Airworthiness Directive · Amendment 39-11558 · Boeing Model 747-100 and −200 Series Airplanes
Boeing Model 747-100 and −200 Series Airplanes
Model 747-100 and -200 series airplanes, listed in Boeing Service Bulletin 747-57-2305, Revision 1, dated January 21, 1999; 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 adopts a new airworthiness directive (AD), applicable to certain Boeing Model 747-100 and -200 series airplanes, that requires repetitive inspections of the upper and lower chords of the wing front spar for cracks, and corrective action, if necessary. For airplanes on which no cracking is detected, this AD also provides an optional terminating action in lieu of repetitive inspections. This amendment is prompted by reports of cracks in the upper chord of the wing front spar. The actions specified by this AD are intended to detect and correct fatigue cracking of the upper and lower chords of the wing front spar, which could result in reduced structural capability and possible fuel leakage onto an engine and a resultant fire.
To detect and correct fatigue cracking of the upper and lower chords of the wing front spar, which could result in reduced structural capability and possible fuel leakage onto an engine and a resultant fire, accomplish the following:
(a) Prior to the accumulation of 12,000 total flight cycles, or within 24 months after the effective date of this AD, whichever occurs later, accomplish an ultrasonic inspection for cracking of the upper and lower chord of the wing front spar, in accordance with Boeing Service Bulletin 747-57-2305, Revision 1, dated January 21, 1999.
Note 2: Accomplishment of an open hole high frequency eddy current inspection in accordance with Figure 6 of Boeing Service Bulletin 747-57-2305, Revision 1, dated January 21, 1999, is acceptable for compliance with the inspection requirement of paragraph (a) of this AD.
(1) If no cracking is found, repeat this inspection thereafter at intervals not to exceed 6,000 flight cycles, until the requirements of paragraph (c) of this AD have been accomplished.
(2) If any cracking is found, prior to further flight, accomplish “Part 2—Terminating Action” of the Accomplishment Instructions of the service bulletin, except as provided by paragraph (b) of this AD. Accomplishment of this action constitutes terminating action for the requirements of this AD.
(b) During accomplishment of the terminating action required by paragraph (a)(2) of this AD, if any crack is found in the upper chord that is outside the limits specified in Boeing Service Bulletin 747-57-2305, Revision 1, dated January 21, 1999; or if any crack is found in the lower chord; 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 FAA to make such findings. For a repair method to be approved by the Manager, Seattle ACO, as required by this AD, the Manager's approval letter must specifically reference this AD.
(c) Accomplishment of “Part 2—Terminating Action” of the Accomplishment Instructions of Boeing Service Bulletin 747-57-2305, Revision 1, dated January 21, 1999, constitutes terminating action for the requirements of this AD.
Note 3: Accomplishment of the wing and strut modification specified in AD 95-10-16, amendment 39-9233, or AD 95-13-07, amendment 39-9287, or the optional terminating action specified in AD 99-10-09, amendment 39-11162, constitutes terminating action for the repetitive inspections required by paragraph (a) of this AD, provided that an HFEC inspection of subject fastener holes has been accomplished in accordance with Boeing 747 Non-Destructive Test Manual D6-7170, Part 6, Subject 51-00-00, Figure 16, prior to oversizing of the holes in accordance with AD 95-10-16, AD 95-13-07, or AD 99-10-09, and the holes were found to be free of cracks, corrosion, or damage.
