Airworthiness Directives; Sikorsky Aircraft Corporation Helicopters

We propose to adopt a new airworthiness directive (AD) for Sikorsky Aircraft Corporation (Sikorsky) Model S-92A helicopters. This proposed AD would require inspecting the main transmission forward (fwd) and aft frame assembly and adjacent skins for a crack and loose fasteners and establishing life limits for certain frame assemblies. This proposed AD is prompted by fatigue analysis indicating stress concentrations as well as the discovery of a crack in the station (STA) 362 frame and skin on a Model S-92A helicopter. The proposed actions are intended to detect a crack in a frame assembly and prevent failure of a frame and subsequent loss of control of the helicopter.