Simviation Forums

Hi all, just a couple of questions for you to help me with:
1) On the EICAS screen on come heavies, there is a temperature given as 'TAT: XX degrees' does anyone know what TAT stands for? its a trivial thing thats been bothering me for a while. I know its an outside air temp, but I just can't fathom the TAT part.
2) is it possible to use the other GPS module with different airraft? I feel far more at home with the one with the default b747 but have just downloaded a plane that uses the alternative one and I dont like it!!!!

Cheers guys
John

TAT=Total Air Temperture

1) On the EICAS screen on come heavies, there is a temperature given as 'TAT: XX degrees' does anyone know what TAT stands for? its a trivial thing thats been bothering me for a while. I know its an outside air temp, but I just can't fathom the TAT part.

TAT = True Air Temperature

2) is it possible to use the other GPS module with different airraft? I feel far more at home with the one with the default b747 but have just downloaded a plane that uses the alternative one and I dont like it!!!!

Yes, you just need to mod the panel.cfg.

I wish I understood TAT better.  I do know that it stands for Total Air Temperature and that it's a function of the "static outside air temperature" and how fast you're going.  The faster you go the higher the TAT will be.  In some of the supersonic planes here I have seen TAT exceed 100 *C.

gw

Your question on TAT has been answered and Chomp Rock is correct on the GPS. Very simple really. Here's how jb2..

Open your 747 panel.cfg.........You will note that at the top where it lists [Window Titles] that Window02 is your GPS, or should be if it is the default 747 and you haven't changed panels or modded the panel.cfg.

Now, scroll down to where you see [Window02] with the all the info below it. This is what you would copy and paste in your other panel.cfg of any acft. you want to add this GPS to.

You would have to look at the panel.cfg of the acft. you want to change GPS's, note where this ones GPS is listed below, not at the top. The top in Windows Titles doesn't matter. It will tell you where in the order the GPS is.

Say in this acft. it is actually listed as [Window04=GPS].
Then you would scroll down to Window04, remove all that info and paste the new info in there. YOu would also have to make sure you give it the correct window #. So the default 747 info is Window02 would have to be changed to Window04. That's all there is to it. Have fun.....make a copy of the panel.cfg you want to change and put on your desktop. Rename the one you leave in the folder as panel.bak, panel.orig or something like that. Edit the one on the desktop and when done, place it back into the acft. Panel folder.

There ya go!! Enjoy......................

In aviation there are a bunch of temp. measurements and acronyms.
TAT is SAT (static air temp) corrected for ram rise effect.
From a practical standpoint, TAT (or RAT) is the temp the aircraft's skin feels and SAT is the free air temp (OAT). TAT is greater than SAT because of the dynamic heating which is proportional to the speed of the aircraft

So what's the point of knowing the different temps? Well TAT is the important number when considering the formation of ice on the airframe, nacelles and inside fuel tanks. TAT is used when deciding to switch on the engine anti-ice.

thanks alot guys that was very helpful!

John

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 . There is a simple relationship between TAT (Tt), SAT (Ts) and Mach Number (M):

Thus if TAT and M are known, SAT (or OAT) can be calculated. Fortunately, the Mach Number is simply related to the ratio of the total (or ram) pressure (pt) measured by the aircraft's pitot tube , and the static air pressure (ps) measured by the static air line:

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

OAT - Outside Air Temperature. Also called SAT . This is the temperature measured by the aircraft avionics , or by a PI instrument , and is one of the two temperature measurements needed to determine the MTP gain. (The other is the target or reference temperature.) It cannot be assumed that the OAT is always correct , and so careful comparisons must be made against radiosondes near the aircrafts flight track . Not only can there be a bias in the OAT relative to radiosondes, but the bias can be pressure altitude dependent, due, for example, to a pin-hole leak in the static air line.

Happy TAT  temp flying. Don't forget to calculate the temp right for take off and landing this is very important

Dosen't Concorde have a 'temperature at the tip' gauge, to measure the outside 'skin' temperature because of the high amount of friction caused by going supersonic?? ?? ??

Fortunately, the Mach Number is simply related to the ratio of the total (or ram) pressure (pt) measured by the aircraft's pitot tube , and the static air pressure (ps) measured by the static air line:

I got a couple of questions. Is Mach # "related" to or actually equivalent to that ratio?

Is knowing the SAT, TAT before takeoff helpful in predicting if there will be downdrafts that could pull an airplane down to crash even in relatively clear weather?

Thanks.

Mach Number - M. The Mach Number,  ,  is the ratio of the aircraft's true air speed (TAS or va) , and the local velocity of sound vs.

The velocity of sound (to first order,  ) depends only on the static air temperature  :o(Ts), where R is the Gas Constant, R , which for dry air is 287.053 J kg-1 K -1 and  is the ratio of the specific heats at constant pressure and volume.

Temperature


Air density decreases with altitude. At high elevation airports, an airplane requires more runway to take off . Its rate of climb will be less, its approach will be faster,   because the true air speed [TAS] will be faster than the indicated air speed [IAS] and the landing roll will be longer  :(

Air density also decreases with temperature. Warm air is less dense than cold air because there are fewer air molecules in a given volume of warm air than in the same volume of cooler air. As a result, on a hot day, an airplane will require more runway to take off, will have a poor rate of climb and a faster approach and will experience a longer landing roll.

In combination, high and hot, a situation exists that can well be disastrous for an unsuspecting, or more accurately, an uninformed pilot. The combination of high temperature and high elevation produces a situation that aerodynamically reduces drastically the performance of the airplane. The horsepower out-put of the engines decrease because its fuel-air mixture is reduced. The propeller develops less thrust because the blades, as airfoils, are less efficient in the thin air. The wings develop less lift because the thin air exerts less force on the airfoils. As a result, the take-off distance is substantially increased, climb performance is substantially reduced and may, in extreme situations, be non-existent.

Mountain airports are particularly treacherous when temperatures are high, especially for a low performance airplane. The actual elevation of the airport may be near the operational ceiling of the airplane without the disadvantage of density altitude. Under some conditions, the airplane may not be able to lift out of ground effect  :oor to maintain a rate of climb  :onecessary to clear obstacles or surrounding terrain.
So in real life with real people yes you do have to firgure temperature fo take-off

But Flight simulator you don't have to worry about it  8)
So tell your passenger to sit down and sut up its time for take-off

Thunder storms produce your downdrafts so stay at least 20 miles or more away from them or you could see a big down draft and have a bad day