures, cuts, and tears, using the quick-cure method, proceed as follows:

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Acetone ASTM D329

7

When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell. (1) Clean the inside surface of the cell with cheesecloth, CCC-C-440, moistened with acetone, ASTM D329, approximately 12 inches beyond the damage in all directions.

NOTE When the repair is being made with the cell still installed in the aircraft, only an inside patch is required. (2) Determine the size of the patches required. (The inside patch size must extend beyond the damaged area at least 1 inch in all directions.)

Only materials specified for use in the following procedures shall be used to repair Goodyear Vithane bladder fuel cells. Substitutions shall not be made.

Isocyanate exposure may produce severe allergic reaction and permanent sensitization. Persons with history of allergies or previous sensitization shall not be assigned tasks involving isocyanates. Personal protective equipment for skin and eyes and proper respiratory protection (BUMEDINST 6260.16) shall be required when polyurethane coatings or adhesives are used for fuel cell repairs. (6) Mix the adhesive, 82C32, (Refer to Table 15-6, usage column 11) for the repair in accordance with paragraph 2a(3).

NOTE Due to short work life, fresh adhesive should be mixed when adhesive becomes thick and unbrushable. Recapping the adhesive between the applications will aid in extending the work life of the adhesive. (7) Apply one brush coat of adhesive to the clean abraded areas; let dry for 15 minutes. (8) Apply second brush coat of adhesive and let dry 15 minutes.

Acetone ASTM D329

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(9) Apply third coat of adhesive. Dip fabric patch, 3604N, in Acetone, ASTM D329 and shake out the excess solvent.

(3) Cut an inside patch from the repair material, 3604N (Refer to Work Package 015, Table 15-3). (The patch must have a rounded outline.)

(10) While the third coat of adhesive is still wet, lay the nylon fabric patch, 3604N, in the wet cement and smooth out with a brush removing all entrapped air.

(4) Center the patch over the defect and mark the cell surface 1/2 inch beyond the patch in all directions.

(11) Apply a final coat of adhesive over the 3604N fabric patch.

(5) Lightly abrade the cell surface surrounding the damage as marked with 120 grit abrasive cloth, P-C-451, moistened with Acetone, ASTM D329.

(12) Allow repair to cure for 6 hours at a minimum temperature of 70ºF (21ºC). (Aircraft may be refueled after 6 hours of curing.)

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4. ALTERNATIVE REPAIR METHODS Alternative repair methods may be used if the conditions for using the quick cure method, described in paragraph 3, is not appropriate or the materials are not available.

Only experienced personnel should use power buffers. Power buffing may produce a polished surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand.

a. INSIDE REPAIR PATCH PROCEDURES. To apply inside repair patches, proceed as follows:

NOTE Buffing and grinding should be conducted in exhaust ventilated booths having a minimum face velocity of 200 linear feet per minute.

Comply with general safety instructions in Work Package 004, and fuel cell entry preparations in Work Package 006.

(2) Buff area to be repaired 1 3/4 inches in all directions from the edge of the damaged area with 120 grit emery cloth Remove surface gloss only, leaving the surface covered with fine scratches.

When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell.

Acetone ASTM D329

7

(1) Support the cell in the area around the damage so that the edges will be in line in their natural position. When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell. When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations. Do not buff the nylon barrier side of the inner liner material. Fuel diffusion will occur if barrier is broken.

Buffing must be heavy enough to remove all gloss, leaving the surface covered with fine scratches. However, care must be exercised to assure that the nylon barrier is not damaged during the buffing operation.

(3) After buffing, dust off the surface and clean the buffed area with cheesecloth, CCC-C-440 moistened with Acetone, ASTM D329. Do not soak the buffed area. (4) Clean lightly until all grit and buffing dust is removed.

NOTE The patch must have a rounded outline and edges skived (beveled) or cut at an angle by tilting the shears or skiving knife instead of cutting straight (See Figure 15-4). (5) Cut a patch from repair material, to extend 1 1/2 inches in all directions from the edge of the damage. (6) Hand buff the side of the repair patch that will be bonded to the fuel cell using 120-grit abrasive cloth, PC-451.

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b. AIR-CURE BONDING METHOD. To bond the repair patch to the fuel cell using the air-cure method, proceed as follows:

Acetone ASTM D329

7

reached the proper stage of tackiness as air bubbles or blisters may form under the patch. If the adhesive has reached the proper stage before the patch is applied, there will be no skidding or sliding of the patch immediately after application. (8) Apply patch immediately after third coat of adhesive is tacky to touch, using knuckle test. (9) Center the patch over the area and roll down firmly with a 1/4-inch hand roller starting from the center of the patch and working to the outer edges. (This will help to prevent trapped air or a blistered condition.)

Comply with general safety instructions in Work Package 004, and fuel cell entry preparations in Work Package 006. When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell. (1) Clean the buffed area of the cell and the repair patch using cheesecloth, CCC-C-440, moistened with Acetone, ASTM D329. (2) Immediately after the buffed areas are dry, apply a thin coat of adhesive (Refer to Table 15-4, usage column 1 or 2) to the fuel cell and to the patch. (3) When the first coat has completely dried (approximately 30 minutes) apply another coat of adhesive to both the cell and the patch and let dry completely. (4) Apply a third coat and allow it to become tacky before placing the coated surfaces together.

(10) Remove trapped air blisters by using a looped wire wet with Acetone, ASTM D329. (11) Snake the looped wire under patch to blister. (12) Close opening created between cell and patch with finger pressure behind loop as wire is slowly withdrawn. (13) Roll patch down firmly. (14) If blisters cannot be removed or poor adhesion is evident in the patch, remove patch. (15) Remove the adhesive on the cell and patch using a piece of cheesecloth moistened with Acetone, ASTM D329 and rub briskly over the adhesive-coated surface. (16) After the solvent has completely evaporated and the area dried (approximately one hour), start the repair over again.

