Engine anti-ice systems must be on for taxi and takeoff when in visible moisture at what temperature?

Engine anti-ice systems must be on for taxi and takeoff when in visible moisture at what temperature?

• A. 0 degrees C or colder
• B. 5 degrees C or colder
• C. 10 degrees C or colder
• D. 5 degrees C or warmer

Answer: (B)

Engine anti-ice is required during taxi and takeoff when visible moisture is present and the ambient air temperature is 5°C or colder. The reason is that at or below this temperature range, supercooled water droplets in visible moisture can freeze on contact with the engine inlets, forming ice that blocks airflow and reduces thrust or even leads to engine damage. Activating the anti-ice system warms the inlet and prevents ice buildup before it starts. If the temperature is warmer than 5°C, the icing risk in typical visible moisture conditions is much lower, so the rule doesn’t require anti-ice for taxi/takeoff in that case.

Engine anti-ice is required during taxi and takeoff when visible moisture is present and the ambient air temperature is 5°C or colder. The reason is that at or below this temperature range, supercooled water droplets in visible moisture can freeze on contact with the engine inlets, forming ice that blocks airflow and reduces thrust or even leads to engine damage. Activating the anti-ice system warms the inlet and prevents ice buildup before it starts. If the temperature is warmer than 5°C, the icing risk in typical visible moisture conditions is much lower, so the rule doesn’t require anti-ice for taxi/takeoff in that case.