Airworthiness Directives; Sikorsky Aircraft Corporation Helicopters

We are superseding an existing Emergency airworthiness directive (AD) for Sikorsky Aircraft Corporation (Sikorsky) Model S-70, S-70A, S-70C, S-70C(M), and S-70C(M1) helicopters with a certain part- numbered intermediate gearbox (IGB). The existing Emergency AD requires a one-time inspection of the internal oil passages of the IGB for an obstruction. That Emergency AD was prompted by an accident that resulted from blockage of oil in the IGB by a plug that was inadvertently left in the IGB during the coating of the IGB housing. We are issuing this supersedure to that Emergency AD to include two additional part numbers of affected IGBs and identify a specific date since new or overhaul of the affected IGBs. The actions specified by this AD are intended to detect a plug in the IGB and prevent overheating and seizing of the IGB, failure of the tail rotor drive output shaft, loss of tail rotor drive, and subsequent loss of control of the helicopter.