(5) If the third coat dries out before the coated surfaces can be placed together, activate by wiping the adhesive-coated surfaces with cheesecloth moistened with Acetone, ASTM D329 to effect a tacky condition. (6) To determine if the adhesive is tacky, test by pressing a knuckle gently against the coated surface and withdrawing it. This is known as the knuckle test (See Figure 9-10). (7) If a few threads of adhesive stick to the knuckle, the adhesive is ready and the patch can be installed.

Do not apply the patch before the adhesive has

Fuel cell patches should air-cure a minimum of 72 hours prior to installation or being subjected to fuel. Do not flex the repaired area for the first 24-hour period. Do not place a repaired cell in any type of heating chamber to accelerate curing; such action will cause the cell to deteriorate and shrink beyond safe dimensions. (17) Apply pressure to the patch during the cure cycle by one of the following methods: (a) Clamping: Place a metal or wooden platten over the patch and apply pressure by clamping the platten in place using regular shop C-clamps.

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(b) Weighting: When the configuration of the cell, or the location of the patch make it difficult or impossible to use clamps, weight may be applied to the patch area using bags of shot. (c) Vacuum Bagging: After the adhesive has been applied and the patch is positioned and properly stitched down, lay a piece of peel ply material (Table 2-5, Item 12u) over the patch and extending 1 to 2 inches in all directions beyond the edge of the patch. Place 2 or 3 layers of breather material (Table 2-5, Item 12v), over the repair area. Surround the area with vacuum bagging tape (Table 2-5, Item 11d), cover the area with vacuum bagging film (Table 2-5, Item 12w), and attach vacuum hose connections (Table 2-5, Item 12x). Obtain a vacuum of at least 25 inches Hg and cure according to adhesive specifications. (18) After two hours, remove plates and clamps and check for patch looseness.

Adhesive MIL-PRF-9117

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(19) Seal the patch edge with two coats of adhesive, MIL-PRF-9117.

aluminum alloy or steel backup plate on the opposite surface of the cell wall. 2 Place a sheet of Holland cloth, MIL-C17564, or equivalent, between the plates and the cell. 3 Apply a heating unit to the plate covering the patch and secure with a C-clamp.

o

4

Tighten until firm. Do not distort the cell.

5

Apply heat for one hour at 285oF to 295oF

(143 C). (b) Vacuum Bagging: Lay a piece of peel ply material (Table 2-5, Item 12u), over the patch and extending 1 to 2 inches in all directions beyond the edge of the patch. If a heated cure is being used, place a heat blanket over the peel ply with a thermocouple underneath the peel ply and near the center of the patch. Next, place 2 or 3 layers of breather material (Table 2-5, Item 12v), over the repair area. Surround the area with vacuum bagging tape (Table 2-5, Item 11d), cover the area with vacuum bagging film (Table 2-5, Item 12w), and attach vacuum hose connections (Table 2-5, Item 12x). Obtain vacuum of at least 25 inches Hg and cure according to adhesive specifications.

(20) Allow to dry completely. c. HOT-CURE BONDING METHOD. The hot-cure (vulcanized) method of applying a cover patch is the same as the air-cure method except for the adhesive (Refer to Table 15-4, usage column 4) and the curing cycle. For this method, proceed as follows:

Comply with general safety instructions in Work Package 004, and fuel cell entry preparations in Work Package 006.

If clamps and platens used in the vulcanization process are disassembled from the patches before room temperature is reached, the bonded patch material will not cure flat but will assume a permanent set conforming to the shape in its relaxed position. (2) Allow the unit to cool to room temperature before removing the C-clamp and plates.

When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell.

(3) Apply two coats of adhesive (Refer to Table 96, usage column 8) to seal the patch skived edge.

(1) When the prepared patch has been placed in position and stitched in place, apply pressure and heat to the repair in one of the following ways:

(5) When the edge coats of adhesive have dried, the fuel cell can be flexed, tested, inspected and installed without affecting the repair. Upon completion of the vulcanization process, the repair patch is considered fully cured, except for the edge coating.

(a) Clamping: 1 Locate a 1/8 to 1/4 inch aluminum alloy or steel plate over the patch and place a rubber-padded

(4) Allow adhesive to dry completely.

d. DOUBLE PATCH REPAIR. A double patch repair is required when damage through the cell is over two

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inches in length. To apply the double patch repair, proceed as follows:

e. CORNER PATCH REPAIR. Corner patching and some internal edge patching necessitate separate ply buildup. Refer to Work Package 015. e. OUTSIDE PATCH REPAIR. To apply outside repair patches, proceed as follows:

Comply with general safety instructions in Work Package 004, and fuel cell entry preparations in Work Package 006. When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell. When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations.

NOTE Wooden blocks or boards may be used as a means of support and should be padded and covered with cloth to protect the liner from damage (See Figure 15-2). (1) Support the fuel cell in the area to which repairs will be made.

Do not buff the nylon barrier side of the inner liner material. Fuel diffusion will occur if barrier is broken. Buffing must be heavy enough to remove all gloss, leaving the surface covered with fine scratches. However, care must be exercised to assure that the nylon barrier is not damaged during the buffing operation. Only experienced personnel should use power buffers. Power buffing may produce a polished surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand.

NOTE

(2) Buff an area on the outside of the cell extending 1 3/4 inches in all directions from the edge of the damaged area.

NOTE Damage more than two inches in length or diameter require a double patch (Refer to Work Package 015).

The double patch may be prefabricated on a workbench and installed in the fuel cell in one operation rather than by a separate ply build-up. This method simplifies application technique and is preferred for flat surface repairs.

(3) For double patch, buff 2 3/4 inches in all directions to allow the proper application of a second patch.

(1) Buff the inner liner of the fuel cell 2 3/4 inches in all directions from the edge of the damaged area.

