Airworthiness Directive · Amendment 39-12027 · Boeing Model 707 and 720 Series Airplanes
Boeing Model 707 and 720 Series Airplanes
All Model 707 and 720 series airplanes, 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 (e) 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 all Boeing Model 707 and 720 series airplanes, that requires repetitive inspections of certain stringers and around certain fastener holes of the lower skin of the wings to detect fatigue cracking, and repair, if necessary. This action is necessary to detect and correct such cracking and consequent damage to adjacent structure, which could result in reduced structural integrity of the airplane. This action is intended to address the identified unsafe condition.
To detect fatigue cracking of certain stringers, and around certain fastener holes of the lower skin of the wings, which could result in damage to adjacent structure and consequent reduced structural integrity of the airplane, accomplish the following:
(a) For Model 720 series airplanes: Within 500 flight cycles after the effective date of this AD, perform an initial high frequency eddy current (HFEC) inspection to detect cracking, in accordance with Figure 1 of Boeing Alert Service Bulletin A3395, Revision 4, dated October 28, 1999.
(b) For Model 707 series airplanes having fewer than 15,000 total flight cycles as of the effective date of this AD: Prior to the accumulation of 15,000 total flight cycles, or within 150 flight cycles after the effective date of this AD, whichever occurs later, perform an initial HFEC inspection in accordance with Figure 2; steps 1, 2, and 3; of Boeing Alert Service Bulletin A3395, Revision 4, dated October 28, 1999. Repeat the inspection thereafter at intervals not to exceed 1,300 flight cycles. Accomplishment of the repetitive HFEC inspections terminates the low frequency eddy current inspections specified in AD 81-11-06 R1, amendment 39-4178.
(c) For Model 707 series airplanes having 15,000 total flight cycles or more as of the effective date of this AD: Within 150 flight cycles after the effective date of this AD, perform an initial HFEC inspection in accordance with Figure 2; steps 4, 5, and 6; of Boeing Alert Service Bulletin A3395, Revision 4, dated October 28, 1999, and accomplish the requirements in paragraphs (c)(1) and (c)(2) of this AD.
(1) Repeat the inspection thereafter at intervals not to exceed 150 flight cycles until accomplishment of the inspections required by paragraph (c)(2) of this AD.
(2) Within 400 flight cycles after accomplishment of the initial inspection required by paragraph (c) of this AD, accomplish the HFEC inspections required by paragraph (b) of this AD. Accomplishment of these inspections terminates the repetitive inspections required by paragraph (c)(1) of this AD.
Note 2: The actions required by AD 81-11-06 R1, amendment 39-4178 [with the exception of the LFEC inspections, as specified in paragraph (b) of this AD] remain in effect.
(d) If any cracking is detected during any inspection required by this AD, prior to further flight, perform an internal inspection in accordance with the Work Instructions specified in Boeing Alert Service Bulletin A3395, Revision 4, dated October 28, 1999; and, prior to further flight, repair in accordance with a method approved by the Manager, Seattle Aircraft Certification Office (ACO), FAA; 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. 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.
