Of what value is TAS?

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dallas

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Archived from groups: alt.games.microsoft.flight-sim (More info?)

So your indicated airspeed is 140 kts. Your true airspeed is 156.8 kts.
Great.

If you are flying into a 40 kt headwind, I'm just not sure what value true
airspeed has to a pilot.

Dallas
 
Archived from groups: alt.games.microsoft.flight-sim (More info?)

On Mon, 02 May 2005 19:27:22 GMT, "Dallas"
<Cybnorm@spam_me_not.Hotmail.Com> brought up the following:
>
>So your indicated airspeed is 140 kts. Your true airspeed is 156.8 kts.
>Great. If you are flying into a 40 kt headwind, I'm just not sure what value
>true airspeed has to a pilot.
>
>Dallas
>


Will do a spreadsheet on this one.. also want to understand it better.


-G
 
Archived from groups: alt.games.microsoft.flight-sim (More info?)

When you file a flight plan with the FAA, you use your
TAS as the airspeed figure for one thing.





On Mon, 02 May 2005 19:27:22 GMT, "Dallas"
<Cybnorm@spam_me_not.Hotmail.Com> wrote:

>
>So your indicated airspeed is 140 kts. Your true airspeed is 156.8 kts.
>Great.
>
>If you are flying into a 40 kt headwind, I'm just not sure what value true
>airspeed has to a pilot.
>
>Dallas
>
 
Archived from groups: alt.games.microsoft.flight-sim (More info?)

Dallas wrote:
> So your indicated airspeed is 140 kts. Your true airspeed is 156.8
> kts. Great.
>
> If you are flying into a 40 kt headwind, I'm just not sure what value
> true airspeed has to a pilot.
>

If these are random figures, none. Are they from a actual readout/flight??
 
Archived from groups: alt.games.microsoft.flight-sim (More info?)

> If you are flying into a 40 kt headwind, I'm just not sure what value
true
> airspeed has to a pilot

In the smaller GA aircraft, true airspeed serves many functions. A
couple off the top of my head:

1) Fuel required: In zero wind, true airspeed equals ground speed.
In a wind scenario, true airspeed plus or minus the wind factor equals
ground speed. The speed across the ground will give you time required
to make your waypoint/destination. Fuel usage in small aircraft is a
measure of fuel burned per hour flown. Thus, if you have the time it
will take to get to your destination and you know how much fuel you
burn per hour, you will know how much fuel you need to get to your
destination.

2) Health of the engine(s): Since true airspeed is a known value for
a given altitude and temperature, a deviation from this known value is
a potential indication of an issue with the engine.

--
Peter
 
Archived from groups: alt.games.microsoft.flight-sim (More info?)

Dallas,
True Airspeed is necessary to know if a pilot is calculating things like
groundspeed and time to waypoint(s), as well as fuel consumption. It's not
too critical if you are simply flying locally, but if you are flying a long
cross country, at near maximum weight, with limited fuel, then TAS comes in
pretty handy. Some airspeed indicators have adjustable rings around the edge
of the dial that can be set for temperature and pressure, and then show TAS.

Randy L.

"Dallas" <Cybnorm@spam_me_not.Hotmail.Com> wrote in message
news:uavde.3240$BE3.1024@newsread2.news.pas.earthlink.net...
>
> So your indicated airspeed is 140 kts. Your true airspeed is 156.8 kts.
> Great.
>
> If you are flying into a 40 kt headwind, I'm just not sure what value true
> airspeed has to a pilot.
>
> Dallas
>
>
 
Archived from groups: alt.games.microsoft.flight-sim (More info?)

Dallas wrote:

> Ok.. perhaps my question should have been how do you accurately
determine
> the wind speed and direction aloft, because without that factor TAS
could be
> dangerously deceptive?

