Incident Overview
An aircraft experienced a right engine fire during the engine start sequence. The pilot reported that the right engine failed to start on the first attempt. On the second attempt, the engine started and was running on the primer when the pilot heard a loud bang and observed flames emanating from the engine.
Pilot Actions
In response, the pilot attempted to run the engine at higher power to draw the flames into the intake, but this did not extinguish the fire. The pilot then secured the aircraft and evacuated. The airport fire department subsequently arrived and fully extinguished the fire.
Investigation Findings
Investigation into the incident revealed that the right engine's carburetor float assembly was cracked, causing the float to sink. When the fuel boost pump was used during engine start, fuel was allowed to flow through the carburetor into the intake scoop and onto the aircraft and ground beneath it. The engine backfire, heard by the pilot, ignited the accumulated fuel, resulting in the fire.
Conclusion
The fire was caused by fuel leakage from a cracked carburetor float assembly, which was ignited by an engine backfire during the start process. The aircraft was damaged by fire, but no further details on the extent of damage or occupant status were provided.