How can the presence of carburetor ice be verified in an aircraft with a fixed pitch propeller?

The verification of carburetor ice in an aircraft with a fixed pitch propeller can indeed be determined by applying carburetor heat and noting a specific sequence of RPM changes. When carburetor ice forms, it restricts airflow through the carburetor, which can lead to a reduction in engine performance and RPM.

When carb heat is applied, the heat causes the ice to melt, which initially leads to a decrease in RPM due to the disrupted airflow and mixture becoming richer as the ice melts. Following this initial decrease, as the airflow normalizes and the engine performance is restored, you can expect a gradual increase in RPM. This sequence—decreasing RPM followed by a gradual increase—is a clear indication that carburetor ice was present and is now being removed.

Recognizing this pattern helps pilots understand not only the symptoms of carburetor ice but also reinforces the importance of using carb heat as a preventative measure during flight operations, particularly in conditions conducive to ice formation, such as high humidity and low temperatures. This knowledge is essential for maintaining engine efficiency and ensuring safety in flight.