che, I would expect that the contaminated data is based on the requirements in
CS 25 Large Aircraft; see page 665 onwards, AMC 25.1591.
Essentially, there is no correlation with a measured Mu and aircraft performance, thus distance tables relate to the observed conditions – contaminant and depth. However, even with these items for guidance there could be a wide range of error.
The AMC explains the background, and rather technically the assumptions and resultant risks of operating in contaminated conditions. Best advice is don’t operate.
Re takeoff on snow. The aircraft performance data would probably allow such an operation; however with the reported Mu (unofficial / unreliable) to aid judgment the operation could have high risk. If (IF) the value of Mu was correct, then the runway braking action (ICAO) would be described as poor to nil – possibly something equivalent to ‘flooded’ or wet ice. (
Managing Threats and Errors During Approach and Landing slide 26). Thus, it would be unwise to operate without some other clarifying data, e.g. specific gravity of contaminant.
Refs:
Runway Operations - Risks and Factors Associated with Operations on Runways Affected by Snow, Slush or Water.
Takeoff / Landing on Wet, Contaminated and Slippery Runways.