What happened
During a circuit and landing training session at Brakpan Aerodrome on 15 March 2006, an instructor and a student pilot were operating a Rans Coyote II (S6S), registration ZU-DUP. While on final approach for Runway 36, the crew observed that the engine RPM remained high despite closing the throttle. Attempting to manage the high power setting, the crew initiated a go-around; however, opening the throttle fully failed to produce any increase in engine power.
As the aircraft moved onto the crosswind leg, airspeed began to decay. The instructor initially considered landing on the grass Runway 21 but aborted that plan due to tall grass and poor visibility of potential ground hazards. The pilot then attempted to land on Runway 18. Because the throttle could not be used to reduce power, the instructor was forced to shut down the engine by switching off the magnetos. The aircraft landed at the turning circle with full flaps, rolling diagonally across the area and into the clearway. During the rollout, the nose wheel struck a hidden object in the grass, causing the gear to collapse and the aircraft to nose over. There were 0 fatalities and 0 injuries.
The investigation
SACAA AIID investigators examined the mechanical state of the aircraft and the flight sequence. The investigation confirmed that the aircraft had a valid Authority to Fly and had undergone its last annual inspection in November 2005. The investigation established that the throttle linkage had failed, which prevented the pilot from controlling engine power via the throttle lever.
Findings
- The primary mechanical cause of the incident was a failure of the throttle linkage.
- The pilot's inability to reduce engine RPM via the throttle necessitated an emergency engine shutdown using the magnetos.
- The aircraft sustained damage to the engine cowlings, engine mounts, wings, rudder, and nose landing gear.