Airworthiness Directives; Bell Helicopter Textron Canada Helicopters
We are adopting a new airworthiness directive (AD) for the Bell Helicopter Textron Canada Limited (BHTC) Model 407 helicopters. This AD requires you to replace tailboom-attachment hardware (attachment hardware), and perform initial and recurring determinations of the torque on the nuts of the tailboom-attachment bolts (bolts) at all four attachment locations. This AD was prompted by a review of the tailboom-attachment installation, which revealed that the torque value of the bolts specified in the BHTC Model 407 Maintenance Manual and applied during manufacturing was incorrect and exceeded the torque range recommended for the bolts. The actions required by this AD are intended to prevent an over-torque of a bolt, bolt failure, loss of the tailboom, and subsequent loss of control of the helicopter.