FAA Powerplant Written Practice Test

What occurs when humidity causes refrigeration icing in a carburetor?

1. The air-fuel mixture becomes too rich

2. Fuel vaporization is unaffected

3. The carburetor becomes clogged with ice

4. The engine performance is enhanced

The correct answer is: The carburetor becomes clogged with ice

When humidity causes refrigeration icing in a carburetor, the primary phenomenon at play is the formation of ice due to the cooling effect of fuel vaporization and the moisture present in the air. As air passes through the carburetor, it expands and cools, and when the air contains a significant amount of moisture (humidity), this can lead to the freezing of water vapor. This ice accumulation can block the airflow and inhibit the flow of the air-fuel mixture, causing the carburetor to become clogged with ice. A clogged carburetor disrupts the normal operation of the engine, often leading to reduced power, loss of efficiency, or even engine stalling. Understanding this principle is crucial for pilots and mechanics, as they must monitor and manage the conditions that could lead to icing. Recognizing the causes and effects of carburetor icing helps in troubleshooting engine performance issues attributed to icing, particularly in conditions of high humidity and low temperatures.