Summary
This document proposes the adoption of a new airworthiness directive (AD) that is applicable to certain Boeing Model 737 series airplanes. This proposal would require repetitive ultrasonic inspections to detect broken bolts that attach the terminal support fittings to the upper part of the Body Station 1088 bulkhead, and corrective actions, if necessary. This proposal also would require eventual replacement of the existing bolts with new, improved bolts, which, when accomplished, would terminate the requirements of the AD. This proposal is prompted by reports that bolts that attach the terminal support fittings to the upper part of the bulkhead were found broken. The actions specified by the proposed AD are intended to prevent such broken bolts, which could result in reduced structural integrity of the vertical fin installation and possible loss of the vertical fin.