At what RPM should the carburetor heat be checked?

The correct RPM for checking the carburetor heat is typically around 2000 RPM. This is because, at this engine speed, the airflow through the carburetor is sufficient to provide a clear indication of any changes in engine performance when the carburetor heat is applied.

At this RPM, the engine is not operating too close to idle, where it may not provide a stable indication, nor too high, where it may mask any potential issues with the carburetor heat system. The 2000 RPM range strikes a balance that allows for an optimal assessment of the engine's response to the application of carb heat, which is crucial for detecting any potential ice buildup that could obstruct airflow and lead to performance issues.

This RPM check is a standard practice during pre-flight checks to ensure that the carburetor heating system is functioning correctly, contributing to the safety and reliability of the flight.