Summary
We propose to adopt a new airworthiness directive (AD) for Sikorsky Aircraft Corporation (Sikorsky) Model 269A, 269A-1, 269B, 269C, 269C-1, 269D, and TH-55A helicopters. This proposed AD would require repetitively inspecting and lubricating the tail rotor (T/R) driveshaft splined fittings. This proposed AD is prompted by a report that the T/R driveshaft can disconnect due to deterioration of the splined coupling. The proposed actions are intended to detect and prevent excessive wear of the splined coupling, which could lead to failure of the T/R driveshaft and subsequent loss of control of the helicopter.