Accident
On the day of the accident, Keystone Air Service Limited Flight 213, a Piper PA31-350 Navajo Chieftain (registration C-GOSU, serial number 31-7752148), departed Winnipeg/James Armstrong Richardson International Airport, Manitoba, en route to North Spirit Lake, Ontario. The flight carried one pilot and four passengers. At 0957 Central Standard Time, while on approach to Runway 13 at North Spirit Lake, the aircraft struck the frozen lake surface 1.1 nautical miles from the threshold of Runway 13. The pilot and three passengers sustained fatal injuries; one passenger sustained serious injuries. The aircraft was destroyed by impact forces and a post-impact fire. The emergency locator transmitter stopped transmitting after the antenna wire was consumed by the fire.
Investigation Findings
The investigation identified several findings as to causes and contributing factors. The pilot's decision to conduct an approach to an aerodrome not serviced by an instrument flight rules approach in adverse weather conditions was likely the result of the pilot's inexperience and may have been influenced by a desire to complete the flight. Additionally, the pilot decided to descend into cloud and continue in icing conditions, which reflected an inadequate awareness of the aircraft's performance in icing and its de-icing capabilities. While holding near North Spirit Lake in icing conditions awaiting runway clearance, ice accumulated on the aircraft's critical surfaces. This ice accumulation increased aerodynamic drag and stall speed, causing the aircraft to stall during final approach at an altitude from which recovery was not possible.
The investigation also highlighted several findings as to risk. Terminology in aircraft flight manuals and regulatory material regarding icing conditions is inconsistent, increasing the risk of confusion about aircraft certification and capability in icing. Lack of procedures and tools for pilot self-dispatch decisions elevates the risk of dispatching into conditions beyond aircraft capability. Management involvement in dispatch decisions may pressure pilots to complete flights in challenging conditions, increasing the risk of flights beyond pilot competence. Current regulations do not require training in crew resource management or threat- and error-management for certain operators, and a breakdown in such management may increase risk in adverse weather. Descending below area minimum altitude in instrument meteorological conditions without a published approach procedure increases the risk of collision with terrain. The absence of onboard flight recorders may preclude identification and communication of safety deficiencies.
Probable Cause
The probable cause, as determined by the investigation, includes the pilot's decision to conduct an approach without an instrument approach in adverse weather, the pilot's inadequate awareness of icing performance and capabilities, and ice accumulation leading to an aerodynamic stall during final approach at low altitude.