Airworthiness Directives; Bell Helicopter Textron, Inc.- manufactured Model HH-1K, SW204, SW204HP, SW205, SW205A-1, TH-1F, TH- 1L, UH-1A, UH-1B, UH-1E, UH-1F, UH-1H, UH-1L, and UH-1P Helicopters

This amendment adopts a new airworthiness directive (AD) that is applicable to Bell Helicopter Textron, Inc. (BHTI)-manufactured Model HH-1K, SW204, SW204HP, SW205, SW205A-1, TH-1F, TH-1L, UH-1A, UH- 1B, UH-1E, UH-1F, UH-1H, UH-1L, and UH-1P helicopters. This action requires inspecting the tail rotor yoke (yoke) assembly historical records to determine if the affected yoke assembly has been involved in any incidents that may have induced a bending load. It further requires replacement of the yoke assembly with a yoke assembly that has been x- ray diffraction inspected or has zero hours time-in-service (TIS); installing and inspecting an airworthy flapping stop or trunnion assembly to detect excessive bending loads; and revising the applicable Rotorcraft Flight Manual. This amendment is prompted by in-flight failures of yokes installed on civilian and military helicopters of similar type design, including three reported accidents. The actions specified in this AD are intended to detect static or dynamic overload on the yoke due to external bending forces, which could result in failure of the yoke, loss of the tail rotor, and subsequent loss of control of the helicopter.