CHI03LA172

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."

On June 20, 2003, at 1418 central daylight time, a Bell 206B, N79BH, operated by Brainerd Helicopter Service, sustained substantial damage during an autorotation following a loss of tail rotor authority near Baxter, Minnesota. Visual meteorological conditions prevailed at the time of the accident. The commercial pilot and one passenger reported minor injuries, and the other passenger was uninjured. The 14 CFR Part 91 business flight was operating without a flight plan. The local flight departed from Brainerd Lakes Regional Airport, Brainerd, Minnesota, at 1416.

The pilot reported he lowered the helicopter's airspeed and proceeded downwind to the north at 300 feet above ground level. The pilot noted he brought the helicopter into a hover after turning to the west. The pilot stated the helicopter began a "slow yaw to the right," which he attempted to correct with left pedal. The pilot reported the pedal inputs, "did not have any results" and "there was no tail rotor authority." The pilot noted the helicopter rotated three or four times in a level attitude. The pilot stated he attempted to maintain a forward airspeed and correct the rotation with "major pedal adjustments." The pilot reported he initiated an autorotation to descend into a clearing. The pilot noted the helicopter contacted trees in a nose level position and came to a rest upright.

A Federal Aviation Administration (FAA) airworthiness inspector conducted an on-scene examination of the helicopter. The examination confirmed engine and flight control continuity.

A weather reporting station at Brainerd Lakes Regional Airport, 3 miles to the southwest of the accident site, reported the winds at 1453 from 170 degrees at 14 knots, gusting to 21 knots.

FAA Advisory Circular (AC) 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."