What happened
During the first flight of the day, a pilot attempted to start the engine of a PA-28 that had been modified to operate on automotive gasoline (Mogas). After the initial start attempt failed, the pilot performed several priming cycles, injecting fuel directly into the cylinders. During a subsequent attempt, the pilot observed black smoke followed by flames emerging from the engine compartment. The pilot immediately shut down the electrical system and fuel supply, and the passengers evacuated the aircraft. Bystanders were able to extinguish the fire using portable extinguishers before the airport fire service arrived.
The investigation
The investigation focused on the engine start sequence and the specific fuel requirements of the aircraft. The PA-28 had been converted with a secondary fuel pump to allow for the use of Mogas, which is less volatile than standard Avgas. Investigators examined the pilot's actions, noting that the pilot had primed the engine eleven times in total. The investigation also reviewed the modified checklist used by the flying club, which mandates minimal priming when using Mogas.
Findings
- The primary cause of the fire was excessive priming, which resulted in an accumulation of fuel that likely leaked outside of the engine cylinders.
- The pilot's limited experience with this specific aircraft type, having primarily flown a Cessna 172, may have contributed to the error.
- The use of Mogas requires a different start procedure than standard Avgas, specifically regarding the use of the primer when fuel pumps are active.
- The fire was contained due to the rapid response of witnesses on the ground.