Airworthiness Directives; Boeing Model 747-400 Series Airplanes Equipped With General Electric CF6-80C2 Series Engines

This amendment adopts a new airworthiness directive (AD) applicable to certain Boeing Model 747-400 series airplanes that requires various inspections and functional tests to detect discrepancies of the thrust reverser control and indication system, and correction of any discrepancy found. This amendment is prompted by reports indicating that several center drive units (CDU) were returned to the manufacturer of the CDU's because of low holding torque of the CDU cone brake. 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 in the thrust reverser control system that can result in inadvertent deployment of a thrust reverser during flight.