Under which conditions must the wing anti-ice be on?

• A. Ground: for takeoff when OAT is 5 C or below with visible moisture on contaminated runways; In flight: TAT 10 C or below with visible moisture except below -40 C; icing conditions detected by system; When Type 2 or 4 anti-ice is applied only just prior to takeoff
• B. Ground: only at 20 C; In flight: only above 10 C
• C. Wing anti-ice is never required
• D. Only during takeoff and landing on dry surfaces

Answer: (A)

Wing anti-ice should be on whenever icing can form on the wing, which happens under specific ground and in-flight conditions, plus when the system or procedures call for it. On the ground, if the airplane is taking off and the outside air temperature is 5 C or colder with visible moisture on a contaminated runway, ice can start to form on the wing during the takeoff roll, so anti-ice must be active. In flight, icing risk exists when the total air temperature is 10 C or below and visible moisture is present; below -40 C icing is usually not a concern for typical aircraft icing conditions, but if the system detects icing, anti-ice should be engaged. Additionally, if Type 2 or 4 anti-ice fluid is applied only just before takeoff, the wing anti-ice must be on to provide protection during takeoff since those fluids are used for short-term pre-takeoff protection. This combination correctly matches when anti-ice is required to prevent ice buildup and maintain wing performance.