Mutt;
i checked the part 25 reference you gave and maybe i have a Reader's Digest Condensed Version since i could see no reference to 20,000 feet.
will take the book with me and look for it between BRU/BCN/BRU/FCO today.
thanks again for the response.
still a doubting thomas about the slush on the runway.
i have been web surfing and haven't found anything to clarify that yet.