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luizcaeiro

True Airspeed vs Indicated Airspeed

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Sorry if it has been analyzed before, but I coudn´t get to find it.

 

The inbound display of 777 shows 2 informations at the top of it at the right side.

First is GS ( Ground speed) the other is TAS (True Airspeed).

Is it not more common to show the IAS ( indicated Airspeed), instead TAS, since sometimes controllers ask you to say the Indicated Airspeed in some vectors approaches?

Is it possible to change the TAS for IAS ?

How can I achieve this task?

 

The Indicated airspeed is ialready tagged at Prepar3d config, but PMDG 777 doesn´t seem to care about this?

 

Thank you for any help.

 

luizcaeiro

 

 

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Sorry if it has been analyzed before, but I coudn´t get to find it.

 

The inbound display of 777 shows 2 informations at the top of it at the right side.

First is GS ( Ground speed) the other is TAS (True Airspeed).

Is it not more common to show the IAS ( indicated Airspeed), instead TAS, since sometimes controllers ask you to say the Indicated Airspeed in some vectors approaches?

Is it possible to change the TAS for IAS ?

How can I achieve this task?

 

The Indicated airspeed is ialready tagged at Prepar3d config, but PMDG 777 doesn´t seem to care about this?

 

Thank you for any help.

 

luizcaeiro

 

 

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Is it possible to change the TAS for IAS ?

How can I achieve this task?

 

The Indicated airspeed is ialready tagged at Prepar3d config, but PMDG 777 doesn´t seem to care about this?

 

Sounds like you're not fully understanding what all the plane is telling you...

 

I'll use the image below to explain:

2014-10-24_18-15-52-630.JPG

 

On the far left display (the blue and brown one - your PFD), you can see the number 140. That is your indicated airspeed, or IAS. This is the one controllers will ask you to report (that, or your commanded Mach speed, which would be displayed at the top left, in magenta, where this display currently shows 141).

 

To the right of that display is your Nav Display (ND). This shows both ground speed (143) and true airspeed (144). These are less important, but good information to have. From this, I can tell that my true speed through the air is actually a little higher than my indicated speed, and that I have a 1 knot headwind. There is no option to change these values because there's no need to. Your IAS is already reported on your PFD.

 

 

 

luizcaeiro

 

Full names in the forum, please.

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You have all three in front of you in the 777.

 

IAS is the speed tape on the left hand side of the Primary Flight Display.

Groundspeed is the speed over the ground...calculated from IAS, altitude, temperature and pressure.

True Airspeed is the groundspeed and the wind component put together.

 

EDIT:  Kyle *just* beat me to it!!  :)

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TAS is actually a lot more than simply GS corrected for wind component, actually it's not based on GS but rather calculated through density altitude, which depends on a few factors related to the airmass you're flying through.

 

The speed in Magenta at the top left corner of the PFD is the speed manually set through the MCP ( speed intervention ) or from your FMS. The speed ( IAS too ) in your speed tape should be as close as possible to that value on the top left corner, but it takes a it's time to get there when you or the FMS intervene to set a new speed to fly, or due to weather factors ( gusting / variable winds or tubulence ).

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TAS is actually a lot more than simply GS corrected for wind component, actually it's not based on GS but rather calculated through density altitude, which depends on a few factors related to the airmass you're flying through.

 

You're right...I mixed them up.  I blame it on the 102* fever I'm fighting!!  That's my excuse and I'm sticking to it.

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You're right...I mixed them up.  I blame it on the 102* fever I'm fighting!!  That's my excuse and I'm sticking to it.

 

Never mind, that's the kind of posts I often write, in the middle of a hundred other tasks sometimes ... And somehow what you answered is not even totally wrong Devin ;-)

 

I wish you get better real soon  !!! For me 37ºC is already a "high" fever :-/  I hate feeling that way  :wacko:

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A little off topic. But has anyone ever tried explaining the concept of different airspeeds to someone that doesn't know? I flew with some co workers a few months back and we got on the subject of how fast aircraft fly and different kinds of speeds. And I gotta say, it's a difficult concept for some to grasp

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