Airworthiness Directive · Amendment 39-11755 · Boeing Model 747-200, -300, and -400 Series Airplanes
Boeing Model 747-200, -300, and -400 Series Airplanes
Model 747-200, -300, and -400 series airplanes; up to and including line number 744; 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 (d) 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 747-200, -300, and -400 series airplanes, that currently requires repetitive high frequency eddy current (HFEC) inspections to detect cracking of the front spar web of the center section of the wing, and repair, if necessary. This amendment requires that the existing inspection be accomplished at a reduced threshold, and adds a requirement that the existing HFEC inspection be accomplished on repaired areas. This amendment is prompted by reports of cracking in repaired areas of the front spar web and cracking of the front spar web on an airplane that had accumulated fewer flight cycles than the inspection threshold of the existing AD. The actions specified by this AD are intended to prevent the leakage of fuel into the forward cargo bay, as a result of fatigue cracking in the front spar web, which could result in a potential fire hazard.
To prevent the leakage of fuel into the forward cargo bay, as a result of fatigue cracking in the front spar web, which could result in a potential fire hazard, accomplish the following:
(a) Perform a high frequency eddy current (HFEC) inspection to detect cracking of the front spar web of the center section of the wing, in accordance with Boeing Alert Service Bulletin 747-57A2298, Revision 1, dated September 12, 1996; Boeing Service Bulletin 747-57A2298, Revision 2, dated October 2, 1997; or Boeing Alert Service Bulletin 747-57A2298, Revision 3, dated January 7, 1999; at the time specified in paragraph (a)(1) or (a)(2) of this AD, as applicable, until accomplishment of the requirements of paragraph (b) of this AD.
(1) For airplanes that have accumulated 12,000 to 17,999 total landings as of April 2, 1997 (the effective date of AD 97-05-01, amendment 39-9945): Perform the initial inspection within 12 months after April 2, 1997, unless previously accomplished within the last 12 months prior to April 2, 1997. Perform this inspection again prior to the accumulation of 18,000 total landings or within 1,400 landings, whichever occurs later; after accomplishing the initial inspection, and thereafter at intervals not to exceed 1,400 landings.
(2) For all other airplanes: Perform the initial inspection prior to the accumulation of 18,000 total landings or within 12 months after April 2, 1997, whichever occurs later. Repeat this inspection thereafter at intervals not to exceed 1,400 landings.
(b) Prior to accumulation of 12,000 total landings, or within 12 months after the effective date of this AD, whichever occurs later, perform an HFEC inspection to detect cracking of the front spar web of the center section of the wing, in accordance with Boeing Service Bulletin 747-57A2298, Revision 2, dated October 2, 1997; or Boeing Alert Service Bulletin 747-57A2298, Revision 3, dated January 7, 1999. Repeat the HFEC inspection thereafter at intervals not to exceed 1,400 landings. Accomplishment of the HFEC inspection constitutes terminating action for the repetitive inspection requirements of paragraph (a) of this AD.
Note 2: Inspections accomplished prior to the effective date of this AD in accordance with Boeing Alert Service Bulletin 747-57A2298, Revision 1, dated September 12, 1996, are acceptable for compliance with the initial inspection required by paragraph (b) of this AD, provided that the airplane does not have a repair installed in the inspection area.
(c) If any cracking is detected during any inspection required by paragraph (a) or (b) of this AD, prior to further flight, confirm the cracking with secondary procedures in accordance with Boeing Service Bulletin 747-57A2298, Revision 2, dated October 2, 1997, or Boeing Alert Service Bulletin 747-57A2298, Revision 3, dated January 7, 1999. Thereafter repeat the HFEC inspection required by paragraph (a) or (b) of this AD at intervals not to exceed 1,400 landings.
(1) If any vertical crack is found that is less than 10 inches in length and has not extended in a diagonal direction, prior to further flight, repair in accordance with the service bulletin.
(2) If any vertical crack is found that is 10 inches or greater in length; or if any crack is found that has extended in a diagonal direction (regardless of the length); or if any crack is found that would affect an existing repair, 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 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 approval letter must specifically reference this AD.
