Summary
This document proposes the adoption of a new airworthiness directive (AD) that is applicable to certain Boeing Model 747 and 767 series airplanes. This proposal would require repetitive functional tests of the directional pilot valve (DPV) of the thrust reversers to detect pneumatic leakage, and corrective action, if necessary. This proposal is prompted by a report of a latent failure mode of the fail- safe features of the thrust reverser system identified as possible leakage of the DPV that is due to a poppet being jammed slightly open or a leaking o-ring. The actions specified by the proposed AD are intended to ensure the integrity of the fail-safe features of the thrust reverser system by preventing possible failure modes, which could result in inadvertent deployment of a thrust reverser during flight, and consequent reduced controllability of the airplane.