For applicable repair material, refer to Work Package 015

(2) Prepare the plies of the double patch as specified in Work Package 015. (3) Use repair materials specified in Work Package 015 for bladder cell repair.

NOTE

(4) Cut the round or oval patch or patches of repair material large enough to extend beyond the edges of the damage 1 1/2 inches for the first patch and 2 1/2 inches for the second patch.

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Acetone ASTM D329

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(5) Clean the buffed surfaces of the cell and patch with cheesecloth, CCC-C-440, moistened with Acetone, ASTM D329. (6) Apply three coats of adhesive (Refer to Table 96, usage column 1 or 2) to each surface, allowing each coat to dry completely before applying the next coat. (7) Allow the third coat to dry tacky. (8) If the third coat is completely dry, wipe the patch and cell with cheesecloth moistened with Acetone, ASTM D329 solvent to produce a tacky condition on both coated areas. (9) Center the patch over the damaged area and roll down starting from the center of the patch and working out, being careful to remove all trapped air.

Adhesive MIL-PRF-9117

BLISTER REPAIR. An inner liner blister is

caused by air, fuel vapor or fuel trapped between the liner and the outer ply, and is often mistaken for separation of plies. Ply separation is the loss of adhesion between successive layers. Repair blisters the same way as selfsealing cells except that bladder cell repair materials are used. Blisters under one inch in diameter are not considered damaged and need not be repaired. Refer to Work Package 015 for materials and repair procedures. i. LOOSE SEAM PATCH REPAIR. Loose lap seams on the inside of the cell should be repaired, as soon as they are noticed, to prevent the separation from spreading. Repair is the same as that for self-sealing cells except that bladder cell materials are used. Refer to Work Package 015 for materials and repair procedures. j. FILLER PLUG REPAIR LIMITATIONS. Structural integrity of fuel cells in repaired areas must be maintained. This is particularly important since damaged areas may result from repeated poking by instruments, structures or other objects. Some damaged conditions may be repaired with filler plugs. The following is a list of limitations and guidelines for filler plug repairs. (1) Use a single patch to repair damage when damage is limited to the inner liner.

8

(10) After 2 hours room temperature cure, seal the edges of the patch with two coats of adhesive, MIL-PRF9117. (11) Allow 8 to 10 hours curing time. (12) Apply two coats of buna vinylite lacquer, which contains organic solvent, on the patch and edge area, allowing each coat to dry. f. INSIDE CORNER PATCH REPAIR. Inside corner repairs require a double (2-layer) patch. To prevent wrinkling or stretching the repair material, these patches must be cone-shaped and must fit accurately into the corner. Apply the inside corner patch repair for bladder cells in the same manner as for self-sealing cells except use the repair material for bladder cells. Refer to Work Package 015 for materials and repair procedures. g. OUTSIDE CORNER PATCH REPAIR. The outside corner patch repairs for bladder cells are the same as for self-sealing cells except that bladder cell repair materials are used. Refer to Work Package 015 for materials and repair procedures.

(2) Use a double patch (interior and exterior) to repair cell wall damage. (3) Replace with undamaged material those injuries such as tears, rips, cuts, cracks and punctures, which have penetrated through the cell wall. (4) Use a double patch (interior and exterior) to repair damage to cell walls when damage is limited to the edge of the injury. (5) Use a filler plug made from vulcanization stock or a built-up plug to repair damage of one inch diameter or less when material removal is required (See Figure 21-1). (6) Use a built-up plug to repair damage over one inch in diameter when material removal is required. This type of plug is made by laminating approved repair materials together, which closely duplicate the original construction (See Figure 12-2). k. FILLER PLUG REPAIR METHOD. To apply the filler plug repair method, proceed as follows:

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Buffing must be heavy enough to remove all gloss, leaving the surface covered with fine scratches. However, care must be exercised to assure that the nylon barrier is not damaged during the buffing operation.

Figure 21-1. Repairing Filler Plug Up to One Inch Diameter

Only experienced personnel should use power buffers. Power buffing may produce a polished surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand. (2) Buff the area of the inner liner extending from the circle outward for a distance of 1 3/4 inches.

Comply with general safety instructions in Work Package 004, and fuel cell entry preparations in Work Package 006. When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell. (1) Mark a circle with a white marking pencil, SSP-00196, around the damaged area on the inside of the fuel cell. (Draw the circle large enough to include all damaged cord plies and ragged edges.)

NOTE A template may be used as a guide if desired. A punch may also be used provided a backup block is held in position to support the cell. (3) Using the circle as a guide, cut away the damaged fuel cell material with a knife blade held at right angles to the cell wall. (4) When the hole is not punched out but cut only by knife, bevel-cut the edge of the hole. (This results in a shallow bevel of about 30 degrees and provides adhesion surface.)

When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations. Do not buff the nylon barrier side of the inner liner material. Fuel diffusion will occur if barrier is broken.

Figure 21-2. Repairing Filler Plug Over One Inch Diameter

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021 00 Page 11 (11) Cut a plug slightly larger in diameter than the cutout of the damaged area.

Buffing must be heavy enough to remove all gloss, leaving the surface covered with fine scratches. However, care must be exercised to assure that the nylon barrier is not damaged during the buffing operation. Only experienced personnel should use power buffers. Power buffing may produce a polished surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand. (5) Buff the outer ply to 1 3/4 inches beyond the edge of the hole. (6) Prepare an inside patch to extend 1 1/2 inches beyond the hole.

(12) Trim to fit from the outside of the fuel cell.

NOTE Rotation and careful alignment of the plug are required to assure proper fit. The interior patch that has been applied to the fuel cell provides a base to support the plug during fitting and installation. (13) When the cell damage has been punched out, the filler plug may also be punched out to the same size and fitted in place. (Material from a scrap cell may be used, new material laminated, or vulcanizing stock stitched and cured in place.) (14) When the plug has been properly prepared and fitted, clean with cheesecloth moistened with Acetone, ASTM D329, and apply three coats of adhesive to the edge and base to the plug and the fuel cell cavity. (15) When the adhesive becomes tacky, knuckle test and install the plug.

