FAA Ground School Practice Test

The presence of carburetor ice can be verified by applying carburetor heat and noting a decrease in RPM followed by a gradual increase. This phenomenon occurs because carburetor ice forms when moisture in the air freezes within the carburetor, restricting airflow and negatively impacting engine performance.

When carburetor heat is applied, the warmer air entering the carburetor melts the ice. Initially, when this warmer air is introduced, the change can cause a slight drop in RPM due to the reduction in airflow caused by the ice. However, as the ice melts and airflow normalizes, the engine’s performance improves, leading to a gradual increase in RPM. This ability of carburetor heat to restore normal engine function is a clear indicator of the presence of carburetor ice.

The other options, such as observing a slight increase in RPM, checking the fuel gauge, or inspecting the air filter, do not provide reliable indicators or methods for verifying the existence of carburetor ice. They do not directly relate to the effects of carburetor ice on engine performance, nor do they reflect the operational changes resulting from the application of carburetor heat.