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Just a test

It's been a long time, and Klem has solved his issue...
However, I like to close open questions, so here's some more information from a discussion over at flightsim.

* Here's how FS calculates "IAS"; unfortunately it's wrong.

"FS IAS" = "FS CAS" = sqrt(Pa/Pssl) * sqrt(1+M^2/4+M^4/40) * M * Assl

This equation exactly fits the "IAS"/TAS test data in FS2004.
However, this equation does not give the correct CAS/IAS.

Index
M: Mach number
Pa: ambient pressure
Pssl: standard atmosphere pressure, sea level
Assl: speed of sound with standard atmosphere at sea level

* Correct relation between TAS (=M*Aa) and CAS is the following:

CAS = sqrt( ( Pa/Pssl * ( (1 + 0.2*M^2)^3.5 - 1 ) + 1 )^(1/3.5) - 1 ) / 0.2 ) * Assl

(valid for M<1)

Correct IAS may be calculated as function of Mach number and ambient pressure (which are available as FS A: variables, all other variables are constants).
Calculated IAS can be used to ... false FS IAS in airspeed gauges.

For further details see the original discussion at flightsim:
http://www.flightsim.com/vbfs/showthread.php?224097-Is-IAS-indicated-wrongly-by-FS

Gunter
 
It's been a long time, and Klem has solved his issue...
However, I like to close open questions, so here's some more information from a discussion over at flightsim.

* Here's how FS calculates "IAS"; unfortunately it's wrong.

"FS IAS" = "FS CAS" = sqrt(Pa/Pssl) * sqrt(1+M^2/4+M^4/40) * M * Assl

This equation exactly fits the "IAS"/TAS test data in FS2004.
However, this equation does not give the correct CAS/IAS.

Index
M: Mach number
Pa: ambient pressure
Pssl: standard atmosphere pressure, sea level
Assl: speed of sound with standard atmosphere at sea level

* Correct relation between TAS (=M*Aa) and CAS is the following:

CAS = sqrt( ( Pa/Pssl * ( (1 + 0.2*M^2)^3.5 - 1 ) + 1 )^(1/3.5) - 1 ) / 0.2 ) * Assl

(valid for M<1)

Correct IAS may be calculated as function of Mach number and ambient pressure (which are available as FS A: variables, all other variables are constants).
Calculated IAS can be used to false FS IAS in airspeed gauges.

For further details see the original discussion at flightsim:
http://www.flightsim.com/vbfs/showthread.php?224097-Is-IAS-indicated-wrongly-by-FS

Gunter
 
It's been a long time, and Klem has solved his issue...
However, I like to close open questions, so here's some more information from a discussion over at flightsim.

* Here's how FS calculates "IAS"; unfortunately it's wrong.

"FS IAS" = "FS CAS" = sqrt(Pa/Pssl) * sqrt(1+M^2/4+M^4/40) * M * Assl

This equation exactly fits the "IAS"/TAS test data in FS2004.
However, this equation does not give the correct CAS/IAS.

Index
M: Mach number
Pa: ambient pressure
Pssl: standard atmosphere pressure, sea level
Assl: speed of sound with standard atmosphere at sea level

* Correct relation between TAS (=M*Aa) and CAS is the following:

CAS = sqrt( ( Pa/Pssl * ( (1 + 0.2*M^2)^3.5 - 1 ) + 1 )^(1/3.5) - 1 ) / 0.2 ) * Assl

(valid for M<1)

Correct IAS may be calculated as function of Mach number and ambient pressure (which are available as FS A: variables, all other variables are constants).
Calculated IAS can be used to xreplace false FS IAS in airspeed gauges.

For further details see the original discussion at flightsim:
http://www.flightsim.com/vbfs/showthread.php?224097-Is-IAS-indicated-wrongly-by-FS

Gunter
 
STRANGE!!!

If Y post the following sentence witin the text I get error message "IE can not display page".

Calculated IAS can be used to false FS IAS in airspeed gauges.

If I post separately, or change xreplace with xreplace, the message goes through...

Otherwise it wouldn't be posted here...

Strange...
 
Correct IAS may be calculated as function of Mach number and ambient pressure (which are available as FS A: variables, all other variables are constants).

Calculated IAS can be used to replace false FS IAS in airspeed gauges.
Click to expand...
It seems to work fine from here!

Let me try it without the quote tag:

Correct IAS may be calculated as function of Mach number and ambient pressure (which are available as FS A: variables, all other variables are constants).

Calculated IAS can be used to replace false FS IAS in airspeed gauges.
 
Last edited:
Seems the message editor does not accept the word "xreplace" under some circumstances...

Had to place an "X" for the message to pass...
 
Hello Bill,
thanks for checking - I had not seen that you have replied to my testing marathon.

I'll again.

Same problem... I have to x_replace the r-word by x_replace...

(Note the r-word just does not pas for me... Must be a problem on my computer...)

Correct IAS may be calculated as function of Mach number and ambient pressure (which are available as FS A: variables, all other variables are constants).
Calculated IAS can be used to x_replace false FS IAS in airspeed gauges.
 
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