AD 2004-20-07 Amendment 39-13812

This amendment adopts a new airworthiness directive (AD) for the specified Bell Helicopter Textron Canada (BHTC) model helicopters that requires certain inspections of the main rotor yoke (yoke) for a crack, fretting, or buffer deterioration. If a crack is found, the AD requires replacing the yoke with an airworthy yoke before further flight. If fretting or buffer deterioration are found, the AD requires further inspecting the main rotor hub assembly (hub assembly) and repairing or replacing any unairworthy parts. Also, the AD requires a torque inspection of the flapping bearing retaining nuts at specified intervals. This amendment is prompted by the discovery of a crack in a yoke. The actions specified by this AD are intended to prevent failure of the yoke and subsequent loss of control of the helicopter.