NTSB Factual Report

On September 5, 2001, at 1830 mountain daylight time, an Aerospatiale AS350BA, N57843, operated by Crew Concepts, Inc., of Boise, Idaho, was substantially damaged when it collided with terrain during aerial taxi at the Kemmerer Municipal Airport, Kemmerer, Wyoming. The commercial pilot, the sole occupant aboard, was not injured. Visual meteorological conditions prevailed, and no flight plan had been filed for the positioning flight being conducted under Title 14 CFR Part 91. The flight originated from Pocatello, Idaho, at an undetermined time.

In a telephone interview with the pilot, he said he was bringing the helicopter to Kemmerer for seismic survey support. He was aerial taxiing over the taxiway parallel to runway 16 when the helicopter started spinning. Opposite anti-torque pedal input had no effect in arresting the spin. The helicopter struck the ground, and rolled over on its side. The tail boom was severed and the main rotor system was torn from its mounts. Recorded winds at Evanston, Wyoming, located 52 miles southwest of Kemmerer, were from 260 degrees at 25 knots, gusting to 36 knots. The peak wind, recorded at 1929, was from 240 degrees at 47 knots.

Upon learning of the accident, the operator dispatched its investigator to the accident scene to conduct a company investigation. According to his report, the pilot said he was aerial taxiing at 10 knots into a slight quartering headwind. There was some thunderstorm activity west of the airport. As the pilot turned towards the tie down area, "a very strong gust of wind seemed to hit the aircraft on the left side." The helicopter yawed to the left and full right pedal had no effect on arresting the counterclockwise spin. The report stated that the pilot lost control "due to severe/weather conditions...The application of full right pedal to correct yaw with no effect precipitated the situation whereby the pilot lost tail rotor effectiveness once the counterclockwise spin began." The report noted that Eurocopter, the helicopter manufacturer, issued Service Letter 1518-67-01 in April 2001, that described three similar mishaps. The report concluded, "Pilots must ensure that the application of LEFT pedal inputs are very slight with immediate correction using right pedal. Additionally, pilots are not to apply LEFT pedal inputs while passing through 'translational lift.' This restriction is to preclude the possibility of 'tail rotor vortex ring state' which may result in a spin to the left from which recovery is not possible."

According to the operator, the pilot had 4,000 total flight hours in helicopters. He had recently transitioned to, and had 8 hours in, the AS350.

NTSB Probable Cause

the loss of tail rotor effectiveness while air taxiing. Contributing factors were the high winds and gusts, and the pilot's limited experience in aircraft make/model.