FAA Ground School Practice Test

At what temperature can carburetor icing still occur?

1. Only below 32 degrees

2. High as 70 degrees with high relative humidity

3. Never above 80 degrees

4. Only at freezing temperatures

The correct answer is: High as 70 degrees with high relative humidity

Carburetor icing can occur at temperatures as high as 70 degrees Fahrenheit, particularly when the relative humidity is high. This phenomenon happens due to the cooling effect associated with the vaporization of fuel in the carburetor, which can lead to ice forming within the carburetor and its components. The critical factor contributing to this icing is not just the temperature but also the moisture content in the air. At high humidity levels, even warmer temperatures can create conditions conducive to icing. Therefore, understanding that carburetor icing is a possible event under a broader range of conditions, including higher temperatures and varying humidity, is essential for informed flying and operational safety. When considering the other possible answers, below 32 degrees is often considered the classic range for carburetor icing, but it's too restrictive. Claiming that icing never occurs above 80 degrees does not account for the effects of humidity and fuel bypassing, which are instrumental in the formation of ice in the carburetor. Lastly, stating that icing only occurs at freezing temperatures overlooks the complexity of atmospheric conditions that can lead to carburetor icing much higher than the freezing point.