CT145D King Air - Epilogue

The accident aircraft was from the Multi-Engine Utility Flight out of 8 Wing Canadian Forces Base Trenton, ON and was on a training mission with three crewmembers on board.

The aircraft departed 8 Wing Trenton on an Instrument Flight Rule flight plan, with a destination of Thunder Bay Airport, ON. Following a routine climb out and cruise, the aircraft was cleared for the RNAV Z 25 instrument approach into Thunder Bay.

The aircraft was configured for the approach and flown utilizing automation. Approximately two miles back from the runway and with the airport visual, the pilot elected to continue the remainder of the approach manually and disconnected the autopilot. As the aircraft crossed over the runway threshold with a height above ground of approximately 50 ft, the pilot flying moved both power levers to idle with the intent of landing.

A left yaw quickly developed followed by a rapid drop of the left wing. The pilot monitoring the approach took control and initiated an overshoot, however the left wing tip contacted the runway surface and the aircraft progressed uncontrolled into the snow-covered infield. Once the aircraft came to rest, the three crewmembers egressed the aircraft.

The aircraft sustained very serious damage and the pilot flying suffered a minor injury, while the other crewmembers were not injured.

The investigation determined that the aircraft was documented serviceable prior to the flight and that no issues were evident to the crew before the power levers were brought to idle. Post-accident analysis of the recovered aircraft flight data and componentry determined that a part within the propeller speed governing system failed to function nominally, specifically the beta valve or the beta solenoid. This led to the left-hand propeller windmilling, which was the most likely cause of the accident. Since the beta valve was damaged and internal parts lost during the accident sequence, a definitive determination of its serviceability could not be conducted.

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