Acetone ASTM D329

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(7) Clean with cheesecloth, CCC-C-440, moistened with Acetone, ASTM D329, and apply three coats of adhesive (Refer to Table 15-4, usage column 1 or 2) to the buffed inner liner of the fuel cell patch. (8) When proper tackiness is obtained, center the patch over the damaged area and stitch in place.

Adhesive MIL-PRF-9117

8

(16) Stitch firmly in place and apply clamp support. (17) Allow two hours drying time.

NOTE If vulcanization stock is used, cure at 290oF (143oC) for one hour. Use 1/8 to 1/4 inch aluminum alloy or steel plates and clamp. (18) Remove clamps and inspect for any defects. (All defects must be corrected before applying the exterior patch.)

(9) When completely dry, seal patch and edge with two coats of adhesive, MIL-PRF-9117. (10) Allow adhesive to dry thoroughly.

NOTE Before installing the filter plug or the outside patch, provide support for the cell interior under the area to be repaired. Wooden blocks and boards used inside cells should be padded or covered with cloth and sponge rubber to protect the inner liner from damage (See Figure 15-2).

When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations. Do not buff the nylon barrier side of the inner liner material. Fuel diffusion will occur if barrier is broken.

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Buffing must be heavy enough to remove all gloss, leaving the surface covered with fine scratches. However, care must be exercised to assure that the nylon barrier is not damaged during the buffing operation. Only experienced personnel should use power buffers. Power buffing may produce a polished surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand. (19) Lightly buff the exposed surface of the plug to provide a good base for the patch and to ensure that the edges are flush with the adjacent retainer outer ply surface. (20) Cut an exterior patch large enough to lap the plug 1 1/2 inches all around.

Acetone ASTM D329

If clamps and plates used in the vulcanization process are disassembled from the patches before room temperature is reached, the bonded patch material will not cure flat but take on a permanent set conforming to the shape in its relaxed position. (27) defects.

Remove clamps and inspect for

Adhesive MIL-PRF-9117

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(28) Apply two coats of adhesive, MIL-PRF-9117, around the edges of the patch.

7

(21) Clean the surface with cheesecloth moistened with Acetone, ASTM D329 prior to the bonding operations.

(23) Allow proper drying time between coats. Check tackiness by the knuckle test.

Fuel cell patches should air-cure a minimum of 72 hours prior to installation or being subjected to fuel. Do not flex the repaired area for the first 24-hour period. Do not place a repaired cell in any type of heating chamber to accelerate curing; such action will cause the cell to deteriorate and shrink beyond safe dimensions.

(24) At the same time, coat the patch with three coats of adhesive. Allow each coat to dry before applying the next coat.

(29) Allow 72 hours drying time after completion of the repair before exposure to fuel.

(22) Apply three coats of adhesive to the prepared outer surface.

(25) When the third coat becomes tacky, position the patch in place and stitch down firmly.

NOTE Patches that are over 8 inches in diameter can be applied with better control if a liner of Holland cloth, MIL-C-17564, or equivalent, is used between the coated patch and the coated area of the fuel cell. This separation sheet shall be removed as the patch is stitched down. (26) Apply sponge-covered plates to the surface and clamp for 8 to 10 hours.

(30) If vulcanization method is used, apply three coats of vulcanizing adhesive (Refer to Table 15-4, usage column 4) and cure at 290oF (143oC) for one hour while under clamp or platen pressure. (31) Allow the bonded patches and clamping tools to return to room temperature before disassembly. l. PLUG BUILD-UP REPAIR METHOD. To apply the plug build-up repair method proceed as follows: (1) Cut as many patches of repair material as there are layers in the damaged area. Use repair material comparable in thickness to the material in the damaged area.

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021 00 Page 13 (5) If vulcanization method is used, apply adhesive and vulcanize at 290oF (143oC) for 1 hour.

Acetone ASTM D329

NOTE

7

It is necessary that either the interior or the exterior patch be applied first to provide a base to support the plug during fitting and installation. Comply with general safety instructions in Work Package 004, and fuel cell entry preparations in Work Package 006. When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell. When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations. Do not buff the nylon barrier side of the inner liner material. Fuel diffusion will occur if barrier is broken.

(6) Trim the buildup plug to fit the prepared hole in the fuel cell.

NOTE Do not apply the patch before the adhesive has reached the proper stage of tackiness; air bubbles or blisters may form under the patch. If the adhesive has reached the proper stage before the patch is applied, there will be no skidding or sliding of the patch immediately after application. (7) Rotation and careful alignment of the patch is required to assure proper fit.

Adhesive MIL-PRF-9117

8

(8) When the plug has been prepared and fitted properly, apply three coats of adhesive, MIL-PRF-9117, to the edge and base of the plug and the fuel cell cavity. Buffing must be heavy enough to remove all gloss, leaving the surface covered with fine scratches. However, care must be exercised to assure that the nylon barrier is not damaged during the buffing operation. Only experienced personnel should use power buffers. Power buffing may produce a polished surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand. (2) Buff, clean with cheesecloth, CCC-C-440, moistened with Acetone, ASTM D329, and apply three coats of adhesive to each layer (Refer to Table 15-4, usage column 1 and 2). (3) Allow the third adhesive coat to become tacky and apply each layer separately, stitching down each layer thoroughly. (4) Bond the layers of coated fabric and inner liner together, clamp, and allow 8 to 10 hours cure.

(9) When the adhesive becomes tacky, knuckle test and install the plug. (10) Stitch firmly in place and apply clamps. (11) Allow 2 hours drying time.

