When icing conditions exist in flight, at what TAT must the cowl anti-ice system be engaged?

The correct answer is that the cowl anti-ice system must be engaged when the total air temperature (TAT) reaches 10°C (50°F) in icing conditions during flight. This specific temperature is significant because it serves as a threshold for activating the anti-ice system to prevent ice accumulation on critical components of the aircraft, particularly the engine inlets which can lead to issues with airflow and engine performance.

The requirement for activating the cowl anti-ice system at this temperature is based on the likelihood of ice accumulation that can occur in the presence of supercooled water droplets, which are often found in clouds at or below this temperature. Engaging the anti-ice system helps ensure safe operation and optimal engine performance in conditions that could compromise flight safety.

Additionally, it's important to note that different temperature thresholds apply to the activation of other ice protection systems, which are designed to address varying risks associated with ice formation. Understanding these limitations is crucial for pilots operating in potentially hazardous weather conditions, thereby enhancing overall flight safety.