TAT or SAT

[BID]

I agree with FurloughedAgain.

So when ATC wants to know your temp, what do you guys give them?

 

[Jeff Helgeson]

FMS Progress page 2....

I agree with FurloughedAgain.

So when ATC wants to know your temp, what do you guys give them?

I usally read what is on the progress page, along with the winds or SAT from the panel.

 

[Saabslime]

ATC is looking for SAT if they ask. I think they could care less what your measured TAT is.

 

[XTW]

SAT= past tense of SIT

TAT= usually slang for "tattoo"

Hope I have been of some help.

Regards,

XTW

 

[banned username 2]

*Sidenote*

I always thought that to determine the possibility of icing in precip, you used SAT rather than TAT. Is that correct?

Typically TAT is used to determine if you need to have the anti-ice on or not... In the Falcon 900EX if we are in at a TAT of +10°C or less in visible moisture we turn on the anti-ice...

 

[h25b]

I disagree with my good friend H25B.
On just about every aircraft that i've flown the manufacturer suggested that TAT be used in order to decide when to turn on the ice protection.

Why? Think of it in simple terms, TAT is the temperature that the skin of the airplane THINKS it is.

So if it is zero degrees C' and you accelerate to 290, ram-air, friction, etc. might yield a TAT of +11'C thereby eliminating the need for ice protection.

Now on those same aircraft SAT is used to determine when you may turn off the antiice when the temperature is so cold that any moisture it carries will be in the form of ice crystals (usually -40'C SAT or colder).

I guess I've always been thinking of it in terms of, "How cold is it outside ???" In which case SAT is the most accurate answer to that simple question. I'll have to look at the Lear manual and see what they recommend using for anti-ice purposes. Sort of splitting hairs but nonetheless interesting...

I've been enlightened...

 

[Hose A. Jiminez]

I guess I've always been thinking of it in terms of, "How cold is it outside ???" In which case SAT is the most accurate answer to that simple question. I'll have to look at the Lear manual and see what they recommend using for anti-ice purposes. Sort of splitting hairs but nonetheless interesting...

I've been enlightened...

Not interesting at all.

 

[LEROY]

Look at the gage in your cockpit. Whatever it reads, reference your CFM (AFM) ... do what it tells you to do. For an in-depth discussion on Bernoulli equations and temperature gradients, there are several great textbooks I remember from college that spell that cr@p out.
As an aero engineer, I say fly what the book tells you to fly....

 

[FDJ2]

And the answer is

SAT - Static Air Temperature. Also called OAT. This is the temperature of the air surrounding the aircraft.

TAT - Total Air Temperature. This is the temperature of the air measured approximately by a temperature probe (such as a Rosemount). It is higher than the static air temperature due to ram pressure, or Mach, heating caused by the motion of the aircraft through the air. I say "approximately" because there are many factors that make the measured temperature slightly different from the true total air temperature.



http://mtp.jpl.nasa.gov/notes/software/Nomenclature%20and%20Abbreviations.html





The simple answer is that static air temperature is the outside temperature and total air temperature is the air temperature adjusted for the ram pressure heating caused by the motion of the aircraft.

 

[banned username 2]

I'll have to look at the Lear manual and see what they recommend using for anti-ice purposes. Sort of splitting hairs but nonetheless interesting...

Splitting hairs???

In the Lear 35 with a SAT of -56°C (ISA) doing Mach 0.78 your TAT would be about -30°C, that is a 24°C difference (43.2°F difference) TAT vs. SAT...

I would hardly call that "Splitting Hairs"...