Background
On the day prior to the accident, the pilot reported an unspecified vibration in the engine during flight. The following day, after an initial takeoff, the pilot again experienced engine vibrations and expressed discomfort about the first banner pickup of the morning. He decided to fly to a holding area to address the vibration issue. After approximately three minutes, he returned and successfully picked up the banner.
Accident Sequence
The flight proceeded for roughly five hours, after which the pilot reported what he described as a low-frequency vibration in the engine. Moments later, the engine lost power, and the pilot was no longer able to maintain flight. Consequently, he elected to ditch the airplane.
Post-Accident Examination
During the examination of the airplane, approximately one ounce of fuel was drained from the fuel line connecting to the left fuel tank. Inspection of the fuel system did not reveal any breaches or leaks. Before departure, the airplane had been topped off with 38 gallons of fuel. The normal fuel consumption for this airplane was approximately eight gallons per hour. The pilot stated that he 'may have run out of fuel.'