Incident Details
The helicopter impacted trees during an autorotation following a loss of tail rotor authority. An on-scene inspection confirmed engine and flight control continuity.
Pilot Report
The pilot reported he was in a westbound hover about 300 feet above ground level with a crosswind. The helicopter began to yaw slowly to the right, and his attempts to correct the yaw were unsuccessful. The yaw accelerated and the tail rotor lost effectiveness. The pilot entered an autorotation after the helicopter had completed three or four rotations. The helicopter contacted trees and came to a stop in an upright position.
Weather Information
A weather reporting station 3 miles to the southwest of the accident site reported winds from 170 degrees at 14 knots, gusting to 21 knots.
References
FAA Advisory Circular 90-95 states, "Loss of tail rotor effectiveness is a critical, low-speed aerodynamic flight characteristic which can result in an uncommanded rapid yaw rate which does not subside of its own accord and, if not corrected, can result in the loss of aircraft control." The AC further states, "Any maneuver which requires the pilot to operate in a high-power, low-airspeed environment with a left crosswind or tailwind creates an environment where unanticipated right yaw may occur."