What happened
On 15 March 2002, a CESSNA 172M, registered ZS-JMK, was involved in an incident at the fuel bay of Wonderboom Aerodrome. The aircraft, being operated for training purposes, was being prepared for a dual navigation exercise. After taxiing to the fuel pumps independently, a student pilot attempted to start the engine multiple times.
Following several unsuccessful start attempts, the pilot engaged in a series of maneuvers involving pumping the throttle lever and using the primer pump to assist the ignition. During these repeated attempts, flames became visible on the left side of the engine cowling. The student pilot immediately evacuated the aircraft. While fuel pump attendants attempted to intervene, they encountered difficulties with their fire extinguisher, and the fire was eventually suppressed by a bystander.
The investigation
SACAA AIID investigators examined the aircraft and its maintenance records following the event. The inspection revealed that the engine cowling had sustained minor burn damage and the engine's electrical wiring had been damaged by the fire.
Crucially, the investigation into the aircraft's maintenance history revealed that the Maintenance Program Interval (MPI) had been exceeded by 3.1 hours. This oversight meant that the aircraft's certificate of release to service was technically invalid at the time of the incident.
Findings
- The fire was triggered by the accumulation of excessive fuel within the inlet manifold.
- The pilot's repeated attempts to start the engine involved over-priming the engine, which provided the necessary fuel-air mixture for ignition within the cowling area.
- There were no injuries to the pilot or any other persons involved.
- The aircraft's maintenance status was non-compliant due to the expired MPI.