When should carb heat be applied during flight?

Carb heat should be applied anytime there is a potential for carb ice because the formation of ice in the carburetor can significantly disrupt engine performance. Carburetor ice can occur in conditions where the air temperature is low, especially when humidity is high, and it can form even in temperatures above freezing.

By applying carb heat when conditions are right, you warm the air entering the carburetor. This warms the surfaces of the carburetor and helps to melt any ice that may have formed as well as prevent further ice formation. It's important to be proactive when flying in conditions where carb ice is likely, which is why the appropriate response is to use carb heat whenever there is potential for it.

Choosing to apply carb heat only during specific situations, such as high power settings, RPM thresholds, or descent, limits the ability to prevent ice formation effectively and can lead to engine performance problems.