# Just a test

#### teson1

Just testing - can't postmessages in forum.

Edit: Found what was wrong; Seems the message editor does not accept the word "x_replace" in a message under some circumstances... (Note I had to put an "x_" before the r-word for the message to pass.)
In other circumstances the r-word goes through... Strange...

Last edited:

#### teson1

Maybe something wrong with the message I'm trying to test?

... Yes ...

Edited and trying to repost...

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.

... Removing part of the message to find out where the error is...

#### teson1

Next part...

* 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)

...

#### teson1

Ok. That went through ok... next part...

Correct IAS may be calculated as function of Mach number and ambient

...

#### teson1

...

Correct IAS may be calculated as function of Mach number and ambient pressure

...

#### teson1

...

(which are available as FS A: variables, all other variables are constants).

...

#### teson1

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)

...

#### teson1

...

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).

...

#### teson1

...

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

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#### teson1

The following part brings me to a "Internet explorer can not display this page" if left within the text ... ???

...

false "FS IAS" in airspeed gauges.

...

#### teson1

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).
... false FS IAS in airspeed gauges.

For further details see the original discussion at flightsim:

Gunter

#### teson1

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 ... false FS IAS in airspeed gauges.

For further details see the original discussion at flightsim: