Incident Overview
A helicopter on an instructional solo cross-country flight experienced an engine power loss approximately 1 hour and 25 minutes after departure. During the subsequent autorotational landing, the helicopter struck trees.
Pilot Actions and Observations
The pilot reported that after the rotor rpm briefly decreased from the normal operating range for the second time, he made the decision to land. He noted that the engine "sounded" okay. During the descent for landing, at an altitude of 1,000 feet mean sea level (msl), the engine began losing power.
A witness observed the helicopter at an estimated altitude of 1,500 feet msl. According to the witness, the engine was "cutting in and out and the aircraft was yawing."
Post-Accident Examination
Federal Aviation Administration (FAA) inspectors examined the accident site and found no evidence of a fuel spill. A total of one cup of fuel was drained from both fuel tanks combined, and approximately one ounce of fuel was found in the gascolator.
According to the helicopter manufacturer, the fuel consumption rate for this model is 12 to 14 gallons per hour.
Pre-Flight Fuel Check
The flight, conducted under instructional supervision, involved an airline transport rated pilot who was undergoing training for a helicopter rating. Prior to departure, the pilot and his flight instructor visually inspected the fuel level. The flight instructor estimated that there was a total of 25 gallons of fuel aboard the helicopter.
Probable Cause
The source does not explicitly state a probable cause for the engine power loss.