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Sukhoi 26M aerobatic

Questions and discussion about creating aircraft. Flight dynamics, 3d models, cockpits, systems, animation, textures.

Re: Sukhoi 26M aerobatic

Postby elmaxo » Sat Mar 14, 2009 11:22 am

Hi all,

It would be nice if somebody with debugging skills could have a look at this aircraft. It looks like its FDM parameters need to be updated. I am using a recent version of Flightgear (CVS from about 3 weeks ago), and although I can start the engine fine, I can not get it to generate more than approx. 50 lbs of thrust. This means that the plane does not move :) Even taxiing is impossible.

See the screenshot for an illustration: airport is LOWW. Throttle, mixture and pitch are at about 80%. However, the engine is in the low RPMs and is generating little thrust.

fgfs-screen-001.jpg


It is a real shame that this aircraft is not working properly, since it is a really nice-looking and detailed design, and there are not so many aerobatics plane in FG :)
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Re: Sukhoi 26M aerobatic

Postby Flying toaster » Sat Mar 14, 2009 9:54 pm

Hi everybody,

The version of the Su-26M I released was a early beta built using FG 0.99 and corresponding JSBSim.

I have halted the development some time ago. I think I should be releasing a new version later on this year in order to make it flyable on FG 1.99 but as of now I am focusing on a MUCH improved X-15.

If you can hold on a little...

BTW if any body has good pictures of a Su-26M cockpit I'd be very grateful.

Cheers

Enrique
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Re: Sukhoi 26M aerobatic

Postby elmaxo » Sun Mar 15, 2009 7:22 pm

Ok, thanks for the answer... I hope I can wait that long :) And cheers again for the great design, Flying Toaster.

Is this kind of problem easy to fix ? I am quite novice at programming for FG, but could try to give it a shot if someone can point me to the right place to start.
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Re: Sukhoi 26M aerobatic

Postby jentron » Tue Mar 17, 2009 2:38 am

The problem is in the engine configuration file Aircraft/Su-26M/Engines/M-14P.xml

The engine code in 1.9.x/CVS is changing a bit right now, it tries to guess a value for /fdm/jsbsim/propulsion/bscf-lbs_hphr to give 360 horsepower at 2700 RPM, but the maxmp value of 63 inHg is confusing it, and its spitting out a bsfc value around 3.9. It should be somewhere in the 0.4 to 1.0 range. For a quickie fix, change maxmp to 29.9 and you should get enough power to fly.

Adding a supercharger section like this:
Code: Select all
  <numboostspeeds>   1 </numboostspeeds>
  <boostoverride>    0 </boostoverride>
  <ratedboost1> 16.25 </ratedboost1>
  <ratedpower1> 360 </ratedpower1>
  <ratedrpm1> 2700 </ratedrpm1>
  <ratedaltitude1> 0 </ratedaltitude1>
 
will bring the manifold pressure back up. If you add the supercharger, you'll need to hand-adjust the value for /fdm/jsbsim/propulsion/bscf-lbs_hphr
It can be written into the file as <bsfc>0.95</bsfc>. There is another tag, volumetric_efficiency, that affects horsepower as well.

These two numbers work like this:
Increasing <volumetric_efficiency> increases fuel-flow and horsepower produced. This value defaults to 0.8
Increasing <bsfc> decreases horsepower produced
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Re: Sukhoi 26M aerobatic

Postby GabiLaser » Sun Feb 26, 2012 9:56 am

I know this looks perhaps like (and it is!) a thread necromancy/resurrection, but i would like to ask - if anybody with knowledge of flight dynamics stuff could revisit this plane and perhaps make it "2.6"-official?

Latest version AFAIK can be found here: http://longfly.square7.ch/download/Su-26M2.zip, while an earlier version also had a nice 'flying manual' pdf (this one: http://mirrors.ibiblio.org/pub/mirrors/ ... 6M_1.0.zip ).
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Re: Sukhoi 26M aerobatic

Postby jentron » Sun Feb 26, 2012 2:40 pm

GabiLaser wrote in Sun Feb 26, 2012 9:56 am:I know this looks perhaps like (and it is!) a thread necromancy/resurrection, but i would like to ask - if anybody with knowledge of flight dynamics stuff could revisit this plane and perhaps make it "2.6"-official?

Latest version AFAIK can be found here: http://longfly.square7.ch/download/Su-26M2.zip, while an earlier version also had a nice 'flying manual' pdf (this one: http://mirrors.ibiblio.org/pub/mirrors/ ... 6M_1.0.zip ).


