Incident Overview
A pilot reported that the airplane, equipped with long-range fuel tanks, had full fuel tanks before departure. After approximately 3.8 hours of flight time, the engine began to surge and subsequently lost power. The pilot executed an off-airport forced landing, during which the airplane nosed over. When the aircraft was righted, it was discovered that the right fuel cap was missing, although the chain and spring clip remained in place.
Flight Details
The pilot stated that the purpose of the flight was to act as a safety aircraft for Operation Migration. She noted that most of the flying involved right-hand turns, which resulted in a higher fuel quantity in the right tank compared to the left. At the time of the power loss, the right fuel quantity indicator showed 3/8 to 1/2 tank of fuel, while the left tank was lower.
Pre-Flight Actions
According to the pilot, both she and a pilot-rated passenger viewed the top of the wings twice after the airplane was fueled: once to install the canopy cover and again to remove it. However, the fuel cap was not checked for security, nor was the fuel level visually inspected after the airplane was fueled five days prior to the incident.
Probable Cause
No probable cause was stated in the source.