We have to clarify a few terms used in this discussion.
"Contaminated" in the strict legal FAR sense means a build up of some sort that retards ACCELERATION on takeoff. If it is hard packed snow/ice, and the temperature is around -3C or colder, the runway is considered "dry" for the purpose of MTOW calculations, and NO weight reduction is required. (I don't agree with that, but that's the rules.)
The 1.67 and 1.92 figures are used for Landing Field Length, and have nothing to do with degraded braking action on an aborted takeoff.
When we're talkng landing, the runways are considered "dry" or "wet and/or slippery", I have no landing charts that have the word "Contaiminated" printed on them. (Mutt, do you?) The pages that we distribute to the flight crews have the Mu, Tapley, Bowmonk, etc. values printed on them for information to be used in decision making. They are not regulatory.
When we pilots use the word "contaminated", we know what we mean, but it's not necessarily the same as the regulatory agency.
