What is the function of the carburetor heat in a piston-engine aircraft?

• A. To enrich the fuel mixture.
• B. To prevent carburetor icing by warming the intake air.
• C. To cool the engine.
• D. To provide additional cooling for cockpit.

Answer: (B)

Carburetor heat is used to prevent carburetor icing by warming the air entering the carburetor. Moist air can cause ice to form inside the carburetor's venturi and throttle area, especially in humid conditions near freezing. This ice restricts airflow and disrupts fuel metering, leading to rough running or a drop in power. By routing warmer air from around the exhaust into the carburetor, ice is melted and the mixture flow becomes steadier, restoring normal operation.

You’ll typically notice a slight drop in engine power and a momentary roughness when heat is first applied, because the air is less dense. After the ice melts and the engine warms, you can manage the mixture accordingly and turn the heat off when icing is no longer a factor. This method is not for cooling the engine or cockpit, and it does not enrich the fuel mixture.