Chris Puglia
Northern News Services

Yellowknife (Oct 21/02) - Ice, snow or frost build-up on the wings and tail of an aircraft can cause serious problems in flight.

The contaminants, as they are called, accumulate causing a roughness that can disrupt airflow and interfere with an aircraft's lift. Or, ice and snow can add weight surpassing aircraft design limits.

In 1994 such an occurrence was blamed for a plane crash that killed 68 passengers in the United States.

Federal regulations dictate that an aircraft cannot take of until all ice, snow and slush is cleared from the top of the fuselage, wings, the vertical and horizontal stabilizers and any flight control surface.

There are a number of ways this can be accomplished, depending on the weather conditions, according to Lee Chan customer service instructor for Canadian North.

"If it is -20 (celsius) with light snow it might be able to be brushed off because it is not adhering to the wings," said Chan.

But in cases where ice and snow are adhering to the wings chemicals can be used to either remove the build up of ice or to prevent ice from accumulating on an aircraft.

Inspecting an aircraft for ice and determining whether it requires de-icing is part of the pre-flight sequence.

"The flight crew in conjunction with the ramp personnel will decide if a plane needs to be de-iced," said Chan.

De-icing a plane takes about six minutes and is actually less common here in the North than it would be at southern airports such as Calgary or Edmonton.

"Once we get cold enough temperatures the snow doesn't stick very well, where in Calgary or Edmonton you'll get wet snow because it is warmer," said Laurence Hamilton of Atco Frontec.

Frontec handles de-icing services in Yellowknife for Canadian North, Transport Canada and the military.

De-icing chemicals vary depending on the company but the most common substances are ethylene glycol, dietylene glycol and propylene glycol.

The chemicals alone are slow to melt ice and therefore are super heated for 30 minutes to 180 degrees fahrenheit and then applied to the aircraft surface.

The substances remove ice, snow and slush and they create a protective barrier that temporarily prevents ice from forming in-flight.