Summary
This document proposes the adoption of a new airworthiness directive (AD) that is applicable to certain Boeing Model 747-100 and - 200 series airplanes. This proposal would require repetitive inspections for cracking of the station 800 frame assembly, and repair, if necessary. This action is necessary to find and fix fatigue cracks that could extend and fully sever the frame, which could result in development of skin cracks that could lead to rapid depressurization of the airplane. This action is intended to address the identified unsafe condition.