Airworthiness Directives; Sikorsky Aircraft Corporation (Sikorsky) Model S-76C Helicopters

This amendment supersedes an existing priority letter airworthiness directive (AD), applicable to Sikorsky Model S-76C helicopters, that currently requires, before further flight, inserting new operating limitations and performance data into the Rotorcraft Flight Manual (RFM) which require lower allowable gross weights for certain operational conditions. This amendment requires the same actions as the priority letter AD, but updates the previously referenced RFM's. This amendment is prompted by the discovery that the RFM's referenced in the priority letter AD have been revised. The actions specified by this AD are intended to provide the correct RFM references and to prevent an inability to achieve the published One- Engine-Inoperative (OEI) performance and subsequent loss of control of the helicopter.