Airworthiness Directives; Bell Helicopter Textron, Inc. Model 214B, 214B-1, and 214ST Helicopters

This amendment supersedes 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 amendment requires changing the method of calculating the retirement life for the trunnion from high-power events to a maximum accumulated Retirement Index Number (RIN). This amendment 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. The actions specified by this 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.