Airworthiness Directives; MD Helicopters, Inc. Model 600N Helicopters

This document publishes in the Federal Register an amendment adopting Airworthiness Directive (AD) 2001-24-51, which was sent previously to all known U.S. owners and operators of MD Helicopters, Inc. (MDHI) Model 600N helicopters by individual letters. This AD requires, within 5 hours time-in-service (TIS), inspecting both upper tailboom attachments, nutplates and both angles for a crack or thread damage and repairing or replacing any cracked or damaged part before further flight. Also, this AD requires replacing the upper right-hand (RH) tailboom attachment bolt (bolt) with a new bolt, and if the upper RH bolt is broken, replacing the three remaining bolts with airworthy bolts before further flight. Adding a washer to each bolt and modifying both upper access covers are also required. Thereafter, at specified intervals, inspecting the upper tailboom attachments and repairing or replacing any cracked part before further flight is required. This AD is prompted by the discovery of a cracked bolt on a helicopter. The actions specified by this AD are intended to prevent failure of a tailboom attachment, loss of the tailboom, and subsequent loss of control of the helicopter.