A Transportation Safety Board report into a crash at Abbotsford International Airport in 2018 shows the risk icing can have on a plane in a surprisingly short time, a poignant reminder as the country slips into the grip of winter.
Fourteen minutes in heavy snow at temperatures near freezing was all it took to contaminate the wings an Island Air Express King Air and knock it out of the air.
“The combination of a warm aircraft surface (i.e., the wings) being exposed to 14 minutes of heavy (wet) snow, in below-freezing temperatures, created a situation that produced conditions highly conducive to ground icing,” reported the TSB. “The fact that the aircraft was above the maximum allowable take-off weight exacerbated the situation by increasing the aircraft’s stall speed.”
The pilot, at the time the owner of Island Express was leaving Abbotsford, British Columbia to take his family to California in February 2018. He could see the snow falling, and asked controllers to expedite his departure, in part so he wouldn’t have to de-ice his plane, a time-consuming and costly measure.
Despite the snow on the ground, he tried to depart 14 minutes after leaving the hangar. It was a fateful decision.
“Having recognized these issues, the pilot did not alter the plan even though the aircraft had spent 14 minutes in heavy snow at temperatures that presented a significant risk of ground icing,” said the TSB. “The pilot’s decision making was affected by continuation bias, which resulted in the pilot attempting a takeoff with an aircraft contaminated with ice and snow adhering to its critical surfaces.
“If pilots rely only on the snowfall intensity reported in aviation routine weather reports or automated terminal information service broadcasts, they will not correctly determine de-icing and anti-icing holdover times (the estimated time that an application of de-icing/anti-icing fluid is effective in preventing frost, ice, or snow from adhering to treated surfaces), increasing the risk of aircraft accidents.”
The pilot and front-seat passenger both received serious head injuries in the crash. Neither was wearing one of the supplied shoulder harnesses. Four other passengers were seriously hurt, while the rest had minor injuries. The most seriously wounded passengers received jackknife injuries when their bodies snapped forward around their lap belts on impact.
The Abbotsford crash was not the first time in recent years that the TSB has highlighted the danger of snow contamination on wings. In 2017, a West Wind ATR-42 crashed on takeoff from Fond-du-Lac, Saskatchewan. The TSB recommended urgent action to address wing contamination in the wake of the crash.
Ice can wreak havoc with the aerodynamic characteristics of a wing, causing the air not to flow smoothly over the surface. It can also impede movement of critical parts. New pilots are taught to recognize the danger from their first lessons, and regulations require zero contamination.
After the crash, Island Express ceased operations. The airline now has a new owner, new staff, and a higher training standard for pilots and was allowed to fly again in June 2018.