FAA Aircraft Dispatcher Practice Exam

At what point must engine anti-ice be activated for takeoff?

1. When outside temperature is below freezing

2. When visible moisture is present

3. When dew point is close to the ambient temperature

4. Immediately prior to takeoff

The correct answer is: When visible moisture is present

Activating engine anti-ice at the point when visible moisture is present is crucial for ensuring that ice does not form on the engine components during flight. Ice accumulation can severely affect engine performance and could lead to possible engine failure, especially in conditions where temperatures are low. Visible moisture, such as rain, fog, snow, or clouds, indicates a higher likelihood of ice forming in the airflow onto the aircraft's engine components, even if ambient temperatures are technically above freezing. By activating the anti-ice systems when visible moisture is detected, it enables the engine to maintain optimal performance and prevents ice-related issues. Other considerations, such as outside temperature or dew point, might help inform decision-making about icing conditions, but they do not directly trigger the need for engine anti-ice activation in the same immediate way that visible moisture does. Therefore, it is critical for pilots and dispatchers to monitor not just the temperature but also the presence of moisture in the air when making the decision to activate anti-ice systems prior to takeoff.