Private Pilot Private Exam

What effect does applying carburetor heat have on the fuel/air mixture?

1. It makes it leaner

2. It enriches the mixture

3. It does not change the mixture

4. It causes fuel to evaporate

The correct answer is: It enriches the mixture

Applying carburetor heat enriches the fuel/air mixture, which is a crucial aspect of managing engine performance, especially in conditions where the engine might be prone to icing. When carburetor heat is applied, it warms the incoming air and the fuel passing through the carburetor. This warming reduces the density of the air while increasing the temperature of the fuel mixture. As a result, the fuel vaporizes more effectively, which increases the total volume of fuel relative to the amount of air. In essence, when air is heated, its density decreases, meaning there is less air in a given volume to mix with the fuel. Consequently, this adjustment makes the mixture richer, providing a higher proportion of fuel relative to air than before. This is particularly important when flying in humid or cold conditions, as it helps to prevent ice formation in the carburetor and ensures that the engine continues to operate smoothly. Therefore, when carburetor heat is used, the mixture becomes enriched, leading to better engine performance in adverse conditions.