Definition
Accretions are layers or deposits of material that build up gradually on a surface over time. In aviation icing contexts, the term refers to ice that accumulates progressively on aircraft surfaces — wings, propellers, antennas, leading edges — as supercooled water droplets strike the airframe and freeze.
Plain English
Build-ups. In icing, it means the ice that gathers on the aircraft as it flies through freezing moisture.
Context Anchor
Seen in icing discussions, especially when describing rime ice forming on wings, windshields, antennas, or other exposed aircraft surfaces.
Derivation
From the Latin accrescere, meaning 'to grow onto' or 'to grow toward.' The same root gives us 'accrue' — things adding up over time. The word fits ice perfectly: it doesn't appear all at once, it grows onto the aircraft layer by layer.
Why Pilots Care
Ice accretions alter wing shape, reduce lift, increase drag, and can lead to dangerous performance loss or control issues.
Grounding Statement
Picture a rough white crust slowly growing on the front edge of a wing as the airplane flies through freezing cloud droplets.
Intuition Check
Do not read accretions as just “dirt” or “stuff stuck on.” In icing, accretions means deposits that build up on the aircraft surface as freezing droplets collect and freeze.
Example Sentence 1
The pilot noticed rime ice accretions forming on the wing's leading edge and activated the de-ice boots.
Example Sentence 2
Rime ice accretions formed a rough, milky coating that the de-icing boots had to remove.