What are the conditions that make carburetor icing more likely to occur?

Carburetor icing is a significant concern for pilots because it can lead to a loss of engine power. The correct choice highlights conditions that favor the formation of carburetor ice. Specifically, when temperatures fall below 70°F combined with high humidity levels, the likelihood of carburetor icing increases due to the cooling effect associated with fuel vaporization.

As fuel is drawn into the carburetor, it evaporates and absorbs heat from the surrounding air. This process can lead to chilling of the carburetor and the fuel-air mixture, potentially dropping temperatures to the point where moisture in the air can freeze, resulting in ice formation. High humidity exacerbates this effect, as there is more moisture available in the air to freeze.

In this context, other scenarios such as warmer temperatures or low humidity do not create the same conditions for carburetor icing. Higher temperatures, specifically above 80°F, typically correspond with lower humidity levels, further reducing the likelihood of icing. Thus, understanding the relationship between temperature and humidity is critical for recognizing when carburetor icing might pose a threat to engine performance.