The old time pilots here are going to get all over my case on this one
<G>, but one method is to use the GPS. The Garmin GNS430/530 has a
winds aloft calculator page that requires the pilot to enter indicated
airspeed, altitude, outside temperature, and barometric pressure, which
results in TAS. The pilot then enters indicated heading and the GPS
will calculate winds aloft.

Of course, since you are interested in groundspeed for fuel usage
monitoring, you don't even need to calculate winds aloft. The GPS
shows groundspeed on many of its navigation pages.

There certainly is a manual method for calculating groundspeed that is
taught during the cross country section of the private pilot training.
This involves timing between two known ground features or navigational
waypoints.

> I was thinking that one use of TAS would be to determine wind speed
by
> timing the distance between two points and subtracting ground speed
from
> TAS. But at that point.. so what? What we really wanted here was
> groundspeed anyway.

Look at the GPS or, if not equipped, do as you suggested. Choose two
points that are only about 30 nm apart, then time the trip between
them. With this groundspeed, you can then calculate an estimated time
of arrival to the next waypoint along your flight. This time can then
be used to calculate an estimated fuel flow. The important point is to
continually perform this calculation in the likely event that winds
aloft changes direction or speed.

--
Peter
 
Archived from groups: alt.games.microsoft.flight-sim (More info?)

Randy wrote:

> The few times that I have calculated and flown a cross country
flights
> using TAS and winds aloft forecasts really surprised me in how
accurate
> those winds aloft predictions were.

And when the actual winds aloft is different than the forecast winds
aloft, it will always be a lot stronger.

Murphy's Aviation Law # 78. :)

--
Peter
 
Archived from groups: alt.games.microsoft.flight-sim (More info?)

Quilljar wrote:

>
http://community.webshots.com/­scripts/editPhotos.fcgi?action­=showMyPh...

<snip>

Hey, Quilly, do you have to somehow allow non-members of Webshots to
see these pictures? I am getting a Webshots error stating that I am
not the owner of these pictures.

> For Dally, my answer is that IAS is needed for you to keep the
aircraft in
> the air. The TAS is essential for navigation. So IAS is for pilots
and TAS
> is for navigators. If you are single handed then you must have both.

Hey, I like this. Right to the point. Very nice...

--
Peter
 
Archived from groups: alt.games.microsoft.flight-sim (More info?)

Gregory wrote:

> Please describe more about the specifics of CAS and TAS.

Calibrated Airspeed (CAS) is Indicated Airspeed (IAS) corrected for
airspeed indicator and/or installation errors. The Pilot's Operating
Handbook of smaller aircraft contains the IAS to CAS table, but
normally the difference between CAS and IAS is only about a knot or two
(at least when discussing the airspeeds of the standard
non-turboprop/jet GA aircraft).

True Airspeed (TAS) is Calibrated Airspeed (CAS) corrected for
temperature and altitude. As Dudley indicated, TAS and CAS are about
the same at sea level, but as an aircraft climbs higher, TAS is greater
than CAS.

--
Peter
 
Archived from groups: alt.games.microsoft.flight-sim (More info?)

Gregory wrote:

> Please describe more about
> the specifics of CAS and TAS.. is that Total or True AS?

[Apologies if my previous response appeared on your server. Google
dropped my first reply, however, which is pretty bizarre considering I
posted from Google. Now I have to type the whole thing over again from
memory]

Calibrated Airspeed (CAS) is Indicated Airspeed (IAS - that which is
shown on the airspeed indicator) corrected for airspeed indicator
and/or installation error. The pilot's operating handbook contains a
table showing the IAS to CAS values. For the non-turboprop/jet GA
aircraft, though, the difference between CAS and IAS is usually only a
few knots or less.

True Airspeed (TAS) is CAS corrected for temperature and altitude. As
Dudley pointed out, TAS and CAS are about the same at sea level.
However, as the aircraft climbs, TAS is greater than CAS.

--
Peter
 
Archived from groups: alt.games.microsoft.flight-sim (More info?)

