combination which is in contact with the runway surface. It is not an aircraft tyre, thus they are not fully representative in size, weight or speed. Many if not all of the tests are accomplished below the normal approach/landing speeds that a code C aircraft will fly; Code C aircraft typically fly an approach speed of up to 140 kt (161 mph or 259 km/h) indicated airspeed (IAS) (aircraft approach speed is mass /pressure altitude/temperature/ centre of gravity/aircraft configuration/ dependent). Runway condition (how old is the tarmac/concrete? is it a grooved or smooth runway surface; does it have an upward or downward slope? Is it clean or has it accumulated rubber on its surface (high/low utilisation)? This reported data is used by the airport operators and authorities to determine whether the runway should be closed for de-icing or contamination removal or remain operational until the next scheduled or requested test or report. Pilots/ATC may request that an official braking action test be carried out prior to a landing. Format of braking action declarations In Europe the format of braking action declarations are given using the Greek term mu which is the co-efficient of friction Good = a mu value of 0.4 and above; measured snowtam decode is 95 Med/Good = a mu value of 0.36 to 0.39; measured snowtam decode is 94 Med = a mu value of 0.30 to 0.35; measured snowtam decode is 93 Med/Poor = a mu value of 0.26 to 0.29; measured snowtam decode is 92 Poor = a mu value of 0.25 and below; measured snowtam decode is 91 UNRELIABLE = reading unreliable; measured snowtam decode is 99 READING not measurable or not operationally significant; snowtam decode is Snowtam Format reference is International Civil Aviation Organization (ICAO) document Annex 15 Appendix 2. References Airport engineering