In carbureted engines, when should you anticipate carburetor icing?

• A. Even when not flying in visible moisture, and in temperatures up to 70°F
• B. Only when visible moisture is present
• C. Only at temperatures below freezing
• D. Only at high altitude

Answer: (A)

Carburetor icing is caused by the cooling of the air-fuel mixture inside the carburetor, which can cause moisture in the air to condense and freeze in the venturi. This can happen even in clear air and at temperatures up to about 70°F, especially when humidity is sufficient. Visible moisture isn’t required for icing to form, so you should anticipate icing in conditions where the air might be humid, not just when you see rain, clouds, or fog. Icing can occur at various altitudes, and it’s not limited to freezing temperatures, so don’t assume higher risk only at low temperatures or only in visible moisture. If icing is suspected, engage carburetor heat and monitor engine response.