The effects of icing on aircraft are cumulative: thrust is reduced, drag increases, lift lessens, and weight increases, resulting in an increase in stall speed and a deterioration in aircraft performance.

In extreme cases 2 to 3 inches of ice can form on the leading edge of an airfoil in less than 5 minutes. 1/2 inch of ice can reduce the lifting power of some aircraft by 50% and increase the drag by an equal percentage.

Ice accumulation on the propeller reduces its efficiency and more power will be required to maintain level flight. Running the engine at higher RPMs will help minimize ice buildup on the propeller blades. However, if ice accumulates and a portion of it is slung off, the resulting unbalanced state can cause severe vibration which has the potential to rip the engine from its mounts. If this occurs, power should be reduced immediately.

When ice forms in the engine induction system, the air necessary for combustion is restricted, resulting in a loss of power. Due to the Venturi Effect, ice can form in the carburetor at temperatures as high as 100 degrees F when there is high humidity. The symptoms of carburetor icing are reduced power and a rough running engine. Carb Heat bypasses the normal induction system and sends heated air into the carburetor from a shroud surrounding the exhaust manifold. Engine heat during the climb and cruise phases of flight is usually sufficient to prevent carburetor icing, but carb heat should be applied whenever engine power is reduced, such as during descent and landing, and whenever flying in icing conditions. Fuel-injected engines don’t have carburetors, but the primary air intakes can still become blocked by ice, reducing power. In this case pilots should activate Alternate Air, which will route air from inside the cabin into the engine intake manifold.