On 2 May 2005 16:01:32 -0700, "pr" <proffice@twcny.rr.com> brought the
following to our attention:

>Gregory wrote:
>
>> Please describe more about the specifics of CAS and TAS.
>
>Calibrated Airspeed (CAS) is Indicated Airspeed (IAS) corrected for air-
>speed indicator and/or installation errors. The Pilot's Operating Handbook
>of smaller aircraft contains the IAS to CAS table, but normally the difference
>between CAS and IAS is only about a knot or two (at least when discussing
>the airspeeds of the standard non-turboprop/jet GA aircraft).

thanks Peter.. very good reply. I mostly enjoy Simming the old
jetliners. Occasionally a Beech turbo-twin!

>True Airspeed (TAS) is Calibrated Airspeed (CAS) corrected for temperature
>and altitude. As Dudley indicated, TAS and CAS are about the same at sea
>level, but as an aircraft climbs higher, TAS is greater than CAS.

Between your reply and discussion from the `old pros'.. it should be
enough to create a series of curves for TAS. I think it would be good,
if users are so inclined and have the time, to work through the math
in the above link.


-Gregory
 
Archived from groups: alt.games.microsoft.flight-sim (More info?)

On 2 May 2005 16:06:16 -0700, "pr" <proffice@twcny.rr.com> brought the
following to our attention:

>[Apologies if my previous response appeared on your server. Google
>dropped my first reply, however, which is pretty bizarre considering I
>posted from Google. Now I have to type the whole thing over again from
>memory]

iT showed up thru giganews ok.. replied to it already.


-G
 
Archived from groups: alt.games.microsoft.flight-sim (More info?)

"pr" <proffice@twcny.rr.com> wrote in message
news:1115071495.603600.88620@l41g2000cwc.googlegroups.com...

> And when the actual winds aloft is different than the forecast winds
> aloft, it will always be a lot stronger.

You mean, "it will always be a lot stronger to your detriment." It's almost
never stronger in your favor (tailwind). :)
--
Chris
http://www.mcmartinville.com
 
Archived from groups: alt.games.microsoft.flight-sim (More info?)

"Dallas" <Cybnorm@spam_me_not.Hotmail.Com> wrote in message
news:uavde.3240$BE3.1024@newsread2.news.pas.earthlink.net...
>
> So your indicated airspeed is 140 kts. Your true airspeed is 156.8 kts.
> Great.
>
> If you are flying into a 40 kt headwind, I'm just not sure what value true
> airspeed has to a pilot.
>
> Dallas

TAS is your ACTUAL speed through the air. Think about the ramifications of
this information as it pertains to all your navigational computations and it
will make more sense.
Dudley
 
Archived from groups: alt.games.microsoft.flight-sim (More info?)

"CRaSH" <sorry@aint-here.spam.com> wrote in message
news:jNvde.681$DC2.173@okepread01...
> Dallas wrote:
>> So your indicated airspeed is 140 kts. Your true airspeed is 156.8
>> kts. Great.
>>
>> If you are flying into a 40 kt headwind, I'm just not sure what value
>> true airspeed has to a pilot.
>>
>
> If these are random figures, none. Are they from a actual
> readout/flight??

True airspeed is IAS (CAS) corrected for air density. It represents the
airplane's ACTUAL speed through the air mass in which it's traveling. In
this case, with a TAS of 157kts, the GROUND SPEED of the airplane with a
40Kt headwind would be 117kts. This ground speed will affect every
navigational computation used in the flight that determines time enroute and
fuel expended. TAS is a VERY important factor to determine in flight
planning.
Using IAS in this case of 140kts, the ground speed would be computed at
100kts deducting for the 40kt headwind. This is a totally incorrect
calculation that would affect all times enroute, and even more important,
all fuel computations for the flight.
The differences in this instance are not all that great, but you take a 747
to high altitude and start using the IAS for your navigational problems and
you'll be in fuel trouble in short order! 🙂)
IAS should be considered as an indicator telling you where you are in
relation to your 1g stall speed. It's useful when considering performance
such as approach speeds, stall speeds, Vx, Vy, and the like, but when it
comes down to needing to know how fast the airplane is ACTUALLY MOVING
through the air mass, you MUST know your TAS, and that means correcting your
IAS for factors affecting air density.
Hope this helps
Dudley
 
Archived from groups: alt.games.microsoft.flight-sim (More info?)

