Airworthiness Directives; Boeing Model 747 and 767 Series Airplanes Equipped With General Electric CF6-80C2 Series Engines

This amendment adopts a new airworthiness directive (AD), applicable to certain Boeing Model 747 and 767 series airplanes, that requires repetitive functional tests of the directional pilot valve (DPV) of the thrust reversers to detect pneumatic leakage, and corrective action, if necessary. This amendment 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 this 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.