Thunder Bay

Findings as to causes and contributing factors:
1. After takeoff from Runway 12 at Thunder Bay Airport, Ontario, as the pilot conducted a rapid, low-level, climbing steep turn, the aircraft entered an accelerated stall that resulted in a loss of control and subsequent collision with the surface of Runway 07 in an inverted attitude.
2. The decision to conduct the rapid, low-level, climbing steep turn was likely influenced by an altered perception of risk from previous similar takeoffs that did not result in any adverse consequences.

Findings as to risk:
1. If air traffic controllers engage in communications that may be perceived by pilots to encourage unusual flight manoeuvres, pilots may perceive this encouragement as a confirmation that the manoeuvres are acceptable to perform, increasing the risk of an accident.
2. If NAV CANADA’s reporting procedures do not contain specific criteria for situations where air traffic services personnel perceive aircraft to be conducting unsafe flight manoeuvres, there is a risk that these manoeuvres will continue and result in an accident.

Other findings
1. Most of the wires that comprised the elevator trim cable failed before the impact as a result of excessive wear; however, this did not contribute to the occurrence because the trim tab remained in the normal take-off position.

Findings as to 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 from Winnipeg, the aircraft encountered in-flight icing conditions in which the aircraftís performance deteriorated until the aircraft was unable to maintain altitude.
3. During the attempt to return to the 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.
Findings as to Risk:
1. Aviation weather forecasts incorporate generic icing forecasts that may not accurately predict the effects of icing conditions on particular aircraft. As a result, specific aircraft types may experience more significant detrimental effects from icing than forecasts indicate.
2. Bulk loading prevented determining the cargo weight in each zone, resulting in a risk that the individual zone weight limits could have been exceeded.
3. The aircraftís centre of gravity (CG) could not be accurately determined, and may have been in the extrapolated shaded warning area on the CG limit chart. Although it was determined that the CG was likely forward of the maximum allowable aft CG, bulk loading increased the risk that the CG could have exceeded the maximum allowable aft CG.
4. The incorrect tare weight on the Toronto cargo container presented a risk that other aircraft carrying cargo from that container could have been inadvertently overloaded.
Other Findings:
1. The pilotís weather information package was incomplete and had to be updated by a telephone briefing.
2. The operatorís pilots were not pressured to avoid using aircraft de-icing facilities or to depart with aircraft unserviceabilities.
3. The aircraft departed Winnipeg without significant contamination of its critical surfaces.
4. The biological material on board the aircraft was disposed of after the accident, with no indication that any of the material had been released into the ground or the atmosphere.
5. The fact that the aircraft was not equipped with flight data recorder or cockpit voice recorder equipment limited the information available for the occurrence investigation and the scope of the investigation.

A NOTAM stated that there were windrows four feet high, 10 feet inside the runway lights on both sides of the runway. This NOTAM also stated that the cleared portion of the runway was covered with ¼ inch of loose snow over 60 percent compacted snow and 40 percent ice patches and that braking action was fair to poor. The take-off was being conducted at dusk in conditions of poor lighting and contrast. Crosswind was not a factor.

The flight crew lost pitch control of the aircraft on take-off when the stabilizer trim actuators became disconnected because they had not been properly reinstalled by the AME during maintenance work conducted before the flight. The crew chief responsible for the inspection did not ensure correct assembly of the stabilizer trim actuators, which contributed to the accident.

Continued operation of the engine following an exhaust valve failure on the n°2 cylinder resulted in a flaming gas path near the right side of the firewall, an exhaust system overheat, and a subsequent cabin fire.

Failure of both engines during initial climb because the fuel was contaminated by water.

At the time of the accident, the visibility was extremely limited due to fog and the crew descended too low until the airplane impacted ground.

Poor flight preparation on part of the crew.