AD 2017-14-06 Amendment 39-18950

We are superseding 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 required installing tachometer markings and inspecting the lower coupling driveshaft (driveshaft). This new AD requires repetitive inspections of the driveshaft and expands the applicability to include Model 269C-1 helicopters. This AD is prompted by reports of accidents because of driveshaft failures. The actions of this AD are intended to prevent the unsafe condition on these products.