What happened
The pilot requested that the aircraft be fully serviced with fuel prior to takeoff but did not perform a visual inspection of the fuel levels himself. Approximately 50 minutes into the flight, the pilot noticed that the right fuel tank, which was currently in use, indicated it was empty.
Because the pilot typically flies for one hour before switching tanks, and believed he had only used 9 gallons from the 30-gallon tank, he decided to delay switching to the alternative tank. Shortly after this decision, the engine lost power. The pilot attempted to move the fuel selector to the other tank, but was unable to restore enough power to maintain flight. During the subsequent emergency landing, the aircraft collided with trees and a fence before coming to rest in an upside-down position.
Findings
Upon inspection of the aircraft, the right fuel tank was found to be empty. Only 7 gallons of fuel were drained from the left tank.