Air Canada Flight 646 - Investigation

Investigation

The Transportation Safety Board probe listed 29 causes and contributing factors and an additional 16 aggravating factors in the crash and rescue performance, including the following:

• Given the weather conditions, runway conditions, and first officer experience, the decision to allow the first officer to land the plane was questionable, though within policy.
• The wings had accumulated ice, degrading their performance, and reducing the maximum angle of attack before stall.
• The stick shaker worked as designed but the reduced wing performance reduced the warning time given by the stick shaker.
• A go-around without impacting the ground would not have been possible at the altitude it was ordered due to weather conditions and wing performance.
• The flight crew was not trained according to legal requirements in emergency procedures, including go-around, rescue and emergency exits.
• Stall-recovery training did not account for the weather conditions at the time of the crash.
• The published go-around procedure did not account for the time required for the engines spin up to sufficient thrust for go-around after idling.