Definition
The buildup of ice on the external surfaces of an aircraft — wings, tail, propeller, antennas, windshield, and other airframe components — caused by supercooled water droplets freezing on contact with the airframe in flight.
Plain English
Ice forming and sticking to the outside of the airplane while flying through cold, moist air. The longer the airplane stays in those conditions, the more ice builds up.
Context Anchor
Seen in instrument flying, icing, and load factor discussions, especially when an aircraft is flying in clouds or precipitation near freezing temperatures.
Derivation
‘Structural’ comes from the Latin structura, meaning ‘a building’ or ‘something built.’ Here it refers to the structure of the aircraft itself — the airframe. So ‘structural ice’ is ice forming on the built parts of the airplane, as distinct from ice forming inside the engine induction system or on instruments.
Why Pilots Care
It reduces lift, raises stall speed, increases drag, and can quickly make controlled flight impossible.
Grounding Statement
Picture a smooth wing becoming rough and slightly misshaped as ice sticks to its front edge; the wing can no longer move air as cleanly.
Intuition Check
Structural ice accumulation does not mean the aircraft structure is breaking. It means ice is collecting on the aircraft’s outside surfaces and changing how the aircraft flies.
Example Sentence 1
After ten minutes in the clouds at freezing temperatures, the pilot noticed structural ice accumulation on the leading edge of the wings and requested a lower altitude.
Example Sentence 2
Even a thin layer of structural ice accumulation raised the load factor needed to maintain altitude in a turn.