On February 14, 1994, about 1802 hours Pacific standard time, a Bell 206L-1, N1077N, crashed during landing at Barstow-Daggett Airport, Barstow, California. The helicopter was engaged in a maintenance test flight performing autorotations to verify the installation of a freewheeling clutch assembly. The helicopter was operated by Aspen Helicopters, Inc., Oxnard, California, and was destroyed by impact. The certificated commercial pilot, the sole occupant, received serious injuries. Visual meteorological conditions prevailed. The flight originated at the Barstow airport on the day of the mishap at 1755 hours. In a verbal statement, the pilot said that he had completed a contract flight for the Department of the Interior and landed at Barstow. The pilot said he intended to do several autorotations to verify a new clutch assembly which was installed on the helicopter and signed off for return to service that morning. The pilot said that it was twilight, but that he could clearly see the runway lights when he lifted off to do the autorotations. The pilot made one successful autorotation and decided to make a second one to check the main rotor autorotational rpm. The pilot reported that during the second autorotation the main rotor rpm was low, but he did not get a low rotor warning horn or light. The pilot said that during the descent he was trying to bring the main rotor rpm up by varying his airspeed until the flare point. Witnesses reported that the helicopter began a flare about 50 feet above the ground on runway 22, then landed hard. The helicopter became airborne again, began to spin, and then landed hard, rolling onto its left side. The helicopter was examined by investigators from the Office of Aviation Safety, U.S. Department of the Interior. They reported finding no evidence of mechanical failure. The operator stated that the engine was still running after the helicopter came to rest and that the pilot shut the engine off. The freewheeling clutch unit was removed from the helicopter and sent to the manufacturer for examination under the supervision of a Federal Aviation Administration (FAA) inspector. No discrepancies were found during the examination. A National Transportation Safety Board computer program was used to determine the times of sunset and the end of civil twilight during the accident flight. According to the data, sunset occurred at 1733, and the end of civil twilight was at 1759. At 1802, the sun was 6.7 degrees below the horizon on a magnetic azimuth of 245.5 degrees.