AD 99-04-01 Airworthiness Directives; Boeing Model 747 Series Airplanes

Models named: 747 series, JT9D-70 series. Read the applicability below — it usually turns on serial or part numbers too.

Model 747 series airplanes, line numbers 202 through 886 inclusive, equipped with General Electric Model CF6-45/ 50 and Pratt & Whitney Model JT9D-70 series engines; on which the strut/wing modification has not been accomplished in accordance with AD 95-13-07, amendment 39-9287; certificated in any category. Note 1: This AD applies to each airplane identified in the preceding applicability provision, regardless of whether it has been otherwise 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 (h) 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 the strut skin and spring beam support fittings on the outboard nacelle struts, and cracked or loose fasteners of the support fittings, which could result in failure of the outboard nacelle struts and consequent separation of the engine, accomplish the following: (a) Prior to the accumulation of 13,000 total flight cycles, or within 6 months after the effective date of this AD, whichever occurs later, perform a detailed visual inspection of the outboard nacelle struts, as specified by paragraphs (a)(1), (a)(2), (a)(3), and (a)(4) of this AD, in accordance with Boeing Alert Service Bulletin 747-54A2172, dated February 23, 1995, or Boeing Service Bulletin 747-54A2172, Revision 1, dated January 4, 1996. (1) Inspect the spring beam support fittings to detect cracks of the support fittings. (2) Inspect the spring beam support fittings at the fasteners, using a borescope to detect cracks of the support fittings. (3) Inspect the fasteners of the outer spring beam support fittings to detect cracked or loose fasteners. (4) Inspect the strut skin to detect cracks. (b) If no discrepancy is found during any inspection required by paragraph (a) of this AD, perform detailed visual inspections of the outboard nacelle struts to detect any discrepancies specified in paragraphs (b)(1), (b)(2), (b)(3), and (b)(4) of this AD, in accordance with Boeing Alert Service Bulletin 747-54A2172, dated February 23, 1995; or Boeing Service Bulletin 747-54A2172, Revision 1, dated January 4, 1996. Perform the inspection at the times specified in paragraph (c) or (d) of this AD, as applicable. (1) Perform a detailed visual inspection, using a borescope, of only the outer spring beam support fittings at the fasteners through the horizontal flange to detect cracks of the support fittings. (2) Perform a detailed visual inspection, using a borescope, of the fasteners through the vertical flange of only the outer spring beam support fittings to detect loose collars. (3) Perform an external detailed visual inspection of only the outer spring beam support fittings to detect cracked or loose fastener heads. (4) Perform a detailed visual inspection of the strut skin to detect cracks. (c) For Model 747-SR series airplanes equipped with General Electric Model CF6-45 series engines, on which no discrepancy is found during any inspection required by paragraph (a) of this AD: Perform the inspection required by paragraph (b) of this AD within 1,600 flight cycles following the accomplishment of the inspection required by paragraph (a) of this AD; and thereafter at intervals not to exceed 1,600 flight cycles until accomplishment of the optional terminating action specified in paragraph (g) of this AD. (d) For Model 747 series airplanes other than those identified in paragraph (c) of this AD, on which no discrepancy is found during any inspection required by paragraph (a) of this AD: Perform the inspection required by paragraph (b) of this AD within 1,000 flight cycles following the accomplishment of the inspection required by paragraph (a) of this AD; and thereafter at intervals not to exceed 1,000 flight cycles until accomplishment of the optional terminating action specified in paragraph (g) of this AD. (e) If any cracking is found in the spring beam support fittings during any inspection required by this AD, prior to further flight, replace the support fitting with a new support fitting, in accordance with the Accomplishment Instructions in Part IV. of Boeing Service Bulletin 747-54A2172, Revision 1, dated January 4, 1996. Accomplishment of this replacement constitutes terminating action for the repetitive inspection requirements of this AD for only the new support fitting. Continue the repetitive inspections required by paragraph (b) of this AD for the other support fitting locations until accomplishment of the terminating action specified by paragraph (g)(1) or (g)(2) of this AD, as applicable. (f) If any crack is found on the strut skin, or if any cracked or loose fastener or collar [[Page 6191]] is found during any inspection required by this AD, prior to further flight, repair in accordance with a method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA, Transport Airplane Directorate; 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. (g) Accomplishment of an open-hole high frequency eddy current (HFEC) inspection, in accordance with Boeing Alert Service Bulletin 747-54A2172, dated February 23, 1995, or Boeing Service Bulletin 747-54A2172, Revision 1, dated January 4, 1996; and either paragraph (g)(1) or (g)(2) of this AD, as applicable; constitutes terminating action for the requirements of this AD. (1) If no discrepancy is found during the HFEC inspection, prior to further flight, rework the fastener holes and install new fasteners, in accordance with Figures 6 and 7 of Boeing Alert Service Bulletin 747-54A2172, dated February 23, 1995, or Boeing Service Bulletin 747-54A2172, Revision 1, dated January 4, 1996. (2) If any cracking is found during the HFEC inspection, prior to further flight, replace any cracked spring beam support fitting with a new support fitting, in accordance with Part IV. of the Accomplishment Instructions specified by Boeing Service Bulletin 747-54A2172, Revision 1, dated January 4, 1996. (h) 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 2: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Seattle ACO. (i) Special flight permits may be issued in accordance with sections 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. (j) Except as provided by paragraph (f), (g), (g)(1), and (g)(2) of this AD, the actions shall be done in accordance with Boeing Alert Service Bulletin 747-54A2172, dated February 23, 1995, and Boeing Service Bulletin 747-54A2172, Revision 1, dated January 4, 1996, as applicable. 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. (k) This amendment becomes effective on March 16, 1999. Issued in Renton, Washington, on February 1, 1999. Dorenda D. Baker, Acting Manager, Transport Airplane Directorate, Aircraft Certification Service. [FR Doc. 99-2723 Filed 2-8-99; 8:45 am] BILLING CODE 4910-13-P