Overview
A helicopter accident occurred when the engine lost power while the pilot was flying in a ravine. The pilot executed a forced landing, but during the landing, a main rotor blade impacted the tail boom. Post-accident examination revealed a leaking fuel drain valve and a fuel quantity indicator displaying 'LOW, NOT EMPTY'.
Pilot Report
According to the pilot's written statement, he visually checked the fuel level during his morning preflight. He reported that he uses a stopwatch to back up the fuel quantity gauge and typically has two hours and twenty-five minutes of usable fuel. At the time of the accident, he had flown 2 hours and 1.5 minutes, and estimated that he would normally have 10 or 11 gallons of usable fuel remaining. He stated that he was in a ravine when the engine lost power. He 'used some of the rotor RPM to get away from the ravine on to an area without rocks and trees.' He then flared and lowered the collective. During the landing, a main rotor blade impacted the tail boom. He reported that the fuel quantity gauge indicated 40 pounds when he shut off the master switch.
Findings
A Federal Aviation Administration (FAA) inspector reported that the drain valve in the main fuel sump was leaking. The fuel quantity indicator displayed 'LOW, NOT EMPTY'. No other evidence of preimpact mechanical malfunction was reported. The fuel quantity gauge reading at shutdown was 40 pounds.
Conclusion
The accident involved a loss of engine power while the helicopter was in a ravine, followed by a forced landing that resulted in a main rotor blade strike to the tail boom. A leaking fuel drain valve and low fuel indication were noted post-accident, but no other mechanical malfunctions were identified.