Summary
This document proposes the adoption of a new airworthiness directive (AD) that is applicable to certain Boeing Model 757 series airplanes powered by Pratt & Whitney engines. This proposal would require modification of the nacelle strut and wing structure. This proposal 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 the proposed AD are intended to prevent fatigue cracking in primary strut structure and consequent reduced structural integrity of the strut.