Why is it necessary to de-ice the wings of a plane before take off?

Answer 1

When ice forms on the wings of an aircraft, it disrupts the laminar (smooth) air flow across the wing surface, and as the air flow becomes more turbulent, the wing's ability to generate a lift force diminishes. As the ice accumulates, the lift of the wing continues to deteriorate, until the wings' lift can no longer offset the weight of the aircraft, causing a condition called a stall, in which the airplane literally falls (in aeronautic terms, stall has nothing to do with the engine). Icing can also impede the thrust created by rotary elements, such as fixed wing propellers and helicopter blades.

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On the ground, specialized equipment sprays an adhesive de-icing fluid to the wings. This de-icing fluid melts any ice that may have formed on the wing surfaces while the aircraft was on the ground, and it further prevents new ice from forming on the treated sections of the wings for a specific period of time, depending upon the class of de-icing method used.

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The aircraft has its own onboard de-icing system (larger aircraft have several systems). These systems either heat the surface (especially for propellers) to prevent ice from forming, or a pneumatic bladder on the exterior upper-leading edge of the wing cyclically expands and contracts, and the continuously changing shape and size cracks the forming ice, and causes the broken ice to fall away.

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It is important to recognize that the onboard de-icing systems only prevents new ice from forming. Should there already be ice on the wing (as when the aircraft has been resting on the ground), the onboard de-icing systems cannot be counted on to remove existing ice. That is why it is necessary to apply the de-icing fluid before take-off.