Definition
A pilot's report of the deceleration and directional control available on a runway or taxiway surface, expressed using one of six standardized terms: Good, Good to Medium, Medium, Medium to Poor, Poor, or Nil. These terms describe how effectively an aircraft's brakes are working against the surface, with Good indicating normal braking effectiveness and Nil indicating no braking effectiveness at all. Pilots provide these reports to air traffic control after landing on contaminated surfaces (snow, ice, slush, water), and ATC relays them to other pilots so they can plan their landing performance accordingly.
Plain English
These are the words pilots use to tell controllers (and other pilots) how well the brakes worked when stopping on a wet, icy, or snowy runway. The scale runs from Good (brakes work normally) down to Nil (brakes don't work at all).
Context Anchor
Pilots encounter braking action in runway condition reports, pilot reports, tower advisories, and landing or taxi decisions during rain, snow, ice, slush, or other contaminated surface conditions.
Derivation
Braking comes from brake, meaning to slow or stop motion. Action means the effect or result of something. Nil comes from a word meaning nothing, which helps because Nil braking action means essentially no useful braking effect.
Why Pilots Care
Directly affects landing distance calculations and the decision to land or divert, preventing runway excursions.
Analogy
It is like describing how much traction your car has on a road. Dry pavement feels normal, wet pavement may feel reduced, and ice may give almost no stopping ability at all.
Intuition Check
Do not read Good, Medium, Poor, or Nil as casual opinions. In this context they are operational reports about stopping and steering ability on airport pavement.
Example Sentence 1
After rolling out, the captain told the tower, 'Braking action medium to poor on Runway 27.'
Example Sentence 2
After touchdown the pilot reported braking action poor on the last 2,000 feet of the runway.