Definition
A semi-liquid mixture of partially melted snow and water, often mixed with ice crystals, that can accumulate on runways, taxiways, and aircraft surfaces. Slush is denser and heavier than dry snow and creates significant drag and contamination hazards during takeoff and landing.
Plain English
Wet, mushy snow — the sloppy mix of melting snow and water you get when temperatures hover around freezing. On a runway, it acts like a wet, heavy sludge that drags on the wheels and sprays up onto the airplane.
Context Anchor
Seen in winter runway condition reports and during takeoff, landing, and taxi planning when snow and water are present on the pavement.
Derivation
The word “slush” has long meant soft, watery snow or mud. That origin helps here because aviation slush is not dry snow and not plain water; it is the heavy, wet mixture between the two.
Why Pilots Care
Slush lengthens required takeoff distance and can reduce directional control or stopping ability on landing.
Grounding Statement
Picture trying to push a cart through wet, heavy snow instead of across clean pavement; the same kind of drag can affect an airplane’s tires.
Intuition Check
Slush does not mean harmless wet snow here. In aviation, slush is a runway surface condition that can seriously affect how the airplane accelerates, steers, and stops.
Example Sentence 1
The crew delayed departure until the runway was cleared because half an inch of slush would have lengthened the takeoff roll well beyond the available distance.
Example Sentence 2
On landing rollout the crew maintained light braking to keep the airplane tracking straight over the slush.