The pilot reported that the accident occurred during his fifth glider aero-tow flight since the Piper PA-25-235 had last been refueled.
The aero-tow and glider release were uneventful, he told investigators.
However, as he was returning to the airport in Boulder, Colo., the engine began to run intermittently before it eventually experienced a total loss of power.
During the subsequent forced landing, the plane became entangled with a chain-link fence and hit a road before it slid into a drainage ditch, resulting in one minor injury.
A post-accident examination of the airplane’s single fuel tank established that it was undamaged and void of any usable fuel.
Before the first flight of the day, the airplane was refueled, and the total usable fuel was about 32.5 gallons.
The airplane recording tachometer indicated that 2.2 tachometer hours had been accumulated since that time.
Although the airplane operator reported that, according to historical fueling and flight data, the average fuel consumption rate was about 10.2 gallons per tachometer hour, the calculated average fuel consumption rate was 14.8 gallons per tachometer hour since the last refueling.
Although the total loss of engine power was caused by fuel exhaustion, the investigation could not determine the reason for the above-normal fuel consumption rate.
However, if the pilot had determined the actual fuel consumption rate between flights, he should have identified that insufficient fuel was available to complete the accident flight.
The NTSB determined the probable cause as the pilot’s failure to adequately monitor the airplane’s actual fuel consumption rate, which resulted in a total loss of engine power due to fuel exhaustion.
NTSB Identification: CEN14LA261
This May 2014 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.