Definition
The accumulation and build-up of ice on an aircraft surface caused by supercooled water droplets striking and freezing onto the airframe, propeller, windshield, or engine inlets during flight through visible moisture at or below freezing temperatures.
Plain English
Ice forming and growing on the aircraft as it flies through cold, wet air. The longer it flies through those conditions, the more ice piles up.
Context Anchor
Seen in instrument flying and weather discussions when describing icing on wings, propellers, windshields, antennas, and other aircraft surfaces.
Derivation
From Latin 'accrescere,' meaning 'to grow onto' or 'to add to.' The same root gives us 'accrue.' The word emphasizes that ice does not just appear — it grows and adds layer by layer onto the surface over time.
Why Pilots Care
Ice accretion adds weight, reduces lift, increases drag, and can block control surfaces or pitot tubes, directly threatening safe flight.
Grounding Statement
Picture cold water droplets hitting the front of a wing and freezing into a layer that keeps getting thicker.
Intuition Check
Ice accretion does not mean ice simply exists somewhere nearby. It means ice is actively building up on the aircraft.
Example Sentence 1
After ten minutes in the clouds at 4,000 feet, the pilot noticed ice accretion on the leading edge of the wing and requested a lower altitude to escape the icing layer.
Example Sentence 2
Rapid ice accretion forced the crew to request a lower altitude to escape the icing conditions.