Helicopter Loss of Tail Rotor Effectiveness and Collision With Terrain
An inspector with the Federal Aviation Administration responded to the accident site and examined the wreckage. The helicopter came to rest on its right side. The main rotor blades received structural damage and remained attached to their hub. The tail rotor drive shaft was sheared in two locations. The tail rotor blades remained attached to their hub. Control continuity was established from the cockpit to the main rotor and tail rotor system except for impact damage. There was sufficient fuel on board and there was oil in the engine. An external examination of the engine revealed no anomalies. His overall assessment of the wreckage did not reveal any evidence of a mechanical malfunction or anomaly.
The FAA issued Advisory Circular ("AC") 90-95, Unanticipated Right Yaw in Helicopters, in February 1995. The AC stated that the loss of tail rotor effectiveness (LTE) was a critical, low-speed aerodynamic flight characteristic which could result in an uncommanded rapid yaw which does no