On June 30, 1983, a Bell 47G-3B-1 SOLOY (registration N1334X) operated by Bear Tooth Helicopters was involved in an aviation accident near Townsend, MT. Investigators recorded the probable cause as: The engine died of fuel starvation because of a low fuel state and because the pilot was descending at high speed with nose low. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A helicopter performed an autorotative forced landing after the engine quit due to fuel starvation. The main rotor severed the tail boom during the hard touchdown. The pilot had stretched the glide and lost rotor RPM.
Accident Details
The helicopter experienced an engine failure and the pilot initiated an autorotative forced landing. During the landing, the main rotor severed the tail boom. The pilot reported that he had stretched the autorotational glide to reach a hay field, which resulted in a loss of main rotor RPM.
The engine quit due to fuel starvation. According to the pilot, the fuel gauges indicated about 10 gallons just before the engine failed. He also stated that he felt starvation occurred. The pilot further noted that he was descending at high speed with a nose-low attitude, approximately 30 degrees nose low.
Fuel System Considerations
The helicopter's fuel tanks are slanted 10 degrees aft to compensate for a 7-degree nose-low attitude during normal high-speed cruise at 80 mph. A test pilot who specializes in this model of aircraft has noted that caution must be used to avoid unusual pitch attitudes when the fuel state is low.
Probable cause
The engine died of fuel starvation because of a low fuel state and because the pilot was descending at high speed with nose low.