Narrative
The pilot was using automotive fuel in the airplane and had made numerous takeoffs and landings in rapid succession. The temperature was 50 degrees Fahrenheit, the sky was clear, and the airstrip elevation was approximately 4,000 feet. Just after lift-off, the engine coughed once, then stopped completely, as if someone had turned it off. Subsequently, the airplane was damaged during a landing on uneven tundra.
Findings
No mechanical irregularities were found with the engine or airplane. The carburetor composite float was weighed and found to be within specified limits, but when sectioned, it gave off a slight hydrocarbon odor. The vapor pressure of the automotive fuel was reported to be 15 psi, compared to 5 psi for 100 octane aviation fuel, indicating that automotive fuel is more susceptible to vapor lock.