AD FAA-2010-1137

This document publishes in the Federal Register an amendment adopting Airworthiness Directive (AD) 2010-19-51, which was sent previously to all known U.S. owners and operators of the specified model Bell Helicopter Textron Canada (Bell) helicopters by individual letters. This AD requires inspecting parts of the main rotor hydraulic servo actuator (servo actuator) for certain conditions and replacing any unairworthy parts before further flight. This AD is prompted by a collective servo actuator malfunction and a subsequent investigation that revealed the output piston rod assembly (piston rod) had fractured at the threaded end because of stress corrosion cracking. Also, during the investigation of that servo actuator malfunction, a nonconforming grind relief was discovered on a separate piston rod. The actions specified by this AD are intended to detect corrosion or a nonconforming piston rod that, if not detected and corrected, could result in failure of the piston rod, failure of the servo actuator, and subsequent loss of control of the helicopter.