If clamps and platens used in the vulcanization process are. disassembled from the patches before room temperature is reached, the bonded patch material will not cure flat but will assume a permanent set conforming to the shape in its relaxed position. (12) Remove clamps and inspect for any defects. (All defects must be corrected before applying the remaining reinforcement patch.)

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021 00 Page 14 m. EXCESSIVE DAMAGE REPAIR. When the original damage exceeds two inches in length or diameter, proceed as follows:

When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations. Do not buff the nylon barrier side of the inner liner material. Fuel diffusion will occur if barrier is broken.

Buffing must be heavy enough to remove all gloss, leaving the surface covered with fine scratches. However, care must be exercised to assure that the nylon barrier is not damaged during the buffing operation. Only experienced personnel should use power buffers. Power buffing may produce a polished surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand. (13) Lightly buff the exposed surface of the plug to provide a good base for the patch and to ensure that the edges are flush with the adjacent surface. (14) Bond the layers and patches together using three coats of adhesive on each surface. (15) Allow 8 to 10 hours cure. (16) If the vulcanization method is used, apply adhesive and vulcanize at 290oF (143oC) for 1 hour.

Comply with general safety instructions in Work Package 004, and fuel cell entry preparations in Work Package 006. When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell. (1) Prepare the double patches require separately and install as described in Work Package 015, or apply each layer separately to fuel cell. (2) The fuel cell will require additional buffing to accommodate the second patch.

Acetone ASTM D329

7

(3) When only one layer of the fuel cell is separated, repair by buffing and cleaning with cheesecloth, CCC-C-440, moistened with Acetone, ASTM D329 and apply adhesive (Refer to Table 15-4, usage columns 1 and 2). (4) Apply three coats to each surface, allowing each coat to dry before applying the next coat. (5) When the last coat becomes tacky, press the two surfaces together, stitch and clamp in place. (6) Allow 8 to 10 hours drying time.

Fuel cell patches should air-cure a minimum of 72 hours prior to installation or being subjected to fuel. Do not flex the repaired area for the first 24-hour period. Do not place a repaired cell in any type of heating chamber to accelerate curing; such action will cause the cell to deteriorate and shrink beyond safe dimensions. (17) Apply three coats of adhesive around the edges of the patches and allow 72 hour lapse time before exposure to fuel.

(7) After buffing the outside surface 1 3/4 inches in all directions from the separation, apply a patch over the repaired area.

When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the

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021 00 Page 15(16 Blank)

exposure. Always wear eye protection when engaged in buffing operations. Do not buff the nylon barrier side of the inner liner material. Fuel diffusion will occur if barrier is broken.

Buffing must be heavy enough to remove all gloss, leaving the surface covered with fine scratches. However, care must be exercised to

assure that the nylon barrier is not damaged during the buffing operation. Only experienced personnel should use power buffers. Power buffing may produce a polished surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand. (8) Buff the patch on one side, skive it and cut it to a size 1 1/2 inches larger in all directions than the separation. (9) Repeat steps (10) through (13).

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022 00

31 August 2005

Page 1 of 12 MAINTENANCE INSTRUCTIONS NON-SELF SEALING (BLADDER) FUEL CELL FITTINGS

Reference Material None

Alphabetical Index Subject

Page

General...........................................................................................................................................................................................1 Nonself-Sealing Fuel Cell Fitting Designs........................................................................................................................1 Nonself-Sealing Fuel Cell Fitting Evaluation ...................................................................................................................2 Nonself-Sealing Fuel Cell Fitting Replacement...........................................................................................................................2 Damaged Nonself-Sealing Fuel Cell Fitting .....................................................................................................................2 Metal Reinforcement Ring.................................................................................................................................................4 Nonself-Sealing Fuel Cell Fitting Installation...................................................................................................................5 Nonself-Sealing Fuel Cell Fitting Installation – New Location .......................................................................................7 Nonself-Sealing Fuel Cell Fitting Removal ......................................................................................................................4 Nonself-Sealing Fuel Cell Fitting Repair .....................................................................................................................................8 Compression-Type Nonself-Sealing Fuel Cell Fitting Damage Repair ...........................................................................8 Fabric Tears, Abrasion, and Surface Defects ..................................................................................................................10 Fitting Insert Replacement...............................................................................................................................................11 Molded Nonself-Sealing Fuel Cell Fitting Face Repair....................................................................................................8 Nonself-Sealing Fuel Cell Fitting Flange Crack Repair ...................................................................................................8 Nonself-Sealing Fuel Cell Fitting Flange Cracks..............................................................................................................8 O-Ring Fitting Replacement and Repair .........................................................................................................................11 Repair of Torn or Elongated Bolt Holes in Nonself-Sealing Fuel Cell Fittings...............................................................9

1. GENERAL. This section provides instructions for evaluating damage to non-self-sealing fuel cell fittings. Additionally, it contains repair and replacement techniques, materials, and procedures.

NOTE The following warning appears many times in this chapter:

When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell.

The use of the air-supplied respirator or SCBA is required when working inside cells installed in an aircraft. If the cells have been removed from the aircraft and are being worked in a shop environment, then the use of a half-face respirator with a cartridge appropriate to the hazard is a suitable alternative to the use of an air supplied respirator. a. Nonself-Sealing Fuel Cell Fitting Designs. There is a variety of different types of fitting and fitting designs that are used in fuel cell construction. On non-self-sealing fuel cell constructions there are rubber-molded fittings with single or double flanges. Fittings may be provided with

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022 00 Page 2

O-ring sealing grooves, exposed metal sealing surfaces, rubber molded sealing surfaces, or some combination of these. (1) Interchangeable fittings. Each fuel cell manufacturer has fittings designed to fit a specific fuel cell structure and perform an interconnector function for internal and external components. Although some fuel cell fittings are interchangeable between manufacturers, a verification of this fact is needed before any repair substitution is made. b. Nonself-Sealing Fuel Cell Fitting Evaluation. Fuel cell fittings should be reevaluated at the same time that the fuel cell structure is being examined. However, there are occasions when a fitting alone is suspect in fuel leaks and should be inspected separately. Close inspection of fuel cell fittings is necessary due to potential fuel leaks resulting from damage to the fitting sealing surfaces and improper installation of connecting plumbing and fuel components. Table 22-1 should be used as an aid in the evaluation of fuel cell fittings.

