I agree too, we are both trying to say the same thing.
Let me try to reword it. Imagine you are stationary in an aircraft. Any temperature that you record will be the ambient air temperature or SAT. This seems to be frequently referred to in GA circles as the OAT. Now imagine flying that aircraft at high speed but at the same ambient temperature. The SAT has not changed but now as the airflow meets the airframe it starts to get compressed before it parts to flow around the structure. This marginal increase in pressure causes that bit of air's temperature to rise (the quantity of which called the ram rise) so the temperature that is sensed in the aircraft is the combination of the ambient temperature AND the ram rise. This is referred to as the Total air temperature (as it is the total effect of SAT and ram rise). In GA aircraft the speeds are so slow that the effect of ram rise is almost negligable so it is generally not considered.
So how do we use these pieces of information?
Well in my company we use engine anti-ice when in icing conditions and the TAT is between 10 degrees or less. This assumes that although the freezing temperature of water is 0 degrees, as we fly at high speed a 0 degree SAT would indicate at a higher temp on a TAT indicator.
On my last aircraft (a modern turboprop) we only had an SAT indication and it was noticeable that ice would only start to stick to the wings at approximately -4 degrees SAT. This was because at ambient temperatures of -3 or greater the ram rise would increase the temperature above freezing.
regards
wizzy
[ 04 August 2001: Message edited by: wysiwyg ]