Summary
This document revises an earlier proposed airworthiness directive (AD), applicable to Bell Helicopter Textron, Inc. (BHTI) Model 214B and 214B-1 helicopters, that would have established a mandatory retirement life of 15,000 high-power events for the pillow block bearing bolts (bearing bolts). That proposal was prompted by fatigue analyses and tests that show certain bearing bolts fail sooner than originally anticipated because of the unanticipated high number of lifts and takeoffs (torque events) performed with those bearing bolts in addition to the time-in-service (TIS) accrued under normal operating conditions. This action revises the proposed rule by proposing the creation of a component history card using a Retirement Index Number (RIN) system, establishment of a system for tracking increases to the accumulated RIN, and establishment of a maximum accumulated RIN for the bearing bolts. The actions specified by this proposed AD are intended to prevent fatigue failure of the bearing bolts, which could result in failure of the main rotor system and subsequent loss of control of the helicopter.