What happened
The pilot was conducting a flight returning to Boulder after completing a previous flight to Aspen. At the start of the day's operations, the pilot had departed with a two-thirds fuel load, totaling approximately 40 gallons, but was uncertain of the total flight time accumulated throughout the day.
While performing a VFR approach to the Boulder airport, the aircraft experienced a loss of engine power. The pilot observed that the left fuel tank indicator showed empty. Although the pilot attempted to switch to the other fuel tank, the engine subsequently quit. Unable to restart the engine, the pilot performed an emergency landing in an open field, where the aircraft ran into a ditch.
The investigation
An examination of the aircraft revealed that while the right fuel tank contained fuel, the left fuel tank was empty.