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Author Topic: JSBsim Flight Modelling is easy  (Read 23298 times)

bomber

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JSBsim Flight Modelling is easy
« on: June 30, 2014, 02:08:38 pm »

Well it is if you've 2 years to learn it....

Hi I'm a jsbsim flight modeller and that's a question I'd like to ask.

Does the modding community and flight modellers here wish this steep learning curve to exist into the future or is there a vision that flight modelling through the use of an interactive building tool be made if not easy, easier ?

Is there any drive towards that end ?

Simon
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John514

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Re: JSBsim Flight Modelling is easy
« Reply #1 on: June 30, 2014, 04:25:18 pm »

I wonder if there`s a program that used the 3D mesh to test aerodynamics and then write the basic JSB file.....
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bomber

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Re: JSBsim Flight Modelling is easy
« Reply #2 on: June 30, 2014, 05:04:35 pm »

That's not what you need, it's really a poor way of flight modelling.. and as a professional 3D modeller I can tell you the flight models would only be 1/3 done, and not that good.

A flight model consists of 3 major elements.

Weight/Mass balance
Aerodynamics
Thrust/drag

There's also 'systems' such as fuel, hydraulics, pneumatics...etc

In my opinion these elements should be linked to damage reductions


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cameni

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Re: JSBsim Flight Modelling is easy
« Reply #3 on: July 01, 2014, 06:41:37 am »

Hmm it would be certainly a nice thing to have for modders and addon makers. Do you have a concrete idea how the tool would work and how it would be used? Could it be some kind of an addon in OT that would allow real-time testing of the airplane as well?
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bomber

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Re: JSBsim Flight Modelling is easy
« Reply #4 on: July 01, 2014, 08:27:14 am »

Well understanding that a tool should do it's job and no more, in the same way that a chissel isn't a screw driver, or a screw driver a hammer... I'd want a tool that's simple and does what it says on the label..

The first tool i'd want to be able to introduce to a fellow moder that wishes to do flight modelling would be mass/ballance tool.

In JSBsim this section can be filled in with a couple of numbers... Empty mass, CoG and moments of inertia.... And it's great if you've got them or are defining a new plane.. But try getting them for a 1917 bi-plane. I'd say 95% of planes built on JSBsim have these numbers guessed.

But here's the thing if someone's doing bi-planes, trawling through documents, over a period of time they've an idea as to how much 'generic' items weigh....
And after a period of study, from the overall weight of the plane minus these individual elements the mass of a planes 'structure' can be narrowed down.

Wing structure has it's own density, that being it's material plus air contained within it's shape.. the internal make-up of one wing to the next is pretty similar, the weight difference being it's plan form and thickness differences...

So the tool I'd want is one that allows me to enter the planes total weight plus on individual tabs add 'point masses' for the objects I know and point masses based on density, area and volume for wings and fuselage.. outputting these values as a complex mass ballance JSBsim section or a collated JSBsim mass ballance section.

Simon.

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Jon S. Berndt

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Re: JSBsim Flight Modelling is easy
« Reply #5 on: August 16, 2014, 09:57:15 am »

Well it is if you've 2 years to learn it....

Hi I'm a jsbsim flight modeller and that's a question I'd like to ask.

Does the modding community and flight modellers here wish this steep learning curve to exist into the future or is there a vision that flight modelling through the use of an interactive building tool be made if not easy, easier ?

Is there any drive towards that end ?

Simon

Greetings, Simon,

Yes, it would be wonderful if there was a GUI tool to help with development of JSBSim aircraft models. Over the past ten years I have started - and stopped - development of such a program, and there was at one time such a project being developed as an open source tool (JSBSim Commander). The more useful I see such a tool being, the less time I have available to develop one myself! :-( It may be that at some point I can develop tools that will help with specific parts of a JSBSim flight model, such as mass properties, systems, aerodynamics, etc. Better documentation and examples would be helpful, too, I am sure. But, myself and the other primary developers of JSBSim have been very busy lately with our day jobs. :-)

Jon
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bomber

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Re: JSBsim Flight Modelling is easy
« Reply #6 on: August 16, 2014, 10:32:43 am »

Oh I understand jon, we all have lives to live.

