Summary
We propose to adopt a new airworthiness directive (AD) for certain Sikorsky Model S-92A helicopters. This proposed AD would require installing a main gearbox (MGB) failed pump sensor and vacuum switch wiring, installing an MGB oil auto bypass system, activating Aircraft Management System (AMS) 7.1 software to show a new visual warning, and installing updated enhanced ground proximity warning system (EGPWS) software that includes an aural annunciation of a complete oil pressure loss condition. This proposed AD would also require inserting a Rotorcraft Flight Manual (RFM) Supplement into the applicable RFM. This proposed AD is prompted by investigation results of in-service oil leakage incidents. The proposed actions are intended to alert and prevent MGB oil loss, which could lead to failure of the MGB and subsequent loss of control of the helicopter.