What happened
On 2 June 2021, a Cessna 172K, registration ZS-FJU, was involved in an aircraft fire at Zebula Airfield in the Limpopo Province. The flight, which was an hour-building mission from Rand Airport, had landed successfully under Visual Flight Rules (VFR) earlier that day. After a two-hour interval, the pilot and a passenger returned to the aircraft to prepare for the return leg to Rand Airport.
During the attempt to depart, the pilot made three unsuccessful attempts to start the engine. Following advice from a safety pilot to wait to prevent engine flooding, the pilot waited several minutes before trying once more. During this period, the master switch was turned off to conserve battery power. Shortly thereafter, smoke was observed emerging from the engine cowlings. Upon disembarking, the occupants observed flames spreading from the engine compartment. The pilot managed to suppress the fire using the aircraft's onboard Halon extinguisher. There were 0 fatalities and 0 injuries.
The investigation
Because the event was a limited investigation, the SACAA AIID relied on information provided by the involved parties. The investigation focused on the sequence of events leading to the ignition of the engine compartment and the resulting substantial damage to the aircraft's cowling and engine area.
Findings
The investigation established that the fire was caused by over-priming the engine. This action resulted in excessive fuel entering the cylinder heads while they were still hot, which subsequently ignited the accumulated fuel.