Well, a Slippery runway is a contaminated one...
Runways can have 4 states, dry, damp, wet and contaminated. Damp can be considered dry for performance according to the JARs and wet when contamination on the runway is inferior to 3mm of standing water, slush or lose snow.
By definition a contaminated runway is when more than 25% of the runway area (in isolated areas or not) is covered by more than 3mm of lose snow, water, slush and compact snow and ice, or melting snow or ice independent on depth.
The slippery definition (if I`m not mistaken) came from SAS on the 50s, to make things easier, instead loosing 20 minutes decoding the snowtam, and that was adopted by everyone. Boeing says that a slippery runway is when you have info about braking action good, medium or poor. If no info on braking action, you can`t use the slippery performance, but the slush/standing water equivalence performance (contaminated performance, that is)
The braking action good is more or less the equivalent to a wet runway and poor to an ice or compact snow contaminated runway. The good, medium and poor terms are used according to braking coefficients obtained after runway examination…
Cheers!
