NTSB Identification: CEN10FA509
14 CFR Part 91: General Aviation
Accident occurred Tuesday, August 31, 2010 in Walnut Grove, AR
Probable Cause Approval Date: 11/17/2011
Aircraft: BELL HELICOPTER TEXTRON 206L-1, registration: N62AE
Injuries: 3 Fatal.

NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.

The air ambulance positioning flight was en route to a landing zone to pick up a patient for transfer. One witness in the accident area described a helicopter circling overhead, and another witness reported that they heard the sound of crashing metal or the impact of the helicopter with the ground.

Radar and global positioning system data depicted the accident helicopter reversing course multiple times just prior to the accident. The flight path of the helicopter prior to the accident was consistent with spatial disorientation and subsequent loss of control due to an inadvertent encounter with instrument meteorological conditions.

The wreckage was located in forested terrain approximately 3.5 miles south of the intended destination. The wreckage distribution was consistent with an in-flight separation of the main rotor and tail boom. An examination of the helicopter airframe, engine, and related systems revealed no pre-impact anomalies. Both the main rotor assembly and tail boom separated in overload. The main rotor tie down strap found wrapped around the blade was a result of the accident sequence and did not contribute to the accident.

Weather information indicated a moist stable environment from the surface to approximately 2,500 feet, which supported low clouds and stratus below 2,500 feet. In addition, an AIRMET had been issued for instrument meteorological conditions (IMC) due to low ceilings and poor visibility. The Area Forecast advised of marginal visual meteorological conditions in the state of Arkansas. Witnesses in the area described the weather as hazy or foggy, with overcast skies. One witness stated that it was very dark and no moon could be seen. The investigation was unable to determine what information the pilot had or method he used to obtain weather information prior to the flight.

The pilot held a commercial pilot certificate and an instrument rating. He had received instrument training, including inadvertent flight into IMC; however, the company did not operate in IMC. The pilot was trained and had recent experience in the use of night vision goggles. The investigation was unable to determine if the pilot was using the night vision goggles at the time of the accident. While toxicological results were positive for ethanol, the samples were contaminated and the source of the ethanol could not be determined.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

The pilot’s loss of aircraft control, due to spatial disorientation, resulting in the in-flight separation of the main rotor and tail boom.

Full narrative available

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