Definition
The frictional force between the aircraft tires and the runway surface that opposes forward motion when the brakes are applied during the landing roll. Its effectiveness depends on tire condition, brake system performance, weight on the wheels, and the runway surface (dry, wet, contaminated with snow, slush, or ice).
Plain English
The grip between the tires and the runway that lets the brakes slow the airplane down after touchdown. Less grip means a longer stop.
Context Anchor
Used in landing performance discussions, especially when considering runway surface condition, landing distance, and stopping after touchdown.
Derivation
“Brake” refers to a device used to slow or stop motion. “Friction” comes from a Latin word meaning “to rub.” Together, the term points to the slowing effect created when the tires press and rub against the runway surface while the brakes are being used.
Why Pilots Care
Directly determines the runway length needed to stop safely; reduced braking friction on wet or icy surfaces can cause the aircraft to overrun if not accounted for in performance planning.
Intuition Check
Braking friction does not mean only how strong the aircraft’s brakes are. In landing performance, it means how much usable grip exists between the tires and the runway while braking.
Example Sentence 1
With a thin layer of slush on the runway, braking friction was poor and the aircraft used nearly the full length to stop.
Example Sentence 2
Low braking friction on a contaminated surface required the crew to use maximum reverse thrust in addition to wheel brakes.