AD 98-20-20 Airworthiness Directives; Boeing Model 747 Series Airplanes

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

Model 747 series airplanes, line positions 1 through 671 inclusive; 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 (i)(1) 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 upper segment of the bulkhead web, which could result in rapid depressurization of the airplane, and consequent reduced controllability of the airplane, accomplish the following: (a) Within 750 landings after December 10, 1987 (the effective date for AD 87-23-10, amendment 39-5758), unless accomplished within the last 1,250 landings [for airplanes subject to a 2,000-landing repeat inspection interval in accordance with paragraph (b) of this AD], or unless accomplished within the last 250 landings [for airplanes subject to a 1,000-landing repeat inspection interval in accordance with paragraph (b) of this AD], perform a detailed visual inspection; in accordance with Boeing Service Bulletin 747-53-2275, dated March 26, 1987, Revision 1, dated August 13, 1987, Revision 2, dated March 31, 1988, Revision 3, dated March 29, 1990, Revision 4, dated March 26, 1992, or Revision 5, dated January 16, 1997, or Boeing Alert Service Bulletin 747-53A2275, Revision 6, dated August 27, 1998; of the aft side of the entire Body Station (BS) 2360 aft pressure bulkhead for damage such as dents, tears, nicks, gouges, or scratches; and cracks at splices and doublers, and around the Auxiliary Power Unit pressure pan cutout; and, for Group 4 airplanes only, inspect from the forward side, the area adjacent to the window cutout for damage or cracks. Note 2: Notwithstanding provisions to the contrary in AD 87-23- 10, and in Boeing Service Bulletin 747-53-2275, dated March 26, 1987, Revision 1, dated August 13, 1987, Revision 2, dated March 31, 1988, Revision 3, dated March 29, 1990, Revision 4, dated March 26, 1992, and Revision 5, dated January 16, 1997: For Model 747SR airplanes operating at a cabin pressure differential lower than 8.6 pounds-per-square-inch (psi), an adjustment factor of 1.2 shall not be used after the effective date of this AD as a multiplier for inspection thresholds and intervals specified in this AD. (b) After initial compliance with paragraph (a) of this AD, continue to inspect as follows: (1) For Group 1 airplanes, repeat the inspections required by paragraph (a) of this AD, at intervals not to exceed 2,000 landings. (2) For Groups 2 and 3 airplanes, repeat the inspections required by paragraph (a) of this AD, at intervals not to exceed 1,000 landings; or optionally, at the applicable time specified in paragraph (b)(2)(i) or (b)(2)(ii) of this AD. (i) For Group 2 airplanes that operate the entire interval with aft lavatory complexes or galleys adjacent to bulkheads, repeat the inspections required by paragraph (a) of this AD at intervals not to exceed 2,000 landings. (ii) For Groups 2 and 3 airplanes that operate the entire interval with an intact protective shield on the lower half of the forward side of the bulkhead, repeat the inspections required by paragraph (a) of this AD at intervals not to exceed 2,000 landings; and perform a detailed visual inspection of the protective shield for damage in accordance with Boeing Service Bulletin 747-53-2275, dated March 26, 1987, Revision 1, dated August 13, 1987, Revision 2, dated March 31, 1988, Revision 3, dated March 29, 1990, Revision 4, dated March 26, 1992, or Revision 5, dated January 16, 1997, or Boeing Alert Service Bulletin 747-53A2275, Revision 6, dated August 27, 1998, at intervals not to exceed 1,000 landings. If damage is found to the protective shield that exceeds the limits indicated in the service bulletin, prior to further flight, repeat the inspection required by paragraph (a) of this AD. (3) For Group 4 airplanes, repeat the inspections required by paragraph (a) of this AD at intervals not to exceed 1,000 landings. (c) Within 750 landings after December 10, 1987, or prior to the accumulation of 20,000 total landings, whichever occurs later, unless accomplished within the last 3,250 landings; and at intervals thereafter not to exceed 4,000 landings; perform eddy current, ultrasonic, and X-ray inspections of the aft side of the BS 2360 aft pressure bulkhead for cracks; in accordance with Boeing Service Bulletin 747-53-2275, dated March 26, 1987, Revision 1, dated August 13, 1987, Revision 2, dated March 31, 1988, Revision 3, dated March 29, 1990, Revision 4, dated March 26, 1992, or Revision 5, dated January 16, 1997, or Boeing Alert Service Bulletin 747-53A2275, Revision 6, dated August 27, 1998. (d) Within 750 landings after December 10, 1987, or prior to the accumulation of 20,000 total landings, whichever occurs later, unless accomplished within the last 6,250 landings; and thereafter at intervals not to exceed 7,000 landings until the inspection required by paragraph (g) of this AD is accomplished: Perform a detailed visual inspection to detect cracking of the BS 2360 aft pressure bulkhead web to Y-ring lap joint area between radial stiffeners from the forward side of the bulkhead, in accordance with Boeing Service Bulletin 747-53-2275, dated March 26, 1987, Revision 1, dated August 13, 1987, Revision 