NOTE Fittings and connections should not be disturbed for inspection unless leakage is suspected. 2. NONSELF-SEALING FUEL CELL FITTING REPLACEMENT. This section describes the procedures for the replacement of several types of fittings considered typical. Other fitting replacements not specifically covered can be accomplished using the same principles contained in this section. When replacing fuel cell fittings, the following guidelines should be observed:

Comply with general safety instructions in Work Package 004, and fuel cell entry preparations in Work Package 006. When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell.

Whenever possible, a replacement fitting should be of the same type as the fitting that was removed from the cell. Relocation of fitting openings requires a great deal of skill and experience. This should not be attempted unless a locating template is used or accurate measuring can be achieved by layout method. Whenever the inspection process has determined that replacement of a fitting is required, the fuel cell shall be cleaned and supported by bracing of the structure internally (See Figure 15-2). a. Damaged Nonself-Sealing Fuel Cell Fittings. When cell fittings are damaged or deteriorated, the cell should be removed from the aircraft as soon as possible and the fitting replaced or another cell installed.

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022 00 Page 3

Table 22-1. Nonself-Sealing (Bladder) Fuel Cell Fitting, Defect Evaluation Defect

Limitation

1. Rubber Face Fittings. a. Gouges, splits or indentations on the sealing surface.

1/16-inch maximum depth by 1/16-inch maximum length.

b. Weather checking of surfaces other than sealing surface.

Acceptable.

2. O-Ring Fittings. a. Sealing surface without groove: (1) Scratches within the sealing area.

Not acceptable (See Figure 16-1.)

(2) Burrs on mating surface.

Not acceptable (See Figure 16-1.)

(3) Corrosion.

Not acceptable.

b. Sealing surface with groove: (1) Minor surface damage outside O-ring groove other than rust, corrosion or burrs.

Acceptable (See Figure 16-1.)

(2) Physical damage to O-ring groove.

Not acceptable.

(3) Corrosion.

Not acceptable.

(4) Cement or other foreign matter in O-ring groove.

Not acceptable.

3. Bent or broken fittings and/or damaged dome nuts.

Not acceptable.

4. Elongated or torn holes in fitting areas of cells using removable two-piece metal compression fittings.

Acceptable provided the elongation or tear does not extend beyond the outer or inner sealing grooves of the inner ring, or over one-half the distance to the next hole.

5. Thread damaged fittings.

Acceptable provided serviceability is not affected.

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022 00 Page 4 (4) Gently apply the flat side of a knife blade all the way around the finishing collar, working the blade between the collar edge of the outside fitting flange and the cell, being careful not to damage the cell undercord by cutting into the cell.

Comply with general safety instructions in Work Package 004, and fuel cell entry preparations in Work Package 006. When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell. b. Metal Reinforcement Ring. The replacement of fittings is required if the metal reinforcement ring is broken or bent sufficiently to cause a weakening in the structure of the fitting. Whenever a bent reinforcement ring is straightened to its original shape, visually inspect the bent area for evidence of continued distortion. Also, carefully inspect bent area for any very small surface cracks and the following: (1) Residual distortion or fine surface cracks are cause for rejection of the ring. (2) Broken or cracked O-ring groove flanges require repair or fitting replacement.

(5) Use the knife to carefully slice the adhesive interface between the collar and the cell (See Figure 16-2). (6) Work the outside fitting flange edge loose with a screwdriver-type dull-pointed tool. (7) By gradually forcing the tool under the flange and prying upward, loosen the flange.

NOTE Always peel fabric in the same direction as the cord, never across the cord. (8) Use duckbill pliers to peel back the outside flange from the fuel cell. (9) Peel the flange back as far as possible to the metal insert ring (See Figure 16-3). (10) Cut the loosened outer flange away from the fitting ring (See Figure 16-4).

(3) Damage to rubber or metal sealing surfaces that cannot be adequately repaired requires fitting replacement. c. Nonself-Sealing Fuel Cell Fitting Removal. To remove fittings, proceed as follows:

Some fuel cell fittings are interchangeable between manufacturers. Interchangeability must be verified before making any repair substitution to avoid fuel leaks.

When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations. Do not buff the nylon barrier side of the inner liner material. Fuel diffusion will occur if barrier is broken.

(1) Locate the old fitting accurately by measuring from selected points of the cell so that the new fitting can be centered exactly in the original position. (2) Use a sharp white marking pencil, SS-P-196, to mark position of the old fitting. (3) Warm the area to be repaired with a heat lamp before beginning repairs. (This makes the rubber and adhesives more pliable and less likely to be damaged during repair.)

Buffing must be heavy enough to remove all gloss, leaving the surface covered with fine scratches. However, care must be exercised to assure that the nylon barrier is not damaged during the buffing operation.

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022 00 Page 5

Only experienced personnel should use power buffers. Power buffing may produce polished surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand. (11) Remove the inside fitting flange by buffing away the flange and part of the inner liner overlap.

When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations. Do not buff the nylon barrier side of the inner liner material. Fuel diffusion will occur if barrier is broken.

Buffing must be heavy enough to remove all gloss, leaving the surface covered with fine scratches. However, care must be exercised to assure that the nylon barrier is not damaged during the buffing operation. Only experienced personnel should use power buffers. Power buffing may produce polished surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand. (14) Mark the cell with white marking pencil, SS-P00196, and lightly buff the inner liner to the mark.

NOTE This worked area should extend approximately 2-3/4 inches beyond the edge of the fitting flange when the new fitting is set in place.

