Definition
The accumulation of ice on the external surfaces of an aircraft in flight, occurring when the aircraft passes through visible moisture (such as clouds, rain, or drizzle) at temperatures at or below freezing. Ice can form on the wings, tail, propeller, windshield, antennas, and other exposed surfaces, altering the airfoil shape, adding weight, increasing drag, and reducing lift.
Plain English
Ice that builds up on the outside of the airplane while flying through cold, moist air. It changes the shape of the wings and other surfaces, which makes the airplane heavier and harder to fly.
Context Anchor
You will see this term in weather, aircraft control, and icing-condition discussions, especially when deciding whether to avoid clouds, rain, or freezing temperatures.
Derivation
"Structural" refers to the airframe — the physical structure of the aircraft — distinguishing this kind of icing from induction icing, which forms inside the engine intake or carburetor. Naming it this way tells you exactly where the ice is: on the body of the airplane.
Why Pilots Care
It alters wing shape, reduces lift, increases drag, and raises the risk of loss of control.
Grounding Statement
Picture flying through a cold cloud and seeing a rough white ridge begin to form on the front of the wing; that is structural icing.
Intuition Check
Structural icing does not mean the airplane structure is broken. It means ice is attached to the aircraft’s outside surfaces.
Example Sentence 1
After picking up structural icing in the clouds, the pilot requested a lower altitude to reach warmer air.
Example Sentence 2
Preflight weather checks help avoid areas where structural icing is forecast.