When is the wing anti-ice system required to be ON for takeoff?

The requirement for the wing anti-ice system to be ON for takeoff stems from the need to prevent ice accumulation on the wings and other critical surfaces, which can significantly impact the aircraft's performance and safety. When the outside air temperature (OAT) is 5°C (41°F) or below and visible moisture is present, conditions are conducive to icing. This moisture can freeze upon contact with the aircraft surfaces, particularly when combined with low temperatures, which necessitates the use of the wing anti-ice system to maintain optimal airflow over the wings during takeoff.

Activating the system under these conditions ensures that any ice that may form is melted away, thereby enhancing lift and reducing the risk of ice-related performance degradation. This is crucial for safe operations, especially during takeoff when high angles of attack and airspeeds are involved.

In contrast, the other choices do not accurately reflect when the wing anti-ice system is mandated for safe operations. While OAT at or below 0°C may lead to icing, the presence of moisture is a critical factor that dictates the actual need for anti-ice activation. Similarly, simply having OAT at 10°C or below is not sufficient; without moisture, the use of anti-