Definition
The process of assessing how much grip a runway surface provides to aircraft tires, typically performed by airport operators using continuous friction measuring equipment (CFME) that measures the coefficient of friction along the runway. Results are reported on a scale (Mu values, generally 0 to 100) where higher numbers indicate better braking action. Friction measurements are used to determine whether a runway is safe for landing operations and whether contaminants such as snow, ice, slush, rubber deposits, or water are degrading surface traction.
Plain English
A test that tells airport staff how slippery or grippy a runway is so they can warn pilots and decide if it is safe to use.
Context Anchor
Seen in runway condition and airport operations information, especially when a runway is wet, icy, snowy, or otherwise not clean and dry.
Derivation
Friction comes from the Latin fricare, meaning 'to rub.' Measurement is simply the act of measuring. Together it means 'measuring how much one surface resists sliding against another' — in this case, a tire against a runway.
Why Pilots Care
Directly affects calculated landing distance, braking performance, and the decision to continue or divert an operation.
Grounding Statement
If a runway has less grip, the airplane’s tires cannot slow the aircraft as effectively.
Intuition Check
Do not read friction measurement as a casual opinion that the runway “seems slippery.” In this FAA context, it means a measured check of runway surface grip, usually made by airport equipment.
Example Sentence 1
After the ice storm, airport operations conducted a friction measurement run before reopening the runway to arrivals.
Example Sentence 2
Before departure the pilot checked the latest friction measurement to confirm the runway was still usable after the snow.