Carburetor icing occurs mainly due to what primary cause?

• A. Temperature drop from fuel vaporization
• B. Excessive air temperature
• C. High humidity only at altitude
• D. Excessive fuel enrichment

Answer: (A)

Carburetor icing is mainly due to the cooling effect created when fuel changes from liquid to vapor inside the carburetor. That phase change requires heat, which is drawn from the surrounding air and surfaces, so the air inside the carburetor actually gets colder. In humid air, this cooling can cause moisture to condense and freeze on the venturi walls and throttle plate, forming ice that restricts airflow and upsets the fuel/air mixture. Warmer air reduces this icing tendency, and while humidity and operating conditions influence how quickly icing forms, the primary cause is the temperature drop from fuel vaporization. Excessive fuel enrichment isn’t the key driver of icing, though it can affect engine operation in other ways.