General Authority of Civil Aviation (GACA) Aeronautical Information Publication (AIP) Practice Exam

If the ice detection system is inoperative, when should you select engine anti-ice?

1. At night only

2. When airborne

3. Based on temperature and visual moisture criteria

4. Only upon visible ice buildup

The correct answer is: Based on temperature and visual moisture criteria

Selecting engine anti-ice in the event of an inoperative ice detection system is critically important for flight safety. Choosing to activate the anti-ice systems based on temperature and visual moisture criteria is the correct approach because it is based on established operational practices that mitigate the risk of ice formation on engines. When considering engine performance and safety, it's essential to monitor temperature and moisture levels, as these are key indicators that may signal conditions conducive to icing. If the outside air temperature is at or below freezing and visual signs of moisture—such as clouds or precipitation—are present, the risk of ice can increase significantly. This proactive approach helps ensure the engines are protected from the adverse effects of ice, which can lead to reduced performance and potential engine failure. Therefore, in the absence of reliable ice detection, using temperature and moisture as criteria is the best practice for ensuring safety during flight operations.