What happened
On 04 October 2002, a Cessna 150G, registered ZS-OWF, was conducting a navigational training flight from Cape Town International Airport to Saldanha/Vredenberg. The flight was being conducted by an instructor accompanied by a student pilot. While cruising at an altitude of approximately 1500ft AMSL, the aircraft experienced a sudden loss of engine power, accompanied by intense vibrations and high noise levels.
In an attempt to restore power, the instructor utilized the carburetor heat and switched fuel tanks. When these actions failed to resolve the issue, the crew performed a forced landing in a wheat field located roughly 4nm east of Langebaan, adjacent to the R27 road. Both occupants escaped the incident without injury, and the aircraft sustained only minor superficial damage.
The investigation
SACAA AIID investigators examined the engine following the incident to determine the source of the power loss. The investigation confirmed that the training organization, Cape Aero Club, held a valid accreditation at the time of the occurrence. Records indicated that the aircraft's last maintenance inspection (MPI) had been completed approximately 64.5 flying hours prior to the event.
Findings
Technical analysis of the engine revealed that the exhaust valve on the No.1 cylinder had failed. This mechanical failure was the direct cause of the engine power loss and the subsequent necessity for the forced landing. The specific reason for the valve failure remains undetermined.