Airworthiness Directives; Sikorsky Aircraft-manufactured Model CH-34A, CH-34C, H-34A, HH-34J, HSS-1, HSS-1N, HUS-1, SH-34J, UH-34D, UH-34E, and UH-34J Helicopters

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This amendment adopts a new airworthiness directive (AD) that is applicable to Sikorsky Aircraft-manufactured Model CH-34A, CH-34C, H- 34A, HH-34J, HSS-1, HSS-1N, HUS-1, SH-34J, UH-34D, UH-34E, and UH-34J helicopters. This action requires initial and repetitive magnetic particle inspections of the main rotor shaft (shaft) for cracks, and defines power limitations for certain helicopter operations. This amendment is prompted by a recent accident in which a shaft failed, resulting in loss of power. Subsequent inspections on other aircraft of the same type revealed cracks in four additional shafts. The actions specified in this AD are intended to prevent failure of the shaft, loss of power to the rotor system, and subsequent loss of control of the helicopter.