Definition
The formation of ice on the exterior surfaces of an aircraft or on components in the induction system when supercooled water droplets in visible moisture strike a surface that is at or below freezing, and freeze on contact. In the context of fuel injection systems, impact icing typically forms on air intake screens, scoops, and bends in the induction air path, restricting airflow to the engine.
Plain English
Ice that forms when very cold water droplets in the air hit a cold surface on the aircraft and instantly freeze. In fuel-injected engines, this ice can build up at the air intake and choke off the air the engine needs.
Context Anchor
Seen in fuel-injected engine and induction system discussions, especially when operating in cold visible moisture such as cloud, rain, mist, or snow.
Derivation
From 'impact,' meaning the moment something strikes a surface. The name describes exactly how the ice forms — droplets impact the surface and freeze on contact, rather than forming through evaporation or temperature drop inside the system.
Why Pilots Care
It can restrict airflow into the engine and cause sudden power loss even in fuel-injected aircraft.
Grounding Statement
Picture cold wet air hitting the front of the engine intake and freezing there layer by layer until the opening gets smaller.
Intuition Check
Impact does not mean crash damage here. It means moisture hits an intake surface and freezes on contact.
Example Sentence 1
Flying through light rain just below freezing, the pilot noticed a slight drop in fuel flow and manifold pressure and suspected impact icing was forming on the intake screen.
Example Sentence 2
In flight through clouds at five degrees Celsius the manifold pressure dropped due to impact icing restricting the air intake.