Summary
We propose to supersede airworthiness directive (AD) 93-17-13 for Schweizer Aircraft Corporation and Hughes Helicopters, Inc. (now Sikorsky Aircraft Corporation) (Sikorsky) Model TH55A, 269A, 269A-1, 269B, and 269C helicopters. AD 93-17-13 requires installing tachometer markings and inspecting the driveshaft. This proposed AD would require recurring inspections of the driveshaft and would expand the applicability to include Model 269C-1 helicopters. This proposed AD is prompted by reports of accidents because of driveshaft failures. The actions of this proposed AD are intended to prevent the unsafe condition on these products.