2, dated March 31, 1988, Revision 3, dated March 29, 1990, Revision 4, dated March 26, 1992, or Revision 5, dated January 16, 1997, or Boeing Alert Service Bulletin 747-53A2275, Revision 6, dated August 27, 1998. (e) If any cracking or damage is found during any inspection required by paragraph (a), (b), (c), or (d) of this AD, repair prior to further flight in accordance with Boeing Service Bulletin 747-53- 2275, dated March 26, 1987, Revision 1, dated August 13, 1987, Revision 2, dated March 31, 1988, Revision 3, dated March 29, 1990, Revision 4, dated March 26, 1992, or Revision 5, dated January 16, 1997, or Boeing Alert Service Bulletin 747-53A2275, Revision 6, dated August 27, 1998. (f) For the purpose of complying with this AD, the number of landings may be determined to equal the number of pressurization cycles where the cabin pressure differential was greater than 2.0 psi. (g) Perform a one-time detailed visual inspection from the forward side of the bulkhead of the upper segment of the bulkhead web at BS 2360 to detect cracking, in accordance with Boeing Alert Service Bulletin 747-53A2275, Revision 6, dated August 27, 1998, at the earlier of the times specified in paragraphs (g)(1) and (g)(2) of this AD. If no cracking is detected during this inspection, no further action is required by this paragraph. Accomplishment of this inspection terminates the repetitive inspection requirement of paragraph (d) of this AD. [[Page 50498]] (1) Within 7,000 landings after the most recent detailed visual inspection accomplished in accordance with paragraph (d) of this AD. (2) At the latest of the times specified in paragraphs (g)(2)(i), (g)(2)(ii), and (g)(2)(iii) of this AD. (i) Prior to the accumulation of 20,000 total landings. (ii) Within 1,500 landings after the most recent detailed visual inspection accomplished in accordance with paragraph (d) of this AD. (iii) Within 90 days after the effective date of this AD. (h) If any cracking is detected during the inspection required by paragraph (g) of this AD, prior to further flight, accomplish a surface probe eddy current inspection from the forward side of the bulkhead to detect cracking of the upper and lower segments of the bulkhead web around the fasteners that attach the web to the outer chord of the Y-ring, in accordance with Boeing Alert Service Bulletin 747-53A2275, Revision 6, dated August 27, 1998. Repair any cracking, prior to further flight, 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. (i)(1) 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 ACO. 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. (i)(2) Alternative methods of compliance for repairs and modifications, approved previously in accordance with AD 87-23-10, amendment 39-5758, are approved as alternative methods of compliance with this AD. Note 3: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Seattle ACO. (j) 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. (k) Except as provided by paragraph (h) of this AD, the actions shall be done in accordance with Boeing Service Bulletin 747-53- 2275, dated March 26, 1987, Revision 1, dated August 13, 1987, Revision 2, dated March 31, 1988, Revision 3, dated March 29, 1990, Revision 4, dated March 26, 1992, or Revision 5, dated January 16, 1997, or Boeing Alert Service Bulletin 747-53A2275, Revision 6, dated August 27, 1998. These Boeing service bulletins contain the following list of effective pages: ---------------------------------------------------------------------------------------------------------------- Service bulletin referenced and Revision level shown date Page No. on page Date shown on page ---------------------------------------------------------------------------------------------------------------- 747-53-2275, March 26, 1987....... 1-50................. Original.............. March 26, 1987. 747-53-2275, Revision 1, August 1-8, 10-17, 26-51.... 1..................... August 13, 1987. 13, 1987. 9, 18-25............. Original.............. March 26, 1987. 747-53-2275, Revision 2, March 31, 1-8, 10-13, 18, 22, 2..................... March 31, 1988. 1998. 29, 35, 42, 49-53. 14-17, 26-28, 30-34, 1..................... August 13, 1987. 36-41, 43-38. 9, 19-21, 23-25...... Original.............. March 26, 1987. 747-53-2275, Revision 3, March 29, 1-33, 35, 54-57...... 3..................... March 29, 1990. 1990. 42, 49-53............ 2..................... March 31, 1988. 34, 36-41, 43-48..... 1..................... August 13, 1987. 747-53-2275, Revision 4, March 26, 1-60................. 4..................... March 26, 1992. 1992. 747-53-2275, Revision 5, January 1-66................. 5..................... January 16, 1997. 16, 1997. 747-53A2275, Revision 6, August 1-76................. 6..................... August 27, 1997. 27, 1997. ---------------------------------------------------------------------------------------------------------------- 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. (l) This amendment becomes effective on October 7, 1998. Issued in Renton, Washington, on September 14, 1998. Darrell M. Pederson, Acting Manager, Transport Airplane Directorate, Aircraft Certification Service. [FR Doc. 98-25123 Filed 9-21-98; 8:45 am] BILLING CODE 4910-13-P