Why de-ice?

English: Why de-ice?

French: Pourquoi dégivrer?

Let’s put aside French for a few posts and talk about why airplanes get de-iced. During flight attendant training, de-icing is covered briefly, and you may not be told anything beyond just “the snow needs to be removed from the wings before take-off.”

Many passengers have flown enough to know that snow needs to be removed from the wings before take-off, but many others don’t know, especially if they don’t fly often, or if they aren’t used to flying in cold climates. As a flight attendant as well, it’ll be very useful to know the reasoning behind de-icing. During long de-icing delays or even cancellations, passengers will inevitably become curious about why we need to de-ice, why it’s taking so long to de-ice, or why their flight was cancelled because of the weather.

As mentioned in the previous post, de-icing is done to remove any snow/ice/frost from the wings and critical surfaces of the airplane. Remember that airplanes fly when air flows below and above the wings. It is the very shape of the wings that creates a speed difference between the air that flows above the wing and the air below the wings. This difference of speed causes a difference in air pressure below and above the wing, which creates lift and allows the airplane to fly. When snow/frost/ice sticks (known as “surface contaminants”) to the wings, this changes the shape of the wings and disrupts air flow, thereby reducing lift and increasing drag. If lift is reduced enough when the plane tries to take off, the consequences can be catastrophic. (For a real-life example, see Air Ontario flight 1363 on 10 March 1989).

When these surface contaminants stick to other critical surfaces of the plane (surfaces that are essential to the airplane's function), such as the flaps, the tail, the rudder, etc., it could also disrupt the air flow there, interfering with the airplane’s ability to turn, bank, roll, change attitude, etc.

When flights get delayed because of winter weather conditions, passengers (and flight attendants as well) can get understandably impatient and frustrated. But knowing the reasoning behind de-icing helps to put things into perspective, ensuring we all understand how crucial it is to flight safety.


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