Airworthiness Directives; Sikorsky Aircraft Corporation Helicopters

We are publishing a new airworthiness directive (AD) for Sikorsky Aircraft Corporation Model S-76A, S-76B, S-76C, and S-76D helicopters, which was sent previously to all known U.S. owners and operators of these helicopters. This AD requires inspecting the main rotor (M/R) and tail rotor (T/R) pushrod assemblies and the jamnuts, and applying slippage marks across the pushrod tubes and jamnuts. This AD is prompted by an accident of a Sikorsky Aircraft Corporation Model S-76C helicopter. During preliminary investigation, a failed pushrod assembly was identified. These actions are intended to prevent loss of M/R or T/R flight control and subsequent loss of control of the helicopter.