Background
The aircraft arrived in Winnipeg, Manitoba, from Thunder Bay, Ontario, the day before the accident. It was parked overnight in a heated hangar and was pulled outside at approximately 0410 central daylight time. The pilot reviewed weather information and completed flight planning for a journey estimated to take two hours and six minutes.
Sequence of Events
After refueling, the aircraft taxied to Apron V at Winnipeg International Airport for cargo loading. Once loading was complete, the pilot obtained an instrument flight rules (IFR) clearance to Thunder Bay, taxied to Runway 36, received take-off clearance, and departed. For about one minute, the aircraft climbed on runway heading to 1,300 feet above sea level (asl), equivalent to 500 feet above ground level (agl). The flight was cleared to 9,000 feet asl direct to Thunder Bay, and the pilot turned on course.
The aircraft continued climbing, reaching a maximum altitude of 2,400 feet asl approximately 2.5 minutes after take-off. It then began a gradual descent averaging about 400 feet per minute (fpm) until it descended below radar coverage.
Accident
The accident occurred during hours of darkness at 0543. The Winnipeg Fire Paramedic Service were notified and responded from a nearby station.
Findings
Official findings identified three causes and contributing factors: (1) The aircraft departed at a weight exceeding the maximum take-off weight and the maximum weight for operation in icing conditions. (2) After departure, the aircraft encountered in-flight icing conditions in which its performance deteriorated until it was unable to maintain altitude. (3) During the attempt to return to Winnipeg International Airport, the pilot lost control of the aircraft, likely with little or no warning, at an altitude from which recovery was not possible.
Additional findings noted that aviation weather forecasts may not accurately predict icing effects on specific aircraft; bulk loading prevented determination of cargo weight in each zone, risking zone weight limit exceedances; the centre of gravity could not be accurately determined and may have been in a warning area; and an incorrect tare weight on a cargo container posed a risk to other aircraft. The pilot's weather briefing was incomplete and had to be updated by telephone. The aircraft departed without significant surface contamination. Biological material on board was disposed of after the accident with no release into the environment. The lack of flight data and cockpit voice recorders limited the investigation's scope.