Incident Summary
The pilot reported that the aircraft had been operating throughout the day without any issues. After landing for another load, the airplane was topped off with 60 gallons of 100LL fuel. During the subsequent takeoff roll, the engine experienced a partial loss of power, which the pilot estimated to be about 50 percent.
Pilot Actions
Faced with a half-mile airstrip and insufficient time or field length to abort the takeoff, the pilot began to dump the load while attempting to get the aircraft airborne. Despite these efforts, the aircraft continued off the departure end of the runway and impacted a dirt bank. The impact separated the landing gear from the aircraft.
Post-Accident Examination
The engine had recently been overhauled by an FAA-certified repair station. Following the accident, the engine was removed from the airframe and test-run at the repair station. According to the repair shop, the engine exhibited good oil pressures and was operated through all RPM and performance ranges without any abnormal characteristics being observed.
Statement from Owner's Representative
The owner's representative stated in a telephone interview with the investigator-in-charge that the power loss was the result of fuel contamination.