AD 2001-13-51 Amendment 39-12443

This document publishes in the Federal Register an amendment adopting Airworthiness Directive (AD) 2001-13-51, which was sent previously to all known U.S. owners and operators of Bell Helicopter Textron Canada (BHTC) Model 206L-4, 407, and 427 helicopters by individual letters. This AD requires visually inspecting certain driveshafts for a crack, a loose bolt or nut, or red powder residue. If a crack, a loose bolt or nut, or red powder residue is found, replacing the driveshaft before further flight and notifying the FAA within 10 days is also required. This amendment is prompted by a driveshaft failure on a BHTC Model 407 helicopter that resulted in an engine shutdown and an emergency landing. Failure of the driveshaft was due to cracking of the flexframe on the forward end of the driveshaft. In addition, three other incidents of a cracked flexframe on the forward end of the driveshaft on other Model 407 helicopters have been reported. The actions specified by this AD are intended to prevent failure of a driveshaft, loss of drive to the main rotor system, and a subsequent emergency forced landing.