Airworthiness Directives; Model HH-1K, TH-1F, TH-1L, UH-1A, UH-1B, UH-1E, UH-1F, UH-1H, UH-1L, UH-1P, and Southwest Florida Aviation Model SW204, SW204HP, SW205, and SW205A-1 Helicopters, Manufactured by Bell Helicopter Textron, Inc. for the Armed Forces of the United States

This amendment supersedes an existing airworthiness directive (AD) that applies to Model HH-1K, TH-1F, TH-1L, UH-1A, UH-1B, UH-1E, UH-1F, UH-1H, UH-1L, UH-1P, and Southwest Florida Aviation Model 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 AD contains 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 AD also adds a note clarifying that the mast serial number (S/N) is defined by 5 or fewer digits plus various prefixes. This amendment 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 this 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.