What happened
On 27 February 2019, a Thruster T600N aircraft, registration G-OBAX, was involved in an accident at Balado Airfield, Kinross, during a private flight. Following a standard preflight inspection, the pilot initiated the engine start sequence. Immediately upon startup, the engine failed to settle into an idle state and instead produced high power.
Despite the pilot's attempts to pull the throttle lever back, the aircraft began moving rapidly down an inclined grass taxiway. The pilot applied the handbrake on the control column, but the engine's thrust overcame the braking force. As the aircraft accelerated over a distance of more than 100 metres, the pilot struggled to maintain directional control and wings-level attitude against a crosswind. While attempting to reach the magnetos to shut down the engine, the aircraft struck a parked digger. The impact caused the cockpit to end up beneath the digger's arm, though the pilot was able to exit the aircraft with no injuries.
The investigation
The investigation examined the mechanical state of the engine and the cockpit controls following the collision. The engine was found to have been shock-loaded during the impact. The pilot noted that while the throttle lever appeared to move through its full range during pre-start checks, the high power persisted once the engine was running. The investigation also considered the cockpit environment, noting that the seat cover had the potential to shift and potentially obstruct the rearward movement of the throttle lever.
Findings
- The engine developed uncontrollable high power immediately following startup.
- The pilot's ability to shut down the engine was hindered by the location of the magneto controls behind the control column.
- The aircraft's rapid acceleration down the incline and the lack of directional control led to the collision with the parked digger.
- The engine sustained shock-loading as a result of the abrupt stop.