Airworthiness Directives; Bell Helicopter Textron, Inc. Model 204B, 205A, 205A-1, 205B, and 212 Helicopters

This document publishes in the Federal Register an amendment adopting superseding Airworthiness Directive (AD) 2000-15-52, which was sent previously to all known U.S. owners and operators of Bell Helicopter Textron, Inc. Model (BHTI) Model 204B, 205A, 205A-1, 205B, and 212 helicopters by individual letters. This AD reduces the retirement index number (RIN) life limit for the main rotor mast (mast); increases the RIN factor for masts and main rotor trunnions (trunnions); applies standard RIN factors for all external load lifts; and requires a one-time inspection of the snap ring groove area of the mast. This AD also establishes RIN factors for masts and trunnions that have been previously installed on military or restricted category helicopters and removes from service those masts that have been previously installed with a hub spring. This amendment is prompted by an occurrence of a cracked mast at a lower value than the established RIN life limit. The actions specified by this AD are intended to preclude the occurrence of fatigue cracks in the damper clamp splined area of a mast. A crack in the damper clamp splined area could result in failure of a mast or trunnion, separation of the main rotor system, and subsequent loss of control of the helicopter.