What happened
On 9 April 2002, a Cessna 150F, registration ZS-EGN, was conducting solo training maneuvers near Nelspruit. The student pilot was performing simulated forced landings when, while climbing through 600 feet, the generator light illuminated in the cockpit. After contacting an instructor via mobile phone and receiving instructions to return to FANS aerodrome, the engine failed suddenly.
Unable to restart the engine, the pilot performed a forced landing in a tobacco field located approximately 12nm southwest of FANS. During the landing on uneven ground, the nose wheel detached from the aircraft, causing the plane to nose over and come to rest in an inverted position. There were no injuries reported following the incident.
The investigation
Investigators examined the aircraft following its recovery to FANS. During the inspection, it was discovered that the wings had been removed for transport and a fuel canister had been temporarily attached to the cabin to supply the fuel selector.
Upon attempting to restart the engine, technicians found that the mixture control cable had failed at the carburetor end. After replacing the cable and setting the mixture to full rich, the engine was able to run normally with all vital parameters, including oil pressure and vacuum, within standard ranges.
Findings
- The primary cause of the engine failure was a fatigue crack within the mixture control cable.
- This crack propagated through the cable, significantly weakening it until it reached ultimate failure.
- The failure allowed the carburetor mixture lever to move freely into the lean or cut-off position, leading to the loss of engine power.