AD 99-07-12 Airworthiness Directives; Boeing Model 747-100, -200, and -300 Series Airplanes

Models named: 747-100, -200, -300 series. Read the applicability below — it usually turns on serial or part numbers too.

Model 747-100, -200, and -300 series airplanes, as listed in Boeing Alert Service Bulletin 747-53A2408, dated April 25, 1996; certificated in any category. Note 1: This AD applies to each airplane identified in the preceding applicability provision, regardless of whether it has been modified, altered, or repaired in the area subject to the requirements of this AD. For airplanes that have been modified, altered, or repaired so that the performance of the requirements of this AD is affected, the owner/operator must request approval for an alternative method of compliance in accordance with paragraph (e) of this AD. The request should include an assessment of the effect of the modification, alteration, or repair on the unsafe condition addressed by this AD; and, if the unsafe condition has not been eliminated, the request should include specific proposed actions to address it.

Required as indicated, unless accomplished previously. To detect and correct fatigue cracking of certain lower lobe fuselage frames, which could lead to fatigue cracks in the fuselage skin, and consequent rapid decompression of the airplane, accomplish the following: Note 2: Although Boeing Alert Service Bulletin 747-53A2408, dated April 25, 1996, allows discount from the compliance threshold of all flight cycles at or below a cabin pressure differential of 2.0 pounds per square inch (psi), this AD requires that all flight cycles be counted. (a) For airplanes on which the initial detailed visual internal inspection of the Section 46 lower lobe frames required by paragraph (a)(3) of AD 93-08-12, amendment 39-8559, has not been accomplished: Perform a detailed visual inspection to detect cracking of the lower lobe fuselage frames from Body Station 1820 to Body Station 2100, in accordance with Boeing Alert Service Bulletin 747-53A2408, dated April 25, 1996, at the later of the times specified in paragraphs (a)(1) and (a)(2) of this AD: (1) Prior to the accumulation of 15,000 total flight cycles; or (2) Within 1,500 flight cycles or 18 months after the effective date of this AD, whichever occurs first. Note 3: Paragraph (a)(3) of AD 93-08-12 requires a detailed visual internal inspection to detect cracks in the Section 46 lower lobe frames, in accordance with Boeing Service Bulletin 747-53-2349, dated June 27, 1991. The initial inspection is required prior to the accumulation of 22,000 total flight cycles, or within 1,000 flight cycles after June 11, 1993 (the effective date of AD 93-08-12), whichever occurs later. Repetitive Inspections (b) If no cracking is detected during the inspection required by paragraph (a) of this AD, repeat the inspection thereafter at intervals not to exceed 3,000 flight cycles. Corrective Actions (c) If any cracking is detected during any inspection required by paragraph (a) of this AD, prior to further flight, accomplish paragraphs (c)(1) and (c)(2) of this AD: (1) Within 20 inches of the crack location on the frame, perform a detailed visual inspection of the adjacent structure to detect cracking. If any cracking is detected, prior to further flight, repair in accordance with a method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate; the Boeing 747 Structural Repair Manual; or in accordance with data meeting the type certification basis of the airplane approved by a Boeing Company Designated Engineering Representative who has been authorized by the Manager, Seattle ACO, to make such findings. (2) Repeat the inspection required by paragraph (a) of this AD thereafter at intervals not to exceed 3,000 flight cycles. Optional Terminating Inspection (d) Accomplishment of the initial detailed visual internal inspection of the Section 46 lower lobe frames required by paragraph (a)(3) of AD 93-08-12 constitutes terminating action for the requirements of this AD. Alternative Methods of Compliance (e) An alternative method of compliance or adjustment of the compliance time that provides an acceptable level of safety may be used if approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate. Operators shall submit their requests through an appropriate FAA Principal Maintenance Inspector, who may add comments and then send it to the Manager, Seattle ACO. Note 4: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Seattle ACO. Special Flight Permits (f) Special flight permits may be issued in accordance with Secs. 21.197 and 21.199 of the Federal Aviation Regulations (14 CFR 21.197 and 21.199) to operate the airplane to a location where the requirements of this AD can be accomplished. Incorporation by Reference (g) Except as provided by paragraphs (c)(1) and (d) of this AD, the actions shall be done in accordance with Boeing Alert Service Bulletin 747-53A2408, dated April 25, 1996. 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 98124-2207. Copies may be inspected at the FAA, Transport Airplane Directorate, 1601 Lind Avenue, SW., Renton, Washington; or at the Office of the Federal Register, 800 North Capitol Street, NW., suite 700, Washington, DC. (h) This amendment becomes effective on May 5, 1999. Issued in Renton, Washington, on March 22, 1999. Darrell M. Pederson, Acting Manager, Transport Airplane Directorate, Aircraft Certification Service. [FR Doc. 99-7554 Filed 3-30-99; 8:45 am] BILLING CODE 4910-13-P