Cowl anti-ice must be ON for ground operations under which condition(s)?

• A. OAT is 8C or below
• B. Visible moisture present
• C. Runway contaminated with snow, ice, standing water, or slush
• D. All of the above

Answer: (D)

Ice can form on engine cowls during ground operations whenever there is moisture and cold temperatures, so the cowl anti-ice system is used to prevent ice buildup that could affect engine performance. If the outside air temperature is 8 C or below, icing potential exists even with modest moisture, so turning the cowl anti-ice on helps protect the inlet and surrounding surfaces. Visible moisture—such as rain, drizzle, fog with moisture, or clouds with precipitation—creates a direct icing risk on the cowl and intake, making anti-ice activation necessary. A runway contaminated with snow, ice, standing water, or slush further increases the chance of ice formation on exposed surfaces and in the engine area, reinforcing the need to keep cowl anti-ice on. Since each of these conditions presents a credible icing risk on the ground, the correct procedure is to have the cowl anti-ice on under all of them.