Summary
This document proposes the adoption of a new airworthiness directive (AD) that is applicable to all Boeing Model 747 series airplanes. This proposal would require repetitive inspections to detect cracking of the forward and aft inner chords and the splice fitting of the forward inner chord of the station 2598 bulkhead, and repair, if necessary. This proposal is prompted by reports of fatigue cracking found in those areas. The actions specified by the proposed AD are intended to detect and correct such cracking, which could result in reduced structural capability of the bulkhead and the inability of the structure to carry horizontal stabilizer flight loads.