On May 29, 1994, at 1347 Pacific daylight time, a homebuilt experimental Parker Rotorway Exec 90 helicopter, N78435, collided with trees and the ground during an attempted autorotation near Fallbrook, California. The autorotation was precipitated by a loss of engine power. The helicopter, owned and operated by the pilot/builder, was on a local area personal flight. Visual meteorological conditions prevailed at the time and no flight plan was filed for the operation. The helicopter was destroyed in the collision sequence. The certificated private pilot, the sole occupant, sustained fatal injuries. The flight is presumed to have originated from the French Valley airport on the day of the accident at an undetermined time. Ground witnesses in the township of Pala, near the accident site, reported that the helicopter had made several low passes over the town at above-ground altitudes estimated at 200 feet. The helicopter then departed the town area flying up a narrow canyon over Highway 76, still at the estimated altitude of 200 feet. The helicopter then descended rapidly to the highway, impacted the pavement, and rolled over. The helicopter contacted an oak tree during the descent. A Federal Aviation Administration (FAA) inspector from the San Diego Flight Standards District Office responded to the accident site and examined the wreckage. In his report, the inspector noted that control system continuity was established throughout the helicopter. Fuel system integrity was also established and the tank was undamaged. No evidence of postimpact fuel leakage was noted. Only residual fuel was found in the tank. According to FAA airman files, the pilot holds a private pilot certificate with an airplane category rating. The pilot does not have a rotorcraft category rating. In a telephone interview, the pilot's son reported that his father had been taking helicopter lessons for about 6 months. Portions of the pilot's logbook were examined and his flight instructor was interviewed. The instructor reported that he had given the pilot about 24 hours of dual instruction in the accident helicopter during February of 1994. He further stated that he had only endorsed the pilot for limited hovering solo flights. The pilot had been given only one introductory lesson in autorotations to a power recovery. The instructor reported that the fuel gauge in the helicopter was "notoriously inaccurate," and he had instructed the pilot to use a dipstick before flight and the clock during flight to determine fuel quantity. The instructor stated that the pilot typically fueled the helicopter with automotive fuel from 5-gallon containers, and "only added the quantity he thought he needed" for a particular flight. An autopsy was conducted by the San Diego County Coroner's Office with specimens retained for toxicological analysis. The toxicological specimens were subsequently determined to be unsuitable for analysis.