Summary
This document proposes the adoption of a new airworthiness directive (AD) that is applicable to certain Boeing Model 747 series airplanes. This proposal would require an internal visual inspection to detect cracks of the skin and internal doublers above main entry door 1 at body station 460, and various follow-on actions. This proposal is prompted by reports indicating that multiple fatigue cracks were found in both internal skin doublers. The actions specified by the proposed AD are intended to detect and correct such fatigue cracking, which could result in reduced structural integrity of the fuselage and consequent rapid depressurization of the cabin.