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glider hopping around on ground


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Hello there,

a few days ago I bought the glider. In principle it's really good. But I have a problem, which is very annoying:

When I start a flight almost always the glider is placed with levelled wings on the runway, then starts to sink down to one side (still normal up to here), but then starts to hop up and down on one wing.

With every little bounce it changes its heading slightly, so that just a few seconds later it's in a position where it makes no sense anymore to continue the run up (Discus BM), for the glider's heading is almost perpendicular to the runway's one. :angry:

Sometimes it helps to switch to slew mode immediately and switch back, but even if it works it takes at least 15 to 20 attempts.

Is there any possibility just to place the glider on the runway motionless?

Does anybody else have this problem?

For I'm a native german-speaker, answers in english as well as in german are very welcome :)

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Enno the 'bouncing plane' issue has been around FS/FSX for years. Out of interest what's your location on the ground, and do you know what the surface is? I've never had the issue you're describing although the dynamic (i.e. flight) model of the Discus is quite finely balanced and I *think* FSX models the 'rebound' effect of different surfaces differently.

Or *maybe* it's to do with FSX feeding in some mesh you have, e.g. see this similar post.

If you search google on "fsx bouncing" you find quite a few suggestions, generally involving tweaking settings on the realism page (i.e. these )or the mesh settings. (these).

TBH I have no clue but I reckon you might be able to calm things down with those suggestions. The funniest post is some guy who has the airport vehicles (baggage truck etc) bouncing as well...


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Not too fast. This is a confirmed problem of CumulusX!.

Few aircraft are very sensitive on 100% exact positioning on ground. Latency in the sim, e.g. can produce slight imperfections here which keeps the aircraft bouncing all the time. In sever cases you can even hop into the air by few feet, and, when hitting the ground again, being informed, that you have crashed.

FSX uses a special variable "Plane On Ground" to distinguish airborne behaviour vs. ground behaviour. Currently, CumulusX! does not recognize this and tries to make very small adjsutments to the plane altitude, even when on ground. Only very few aircraft are affected. I think I will fix it in a next patch.

If it is too annoying, an immediate workaround is to disable lift in the CumulusX!-add-on menu until airborne. It helps also to disable lift, let the aircraft come to rest and re-enable again.



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Peter, you.....

LOL so you don't get confused, "the freeware CumulusX! by Peter Luerkens" is software written by Peter and made available to you, for free.

I worked closely with Peter on the related freeware 'sim_probe' and now CumulusX dynamically provides thermal lift *and* ridge lift throughout the FSX world. For free. If you haven't tried soaring along the Appalacian ridges in the Discus running Cx, you should try it, and you'll appreciate just how talented a programmer he is, and we're lucky to have him.

On the subject of freeware, sim_probe used to be needed for ridge lift in FSX but Peter has now incorporated that kind of computation into CumulusX, which leaves the extra 'flight logging' function of sim_probe the only reason for its existence. As an illustration, the logs are in a standard format so they can be viewed in *real* gliding software (e.g. SeeYou) but also posted on GPS-log sharing sites like everytrail.com. Here is a display of a logfile from a flight by a SOAR member in FSX, flying a freeware mission I wrote and will convert for the Discus, using the sim_probe and Cx. But please don't forget this software is created in our own time, and provided to you guys for free.


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My two pence...,


If you don't like/ cant get on with the software simply uninstall it.

All programs have bugs & glitches,

it is just trial and error and diagnosing them to get them fixed.

Nothing's perfect,


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Hey Peter I use (A:SIM ON GROUND, bool) in a variety of circumstances and FYI you just want to monitor its behaviour in the situations you're considering - as with all things FSX the var doesn't behave totally in the black-and-white way you might expect. E.g. your code might have to cope with (erroneous) rapid (framerate) on-off-on-off sequences in the variable, or also there can be delay to the variable altering on take-off and landing (i.e. the transition isn't *exactly* when you'd expect). I reckon your usage might be entirely satisfied with the basic use of the variable, but you might also consider the ground proximity calculation you're already doing in the ridge lift.

There was no need really to post this comment in this thread but hey, I thought I'd change the tone.



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Sorry guys,

the last few days had been a little bit busy at work. As I'm typing, FSX is booting in the background. As far as FSX is ready to go I'll test it . Thank you very much for your hints!

I'll let you know if it worked (CumulusX) later!:)

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Same for me, CumulusX didn't cause the problem, disabling didn't solve it.

