What happened
On 22 January 2009, a private flight involving an Extra 300 L, registration ZS-CPC, was returning to Kitty Hawk Aerodrome in Gauteng Province. After approximately ten minutes of flight in the general flying area, the pilot began the landing circuit. During the downwind leg, the pilot reduced engine power; however, as the aircraft transitioned to the base leg, the engine failed to respond to increased throttle demands.
Despite adjustments to the mixture setting, the engine could not produce the necessary power to maintain altitude or reach the runway. The pilot attempted to clear power lines and telephone wires before executing a forced landing on a nearby gravel road. The aircraft struck the ground heavily, causing the left main landing gear to separate from the airframe. The impact caused the aircraft to veer left and skid approximately 30 metres, eventually striking vegetation and coming to rest against a brick wall. The pilot and passenger escaped the wreckage without injury.
The investigation
SACAA AIID investigators examined the wreckage and the engine' and maintenance records. The investigation focused on why the engine failed to respond to throttle inputs. While the fuel management system and fuel injector were found to be functional during bench testing, a critical mechanical failure was identified within the engine's control mechanism.
Findings
- The engine power loss was caused by the fracture of a spring steel roller pin located on the idle control lever.
- This failure prevented the throttle lever movement from transmitting the necessary input to the fuel injector.
- Evidence suggests the pin had developed fatigue cracks over time, likely due to excessive pressure exerted by the clamping screw during a previous installation.
- The pilot was experienced, holding an Airline Transport Pilot License, and had performed a satisfactory pre-flight inspection.
- The aircraft was maintained by an approved maintenance organization in accordance with all regulatory requirements.