Dudley Henriques wrote:
>
> True airspeed

Geezz, I just hate it when people make sense....

When I first glanced at the figures I was comparing 100kt ground speed with
157kt TAS and it just didn't compute in my confuluted (that's an Arky term)
logic.......... d:->))
 
Archived from groups: alt.games.microsoft.flight-sim (More info?)

On Mon, 02 May 2005 20:22:06 GMT, "Dudley Henriques"
<dhenriques@noware .net> brought the following to our attention:

>True airspeed is IAS (CAS) corrected for air density. It represents the
>airplane's ACTUAL speed through the air mass in which it's traveling. In
>this case, with a TAS of 157kts, the GROUND SPEED of the airplane with a
>40Kt headwind would be 117kts. This ground speed will affect every
>navigational computation used in the flight that determines time enroute and
>fuel expended. TAS is a VERY important factor to determine in flight planning.

yep.. Yippie.... a spreadsheet. :)


Ok here's a GOOD link for the relations needed..

http://www.aerospaceweb.org/question/atmosphere/q0049.shtml


Now you can determine atmospheric..

Pressure ratio - Delta

Temperature ratio - Theta

Density ratio - Sigma


Found some other web pages which provide definitions.. so the
next step is to put it ALL together. Please describe more about
the specifics of CAS and TAS.. is that Total or True AS?


-Gregory
 
Archived from groups: alt.games.microsoft.flight-sim (More info?)

"Dudley Henriques"
> In this case, with a TAS of 157kts, the GROUND SPEED of
> the airplane with a 40Kt headwind would be 117kts.

Ok.. perhaps my question should have been how do you accurately determine
the wind speed and direction aloft, because without that factor TAS could be
dangerously deceptive?

I was thinking that one use of TAS would be to determine wind speed by
timing the distance between two points and subtracting ground speed from
TAS. But at that point.. so what? What we really wanted here was
groundspeed anyway.


Dallas
 
Archived from groups: alt.games.microsoft.flight-sim (More info?)

"Dallas" <Cybnorm@spam_me_not.Hotmail.Com> wrote in message
news:6swde.4055$GQ5.2873@newsread1.news.pas.earthlink.net...
>
> Ok.. perhaps my question should have been how do you accurately determine
> the wind speed and direction aloft, because without that factor TAS could
> be
> dangerously deceptive?
>
Dallas,
The "winds aloft" prediction is part of the weather briefing that most
pilots study before a flight. In the US these winds are part of the Area
Forcast (FA) that can be gotten several ways. One way is using the internet,
and a program like DUATS, which is a service that helps pilots plan cross
country flights. Another way is to call the local Flight Service Station
when you file your initial flightplan and request the winds aloft forecast.
Or you can contact FSS while in the air for an updated Winds Aloft briefing.
Winds Aloft data is gathered by the National Weather Service using weather
balloons that collect data such as barometric pressure, temperature,
humidity, and wind speed & direction. The NWS releases these balloons on a
regular schedule, and use the collected data from them to make their
precdictions and forecasts. Another source of winds aloft data comes from
pilots who make PIREPS (Pilot REPorts) while in flight.
The few times that I have calculated and flown a cross country flights
using TAS and winds aloft forecasts really surprised me in how accurate
those winds aloft predictions were. I was reaching my waypoints within only
a few miunutes difference from the time that I had calculated.

Randy L.
 
Archived from groups: alt.games.microsoft.flight-sim (More info?)

"CRaSH"
> If these are random figures, none. Are they from a actual
readout/flight??

