Summary
We propose to adopt a new airworthiness directive (AD) for Sikorsky Aircraft Corporation (Sikorsky) Model S-92A helicopters. This proposed AD would require removing from service the tail gearbox center housing (housing) when it has 12,200 or more hours time-in-service (TIS). This proposed AD is prompted by fatigue analysis conducted by Sikorsky that determined the housing required a retirement life. The proposed actions are intended to prevent a crack in the housing, which could lead to loss of tail rotor drive and loss of helicopter control.