What happened
During a daylight departure from Island Lake airport, a Beech 1900D, operated by Minatis Flight 303, experienced a runway excursion following a rejected take-off. The aircraft, carrying two crew members and 17 passengers, was en route to Winnipeg. During the take-off roll, the aircraft reached rotation speed, but the stall warning horn immediately activated. Fearing a loss of flight capability, the first officer initiated a rejected take-off.
Despite the application of reverse thrust and braking, the aircraft could not be stopped within the runway or the stopway. The aircraft exited the prepared surface and came to rest against a snow bank, resulting in substantial damage to the airframe. There was one minor injury reported among the occupants, and all passengers and crew evacuated successfully.
The investigation
Investigators examined the aircraft's flight data recorder and cockpit voice recorder, which revealed that the engines were producing rated torque and the propellers were at maximum RPM during the initial roll. The data showed that the crew reduced engine power to idle approximately four seconds after rotation, and the aircraft's airspeed peaked at 126 knots before declining.
Technical analysis of the stall warning system revealed that the lift transducer vane had frozen in the "stalled" position. While the crew had activated the stall warning heat during their final checks, the period of time between the activation and the take-off was insufficient to melt the ice that had accumulated in the system during previous flights through heavy snow. Furthermore, investigators found that the runway surface was covered in hard-packed, slippery snow, which increased rolling resistance and decreased braking traction.
Findings
- The stall warning activated because the lift transducer vane was frozen in the stalled position due to moisture entering the system and freezing during the station stop.
- The rejected take-off was initiated at a speed and position from which the aircraft could not be stopped within the available runway and stopway.
- The aircraft's stopping performance was compromised by the slippery, snow-covered runway conditions.
- The crew lacked specific performance data to calculate the required accelerate-stop distance for a runway covered in loose snow and ice.
- The stall warning heat was not active for a long enough duration prior to rotation to effectively clear the ice from the vane and backing plate.
Safety action
Following the investigation, the operator updated its pilot training to include information regarding the specific design of the Beech 1900 stall warning system and potential malfunctions. Additionally, the manufacturer amended the aircraft's checklist to require a freedom of movement check for the stall warning vane before every flight and moved the stall warning heat activation to an earlier stage in the pre-flight sequence to ensure the system is sufficiently warmed before take-off.