Summary
This document proposes the adoption of a new airworthiness directive (AD) that is applicable to certain Boeing Model 757 series airplanes. This proposal would require revising the Airworthiness Limitations Section of the Instructions for maintenance manual [757 Airworthiness Limitations Instructions (ALI)]. The revision would incorporate certain inspections and compliance times to detect fatigue cracking of principal structural elements (PSE). This proposal is prompted by analysis of data that identified specific initial inspection thresholds and repetitive inspection intervals for certain PSE's to be added to the ALI. The actions specified by the proposed AD are intended to ensure that fatigue cracking of various PSE's is detected and corrected; such fatigue cracking could adversely affect the structural integrity of these airplanes.