Summary
This document proposes the adoption of a new airworthiness directive (AD) applicable 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 would require removing and replacing certain main rotor mast (mast) assemblies. This proposal is prompted by the crash of a BHTI-manufactured Model UH-1B due to failure of a thin-wall mast installed on the helicopter. The actions specified by the proposed AD are intended to prevent fatigue failure of the mast and subsequent loss of control of the helicopter.