What happened
On the morning of April 7, 2003, a Found Aircraft Canada Inc. FBA-2C1 Bush Hawk XP, registered C-GTUP, departed from an ice strip on Lake Temagami, Ontario. The flight was intended to be a visual flight rules trip to Parry Sound. Shortly after takeoff, the aircraft climbed to an altitude of between 200 and 30 and feet before the pilot initiated a left-hand bank. During this maneuver, the aircraft rolled approximately 90 degrees, the nose dropped, and the plane entered a stall and an incipient left-hand spin. The aircraft struck the frozen surface of the lake in a near-vertical attitude. The impact resulted in two fatalities.
The investigation
The investigation examined the aircraft's condition, the environmental factors, and the aerodynamic performance of the wing surfaces. Investigators noted that the aircraft had been parked outside overnight in temperatures below -20°C, with frost present during the early morning hours. While the pilot had access to brooms to clear the wings, no de-icing fluids were available. The investigation also reviewed the pilot's experience, noting approximately 2,800 total flying hours and 30 hours on this specific type. Post-mortem examinations showed that both occupants were attempting to regain control of the aircraft at the moment of impact, and toxicology reports were unremarkable.
Findings
- Frost contamination was present on the upper surface of the wing, which had either gone undetected or was not entirely removed during pre-flight preparations.
- The frost significantly degraded aerodynamic performance, increasing the stall speed and creating additional drag, which prevented the aircraft from reaching its expected climb altitude.
- A tailwind increasing with height created a negative performance wind shear, further reducing airspeed.
- The pilot likely experienced an illusion of higher airspeed due to the low-altitude turn into a downwind component, masking the actual loss of speed.
- Reduced longitudinal stability caused by the frost, combined with the pitch changes from flap retraction, removed the typical aerodynamic cues that would have alerted the pilot to the impending stall.