What occurs first when applying heat to a carburetor suspected of icing?

When heat is applied to a carburetor that is experiencing ice, the first observable effect is typically a drop in the RPM. Carburetor icing happens when moisture in the air freezes the throttle plate, which restricts air and fuel flow into the engine. When heat is applied, it helps to melt the ice, but this process can momentarily disrupt the airflow and fuel mixture, leading to a decrease in engine power or RPM.

As the ice begins to melt, the engine may not yet receive the optimal fuel-air mixture needed for normal operation, causing a temporary drop rather than an immediate increase in performance. Once the ice is fully melted and the fuel-air mixture stabilizes, you would likely observe an increase in RPM. Understanding this sequence is crucial for pilots to effectively manage an engine potentially impacted by carburetor icing.