What is the difference between anti-icing and de-icing, and how are they used on a narrowbody?

• A. Anti-icing prevents ice buildup with continuous heating; de-icing removes existing ice using fluids or heat before flight or on the ground.
• B. Anti-icing removes ice after formation; de-icing prevents ice buildup with continuous heating.
• C. Both processes are identical and interchangeable.
• D. Anti-icing is only used in flight; de-icing is only used on the ground.

Answer: (A)

Anti-icing and de-icing manage ice in two different ways: one is preventive and the other is corrective. Anti-icing is used to stop ice from forming by keeping critical surfaces warm with continuous heating—either electrical power or bleed-air heating of leading edges, engine inlets, and sometimes the windshield. On a narrowbody, this means surfaces like the wing leading edges and other hot-air or electrically heated areas are kept above freezing so any onset of ice doesn’t stick and grow.

De-icing, on the other hand, removes ice that has already formed. This is typically done on the ground before takeoff with glycol-based fluids sprayed on the surfaces, sometimes combined with heat to help breakup and drain the ice away. The fluids are temporary; they protect surfaces for a limited time, after which takeoff must occur within a specified window or reapplication is needed.

In practice, you may de-ice first to clear existing ice, then apply anti-ice just before takeoff to prevent new ice from forming during taxi and the takeoff run. The key idea is clear: anti-icing prevents ice, de-icing removes it.