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That’s because if ice forms on an airplane’s leading edges, that formation will disrupt the flow of air over an airfoil and—basic Bernoulli—create drag while destroying lift. What can happen next? A stall at a higher airspeed and/or lower angle of attack, possibly uncontrollable roll and pitch.
Some general aviation airplanes are equipped with deicing systems to be used in the event ice begins to form on the airplane in flight. These systems do not give pilots a green light to blast off into freezing rain. Rather, they are meant to buy some time to exit the icing conditions.
Deicing boots are designed to knock off the ice as it begins to form over leading edges. The boots—which are not boot shaped, nor are they on the wheel pants—are rubber strips attached to the leading edges of the wings and tail surfaces. Once activated, they are pressurized with air and they expand to break the ice off the boot surfaces. Then suction is applied to the boots, and they return to their original shape.
You might also spy boots on an airplane’s propeller. Rather than pneumatics, these systems use heating wires, or a layer of etched foil embedded inside the boots and attached to the inner part of the leading edge of each propeller blade. The pilot activates a switch, and the boots receive an electric current from a slip ring and brush assembly to the spinner. The electrical energy activates the heating elements inside each boot, and thus melts ice from the surface of the propeller blades.
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