Airworthiness Directives; Sikorsky Aircraft Corporation Model S-61L, S-61N, S-61-NM, and S-61R Helicopters

This amendment adopts a new airworthiness directive (AD) for the specified Sikorsky Aircraft Corporation (Sikorsky) model helicopters that requires installing a Number 5 bearing chip detector in each engine, installing an on-board chip detector annunciation system, and revising the Rotorcraft Flight Manual (RFM) to add procedures for crew response to an on-board chip detector annunciation. This amendment is prompted by reports of the failure of the engine's Number 5 bearing that resulted in erratic movement of the high-speed engine-to-transmission shaft (shaft), oil leakage, an in-flight fire and an emergency landing. The actions specified by this AD are intended to detect an impending engine bearing (bearing) failure, which, if undetected and not addressed by appropriate crew action, may result in oil leakage, severing of the shaft housing, an uncontained in-flight fire, and a subsequent emergency landing.