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Unrealistic thermals?

Postby D-ECHO » Sun Jan 26, 2020 3:31 pm

Hey,
this is kind of a "meh" post, as I can't really speak factually but only subjectively.

I have the impression that thermals in FG (_only_ when using JSBSim gliders) are way to turbulent and "harsh"). In the sense of, I have not ever been able to center or gain any lift from any thermal in any JSBSim glider, while it works fine with YASim (and by that note, I know how to fly thermals, having flown them numerous times IRL).

Could someone tell me whether they experienced similar behaviour, maybe which preferences to adjust (I worked with Rough/low convection and turbulence until now, but haven't gotten anything realistic) or what may be happening / how to debug better?

Regards and I hope I don't offend anybody with this, I love AW etc., just have difficulties with this.
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Re: Unrealistic thermals?

Postby Knüppelrührer » Sun Jan 26, 2020 7:32 pm

in a way I second that.

Last time in the thermal El Dorados Peru and South Africa I have tried a search pattern with the map to identify correct placement of the flown circles, which should be drifting with wind. Not very successful.

So looking forward to read some mysteries about it. Yes, the soaring wiki has been followed.
Maybe just more practise is the answer. As so often.
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Re: Unrealistic thermals?

Postby Thorsten » Sun Jan 26, 2020 8:01 pm

I have the impression that thermals in FG (_only_ when using JSBSim gliders) are way to turbulent and "harsh").


Since JSBSim and YaSim actually respond differently to the same value of turbulence, that's kind of an inevitable outcome of any default, which is why you can configure the turbulence strength to the need of your current glider.
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Re: Unrealistic thermals?

Postby wlbragg » Sun Jan 26, 2020 8:39 pm

@D-ECHO if you get the settings to your liking for a particular glider, would you mind posting the settings and the name of the glider your using here in this thread?
I've been interested in this aspect of flying and would like to know I am starting from a known "good" configuration by an experienced pilot.
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Re: Unrealistic thermals?

Postby danielHL » Sun Jan 26, 2020 10:19 pm

I can second that also. I have flown the ASK-21 for a while now. With the yasim model I can make perfect use of updrafts and thermals to gain altitude. The JSBsim variant of course flies and handles much nicer. But I never got it to climb one foot in a thermal. There's just violent shaking and too much downdraft when entering the thermal.

I wouldn't mind if someone posted weather settings, either.

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Re: Unrealistic thermals?

Postby D-ECHO » Mon Jan 27, 2020 7:33 am

Thorsten wrote in Sun Jan 26, 2020 8:01 pm:Since JSBSim and YaSim actually respond differently to the same value of turbulence, that's kind of an inevitable outcome of any default, which is why you can configure the turbulence strength to the need of your current glider.

This makes sense to me... :oops:

Thorsten, do you by chance have a set of settings that allow you to fly thermals realistically? I have not yet been able to find one.
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Re: Unrealistic thermals?  

Postby Thorsten » Mon Jan 27, 2020 7:48 am

At the time AW was implemented, there were chiefly YaSim gliders around, so the default is pretty realistic for them. For a JSBSim glider, I'd simply reduce the turbulence strength till it feels about the same

From some quick tests, there seem to be JSBSim gliders around for which the FDM is... less then perfect - I remember trying an aerotow (something I have flown in real life and definitely am capable of flying) and the glider was bouncing around like mad, indicating some deep issue with inertia. So of course if the FDM has that kind of issue, then also thermals won't ever feel right.
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Re: Unrealistic thermals?

Postby D-ECHO » Mon Jan 27, 2020 7:59 am

Considering there is a high probability (statistically ;) ) that said glider is maintained by me, do you remember which one it is, so that I can have a look and maybe adjust it? Also, it would be helpful to report such behaviour. The automated winch code is far from perfect and it may well be that a slight difference in flight path leads to an "OK"-experience for me and an unacceptable one for you and this way I would not be able to encounter the issue.

[EDIT] Almost forgotten, thanks for the hints, will try later :)
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Re: Unrealistic thermals?

Postby Thorsten » Mon Jan 27, 2020 8:22 am

Also, it would be helpful to report such behaviour


It was years ago though, I don't remember which glider, and I remember mentioning it on the mailing list (in the context of a past turbulence discussion).

But generally I do not comment on FDMs at all - it rarely leads to useful discussions - I just skip the plane and move on to the next, there's too much to be fixed all over the repository in that department.
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Re: Unrealistic thermals?

Postby D-ECHO » Mon Jan 27, 2020 9:24 am

Okay, no problem.
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Re: Unrealistic thermals?

Postby D-ECHO » Sat Feb 01, 2020 1:41 pm

Having experimented a bit, I was able to finally do a glider thermal flight again with a JSBSim glider :)
Here is my configuration:
Image
(Of course, this is more or less the easiest-to-fly thermal weather)
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Re: Unrealistic thermals?

Postby wkitty42 » Sat Feb 01, 2020 3:03 pm

and you don't make any changes in the "wind configuration" dialog?
"You get more air close to the ground," said Angalo. "I read that in a book. You get lots of air low down, and not much when you go up."
"Why not?" said Gurder.
"Dunno. It's frightened of heights, I guess."
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Re: Unrealistic thermals?

Postby jano » Fri Mar 27, 2020 8:18 pm

I'm stuck with the same kind of problem, the thermals don't work at all for me, tried the ask21 and the asg29-jsb, and not even a bit of change in the lift department...
So far i managed to fly using the wind and montains, (there are some nice rift oriented in the same direction in the region i usually do paraglider :( ) but now i'm in a rather flat scenery and a bit of thermal would be a big help :D
next as of yesterdays if that matters ...
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