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FSXA Catapults

S

SkippyBing

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368
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unitedkingdom
For the last few days I've been trying to write a gauge to control the attitude of an aircraft on a carrier catapult. Basically it sits with its nose 8 degrees up when properly attached to the catapult and the front wheel dangling in the air. I can get it to do that when it locks on to the cat initially, and even increment the pitch over a short time period so it looks more realistic.
However when I trigger the cat it shoots up into the air at a random angle, that may be influenced by flap and throttle settings but it's hard to see any consistency. Sometimes it's almost vertical, others it's more like it's going over a roadbump.
Alternatively if I don't change the pitch until the cat goes off, i.e. when the holdback bar is disengaged, it works perfectly.
I've tried freezing the altitude until it's off the cat completely but this results in it moving forward a short distance, then reversing, then coming off the cat and jumping 50 feet up vertically. Interestingly the forward/back motion corresponds to the ACCELERATION WORLD Y values I was seeing without the altitude freeze.
Has anyone got any insight into how the catapult system was implemented so I can figure a way round this problem?
 
SkippyBing said:
For the last few days I've been trying to write a gauge to control the attitude of an aircraft on a carrier catapult. Basically it sits with its nose 8 degrees up when properly attached to the catapult and the front wheel dangling in the air. I can get it to do that when it locks on to the cat initially, and even increment the pitch over a short time period so it looks more realistic.
However when I trigger the cat it shoots up into the air at a random angle, that may be influenced by flap and throttle settings but it's hard to see any consistency. Sometimes it's almost vertical, others it's more like it's going over a roadbump.
Alternatively if I don't change the pitch until the cat goes off, i.e. when the holdback bar is disengaged, it works perfectly.
I've tried freezing the altitude until it's off the cat completely but this results in it moving forward a short distance, then reversing, then coming off the cat and jumping 50 feet up vertically. Interestingly the forward/back motion corresponds to the ACCELERATION WORLD Y values I was seeing without the altitude freeze.
Has anyone got any insight into how the catapult system was implemented so I can figure a way round this problem?
Click to expand...

Something to try ..( just a idea that may or may not help)

Try setting the Pitch to your 8 Degrees, and then just before triggering the catapault, send one (or more ) Pitch settings to level (or near level - maybe 1 or 2 degress up), then release.

Not tried it, but it might fool the FSX into doing more what you are looking for.

Geoff
 
Hmm... I think I've tried that, i.e. dropping to 0 degrees pitch as soon as the holdback is released, but it seems to take the pitch at the moment of release to calculate the initial acceleration so the change is happening a fraction too late!! I'm wondering if I can overwrite the initial ACCELERATION BODY Y and Z variables to get it moving in the right direction? The only problem at the moment is I can't seem to get that to work despite having done something similar on my home PC a few months ago!! Unfortunately I won't have access to it for a few months.
For my test I had the gauge listen for a key combination and then apply the acceleration, nothing happened, swapped the Data Definition to be Plane Altitude and happily teleported the aircraft up 60' when I pressed the combination! Is there anything special I'm forgetting to do when setting the ACCELERATION variables?
 
SkippyBing said:
Hmm... I think I've tried that, i.e. dropping to 0 degrees pitch as soon as the holdback is released, but it seems to take the pitch at the moment of release to calculate the initial acceleration so the change is happening a fraction too late!! I'm wondering if I can overwrite the initial ACCELERATION BODY Y and Z variables to get it moving in the right direction? The only problem at the moment is I can't seem to get that to work despite having done something similar on my home PC a few months ago!! Unfortunately I won't have access to it for a few months.
For my test I had the gauge listen for a key combination and then apply the acceleration, nothing happened, swapped the Data Definition to be Plane Altitude and happily teleported the aircraft up 60' when I pressed the combination! Is there anything special I'm forgetting to do when setting the ACCELERATION variables?
Click to expand...

NO .. PITCH to ZERO "BEFORE" you release... the idea is to send FSX one or more PITCH=0 so that the FSX engine uses those past Zero Pitch values, to predict the next position. When you signal the release, it does NOT have to release immediately .. there is no reason why you cannot accept a delay, maybe as much as a second or so, to Initilaize the dynamics engine to have a history of Pitch =0 ( or whatever - but probably significantly less that 8 degress )

I also suspect, that even in the real world, if the aircraft is pitched up at 8 degrees on the catapault, as soon as the catapault fires, and starts to accel the aircarft, it will pitch down some. So the above idea, of starting the pitch down adjsutment just before the catapault fires, might result in an even more realistic movement ??

Note: All Guesswork here, never tried any of this :)

Geoff
 
Last edited:
How can I stop the catapult releasing immediately? As soon as the user presses Shift+Space the catapult fires, I tried a little routine that froze the aircraft's position for a second and sent PITCH=0 as soon as the key press was made, but it still results in the aircraft going the wrong way.

I still can't figure out why I can't update the ACCELERATION BODY values, when the same code base works fine for any other variable I try and update!
 
Alas I've already read that thread!!

I'm happy with the names of the variables I'm trying to change, and I've happily changed others, e.g. VELOCITY BODY Z, but when I use the same code to try and change ACCELERATION BODY Z, nada, zip, nothing, zilch. Very odd. Incidentally the effect I'm after is for the second aircraft in this video:

http://www.youtube.com/watch?v=NOKKah5mTTE
 
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