Incident Overview
On Saturday, May 24, 2003, at 08:30 hours, a Cessna F172-M (registration EC-DZF) was being prepared for a local private flight from Sevilla Airport. The pilot, a 31-year-old private pilot with 80 total flight hours (all on type), completed a pre-flight inspection and began the engine start procedure.
Engine Start Attempt and Fire
According to the pilot's statement, he actuated the primer three times and then engaged the starter, but the engine did not start. After a brief pause, he attempted to start again. During the second attempt, a flame emerged from the induction system. The pilot immediately shut off electrical power and fuel. He used the aircraft's onboard fire extinguisher and the fire appeared to go out, but it rekindled from the same area. The pilot then obtained a second extinguisher from a nearby hangar and fully extinguished the fire. The airport fire service arrived but did not need to intervene.
Aircraft Damage
As a result of the fire, the aircraft suffered significant damage to the induction system, propeller, and engine cowling. No other damage occurred.
Pilot and Aircraft Information
The pilot held a private pilot license and was flying to gain experience. The aircraft was maintained in accordance with its approved maintenance program. The temperature at the time was 19 °C.
Flight Manual Guidance
The aircraft flight manual contained relevant procedures. In the emergency procedures section, it advised for a fire during engine start on the ground: "Continue, to get a start which would suck the flames and accumulated fuel through the carburettor and the engine." The normal procedures section described how to clear excess fuel: set mixture to full lean, throttle full open, and crank the engine through several revolutions with the starter, then repeat the starting procedure without additional priming. It also noted that in moderate temperatures, one or two primer strokes are sufficient, and priming is not recommended when the engine is hot.
Analysis
The investigation noted that engine induction fires during start are typically caused by excess fuel in the cylinders. Priming three times is considered normal, but failing to start on the first attempt and then trying again likely introduced additional fuel, creating an overpriming condition. When the pilot observed the fire and cut electrical power, unburned fuel remained in the induction system, which later ignited. The flight manual recommended continuing to crank the engine to draw flames and fuel through the carburetor, and also suggested closing the fuel valve and opening the throttle.