Definition
Ice that forms when supercooled water droplets in visible moisture strike and freeze on exposed surfaces of an aircraft, including the airframe, propeller, windshield, and the air intake openings of the induction system.
Plain English
Ice that builds up where the airplane hits cold water droplets in clouds, rain, or wet snow, freezing on contact with leading edges and intake openings.
Context Anchor
Seen in icing discussions, especially when flying in clouds, freezing rain, freezing drizzle, or other cold, wet conditions.
Derivation
From 'impact' (Latin impactus, 'struck against') and 'ice.' The name describes how it forms: droplets strike the aircraft and freeze on impact, rather than forming gradually from condensation or fuel vaporization.
Why Pilots Care
Impact ice reduces lift, increases drag, and can block air intakes or propeller efficiency, creating immediate handling and performance problems.
Grounding Statement
Picture cold water droplets hitting the front edges of the airplane in flight and freezing into a rough coating of ice.
Intuition Check
Impact ice does not mean ice caused by a crash or hard landing. Here, “impact” means water droplets hitting the aircraft surface and freezing.
Example Sentence 1
After flying through a band of freezing rain, the pilot noticed impact ice forming along the wing leading edges and activated the deicing boots.
Example Sentence 2
The pilot monitored the propeller for impact ice accumulation while flying in the icing conditions.