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Please help to create a list of YASim aircrafts

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Re: Please help to create a list of YASim aircrafts

Postby jsb » Sat Feb 10, 2018 11:18 pm

vslash wrote in Fri Feb 09, 2018 8:59 pm:
the solver will work again if you slightly move the CG


I'm not sure to understand what you mean, but changing the CG means changing the whole behavior of the aircraft. I spend hundred hours myself to put the CG where it must be - and where it is currently - and all Yasim parameters have been set according to this CG. The CG is the cornerstone and the 1st step for everything else, so changing the way Yasim computes the CG is like changing ... everything. No other way from your side ? BR, Val.


I know about the importance of the CG but it is not as "everything" as you might think, the CG will move anyhow due to adding and removing (burning) fuel or adding cargo, passenger etc (if your aircraft supports those).
I do NOT suggest to move the CG a big step, just very little if it helps the solver to converge and am still searching for better ideas but to the best of my current understanding it is likely that some of the mentioned aircrafts are at the limit of stability anyhow and need repair - this might not apply to your aircraft.
Kindly provide the name of one of your aircrafts so I can have a look why the solver does not work anymore for you. Thanks :)
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Re: Please help to create a list of YASim aircrafts

Postby D-ECHO » Sun Feb 11, 2018 4:30 am

jsb wrote in Sat Feb 10, 2018 11:11 pm:
Could you name one of the aircrafts so I can have a look?


For example the EV-55, or one of the glider ASG29, ASK13 etc. Thank you :D

(oh, and the FDM isn't very good for them, so they might just need some more tuning by me, if that's the case, I can do so)
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Re: Please help to create a list of YASim aircrafts

Postby vslash » Sun Feb 11, 2018 7:39 am

the CG will move anyhow due to adding and removing (burning) fuel or adding cargo


I'm affraid the CG don't move anyhow, the fuel cells are accurately located:
Image

... and burned. The picture above has required a lot of work.
Stations you see are located according to the CG. On the Bell412 I'm working on, they are even printed on the fuselage. I'm sorry, but changing the CG in my case, and I guess in all cases, will change everything.
I understand you perhaps has no other way to make your changes, but it would be more friendly to ask to aircraft developers BEFORE changing things, and share your troubles with them, because changing the CG of an aircraft (or a boat, or a car) will change its whole behavior. And last, changing the CG will change the IT too, right ? So changing the CG will require to move ballast, perhaps changing their weights, so to re-compute the IT, see what append, then to re-change the ballast, and the fuel cells location, and the weights, and see what append, etc, at all speed, at hover, and so on. As I said, it changes everything.

Finally, could you make the Yasim version according to the FG version:

Code: Select all
  enum YASIM_VERSION {
    YASIM_VERSION_ORIGINAL = 0,
    YASIM_VERSION_32,
    YASIM_VERSION_2017_2,
    YASIM_VERSION_2018_1,
    YASIM_VERSION_CURRENT = YASIM_VERSION_2018_1
  } ;

==> https://sourceforge.net/p/flightgear/flightgear/ci/next/tree/src/FDM/YASim/Version.hpp

If I understood well, the next version will not be 2018.1 but 2017.4.
Perhaps adding some comments from your changes in the Docs/README_Yasim will be smart too.
BR, Val.

[EDIT]
Using:
Code: Select all
<airplane mass="6861" version="YASIM_VERSION_2017_2">


leads to:
Code: Select all
unknown yasim version 'YASIM_VERSION_2017_2' ignored, using YASIM_VERSION_ORIGINAL


Will this be fixed next release or perhaps I'm wrong using like that ?
Simply: how to be sure using the Yasim version that was coming with FG-2017.3 ?
Thanks.
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Re: Please help to create a list of YASim aircrafts

Postby DFaber » Sun Feb 11, 2018 10:05 am

vslash wrote in Sun Feb 11, 2018 7:39 am:I'm affraid the CG don't move anyhow, the fuel cells are accurately located:


I guess the things jsb changed shouldn't affect Helicopters at all, because there is no main wing. Maybe a problem with vstab handling?
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Re: Please help to create a list of YASim aircrafts

