FAA Powerplant Written Practice Test

What is the consequence of using carburetor heat when it is not needed?

1. Increased fuel consumption

2. A decrease in power and possible detonation

3. Improved engine efficiency

4. Increased engine temperature

The correct answer is: A decrease in power and possible detonation

Using carburetor heat when it is unnecessary can lead to a decrease in power and may also increase the risk of detonation. When carburetor heat is applied, it enriches the fuel-air mixture by making it less dense, resulting in a warmer intake charge entering the engine. This warmer air can lead to reduced air density and less power being produced, as the engine may not be receiving the optimal amount of oxygen for combustion. Additionally, if the mixture becomes too rich due to the heat, it can contribute to abnormal combustion phenomena such as detonation. Detonation occurs when the fuel-air mixture explodes rather than burning smoothly, potentially damaging engine components. Therefore, it's essential to use carburetor heat only when conditions such as carburetor icing warrant its use to ensure efficient engine operation and performance.