91-15-21 BOEING: Amendment 39-7086. Docket No. 91-NM-08-AD. \n\n\tApplicability: Model 727 series airplanes, equipped with Boeing manufactured auxiliary fuel tanks installed in the lower cargo compartments, certificated in any category. \n\n\tCompliance: Required as indicated, unless previously accomplished. \n\n\tTo reduce the potential for fire in the cargo compartment due to fuel leaking from the auxiliary fuel tanks installed in the fuselage cargo compartments, accomplish the following: \n\n\tA.\tWithin the next 1,000 flight cycles after the effective date of this AD, accomplish one of the following: \n\n\t\t1.\tConduct an ultrasonic inspection for disbonding of the lower sidewall (curved) panels of the auxiliary fuel tanks in accordance with Part I of the Accomplishment Instructions in Boeing Service Bulletin 727-28-0110, dated September 6, 1990; or \n\n\t\t2.\tPerform a leak check of the auxiliary fuel tanks in accordance with Part III of the Accomplishment Instruction in Boeing Service Bulletin 727-28-0110, dated September 6, 1990. If any fuel leakage is detected, prior to further flight repair, deactivate or remove the auxiliary fuel tanks, in accordance with Part III of the Accomplishment Instructions in the service bulletin. Repeat the leak check prior to each flight: \n\n\tB.\tWithin the next 12,000 flight cycles after the effective date of this AD, accomplish the inspections of the auxiliary fuel tank and support structure in accordance with Part II of the Accomplishment Instructions in Boeing Service Bulletin 727-28-0110, dated September 6, 1990. Repeat this inspection at intervals not to exceed 12,000 flight cycles. Accomplishment of this inspection constitutes terminating action for the inspection/check requirements of paragraph A. of this AD. \n\n\tC.\tDeactivation of the auxiliary fuel tank in accordance with Part V of the Accomplishment Instructions in Boeing Service Bulletin 727-28-0110, dated September 6, 1990, constitutes terminating action for theinspection requirements of this AD. If the auxiliary fuel tanks are reactivated, the inspections required by paragraphs A. and B. of this AD must be accomplished prior to exceeding the flight cycle thresholds required by those paragraphs. \n\n\tNOTE: Fuel tanks deactivated, but installed in an airplane, accumulate the same number of flight cycles as the airplane. \n\n\tD.\tAuxiliary fuel tanks currently not installed in an airplane must be inspected in accordance with Part II of the Accomplishment Instructions in Boeing Service Bulletin 727-28-0110, dated September 6, 1990, prior to installation in an airplane.\n \n\tE.\tIf a disbonded or cracked panel is detected during the inspections required by paragraphs A.1., B., C., or D. of this AD, accomplish one of the following prior to further flight. \n\n\t\t1.\tReplace the panel in accordance with Part IV of the Accomplishment Instructions in Boeing Service Bulletin 727-28-0110, dated September 6, 1990; or \n\n\t\t2.\tDeactivate the auxiliary fueltank in accordance with Part V of the Accomplishment Instructions in Boeing Service Bulletin 727-28-0110, dated September 6, 1990; or \n\n\t\t3.\tRemove the auxiliary fuel tank in accordance with the Boeing 727 Maintenance Manual Subject 53-20-31. \n\n\tF.\tAn alternative method of compliance or adjustment of the compliance time, which provides an acceptable level of safety, may be used when approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate. \n\n\tNOTE: The request should be forwarded through an FAA Principal Maintenance Inspector, who may concur or comment and then send it to the Manager, Seattle ACO. \n\n\tG.\tSpecial flight permits may be issued in accordance with FAR 21.197 and 21.199 to operate airplanes to a base in order to comply with the requirements of this AD. \n\n\tH.\tThe inspection, deactivation, and replacement requirements shall be done in accordance with Boeing Service Bulletin 727-28-0110, dated September 6, 1990. Thisincorporation by reference was approved by the Director of the Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR Part 51. Copies may be obtained from Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124. Copies may be inspected at the FAA, Transport Airplane Directorate, 1601 Lind Avenue S.W., Renton, Washington; or at the Office of the Federal Register, 1100 L Street N.W., Room 8401, Washington, D.C. \n\n\tThis amendment (39-7086, AD 91-15-21) becomes effective on September 9, 1991.