Fuel Cell Damage Classification and Repair Limits.

TM 1-1500-204-23-3 CAUTION Crashworthy, self-sealing fuel cells shall not be folded and/or collapsed for periods of more than four (4) hours. Fuel cells must be supported when stored, shipped, and/or repaired. CAUTION Purge fuel cell prior to inspection and repair. Refer to paragraph 2-5f (4) purging procedure. CAUTION Preservation of a fuel cell shall be delayed until repair work is completed, unless it will be more than 30 days before repairs are started. This reduces the cleanup effort by repair personnel prior to making repairs. Refer to paragraph 2-5f (5) for preservation procedure. b. Fuel Cell Damage Classification and Repair Limits. General Information. WARNING Remove fuel cell from aircraft, dean and purge before doing any repair. (1) Classify fuel cell damage as follows: Minor damage. See table 2-5 for serviceable limits. (2) Reparable damage is classified as follows: (a) Internal Blister Damage. Blisters exceeding 1/4 inch diameter must be repaired. If the innerliner is damaged, missing, or blistered, trim away the loose material, dean, buff, dean and make an innerliner/barrier repair. If the inner fabric ply is damaged, then apply a fabric patch repair, and then make an innerliner/barrier repair. (b) External Blister Damage. Blisters exceeding 1/4 inch diameter must be repaired. If only the outer coating is missing or blistered, trim away the loose material, dean, buff, dean and apply repair cement. If the outer fabric ply is damaged, then apply a fabric patch repair. (c) Interior Loose Seam Damage. Refers to innerliner laps and associated gum strips. In addition, reinforcement ply seams. If gum strip is damaged or loose, remove loose material, dean, buff, dean and make an innerliner/barrier repair. Innerliner laps are generally 1 1/4 inches to 1 1/2 inches. For innerliner lap, looseness, if at least 1 inch of seal remains, cut off loose material and make an innerliner/barrier repair. If less than 1 inch of seal remains, do not trim innerliner ply, gum strip can be trimmed. Clean, buff, and dean the bonding surfaces, apply repair adhesive (item 1, table 2-11) and apply pressure until adhesive cures. Then make an innerliner/barrier repair, para 2- 7e(1 )(b). (d) Exterior Loose Seam Damage. Refers to gum strips and reinforcement ply seams. If gum strip is damaged or loose, remove loose material, dean, buff, dean and apply repair adhesive (item 1, table 2-11). If the fabric reinforcement ply has looseness greater than 0.50 inch or is damaged, then a fabric repair patch must be used. Reinforcement plies may have 3 to 4 inches of lap as originally built and this must be maintained. (e) Internal Cuts, Tears, Chafing, or Snag Damage. All internal cuts, tears, chafing, and snags must be repaired with an innerliner/barrier repair. (f) External Cuts, Tears, Chafing, or Snag Damage. If the fabric ply is not damaged an adhesive repair is acceptable. (g) Cuts, Tears, Snags and Holes. All cuts, tears, snags and holes (not including holes which penetrate the entire cell wall) without sealant activation, penetrating one or more plies require an internal or external reinforced cover patch, depending on side of hole. Repair is limited to damages not exceeding a length or diameter of 4 inches after trimming. Remove loose material and ragged edges. (h) Loose Fitting Flange Damage (Internal and External). Trim away up to 1/8 inch of radial looseness. If radial looseness is greater than 1/8 inch; dean, buff and clean contact surfaces. Apply repair adhesive to both surfaces and bond together. Use Repair Fuel Cell Outer Coating procedure, except buff only contact surfaces and do not trim away loose material if loosenss is greater than 1/8 inch. (i ) Replacement of Fitting Thread Inserts (Helicoils). (TM 1-1500-204-23-6). 2-44 Change 2