Airworthiness Directive · Amendment 39-11840 · Boeing Model 747 Series Airplanes
Boeing Model 747 Series Airplanes
Model 747 series airplanes, line numbers 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 (j)(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.
This amendment supersedes an existing airworthiness directive (AD), applicable to certain Boeing Model 747 series airplanes, that currently requires repetitive inspections for damage or cracking of the aft pressure bulkhead, and cracking of the bulkhead web-to-Y-ring lap joint area and the upper segment of the bulkhead web. That AD also requires certain follow-on actions, if necessary. This amendment requires that a currently required one-time inspection to detect cracking of the upper segment of the bulkhead web be accomplished repetitively, and adds additional repetitive inspections to detect cracking of the upper and lower segments of the aft bulkhead web. The actions specified by this AD are intended to detect and correct fatigue cracking of the bulkhead web, which could result in rapid depressurization of the airplane, and consequent reduced controllability of the airplane.
To detect and correct fatigue cracking 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 October 7, 1998 (the effective date for AD 98-20-20), as a multiplier for inspection thresholds and intervals specified in this AD.
Note 3: For the purposes of this AD, a detailed visual inspection is defined as: “An intensive visual examination of a specific structural area, system, installation, or assembly to detect damage, failure, or irregularity. Available lighting is normally supplemented with a direct source of good lighting at intensity deemed appropriate by the inspector. Inspection aids such as mirror, magnifying lenses, etc. may be used. Surface cleaning and elaborate access procedures may be required.”
(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 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. Accomplishment of this inspection terminates the repetitive inspection requirement of paragraph (d) of this AD.
(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 October 7, 1998 (the effective date of AD 98-20-20).
(h) If any cracking is detected during the detailed visual inspections required by paragraph (g) of this AD, prior to further flight, accomplish a surface probe high frequency eddy current (HFEC) 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. For the inspection of the lower segment of the bulkhead web, the area between the 149 degree radial zee stiffeners may be omitted. 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) If no cracking is detected during the detailed visual inspection required by paragraph (g) of this AD, within 1,500 flight cycles after accomplishment of that inspection or within 250 flight cycles after the effective date of this AD, whichever occurs later: Repeat the detailed visual inspection, as specified in paragraph (g); and perform a surface probe HFEC inspection from the forward side of the bulkhead to detect cracking of the upper and lower segments of the bulkhead web, in accordance with Figure 15 of Boeing Alert Service Bulletin 747-53A2275, Revision 6, dated August 27, 1998. For the inspection of the lower segment of the bulkhead web, the area between the 149 degree radial zee stiffeners may be omitted.
(1) If no cracking is detected, repeat the detailed visual inspection thereafter at intervals not to exceed 1,500 flight cycles; and repeat the surface probe HFEC inspection thereafter at intervals not to exceed 3,000 flight cycles.
(2) 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, or a Boeing Company Designated Engineering Representative who has been authorized by the FAA to make such findings. For a repair method to be approved by the Manager, Seattle ACO, as required by this paragraph, the Manager's approval letter must specifically reference this AD.
(j)(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.
(2) Alternative methods of compliance, approved previously in accordance with AD 98-20-20, amendment 39-10786, are approved as alternative methods of compliance with this AD.
Note 4: Information concerning the existence of approved alternative methods of compliance with this AD, if any, may be obtained from the Seattle ACO.
