FAA Powerplant Written Practice Test

Refrigeration icing in carburetors occurs under which condition?

1. When the fuel evaporates rapidly

2. When humidity surrounding the fuel freezes

3. During high-speed operations

4. When temperatures exceed freezing

The correct answer is: When humidity surrounding the fuel freezes

The correct answer is that refrigeration icing in carburetors occurs when humidity surrounding the fuel freezes. This phenomenon is a result of the principles of thermodynamics and the behavior of air and fuel mixtures within the carburetor. When the fuel enters the carburetor, it undergoes a rapid phase change from liquid to vapor, which requires energy. This process absorbs heat from the surrounding environment, leading to a drop in temperature that can cause moisture in the air to cool to the point of freezing. As the air temperature decreases, any humidity present can condense and subsequently freeze, forming ice within the carburetor. This icing can obstruct fuel flow and disrupt the normal operation of the engine, creating challenges for the pilot. Therefore, understanding the relationship between humidity, temperature, and fuel evaporation is crucial for recognizing conditions that can lead to refrigeration icing.