Definition
A NOTAM contraction used to report that one or more runway surfaces are covered with slush — a partly melted mixture of snow and water with the consistency of a soft, wet, semi-liquid layer. SLR alerts pilots to a runway condition that significantly degrades braking action, increases takeoff and landing distance, and can throw spray into engines, flaps, and landing gear.
Plain English
The runway is covered in wet, slushy snow. Slush is the mushy in-between stage between snow and water, and it makes the runway slippery and harder to use safely.
Context Anchor
Seen in airport notices and runway condition information during winter or freezing-weather operations.
Why Pilots Care
Slush reduces braking effectiveness and raises the risk of hydroplaning or loss of directional control during takeoff and landing.
Grounding Statement
Picture driving through heavy, wet snow on a road: the surface is not dry, not just wet, and the wheels do not grip normally.
Intuition Check
Slush does not mean just a wet runway. Here it means a loose, water-heavy snow or ice mixture lying on the runway surface.
Example Sentence 1
The NOTAM included SLR for runway 27, so we recalculated our landing distance before continuing the approach.
Example Sentence 2
Landing performance must be recalculated when SLR conditions are reported.