Not random, they are the TAS for ISA 140 kt. and Altitude 6,000.

Dallas
 
Archived from groups: alt.games.microsoft.flight-sim (More info?)

Dallas wrote:
> So your indicated airspeed is 140 kts. Your true airspeed is
> 156.8 kts [...]
>
>> If these are random figures, none. Are they from a actual
>> readout/flight??
>
> Not random, they are the TAS for ISA 140 kt. and Altitude 6,000.

That's the TAS if the temperature at 6,000' is 15C (which is NOT ISA
temp). But if it's 0C (32F) outside, then your TAS is only 152 kts...
about 5 kts less... so after six hours of flight, you'll land about 30
nm short of your destination if you used the ~157 kt figure to
calculate fuel duration <grin>.

Too many online TAS "calculators" use the 2% per 1000' rule of thumb
instead of real formulae. I can't seem to easily find one that does
the right thing, though.

Cheers,
Kev
 
Archived from groups: alt.games.microsoft.flight-sim (More info?)

"Dallas" <Cybnorm@spam_me_not.Hotmail.Com> wrote in message
news:6swde.4055$GQ5.2873@newsread1.news.pas.earthlink.net...
>
> "Dudley Henriques"
>> In this case, with a TAS of 157kts, the GROUND SPEED of
>> the airplane with a 40Kt headwind would be 117kts.
>
> Ok.. perhaps my question should have been how do you accurately determine
> the wind speed and direction aloft, because without that factor TAS could
> be
> dangerously deceptive?

Depends. It can be determined with instruments, or visually using points of
reference along a known course line. Visually, wind is estimated, then
corrected to produce a new point of reference down the line affirming the
correction's effect. Basically, in light airplanes, you are starting out
with an estimated correction based on forcast winds aloft at your cruising
altitude, then correcting for drift as you progress along your course line.
The difference between your desired course and the heading you have to
maintain to realize that course is your wind correction angle.
Modern navigation devices can produce this for you electronically.
Same with airspeed. You begin with an estimated TAS based on your IAS at
cruise corrected for temp and density. Then you time between two known
points to obtain enroute data. Then you adjust for any time difference shown
on your estimate and get your ground speed. Then you use the ground speed to
determine your arrival time at the next point or destination.
Basically, all flying is is starting with an estimate based on known data,
then adjusting that estimate (on the fly so to speak) to reflect any
changes. Finally, using this process of constant correction, you should
arrive at some hard data that will produce an accurate result for your final
figures for the trip.
Simple!! Sort of a "check" and re-check thing gets it done for you. 🙂)
Dudley
Dudley
>
> I was thinking that one use of TAS would be to determine wind speed by
> timing the distance between two points and subtracting ground speed from
> TAS. But at that point.. so what? What we really wanted here was
> groundspeed anyway.
>
>
> Dallas
>
>
 
Archived from groups: alt.games.microsoft.flight-sim (More info?)

"Dudley Henriques" <dhenriques@noware .net> schreef in bericht
news:5uvde.2725$pe3.326@newsread3.news.atl.earthlink.net...
>
> "Dallas" <Cybnorm@spam_me_not.Hotmail.Com> wrote in message
> news:uavde.3240$BE3.1024@newsread2.news.pas.earthlink.net...
>>
>> So your indicated airspeed is 140 kts. Your true airspeed is 156.8 kts.
>> Great.
>>
>> If you are flying into a 40 kt headwind, I'm just not sure what value
>> true
>> airspeed has to a pilot.
>>
>> Dallas
>
> TAS is your ACTUAL speed through the air. Think about the ramifications of
> this information as it pertains to all your navigational computations and
> it will make more sense.
> Dudley
>
Dudley,

In the times we did not have groundspeed readout readily available, I used
it as an estimate for my groundspeed. It gets quite close. The same for Mach
no. M 0.7 is almost 7 (statute) miles a minute. Agree?

Loek
 
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