Airworthiness Directives; Sikorsky Aircraft Corporation Model S-92A Helicopters

This amendment supersedes an existing airworthiness directive (AD) for Sikorsky Aircraft Corporation (Sikorsky) Model S-92A helicopters. That AD currently requires removing all main gearbox (MGB) filter bowl assembly mounting titanium studs (titanium studs) and replacing them with steel studs. This amendment requires the same actions as the existing AD as well as changes to the Rotorcraft Flight Manual (RFM). This amendment is prompted by an accident, by recent RFM changes made by the manufacturer that were not available when we issued the existing AD, and by our determination that certain MGB Normal and Emergency procedures in the RFM are unclear, may cause confusion, and may mislead the crew regarding MGB malfunctions, in particular the urgency to land immediately after warning indications of loss of MGB oil pressure and oil pressure below 5 pounds per square inch (psi). Replacing the titanium studs is intended to prevent their failure, which could result in rapid loss of oil, failure of the MGB, and subsequent loss of control of the helicopter. Changing the RFM procedures is intended to clarify and emphasize certain Normal and Emergency procedures to give the crew the best available information in the event of certain MGB malfunctions.