What temperature and moisture conditions must be met for the use of wing anti-ice in flight?

The correct answer indicates that wing anti-ice must be used when temperatures are below 10°C and there is visible moisture present in any form. This condition is crucial because when the temperature is at or below this threshold, any moisture, be it rain, snow, or clouds, can lead to the formation of ice on the wings of an aircraft. Ice buildup can significantly affect the aerodynamics of the wing, resulting in reduced lift and increased drag, which can jeopardize flight safety.

When operating in temperatures below 10°C, pilots must remain vigilant for signs of moisture since the combination of low temperatures and moisture increases the risk of ice formation. Activating the wing anti-ice system in these conditions ensures that the wing surfaces are kept clear of ice, maintaining optimal performance and safety during flight.

In contrast, temperatures above this threshold or in the absence of visible moisture do not present the same level of risk for icing, making the operational need for anti-ice systems unnecessary.