TAT and SAT

[Guest lou ross]

Could someone give me an explanation of these two temps? thanks, louross.

[Guest erjboy]

Hi Lou this one is pretty easy....Well SAT or Static Air Temp is basically your outside air temperature that you read directly from a thermometer....Now the difficult one,....TAT or Total or Temperature is SAT corrected for compressiblity, what I mean you the is as an object moves thru the atmosphere it gets heated up by friction, so TAT is always warmer up in the Altitudes...For instance yesterday we were cruising the 767 at FL380 and the SAT was around -45C but the TAT was only -20C this is due to compressiblity, its warmer..Anyway I hope this makes it a little clearer, hope I didn't confuse the S%^^& out of you...Later

[Guest]

Hi Joseph,What is the specific use of TAT?Why would you want to know TAT if it is a temperature that is so dependent on external variables like speed, height etc.?thx!Gideon

[Guest erjboy]

Well for us we use it for Engine Anti-ice purposes...When I was flying the ERJ's for eagle we use to turn on the Anti-Ice on for TAT 10C or colder with visible moisture such as clouds fog and rain. But boeing uses SAT for both ground and flight opps, so in the case we really don't use TAT much but SAT.. That is the only thing I can think of for using TAT....Hope this helps again...