I'm not totally convinced that a single tool would be the best approach as this could very well 'straight jacket' fdm'ers into creating flight models in a single way.... As you know I don't create my flight models similar to how others do....I basically took your manual as a 'guide' to creating flight models within JSBsim with the understanding that I had a free hand if I thought to do it differently.

I think a series of small tools that link up even loosely, javafoil, javaprop, spreadsheets for weight ballance and the such  I think would work better than an all enfolding tool.

Simon

 
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Steve.Wilson

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Re: JSBsim Flight Modelling is easy
« Reply #7 on: August 16, 2014, 12:50:37 pm »

While JSBSim is a well accepted and capable flight simulation dynamics application, it may be possible to create it's parameter tables using another well accepted and capable flight dynamics application that generates much of this data literally on the fly using blade element theory.  One of these is X-Plane.  I wonder if a plugin could be written for X-Plane to export JSBSim parameter files. 

First, you model that aircraft in X-Plane's Planemaker application with a high level of accuracy.

All one would then need to do is to fly a series of development flights with this model that hit all of the regimes that would be need to be measured.  Naturally this sort of data could then be "massaged" with reference to real world performance values for the aircraft in question, if it actually exists.

« Last Edit: August 16, 2014, 12:52:39 pm by Steve.Wilson »
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bomber

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Re: JSBsim Flight Modelling is easy
« Reply #8 on: August 17, 2014, 07:55:16 am »

Steve. I think you've misunderstood how JSBsim works in that it also generates the data 'on the fly'

The problem people have is that they've heard that JSBsim uses 'tables' of data and come to the conclusion that JSBsim is somehow not working things out..

Blade theory is simply splitting of the wing into smaller sections and then calculating the forces generated by these sections and then integrating these forces back together to come up with the total forces generated by the wing.

I genuinely think that's the correct way of doing it, especially if the wing has different airfoils, twist, dihedral, sweep along it's length, simply averaging out the wing and generating a co-efficient table for the whole wing just to my mind doesn't cut it.

In JSBsim you can split the wing up into sections, you can calculate the forces for these sections and you can use these values to calculate the overall lift and moments of the whole....

Simomn

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CTR

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Re: JSBsim Flight Modelling is easy
« Reply #9 on: August 29, 2014, 06:22:34 am »

One guy of the 3rd party dev's on the DCS-Forum has made a nice tool to debug flight models see ->http://forums.eagle.ru/showpost.php?p=2159719&postcount=26



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bomber

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Re: JSBsim Flight Modelling is easy
« Reply #10 on: August 29, 2014, 07:37:38 am »

Any chance of opening a dialogue with these guys ?

Gota be careful as there’s normally a mine field of politics to avoid in flight sim cross community com's.

But I'd welcome that kinda of tool.
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CTR

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Re: JSBsim Flight Modelling is easy
« Reply #11 on: August 29, 2014, 07:55:55 am »

Any chance of opening a dialogue with these guys ?

I don't know if they are willing to release it to the public, cause they made there business indirect with these kind of tools.

You can contact Cory Parks he is the developer, currently i see 2 way to get in contact with him:
DCS-Forum -> User: SilentEagle
YouTube ->

Maybe there is a way to motivate him to open his business for a future Outerra Flight Sim. It would be nice to see a proove of concept to  see if it is possible to port an DCS aircraft to Outerra.
« Last Edit: August 29, 2014, 08:00:34 am by CTR »
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bomber

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Re: JSBsim Flight Modelling is easy
« Reply #12 on: August 29, 2014, 09:06:12 am »

No harm in asking....
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cameni

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Re: JSBsim Flight Modelling is easy
« Reply #13 on: August 29, 2014, 10:47:22 am »

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PytonPago

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Re: JSBsim Flight Modelling is easy
« Reply #14 on: August 29, 2014, 12:50:26 pm »

well ... just rendering the KA-50 in OT would be a crazy thing -would fly that piece of beauty all around the world !
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