Background
The aircraft was refueled at Ames, Iowa, prior to the last leg of the flight. According to the lineman, he opened the left fuel cap, observed that the left tank was full, replaced the cap, and then refueled the right fuel tank. The pilot reported that he did not visually check the fuel level but instead relied on visually checking the fuel caps from behind the wing. The aircraft's fuel burn rate averaged 7.5 gallons per hour. The aircraft had between 4.5 and 4.8 hours of fuel on board at departure. The flight lasted approximately 3.7 hours.
Accident Sequence
Witnesses reported seeing the aircraft circling at about 300 feet above ground level. The engine sputtered before it quit. During the subsequent forced landing, the left wing struck a tree before the aircraft impacted the ground. After impact, the aircraft skidded up onto its nose, leaving the tail nearly vertical.
Post-Accident Examination
Examination of the aircraft revealed a fuel stain originating from the left fuel cap and streaming toward the rear of the wing. The engine and flight controls exhibited continuity. There were open fields near the crash site. The pilot reported that the fuel gauges were unreliable.