Summary
We propose to adopt a new airworthiness directive (AD) for the Bell Helicopter Textron Canada Limited (BHTC) Model 427 helicopters. This proposed AD is prompted by a review of the tailboom attachment installation, which revealed that the torque value of the bolts specified in the BHTC Model 427 Maintenance Manual and applied during manufacturing was incorrect and exceeded the torque range recommended for the bolts. The proposed actions are intended to prevent an over- torque of the tailboom attachment bolt (bolt), bolt failure, loss of the tailboom, and subsequent loss of control of the helicopter.