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 40,000 high-power events for the lower planetary spider (spider). This amendment changes the method of calculating the retirement life for the spider from high-power events to a maximum accumulated Retirement Index Number (RIN) of 80,000, and makes this RIN applicable to an additional part-numbered spider. This amendment is prompted by fatigue analyses and tests that show certain spiders fail sooner than originally anticipated because of the unanticipated higher number of external load lifts and takeoffs (torque events) performed with those spiders, in addition to the time-in-service (TIS) accrued under other operating conditions. The actions specified by this AD are intended to prevent fatigue failure of the spider, which could result in failure of the main transmission and subsequent loss of control of the helicopter.