How can pilots determine if they are experiencing carburetor icing?

The correct choice indicates that pilots can determine if they are experiencing carburetor icing by observing a loss of engine power or rough engine operation. Carburetor icing typically occurs in certain atmospheric conditions, especially at temperatures between approximately 20°F and 70°F with high humidity. The cooling effect from fuel vaporization can cause ice to form on the carburetor components, obstructing airflow and causing the engine to lose power or run unevenly.

When pilots notice a drop in engine performance, such as a decrease in RPM, roughness in engine operation, or unexpected performance issues, it may be a clear indication of carburetor icing. Addressing this situation quickly is critical; pilots are trained to manage this by applying carburetor heat, which reduces the likelihood of ice formation by warming the air-fuel mixture.

The other choices do not directly relate to determining carburetor icing. Checking altimeter readings pertains to altitude assessment, monitoring outside temperature might provide some environmental context but doesn't give a definitive indication of icing, and evaluating weight and balance is crucial for overall aircraft performance but irrelevant to the specific issue of carburetor icing.