Definition
An ice-prevention system that uses heat to keep ice from forming on critical aircraft surfaces such as wing leading edges, engine inlets, and tail surfaces. Heat is typically supplied by hot bleed air from the engine compressor, exhaust-heated air, or electrical heating elements, and is directed through ducts or embedded into the surface skin to keep it warm enough that supercooled water cannot freeze on contact.
Plain English
A system that warms certain parts of the aircraft so ice never gets a chance to form on them.
Context Anchor
Seen in aircraft systems descriptions, cold-weather operations, icing checks, and procedures for flight in visible moisture near freezing temperatures.
Derivation
Thermal comes from the Greek thermē meaning heat. Anti-icing means preventing ice rather than removing it after it forms. So the name describes exactly what the system does: uses heat to stop ice from forming.
Why Pilots Care
Ice on wings or inlets changes airfoil shape, reduces lift, increases drag and stall speed, and can lead to loss of control if not prevented.
Analogy
It is similar to using a car’s windshield defroster before the glass ices over. The goal is to keep the surface warm enough that ice cannot take hold.
Intuition Check
Do not read anti-icing as the same thing as de-icing. Anti-icing is used to prevent ice from forming; de-icing removes ice that is already there.
Example Sentence 1
Before entering the cloud layer, the crew switched on the thermal anti-icing system to keep the wing leading edges clear.
Example Sentence 2
During preflight the crew tested the thermal anti-icing system valves to confirm they would work in expected icing conditions.