Action
Final rule.
Summary
We are superseding an existing airworthiness directive (AD) for certain The Boeing Company Model 757-200 and -200PF series airplanes. That AD currently requires modifying the nacelle strut and wing structure, and repairing any damage found during the modification. This new AD specifies a maximum compliance time limit that overrides the optional threshold formula results. This AD was 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. Subsequent analysis and service history, which includes numerous reports of fatigue cracking on certain strut and wing structure, indicated that fatigue cracking can occur on the primary strut structure before an airplane reaches its design service objective. We are issuing this AD to prevent fatigue cracking in primary strut structure and consequent reduced structural integrity of the strut.