What happened
On the evening of 16 November 2021, a flight instructor and a student pilot were preparing for a night navigation training flight at Cape Town International Airport. The aircraft, a Piper PA-28-161 Warrior II with registration ZS-KBable, had recently completed a previous training sortie and was parked at the Cape Town Flying Club apron.
After conducting a pre-flight inspection and a safety briefing, the crew attempted to start the engine. The student pilot followed the engine start-up procedures, but the engine failed to ignite on the first attempt. Following a brief cooling period for the starter, a second attempt was made. During this second cranking, flames were observed emerging from the lower engine cowling area.
The instructor immediately took control, shutting off the electrical systems, leaning the fuel mixture, and closing the throttle and ignition. While the crew attempted to use an onboard fire extinguisher, the safety pin was stuck. The fire was eventually extinguished by a pilot from a nearby aircraft who provided a secondary fire extinguisher. Although the substantial fire caused significant damage to the engine mount, wiring, and hoses, there were no injuries to the occupants.
The investigation
SACAA AIID examined the aircraft and its maintenance history following the incident. The investigation confirmed that the aircraft was properly maintained, certified, and equipped according to regulations, with no outstanding defects noted in the flight records. A technical inspection of the fuel system by a maintenance organization found no leaks or operational errors. The investigation focused on the physical state of the engine compartment, noting that the fire primarily affected the electrical wiring and hoses on the right side of the engine and the cowling areas.
Findings
- The fire was likely triggered by excessive fuel accumulation in the carburettor heat box.
- It is believed that the engine was over-primed during the start sequence, causing excess fuel to drip from the carburettor venturi.
- Because the engine was still hot from a previous flight, the heat from the exhaust system likely caused the pooled fuel to vaporize, creating an ignitable vapor that caught fire.
- An incorrect engine start technique contributed to the accumulation of fuel.