Buffing must be heavy enough to remove all gloss, leaving the surface covered with fine scratches. However, care must be exercised to assure that the nylon barrier is not damaged during the buffing operation.

(15) On fittings without a molded-in ring, cut the fitting and flange flush with the outside surface of the cell.

Only experienced personnel should use power buffers. Power buffing may produce polished surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand.

Avoid cutting the cell, which would enlarge the original opening.

(12) Buff down to the inner liner surface but do not buff down to the nylon barrier (See Figure 16-5).

NOTE The molded-in metal ring of the fitting is not removed until after buffing. The ring supports the cell opening edge during the buffing operation. (13) After all of the excess rubber has been removed, line up the template for the location of the inside reinforcement patches.

NOTE

(16) Cut out the core of the fitting to the edge of the cell wall.

NOTE Frequently dip knife blade in water. This will lubricate the blade and make cutting easier. (17) Remove the fitting ring by cutting the fitting through with a sharp knife at the edge of the metal insert ring (See Figure 16-6). d. Nonself-Sealing Fuel Cell Fitting Installation. To install new fittings, proceed as follows:

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022 00 Page 6 NOTE

Comply with general safety instructions in Work Package 004, and fuel cell entry preparations in Work Package 006. When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell. When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations. Do not buff the nylon barrier side of the inner liner material. Fuel diffusion will occur if barrier is broken.

Buffing must be heavy enough to remove all gloss, leaving the surface covered with fine scratches. However, care must be exercised to assure that the nylon barrier is not damaged during the buffing operation. Whenever possible, a replacement fitting should be of the same type as the fitting that was removed from the cell. Relocation of fitting openings requires a great deal of skill and experience. This should not be attempted unless a locating template is used or accurate measuring can be achieved by layout method. Only experienced personnel should use power buffers. Power buffing may produce a polished surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand.

Before inserting the fitting through the opening, measure the size and shape carefully with calipers. The cutout opening should conform exactly with the size and shape of the throat of the new fitting. (1) Place an outside patch template on the cell, mark the area with white marking pencil, SS-P-196, and buff to the mark (See Figure 16-7). (2) Buff approximately 1 3/4 inches in all directions from the depth of the new fitting flange. (3) Constantly check the new fitting in the cell opening.

NOTE If the opening is too small, it must be buffed out until the new fitting fits exactly. (4) If the opening is too large, the excess area should be filled with sufficient vulcanizing stock (Refer to Table 15-3, usage column 11) to assure a perfect fit. (5) If the cell wall does not have sufficient thickness to fill the space between the flanges of the new fitting, apply a filler patch of material similar to the inside construction of the cell.

NOTE Apply filler patch in the same manner as applying an inside patch. This patch must be large enough to extend oneinch beyond the area to be covered by the fitting flange. The center must be cut out to match the hole in the cell.

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022 00 Page 7 NOTE

When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations. Do not buff the nylon barrier side of the inner liner material. Fuel diffusion will occur if barrier is broken.

Buffing must be heavy enough to remove all gloss, leaving the surface covered with fine scratches. However, care must be exercised to assure that the nylon barrier is not damaged during the buffing operation. Only experienced personnel should use power buffers. Power buffing may produce a polished surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand. (6) Before applying the filler patch, buff the surfaces and feather the outside edge. (7) Apply three coats of adhesive (Refer to Table 15-4, usage column 4 and 5) and stitch in place.

If the vulcanization method is used, the application technique will be the same with the exception that the adhesive shall be selected from Work Package 015, Table 15-4, usage column 4 or 5. e. Nonself-Sealing Fuel Cell Fitting Installation-New Location. To install fittings in a new location, proceed as follows:

NOTE When a fitting is to be installed in a new location in a nonself-sealing fuel cell it is important that the location be accurately marked. Dimensions taken from a drawing can be accurately duplicated on the fuel cell surface if a layout template is used. Where possible, use adjacent fittings or other attachments as tram points. (1) Mark the location with a sharp while marking pencil, SS-P-00196, or equivalent. (2) Extend the lines beyond the adjacent surface sufficiently to assure retention after the required buffing operation is performed.

(8) After making sure the fit is satisfactory, remove the fitting and prepare it for installation. (9) The installation is accomplished in the same manner as self-sealing cell fittings except materials specified for bladder cells shall be used. Refer to Work Package 016. (10) Fittings that are not to be used as a result of a new location shall be blanked off with a cover place, bolts installed and properly torqued, and safety-wired as applicable. Use the gasket seal method adaptable to the fitting.

When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations. Do not buff the nylon barrier side of the inner liner material. Fuel diffusion will occur if barrier is broken.

NAVAIR 01-1A-35

022 00 Page 8 suitable to the exposure and ensure continuous ventilation of the cell.

Buffing must be heavy enough to remove all gloss, leaving the surface covered with fine scratches. However, care must be exercised to assure that the nylon barrier is not damaged during the buffing operation. Only experienced personnel should use power buffers. Power buffing may produce polished surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand. (3) Buff the marked area. (4) Cut out the fuel cell to receive the fitting. (5) Install as described in preceding paragraph 2d. 3. NONSELF-SEALING FUEL CELL FITTING REPAIR. The following paragraphs provide information and procedures for the repair of non-self-sealing fuel cell fittings. a. Nonself-Sealing Fuel Cell Fitting Flange Cracks. When the fitting flanges are cracked, check the crack in the fitting area to determine the extent of damage. Remove the damaged fitting and replace with a new fitting if there is any doubt as to the remaining structural integrity. b. Non-self-Sealing Fuel Cell Fitting Flange Crack Repair. To repair fitting flange cracks the procedure is the same as Work Package 016 with one exception. When the depth of the crack is through to the fuel fabric, proceed as follows:

Acetone ASTM D329

(1) Clean the cracked flange area with cheesecloth, CCC-C-440, moistened with Acetone, ASTM D329.

