In a constant speed propeller engine, what is an indication of carburetor icing?

The indication of carburetor icing in a constant speed propeller engine is primarily associated with a loss of airspeed and a drop in manifold pressure. This occurs because as ice builds up in the carburetor, it restricts airflow and disrupts the carburetor's ability to mix fuel and air effectively.

When icing occurs, fuel may not be atomized properly, leading to a rich mixture that can result in stalling or loss of engine power. This reduced power output directly causes a drop in manifold pressure, which is a critical performance metric for assessing engine power. Simultaneously, the loss of engine performance also tends to manifest as a decrease in airspeed, as the aircraft cannot maintain the necessary thrust to keep up its velocity.

In contrast, the other options do not reflect the symptoms of carburetor icing. Increased airspeed would suggest that the engine is performing well, which is not the case with carburetor icing. Higher engine RPM may indicate that the engine is running efficiently but does not provide clear evidence of carburetor icing, which usually leads to reduced engine performance. Improved fuel economy would suggest better engine efficiency, which would not align with the performance degradation caused by icing in the carburetor.