91-18-04 BOEING: Amendment 39-8007. Docket No. 91-NM-73-AD. \n\n\tApplicability: Model 747 series airplanes, listed in Boeing Service Bulletin 747-53- 2302, dated December 13, 1990, certificated in any category. \n\n\tCompliance: Required as indicated, unless previously accomplished. \n\n\tTo prevent sudden decompression of the airplane, accomplish the following: \n\n\tA.\tAccomplish a detailed visual inspection of the fuselage frames at body station (BS) 2200 and BS 2220, in accordance with Boeing Service Bulletin 747-53-2302, dated December 13, 1990, for evidence of cracking at the latest of the following times, as applicable. Repeat the inspections thereafter at intervals not to exceed 2,000 flight cycles. \n\n\t\t1.\tPrior to the accumulation of 10,000 total airplane flight cycles; or \n\n\t\t2.\tPrior to the accumulation of 10,000 flight cycles since frame replacement in accordance with Boeing Service Bulletin 747-53-2302, dated December 13, 1990; or \n\n\t\t3.\tWithin 1,000 flight cycles after the effective date of this AD. \n\n\tB.\tIf cracking is found as a result of the inspections required by paragraph A. of this AD, prior to further flight, perform a close visual inspection of the adjacent frames, stringers, skin, skin lap joints, and skin adjacent to the outflow valve, in accordance with Boeing Service Bulletin 747-53-2302, dated December 13, 1990, and continue to reinspect in accordance with paragraph A. of this AD. \n\n\tC.\tIf cracks are found as a result of the inspections required by paragraph A. or B. of this AD, prior to further flight, repair in accordance with Boeing Service Bulletin 747-53- 2302, dated December 13, 1990, and continue to reinspect in accordance with paragraph A. of this AD. \n\n\tD.\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\tE.\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\tF.\tThe inspections shall be done in accordance with Boeing Service Bulletin 747- 53-2302, dated December 13, 1990. This incorporation 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, Northwest Mountain Region, Transport Airplane Directorate, 1601 Lind Avenue SW., Renton, Washington, or at the Office of the Federal Register, 1100 L Street NW., Room 8401, Washington, D.C. \n\n\tThis amendment (39-8007, AD 91-18-04) becomes effective on September 20, 1991.