Summary
This document proposes superseding an existing airworthiness directive (AD) for Model HH-1K, TH-1F, TH-1L, UH-1A, UH-1B, UH-1E, UH-1F, UH-1H, UH-1L, and UH-1P; and Southwest Florida Aviation SW204, SW204HP, SW205, and SW205A-1 helicopters manufactured by Bell Helicopter Textron, Inc. (BHTI) for the Armed Forces of the United States. That AD currently requires establishing retirement lives for certain main rotor masts, creating a component history card or equivalent record, and identifying and replacing any unairworthy masts. That AD also contains certain requirements regarding the hub spring, conducting inspections based on the retirement index number (RIN), and sending information to the FAA. This action would contain the same requirements but would establish a retirement life for the main rotor trunnion (trunnion) based on monitoring the number of torque events and flight hours rather than flight hours only as currently required. This action would also add a note clarifyingthat the mast serial number (S/N) is defined by 5 or fewer digits plus various prefixes. This proposal is prompted by the determination that monitoring the number of torque events and flight hours for the trunnion is more accurate than by monitoring flight hours only to establish a retirement life. The actions specified by the proposed AD are intended to prevent failure of a mast or trunnion, separation of the main rotor system, and subsequent loss of control of the helicopter.