Summary
This document proposes the adoption of a new airworthiness directive (AD) that is applicable to all Boeing Model 727 series airplanes. This proposal would require repetitive inspections to detect cracks in the forward flange of the vertical beam of the aft fuselage bulkhead at certain buttock lines, and installation of a splice repair, if necessary. The proposed AD also would require installation of a preventative modification on the door frames in certain cases. This proposal is prompted by reports of fatigue cracks found in the vertical beam web and forward flange of the aft fuselage bulkhead. The actions specified by the proposed AD are intended to detect and correct such fatigue cracking, which could result in the inability of the subject vertical beam to withstand the fail-safe loads, and consequent loss of cabin pressurization.