Airworthiness Directives; Bell Helicopter Textron, A Division of Textron Canada, Model 206L, L-1, L-3, and L-4 Helicopters

This amendment supersedes an existing airworthiness directive (AD), applicable to Bell Helicopter Textron, A Division of Textron Canada (BHTC), Model 206L, L-1, L-3, and L-4 helicopters, that currently requires the creation of a component history card or equivalent record using the Retirement Index Number (RIN) system for certain mast and trunnions and a system for tracking increases to the accumulated RIN. That AD also establishes retirement lives for the mast and trunnion. This amendment requires the same actions required by the existing AD but increases the RIN multiplier for the mast and corrects a helicopter model number. This amendment is prompted by further tests and analyses that indicate the RIN multiplier for the Model 206L-4 helicopters needs to be increased and the discovery of an error in a model designation in the existing AD. The actions specified by this AD are intended to prevent fatigue failure of the mast or trunnion, which could result in loss of the main rotor system and subsequent loss of control of the helicopter.