Airworthiness Directive · Amendment 39-11920 · Boeing Model 757 Series Airplanes Powered by Pratt & Whitney Engines
Boeing Model 757 Series Airplanes Powered by Pratt & Whitney Engines
Superseded. A later AD replaced this one: AD 2003-18-05. Comply with the one in force.
Model 757 series airplanes powered by Pratt & Whitney engines, line numbers 1 through 735 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 (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 757 series airplanes, that requires modification of the nacelle strut and wing structure. This amendment is prompted by reports indicating that the actual operational loads applied to the nacelle are higher than the analytical loads that were used during the initial design. Such an increase in loading can lead to fatigue cracking in primary strut structure prior to an airplane reaching its design service objective. The actions specified by this AD are intended to prevent fatigue cracking in primary strut structure and consequent reduced structural integrity of the strut.
To prevent fatigue cracking in primary strut structure and consequent reduced structural integrity of the strut, accomplish the following:
(a) Modify the nacelle strut and wing structure on both the left and right sides of the airplane, in accordance with Boeing Service Bulletin 757-54-0034, dated May 14, 1998, at the later of the times specified in paragraph (a)(1) or (a)(2) of this AD.
(1) Prior to the accumulation of 37,500 total flight cycles, or within 20 years since the date of manufacture, whichever occurs first. Use of the optional threshold formula described in paragraph I.D. of the service bulletin is an acceptable alternative to the 20-year threshold.
(2) Within 3,000 flight cycles after the effective date of this AD.
(b) Prior to or concurrently with the accomplishment of the modification of the nacelle strut and wing structure required by paragraph (a) of this AD; as specified in paragraph I.D., Table I, “Strut Improvement Bulletins,” on page 5 of Boeing Service Bulletin 757-54-0034, dated May 14, 1998; accomplish the actions specified in Boeing Service Bulletin 757-54-0027, Revision 1, dated October 27, 1994, and Boeing Service Bulletin 757-54-0036, dated May 14, 1998, as applicable, in accordance with those service bulletins.
(c) If any damage to airplane structure is found during the accomplishment of the modification required by paragraph (a) of this AD; and the service bulletin specifies to contact Boeing for appropriate action: 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 (DER) 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 approval letter must specifically reference this AD.
