Airworthiness Directives; Boeing Model 757 Series Airplanes Powered by Pratt & Whitney Engines

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.