90-15-51 BOEING: Amendment 39-6712. Final rule of telegraphic AD. Docket No. 90-NM- 149-AD.\n\n\tApplicability: Model 747 series airplanes, line numbers 001 through 685, certificated in any category, which have accumulated over 15,000 flight cycles upon the effective date of this AD, and on which the inspections or modifications required by AD 90-06-14 R1, Amendment 39-6605, have not been accomplished. \n\n\tCompliance: Required as indicated, unless previously accomplished. \n\n\tTo prevent rapid decompression of the airplane, accomplish the following: \n\n\tA.\tFor airplanes that have accumulated 17,500 or more flight cycles, upon the effective date of this AD, within the next 50 flight cycles or 30 days, whichever occurs first, perform an internal detailed visual inspection of the nose wheel well vertical beams in accordance with Boeing Alert Service Bulletin 747-53A2338, dated July 23, 1990. If cracks are found, repair prior to further flight in accordance with the service bulletin. \n\n\tB.\tFor airplanes that have accumulated more than 15,000 flight cycles, but fewer than 17,500 flight cycles upon the effective date of this AD, within the next 50 flight cycles or 30 days, whichever occurs first, accomplish the following in accordance with Boeing Alert Service Bulletin 747-53A2338, dated July 23, 1990. \n\n\t\t1.\tPerform an external inspection of the nose wheel well side walls for distortions. If distortions are found in excess of the allowable limits specified in the service bulletin, prior to further flight, perform the inspections and repairs, if necessary, required by paragraph A., of this AD. \n\n\t\t2.\tPerform an external detailed visual inspection of the nose wheel well side walls for cracks. If cracks are found repair prior to further flight in accordance with the service bulletin. \n\n\t\t3.\tPerform an external detailed visual inspection of the nose wheel well side walls for loose, missing, or damaged fasteners in accordance with the service bulletin. Ifloose, missing, or damaged fasteners are found, replace prior to further flight in accordance with the service bulletin. \n\n\tC.\tAn alternate means 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 (ACO), FAA, Transport Airplane Directorate.\n \n\tNOTE: The request should be submitted directly to the Manager, Seattle ACO, and a copy sent to the cognizant FAA Principal Inspector (PI). The PI will then forward comments or concurrence to the Seattle ACO. \n\n\tD.\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\tAll persons affected by this directive who have not already received the appropriate service documents from the manufacturer, may obtain copies upon request to Boeing Commercial Airplane Group, P.O. Box 3707, Seattle, Washington 98124. These documents may be examined at the FAA, Northwest Mountain Region, Transport Airplane Directorate, 1601 Lind Avenue SW, 5th Floor, Renton, Washington, or Seattle Aircraft Certification Office, 1601 Lind Avenue SW, 2nd Floor, Renton, Washington. \n\n\tThis amendment (39-6712, AD 90-15-51) becomes effective on September 17, 1990, as to all persons, except those persons to whom it was made immediately effective by telegraphic AD T90-15-51, issued on July 23, 1990, which contained this amendment.