Incident Overview
During takeoff for a sport parachute operation, the aircraft's engine sputtered and subsequently quit. The pilot executed a forced landing in a residential yard. No injuries or damage to persons on the ground were reported in the investigation.
Examination Findings
Post-incident examination of the aircraft revealed that fuel flow through the fuel selector valve was restricted. The fuel selector valve was disassembled for further inspection, and the O-rings for the left side of the valve were found to be swollen.
Cause of Swelling
Investigators placed the O-rings in the same automotive fuel that had been used in the airplane. The O-rings swelled, confirming that exposure to the automotive fuel caused the swelling that restricted fuel flow through the selector valve.
Aircraft Modification and Maintenance Records
The aircraft had been modified under a Supplemental Type Certificate (STC) to permit the use of automotive fuel. However, no maintenance records were available for the fuel selector valve, leaving the history of the valve's service and component replacement unknown.