Definition
The aerodynamic and performance penalties caused when ice accumulates on the lifting and control surfaces of an aircraft. Ice changes the shape of the airfoil, which reduces lift, increases drag, increases stall speed, adds weight, and can degrade or jam control surfaces. Even thin or rough ice deposits — sometimes no thicker than coarse sandpaper — can produce significant losses in lift and large increases in drag.
Plain English
When ice builds up on the wings or tail, it changes the smooth shape that makes the aircraft fly well. The wings produce less lift, the airplane has to work harder to stay in the air, it stalls at a higher speed, and the controls can get heavy or stuck.
Context Anchor
Seen in instrument flying when studying flight in visible moisture, freezing temperatures, and the hazards of structural ice on aircraft surfaces.
Derivation
‘Airfoil’ comes from ‘air’ plus the French ‘feuille’ meaning ‘leaf’ or thin sheet — describing the shaped surface (wing, tail, propeller blade) designed to produce lift as air flows over it. ‘Icing’ simply refers to ice forming on that surface. Knowing the shape is what creates the lift makes it clear why even a small change to that shape causes outsized performance loss.
Why Pilots Care
These effects can cause an aircraft to lose altitude, require higher power settings, or become uncontrollable at speeds that would normally be safe.
Grounding Statement
A clean wing is a precisely shaped surface. Ice ruins that shape, and the airplane pays for it in lift, drag, weight, and control.
Intuition Check
Do not think of icing as mainly a weight problem. The bigger danger is often that ice changes the airfoil’s shape and roughens its surface, so the aircraft can lose lift and control before the pilot expects it.
Example Sentence 1
The instructor explained the general effects of icing on airfoils, emphasizing that even light ice can raise stall speed well above the published value.
Example Sentence 2
Understanding the general effects of icing on airfoils helps the crew recognize why the airplane requires more power and a higher approach speed after encountering rime ice.