There is an old thread that discusses this in some detail here: http://www.vansairforce.com/community/showthread.php?t=30022&highlight=GRT+TAT
I have a G3X Touch and a GRT Mini in my panel, each with their own OAT probe. The probes are mounted side by side under the wing on an inspection panel. In the hangar the GRT reads 2*F higher than both the G3X and the thermometer on the wall.
Level at an altitude of 8000 ft with a true airspeed of 195 knots (174 indicated, 2300 rpm, lean of peak, 11.5 gph) there is a difference of 9* F between the two OAT readouts, with the GRT Mini being the higher reading. I have confirmed that the G3X converts their probe's data for "Ram Rise" to provide Static Air Temperature (SAT). It is obvious the GRT Mini is displaying Total Air Temperature (TAT).
Why should you care?
I have a G3X Touch and a GRT Mini in my panel, each with their own OAT probe. The probes are mounted side by side under the wing on an inspection panel. In the hangar the GRT reads 2*F higher than both the G3X and the thermometer on the wall.
Level at an altitude of 8000 ft with a true airspeed of 195 knots (174 indicated, 2300 rpm, lean of peak, 11.5 gph) there is a difference of 9* F between the two OAT readouts, with the GRT Mini being the higher reading. I have confirmed that the G3X converts their probe's data for "Ram Rise" to provide Static Air Temperature (SAT). It is obvious the GRT Mini is displaying Total Air Temperature (TAT).
Why should you care?
- If you fly IFR;
- If your OAT displays TAT and you think it is displaying SAT;
- If you are about to enter a cloud and are not concerned about icing because your OAT is reading high enough;