When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations. Do not buff the nylon barrier side of the inner liner material. Fuel diffusion will occur if barrier is broken. Only experienced personnel should use power buffers. Power buffing may produce a polished surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand. (2) Buff the crack to a V-shape, being extremely careful not to remove the fabric of the fuel cell. (3) Clean the buffed area with moistened with Acetone, ASTM D329.

cheesecloth

(4) Coat the exposed fabric and V-shape patch with two coats of adhesive (Refer to Table 15-4, usage column 4 or 5). (5) Allow each coat to dry 20 minutes. (6) Complete the repair in the manner described in Work Package 016.

7

Comply with general safety instructions in Work Package 004, and fuel cell entry preparations in Work Package 006. When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection

c. Molded Non-self-Sealing Fuel Cell Fitting Face Repair. The molded fitting face on non-self-sealing fuel cells is used with or without a gasket for sealing against fuel leaks during installation and use in the aircraft. Cuts, deformities, etc., in the rubber surface of the sealing face of fittings must be repaired to restore the surface to the original condition as outlined in Work Package 016. d. Compression-Type Non-self-Sealing Fuel Cell Fitting Damage Repair. A compression-type fitting is a two-part removable metal fitting, not attached to the cell. The fitting area in the cell is critical and sealing is dependent upon the correct thickness of material between

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022 00 Page 9

the metal rings. When damage occurs to the fuel cell in this area, such as elongated bolt holes, torn bolt holes, fabric tears or abrasions, the repair must result in a uniform thickness throughout the fitting clamp ring area. e. Repair of Torn or Elongated Bolt Holes in Nonself-Sealing Fuel Cell Fittings. To repair fabric or rubber bolt holes as used in compression-type fittings, proceed as follows:

Acetone ASTM D329

7

Acetone ASTM D329

7

(2) Clean again with Acetone, ASTM D329, and coat the damaged bolt hole with three coats of adhesive (Refer to Table 15-4, usage column 4 or 5). (3) Allow each coat to dry, then stitch vulcanizing stock into the bolt hole.

NOTE The stock should fill the hole and extend not over 1/32 inch above the surface on one side only.

Comply with general safety instructions in Work Package 004, and fuel cell entry preparations in Work Package 006.

(4) Apply plates and heating unit, clamp and vulcanize at 290oF (143oC) + 5oF for 1 hour.

When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell. When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations. Do not buff the nylon barrier side of the inner liner material. Fuel diffusion will occur if barrier is broken.

If clamps and platens used in the vulcanization process are disassembled from the patches before room temperature is reached, the bonded patch material will not cure flat but will assume a permanent set conforming to the shape in its relaxed position. (5) Allow plates to return to room temperature, then remove and inspect the repair.

Only experienced personnel should use power buffers. Power buffing may produce a polished surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand.

When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations.

(1) Clean the bolt hole with Acetone, ASTM D329, and cut or buff off any ragged edges or material extending from the surface.

Do not buff the nylon barrier side of the inner liner material. Fuel diffusion will occur if barrier is broken.

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022 00 Page 10 Do not buff the nylon barrier side of the inner liner material. Fuel, diffusion will occur if barrier is broken.

Only experienced personnel should use power buffers. Power buffing may produce a polished surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand. Only experienced personnel should use power buffers. Power buffing may produce a polished surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand.

(6) Any excess rubber should be uniformly buffed flush with the adjacent surface.

NOTE The use of a template will accurately locate hole for punching.

(1) Buff the surface, wipe, and clean with Acetone, ASTM D329. (2) Apply three coats of adhesive (Refer to Table 15-4, usage column 4 or 5).

(7) Locate new hole. (3) Allow each coat to dry before applying the next (8) Select a leather punch or equivalent and punch a new hole in the vulcanized area. f. Fabric Tears, Abrasions, and Surface Defects Repair. To repair fabric tears, abrasions, and surface defects in the compression-type fitting area, proceed as follows:

Acetone ASTM D329

7

Comply with general safety instructions in Work Package 004, and fuel cell entry preparations in Work Package 006. When working inside uninstalled fuel cells, wear NIOSH approved respiratory protection suitable to the exposure and ensure continuous ventilation of the cell. When buffing uninstalled fuel cells, either buff them in a booth or while wearing NIOSH approved respiratory protection suitable to the exposure. Always wear eye protection when engaged in buffing operations.

coat. (4) Cut a reinforcement ring patch of material similar to the fuel cell material to fit the sealing ring area.

Do not buff the nylon barrier side of the inner liner material. Fuel diffusion will occur if barrier is broken.

Only experienced personnel should use power buffers. Power buffing may produce a polished surface that is too smooth for good adhesion. If this occurs, surface should be rebuffed by hand. (5) Buff the surface to be cemented. (6) Apply three coats of vulcanizing adhesive to the patch (Refer to Table 15-4, usage column 4 or 5). (7) Position the patch in place and stitch down firmly.

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022 00 Page 11/(12 Blank)

(8) Apply platens, heating unit, and clamp in place.

(10) When room temperature is reached, remove platens, heating unit, and clamps.

(9) Vulcanize for 1 hour at 290oF (143oC) + 5oF.

(11) Inspect the surface area for uniformity and defects. (12) Punch out the required holes in the reinforcement patch, assemble fitting rings, and check for fit and seal.

If clamps and platens used in the vulcanization process are disassembled from the patches before room temperature is reached, the bonded patch material will not cure flat but will assume a permanent set conforming to the shape in its relaxed position.

g. Fitting Insert Replacement. Fitting inserts can be replaced as outlined in Work Package 016. h. O-Ring Fitting Replacement and Repair. When the O-ring groove is cracked, the O-ring generally ceases to prevent fuel from leaking out. Replace or repair the damaged fitting as outlined in Work Package 016

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