Postby vslash » Sun Feb 11, 2018 10:27 am

@dfaber: good to know ! Hope it will be ok. thanks.
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Re: Please help to create a list of YASim aircrafts

Postby jsb » Sun Feb 11, 2018 10:32 am

There will be no Version 2017.4 for obvious reasons, next release is 2018.1, so that would be the version string to use.

https://sourceforge.net/p/flightgear/fl ... ersion.cpp
Code: Select all
static const std::vector<std::string> VersionStrings = {
    "YASIM_VERSION_ORIGINAL",
    "YASIM_VERSION_32",
    "2017.2",
    "2018.1",
};


I will have a look at the bell412 tonight
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Re: Please help to create a list of YASim aircrafts

Postby jsb » Sun Feb 11, 2018 10:35 am

Please provide a link to the bell, I could not find it.
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Re: Please help to create a list of YASim aircrafts

Postby vslash » Sun Feb 11, 2018 11:15 am

Thanks for your help and time ;
You could find the latest here (updated today):
https://sourceforge.net/projects/bell-412/files/latest/download?source=directory

Main forum thread is here:
https://forum.flightgear.org/viewtopic.php?f=4&t=29660

- well noticed for the YASIM_VERSION.

FYI:
Code: Select all
This aircraft uses yasim version 'YASIM_VERSION_CURRENT'
==========================
= YASim solution results =
==========================
       Iterations: 0
 Drag Coefficient: 40.000
       Lift Ratio: 140.000
       Cruise AoA: 0.00 deg
   Tail Incidence: -0.00 deg
Approach Elevator: 0.000

               CG: x:-0.008, y:-0.000, z:-0.009

Inertia tensor [kg*m^2], origo at CG:

  4172.372,  -0.000, 767.599
   -0.000, 25090.182,   0.000
  767.599,   0.000, 23818.109


BR
Val.
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Re: Please help to create a list of YASim aircrafts

Postby wkitty42 » Sun Feb 11, 2018 2:27 pm

vslash wrote in Sun Feb 11, 2018 7:39 am:but it would be more friendly to ask to aircraft developers BEFORE changing things

this grabs me the wrong way and comes across a bit rude... craft have to adhere to the FDM they are using... if they don't or can't then changes to them are made... that's life... especially when you are using someone's else's product... what would you do if it was discovered that something was using the wrong sign and it was fixed? would you fix your craft or whine that it is now flying upside down? :roll: :roll: :roll:

vslash wrote in Sun Feb 11, 2018 7:39 am:If I understood well, the next version will not be 2018.1 but 2017.4.

2017.4 was skipped... it would have already been released if it were to be used... there were too many real life things getting in the way for releasing it last Nov...

2016.1.1 released 2016 Feb 17
2016.1.2 - 2016 May 07
2016.2.1 released 2016 May 17
2016.3.1 released 2016 Sep 08
2016.4.1 released 2016 Nov 17
2016.4.2 - 2016 Nov 22
2016.4.3 - 2016 Dec 05
2016.4.4 - 2016 Dec 28

2017.1.1 released 2017 Feb 22
2017.1.2 - 2017 Mar 01
2017.1.3 - 2017 Apr 04
2017.2.1 released 2017 May 21
2017.3.1 released 2017 Sep 20
2017.4.1 skipped

2018.1.1 to be released 2018 Feb 17 (upcoming in 6 days)
2018.2.1 to be released 2018 May
2018.3.1 to be released 2018 Aug
2018.4.1 to be released 2018 Nov
"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: Please help to create a list of YASim aircrafts

Postby Hooray » Sun Feb 11, 2018 2:37 pm

Actually, I do agree that any "invasive" (i.e. non-trivial) changes affecting behavior should normally be strictly "opt-in" - but please let's also keep in mind here, that without this work, YASim would be de-facto unmaintained - thus, this is a pain/gain issue.

https://sourceforge.net/p/flightgear/ma ... /29999552/
Andy Ross (YASim developer) wrote:I'm busy with other things these days, but am still broadly
happy to answer questions if posed (as long as I remember enough to
come up with a meaningful answer). Just cc: me if you do, because my
latencies here are measured in weeks.
[...]
Bugs can always be fixed. What YASim needs is a maintainer, not
really expertise per se. The latter comes from the former.



