Action
Final rule.
Summary
We are superseding revised Airworthiness Directive (AD) 76-12- 07 for all Bell Model 204B and certain serial-numbered Model 205A-1 helicopters with a certain tail rotor pitch control chain (chain) installed. AD 76-12-07 required visually inspecting the chain to detect a crack in the link segments and, for affected Model 205A-1 helicopters, replacing the chain and cable control system with a push- pull control system. This new AD requires, for Bell Model 204B, inspecting certain chains at specified intervals, revising the inspection procedures, installing a tail rotor cable and chain damper kit (damper kit), and revising the maintenance manual or Instructions for Continued Airworthiness (ICAs) to include the inspection intervals. This new AD also requires, for certain Bell Model 205A-1 helicopters, replacing the chain and cable control system with an airworthy tail rotor push-pull control system kit. This AD was prompted by the rapid growth of a crack leading to premature chain failure. The actions are intended to prevent failure of the chain, loss of tail rotor blade pitch control, and subsequent loss of control of the helicopter.