Summary
This document proposes the adoption of a new airworthiness directive (AD) for Bell Helicopter Textron, Inc. (BHTI) Model 205A-1, 205B, 212, 412, 412EP, and 412CF helicopters. The AD would require removing each existing tail rotor counterweight bellcrank (bellcrank) retention nut (retention nut), replacing each retention nut with a zero hours time-in-service (TIS) retention nut; and follow-up inspections of installed retention nuts. This proposal is prompted by an in-flight loss of a bellcrank due to failure of the retention nut. The actions specified by the proposed AD are intended to prevent failure of the retention nut, which could result in the bellcrank migrating off the crosshead spindle, loss of tail rotor control, and subsequent loss of control of the helicopter.