Airworthiness Directives; Bell Helicopter Textron Inc.-Manufactured 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

This amendment adopts a new airworthiness directive (AD) that applies to Bell Helicopter Textron Inc. (BHTI)-manufactured 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. This AD requires removing and replacing certain main rotor mast (mast) assemblies. This AD is prompted by a BHTI-manufactured Model UH-1B accident due to fatigue failure of a thin-wall mast installed on the helicopter. The actions specified by this AD are intended to prevent fatigue failure of the mast and subsequent loss of control of the helicopter.