In fact the situation turned out to be even more severe now:

I bought the Discus Last sunday evening, Due to work reasons last week I tested it but didn't have the time to test it intensively.

Yesterday I had that time.

Result after several attempts and one complete defragmentation:

The glider showed the annoying hopping in ca. 90% of the times I loaded it,

I had in total 14 CTDs yesterday, as well as

3 total windows system crashes.

If it had been a boxed product, bought in a shop near my home, I would have come to the conclusion now to go to the shop tomorrow and to want my money back.

For it is a download product this isn't possible of course.

So instead of that I will uninstall the Discus now and not reinstall until a patch/ an update is released.

At least there are still some very good freeware gliders on my harddisk, which don't hop around and don't cause the computer to crash.

But the discus (at least unpatched, not updated) turnes out to be a disappointment... :(

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Enno, renaming FSXBASE/Modules/b21_vario.dll to b21_varioX.dll has stopped the CTD's for those users that have seen then - please try that before you give up on the Discus! The C4 will function exactly the same except for a very small feature I am certain you wouldn't have got to for a couple of weeks and in the meantime I'm working on a fix for that DLL.


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@ Enno

Warum muss alles 34 mal durchgekaut werden?

Thema "Bouncing"

Direkt in der 2. Antwort ist beschrieben, dass es sich hierbei um einen FSX "bug" handelt. Ich kann da fast nichts machen. Wir könnten versuchen die Contaktpoints zu ändern, das hätte aber höchstwahrscheinlich Probleme auf anderen Systemen zur Folge.

Thema "CTD"

Wenn schon IM ERSTEN POST des Forums eine Hilfe angeboten wird, und dann in diversen anderen Posts auf diese Hilfe verlinkt wird, WARUM fragst du dann hier ebenfalls danach?

Extra für dich noch einmal der link.


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I'll try it with the dll renaming.

"die Hoffnung stirbt zuletzt" - hope dies last, as we germans say.

Joachim: Ich will keinen Streit anfangen. Aber bitte lies mein Posting richtig durch. Dann wirst du feststellen, daß ich nach den CTDs oder deren Ursache überhaupt nicht gefragt habe, ich habe es nur berichtet.

Was das Bouncing angeht: Wenn es ein FSX-Bug ist, dann beschuldige ich dich gewiß nicht, da kannst du nichts dafür, ist mir klar.

Vielleicht kannst du aber verstehen, daß man etwas angesägt ist, wenn man -nachdem man ja Geld dafür bezahlt hatte- die Maschine fast nicht nutzen kann, weil das Problem derartige Ausmaße annimmt, daß man fast keinen vernünftigen Start durchführen kann. Sollte ich da zu heftig reagiert haben: Sorry.

Vollkommen ohne Aggressionen nun: Hättest du evtl. eine Idee, ob man irgend etwas tricksen könnte, um der Sache irgendwie aus dem Weg zu gehen?

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Gewiss habe ich eine Idee. Für die müsstest du aber die aircraft.cfg öffnen und an diversen Punkten "herumspielen".

Wenn das für dich ok ist, versuche folgendes:

In der cfg findest du folgendes

point.2= 3, -1.40, -24.65, 1.080, 1575, 0, 0.100, 0.000, 0.100, 1.10, 0.80, 0.0, 0.00, 5, 0, 0 //Port Wing tip

point.3= 3, -1.40, 25.00, 0.700, 1575, 0, 0.100, 0.000, 0.100, 1.10, 0.80, 0.0, 0.00, 6, 0, 0 //Starboard

Der wert, bei dem hier 0.80 steht ist die Dämpfung.

Je höher desto gedämpfter die "Federung" -theoretisch.

Wenn du den noch höher machst (0.9) wurde es seltsamerweise auf den meisten Rechnern schlimmer, wohingegen auf einem System eine deutliche Reduzierung auf 0.1 den gewünschten Effekt gebracht hat.

Man frage sich wieso... oder besser nicht.

Gehe bei den Werten NICHT unter 0, oder über 1.

Du musst hier echt deinen Wert probieren.

Gruß Joachim

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I have been experiencing the same Discus bouncing issue, only when flying at Dillingham Hawaii, with Megasoft Hawaii.

I have changed the damping value of both the wing tips in all three aircraft.cfg from .80 to .90. (with .50 the bouncing got much worse.)

Initial testing seems to have cured the problem.

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