Which braking action descriptor indicates the worst braking performance?

• A. Nil
• B. Good
• C. Medium
• D. Poor

Answer: (A)

Braking action descriptors describe how well a runway surface allows an aircraft to slow down, especially when the surface is contaminated with ice, slush, water, or snow. Nil means zero braking action — there is effectively no friction from the brakes, so deceleration is minimal and you likely cannot stop within the available runway length. This is the worst case because you can’t rely on wheel brakes to slow the airplane, so you must plan for scrubbed speed, potential overrun, or alternative options such as using additional deceleration methods and possibly a different runway or approach plan.

In comparison, the other descriptors indicate progressively better deceleration: poor means some braking but limited effectiveness, medium indicates moderate deceleration, and good represents strong braking action.