Aircraft Accident/Incident Report

Baxter, Minnesota 56425
Friday, June 20, 2003 14:18 CDT

The helicopter impacted trees during an autorotation following a loss of tail rotor authority. The pilot reported he was in a westbound hover about 300 feet above ground level, with a crosswind. The pilot noted the helicopter began to yaw slowly to the right and that his attempts to correct the yaw were unsuccessful. The pilot stated the yaw accelerated and the tail rotor lost effectiveness. The pilot reported he entered an autorotation after the helicopter had completed three or four rotations. The pilot noted the helicopter contacted trees and came to a stop in an upright position. An on-scene inspection of the helicopter confirmed engine and flight control continuity. A weather reporting station 3 miles to the southwest of the accident site reported the winds from 170 degrees at 14 knots, gusting to 21 knots. FAA Advisory Circular 90-95 states, "Loss of tail rotor effectiveness is a critical, low-speed aerodynamic flight characteristic which can result in a 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."

The pilot's failure to maintain control of the helicopter due to a loss of tail rotor effectiveness. Factors contributing to this accident were the helicopter's low airspeed, low altitude, the crosswind, and the trees.