FAA Ground School Practice Test

Which type of carburetor system is generally considered more susceptible to icing?

1. Fuel injection systems

2. Float-type carburetor systems

3. Diesel fuel systems

4. Pressure-type carburetor systems

The correct answer is: Float-type carburetor systems

Float-type carburetor systems are generally considered more susceptible to icing due to the way they mix fuel and air to create the combustible mixture for the engine. In these systems, the process of vaporizing fuel causes a drop in temperature, which can lead to the formation of ice in critical areas of the carburetor, particularly in the venturi where the air is accelerating and the temperature continues to drop. The conditions most conducive to carburetor icing occur when the relative humidity is high and the temperature is close to or below freezing. In float-type carburetors, the mixture control and the fuel delivery mechanism can lead to sufficient cooling to promote icing when humidity levels are high. This can restrict airflow and lead to an engine that runs poorly or doesn't run at all. Other systems, such as fuel injection and pressure-type carburetors, are less affected by these icing mechanisms because they may not utilize the same process to mix air and fuel or may employ different engineering designs that mitigate the cooling effects associated with vaporization. Diesel fuel systems operate on a different principle entirely—using compression ignition rather than relying on a mixture that could freeze.