Airworthiness Directives; Boeing Model 777-200 and -300 Series Airplanes

This amendment supersedes an existing airworthiness directive (AD), applicable to all Boeing Model 777-200 and -300 series airplanes, that currently requires revising the Limitations Section of the Airplane Flight Manual (AFM) to prohibit the dispatch of certain airplanes under certain conditions. That amendment also requires repetitive inspections to ensure correct operation of the backup generators; and, for certain airplanes, a one-time inspection to detect damage of the engine external gearbox; and corrective actions, if necessary. This amendment continues the AFM and inspection requirements and expands certain corrective action requirements. This amendment is prompted by reports of inflight shutdowns due to sheared backup generator shafts. The actions specified in this AD are intended to prohibit the dispatch of an airplane with an engine-mounted backup generator having a sheared shaft; and to detect and correct damage to the engine, which could result in inflight shutdowns.