Summary
This document proposes the supersedure of an existing airworthiness directive (AD), applicable to Bell Helicopter Textron, Inc. (BHTI) Model 214B, 214B-1, and 214ST helicopters, that currently establishes a retirement life of 60,000 high-power events for the main rotor trunnion (trunnion). This proposal would require changing the method of calculating retirement life for the trunnion from high power events to a maximum accumulated Retirement Index Number (RIN). This proposal is prompted by fatigue analyses and tests that show certain trunnions fail sooner than originally anticipated because of the unanticipated higher number of lifts or takeoffs (torque events) performed with those trunnions in addition to the time-in-service (TIS) accrued under other operating conditions. The actions specified by the proposed AD are intended to prevent fatigue failure of the trunnion, which could result in loss of the main rotor and subsequent loss of control of the helicopter.