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Aircaft accelerations

  • Thread starter Thread starter mgh
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mgh

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The FSX SDK has 6 body accelerations in the Aircraft Position and Speed Data section in Simulation Variables. That's to be expected given FS uses a 6 degree-of-freedom model.

the first three (ACCELERATION BODY ...) are linear accelerations (X, Y, Z) with units of ft/sec/sec as expected.

The next three (ROTATION VELOCITY BODY ...) I'd expect to be angular accelerations but they also have units of ft/sec/sec! I'd expect them to be radians (degrees?)/sec/sec.

Can anyone confirm what they actually are?
 
My SDK gives units of feet per second for ROTATION VELOCITY which is even more odd. I checked out ROTATION VELOCITY BODY Z, feet per second in the air. It gave a reading of 9 when in a very rapid roll to the left
Roy
 
And if you make it ROTATION VELOCITY BODY Z, degrees per second, that is what you get
Roy
 
My error!!!!

I saw what I wanted to see angular accelerations. In fact they are angular velocities.

That's a bit of a blow because I can't find the pitch, roll, and yaw angular accelerations which I need in Simconnect.

These can be read but not written in FSUIPC - offsets 0x3078, ox3080 and 0x3088.
 
The A:Vars generally represent a snapshot in time. If you want to see how they change over time you need to compare the next snapshot with the first.

In general, A:Vars give a static result, their change over time gives the dynamic result.

Roy
 
Last edited:
mgh said:
That's a bit of a blow because I can't find the pitch, roll, and yaw angular accelerations which I need in Simconnect.

These can be read but not written in FSUIPC - offsets 0x3078, ox3080 and 0x3088.
Click to expand...

Maybe this works?

ACCELETATION ANGLE X (Radians) in XML = ROTATION VELOCITY BODY X ACCELERATION BODY X / atan

or

Arctan( opposite side / adyacent side )


Tom
 
In the acceleration SDK there is no rotational acceleration variable. Only velocity. So if you are trying to do your own external flight model system you would have to make your own rotational acceleration variable. However all these variables are settable via Simconnect.
 
Tom

Angular accelerations can't be derived from he other variables.

Naruto-kun

You seem to confirm that it ism't possible to set angular accelerations in Simconnect.

I'll have to think of a workround.

Is frame rate available in Simconnct - I can't find it?
 
Well to clarify....There is no such thing as a rotational acceleration variable in FSX at all. Nada. Only velocity.

And yes it is possible to get frame rate from FSX but it is NOT a reliable system for setting A vars. The Sim normally gets in the way in between frames and they are constantly changing besides. However running from a gauge callback function at 18Hz gives you a steady timing system to create your own acceleration system etc and you dont experience the conflict between the sim and the code. At least, not in my experience.
 
As I'm coding for Simconnect in C++. I'll use the high-resolution timer to get the time intervals to get the timker intervals.
 
Can't you simply approximate the accelerations by using (w2 - w1) / (t2 -t1) where w1 is the angular velocity at time t1 and w2 at time t2?
 
Christopher Coon said:
Can't you simply approximate the accelerations by using (w2 - w1) / (t2 -t1) where w1 is the angular velocity at time t1 and w2 at time t2?
Click to expand...

Numerical differentiation like that can be very "noisy", and I also wanted to be able to set the accelerations.
 
Are you freezing the AI and moving the object's position and rotation yourself every frame, mgh? Or are you trying to modify what the AI and FSX physics is doing?
 
Any way to calculate ROTATION VELOCITY BODY xy and Z for FS9 sim bacause not accesible via parameter like in fsx. thx.
 
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