The License prevents anyone from doing that:
Copyright 2006 Enrique Laso Leon
Final releases will be released under GPL or LGPL but for the time being I
reserve the rights to release any modification on the model.
This is in order to get only one thread of development.
This will NEVER be a commercial product.
Aircraft: F-4E, Cessna 182RG, Fi-156 Storch, Diamond DA20 Katana and Eclipse, Ercoupe, LZ-129, Gossamer Albatross
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Re: Sukhoi 26M aerobatic

Postby GabiLaser » Sun Feb 26, 2012 4:42 pm

I see, thank you! But, i suppose, if somebody makes some fdm/jsbsim corrections and posts them here, this would not be illegitimate?
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Re: Sukhoi 26M aerobatic

Postby jentron » Sun Feb 26, 2012 7:13 pm

GabiLaser wrote in Sun Feb 26, 2012 4:42 pm:I see, thank you! But, i suppose, if somebody makes some fdm/jsbsim corrections and posts them here, this would not be illegitimate?


The power of the GPL lies in allowing others to help. Mr. Laso Leon specifically says in this statement he does not want that help. You would have to start a fresh FDM to be legitimate. And every other file, too. Not worth my time.

Ron
Last edited by jentron on Mon Feb 27, 2012 12:41 am, edited 1 time in total.
Aircraft: F-4E, Cessna 182RG, Fi-156 Storch, Diamond DA20 Katana and Eclipse, Ercoupe, LZ-129, Gossamer Albatross
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Re: Sukhoi 26M aerobatic

Postby GabiLaser » Sun Feb 26, 2012 8:07 pm

jentron wrote in Sun Feb 26, 2012 7:13 pm:
The power of the GPL lies in allowing others to help. Mr. Leon specifically says in this statement he does not want that help. You would have to start a fresh FDM to be legitimate. And every other file, too. Not worth my time.

Ron


Yet it is i (and maybe others) who want that help, not the author of the aircraft. But of course i do understand & respect your point, and thank you for answering.
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Re: Sukhoi 26M aerobatic

Postby Flying toaster » Sun Feb 26, 2012 9:19 pm

Hum wait,

I did not mean to be THAT restrictive, it's just that I wanted to avoid having too many versions worked on at once. Refusing help is definitely not my purpose. I have a huge list of todo things to make that aircraft a production version, and I am a slow developper. I have been aware of the regression on the engine model, and I wanted also to improve the flight dynamics regarding the moment coefficients (which are not implemented yet).
In the 3D department I have issues with the transparencies and I would like to improve vastly the 3D cockpit. Finally I want to have all the systems working as per design. All this takes time and so far I only managed to get the engine working again, even though I am battling on the supercharger department. If you want to contribute feel free to do so, but I am willing to go on improving on my side too... Heck I may even release it as GPL but I definitely do not consider what is available as production status :-)
BTW the name is LASO LEON (naming scheme in Spain : first name - second name father -second name mother)

Cheers

Enrique
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Re: Sukhoi 26M aerobatic

Postby GabiLaser » Mon Feb 27, 2012 9:03 am

Ok, all it's good when also the original author pops in :) So what should i do in order to fly this plane in FG 2.6?

Also: i'm not good at flight models or 3d modelling unfortunately, i have some programming skills (i did a few small utilities for red baron 3d and rise of flight) so if i offer to help (as i can), it may not mean much for your purposes.
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Re: Sukhoi 26M aerobatic

Postby Flying toaster » Tue Mar 20, 2012 5:30 am

BTW

I had a look at the flightgear.ru forums and I have noticed that there is a discussion thread on the Su-26 ! Too bad I hardly read cyrillic, let alone understand Russian :-( I am a big fan of Soviet/Russian/Ukrainian (hey there's Antonov) aviation as you may have noticed and I could take some help from people from the CIS in having the labels in the flightdeck, and system simulations right.
I have a very early stage Tu-144D 3D model on the drawing board but I somehow given up on it because I thought I could not get a decent flight deck simulation...

Hope somebody could help

Cheers

Enrique
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Re: Sukhoi 26M aerobatic

Postby mermar » Thu Feb 22, 2018 8:02 pm

Hello,
I would like to humbly ask SU-26 author(s) if it would be possible to release it under GPL2+ to include this plane to FGFS.
Thank you in advance.
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