News release

Today, the Transportation Safety Board of Canada (TSB) released its investigation report (A23W0040) into the 2023 aircraft collision with terrain at the Whitehorse/Erik Nielsen International Airport, Yukon.

On April 17, 2023, a Royal Canadian Mounted Police (RCMP) Pilatus PC-12/47E was conducting an instrument flight rules flight from Whitehorse, Yukon to Yellowknife, NWT. The pilot was the sole occupant. Shortly after takeoff, the aircraft’s stall warning system activated, triggering an aural warning and activating the stick shaker. The pilot decided to remain below the cloud layer and returned to Whitehorse in low visibility conditions. Following an initial attempt to land in the opposite direction, the pilot maneuvered to land on Runway 32 Left. While attempting to line up with the runway, the aircraft made a steep descending right turn at low airspeed. The aircraft struck the ground right-wing first, then impacted a ground obstacle that caused the left wing to separate. The aircraft came to rest on its left side. The pilot was seriously injured but was able to exit the aircraft with the help of airport firefighting personnel.

The investigation found that a sensor in the stall warning system failed resulting in a false stall signal being emitted. The stall system aural warning remained activated for the duration of the occurrence flight, thus it created a distraction and increased pilot workload. While attempting to align the aircraft for landing, the pilot experienced attentional narrowing due to an intense stress reaction in response to the continuous stall warning. As a result, the pilot’s attention was focused outside the aircraft, and the pilot unknowingly placed the aircraft in a flight regime that likely resulted in an aerodynamic stall at a very low height above ground.

The RCMP’s training for stall warning malfunctions focused on emergencies related to inadvertent stick pusher activation rather than an inadvertent stall warning. Additionally, the PC-12 pilot operating handbook provided limited guidance regarding the potential use of the aural warning inhibit switch during an inadvertent stall warning emergency. As a result, the pilot was unaware that this switch could be used during high-workload situations to quickly eliminate the false aural stall warning that was a distraction for the duration of the flight.

Following the occurrence, the RCMP enhanced its training regarding stall warning system-related emergency scenarios and single pilot operating procedures for its PC-12 crews. It also reviewed technical records of its PC-12 fleet related to angle of attack sensors and consulted the manufacturer about new sensors.

See the investigation page for more information.