As things are currently standing, jsb is the most likely candidate to actually become the YASim next maintainer ...
Please don't send support requests by PM, instead post your questions on the forum so that all users can contribute and benefit
Thanks & all the best,
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Re: Please help to create a list of YASim aircrafts

Postby jsb » Sun Feb 11, 2018 2:54 pm

Believe me, I spent hours to avoid such issues but for some refactoring of the code it is just pointless to add if-version-checks as the logic is unchanged - that is unless I and my reviewers missed something. We considered minor nummerical changes in the 4th or 5th digit after the comma to be acceptable. I am still thinking about how to trick the solver working again with the models that do not solve anymore... I have an idea already but this needs more testing and I cannot guarantee to get this ready for release 2018.1
I will update you ASAP
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Re: Please help to create a list of YASim aircrafts

Postby jsb » Sun Feb 11, 2018 3:13 pm

Ähm... next time kindly check if your aircraft is on the list. Everything is fine with your Bell412 :)


Code: Select all
diff Bell-412-yasim.xml.2017.3.txt Bell-412-yasim.xml.test.txt
9c8
< Tail Incidence    : -0.00 deg
---
> Tail Incidence    : 0.00 deg
129,130c128,129
< # cd_min 0.04318 at 0 deg
< # ld_max 1.315 at 22 deg
---
> # cd_min 0.0432 at 0 deg
> # ld_max 1.3148 at 22 deg


vslash wrote in Sun Feb 11, 2018 11:15 am:Thanks for your help and time ;
You could find the latest here (updated today):
https://sourceforge.net/projects/bell-412/files/latest/download?source=directory

Main forum thread is here:
https://forum.flightgear.org/viewtopic.php?f=4&t=29660

- well noticed for the YASIM_VERSION.

FYI:
Code: Select all
This aircraft uses yasim version 'YASIM_VERSION_CURRENT'
==========================
= YASim solution results =
==========================
       Iterations: 0
 Drag Coefficient: 40.000
       Lift Ratio: 140.000
       Cruise AoA: 0.00 deg
   Tail Incidence: -0.00 deg
Approach Elevator: 0.000

               CG: x:-0.008, y:-0.000, z:-0.009

Inertia tensor [kg*m^2], origo at CG:

  4172.372,  -0.000, 767.599
   -0.000, 25090.182,   0.000
  767.599,   0.000, 23818.109


BR
Val.
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Re: Please help to create a list of YASim aircrafts

Postby vslash » Sun Feb 11, 2018 3:29 pm

@jsb: thank you very much, I really appreciate you test the Bell-412 (it is not on the main stream ... so I guessed it was not on the list anyway).
Well understood the way you work, thanks again for your time;

Have a nice day,

Val.
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Re: Please help to create a list of YASim aircrafts

Postby jsb » Sun Feb 11, 2018 3:54 pm

Ok, good news. I found something. For quick testing I reduced the max. number of iterations for the solver to 4000 - I changed this back to the original value of 10000 and the following models seem to be ok again.
(Merge request is pending, will be in the nightly hopefully soon)
Code: Select all
asg29.xml.test.txt:Iterations        : 4022
ask21.xml.test.txt:Iterations        : 4249
c421-yasim.xml.test.txt:Iterations        : 4496
E-2C-yasim.xml.test.txt:Iterations        : 7183
f106-yasim.xml.test.txt:Iterations        : 7746
hurricaneIIb.xml.test.txt:Iterations        : 4574
ju87-yasim.xml.test.txt:Iterations        : 8842
mirage5-yasim.xml.test.txt:Iterations        : 6232
mirageIIING-yasim.xml.test.txt:Iterations        : 4805
mirageIV-yasim.xml.test.txt:Iterations        : 8368
mosquito-yasim.xml.test.txt:Iterations        : 6397
sg38.xml.test.txt:Iterations        : 8723
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Re: Please help to create a list of YASim aircrafts

Postby bugman » Sun Feb 11, 2018 10:49 pm

@jsb: Talking about floating point issues, I highly suggest you read the following thread:


Regards,
Edward
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