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-set.xml and model.xml documentation

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-set.xml and model.xml documentation

Postby CaptB » Fri Jul 31, 2015 8:28 am

Hello folks,

Browsed the wiki and found the information on expected tags in -set.xml and model.xml scarce and limited to:

http://wiki.flightgear.org/Standard_aircraft_structure
http://wiki.flightgear.org/Aircraft-set.xml

Yes there's information how to create some systems, but for instance I found no better explanation on how to use <engine> within the -set.xml & model.xml, I have found little in the FG docs and jsbsim docs and just by browsing aircraft .xml files i find that this tag can be used like this:

Code (): Select all
<engine file="nk-8-2u">


or

Code (): Select all
<engine n="0">


If this is indeed missing from the wiki I'd gladly add a new article if you would point me to some reference material.

Thanks!
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Re: -set.xml and model.xml documentation

Postby Thorsten » Fri Jul 31, 2015 8:31 am

Since JSBSIm comes with a fairly detailed manual, documenting it on the wiki would seem to be a bit redundant, although some particular tricks how to use JSBSim (for instance how to make a fuel system) are illustrated on the wiki and not found in the manual.

I guess writing a proper guide to how to make an FDM is a huge task which requires plenty of hands-on knowledge. It wouldn't be bad to have, but I don't think it's easy to create.
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Re: -set.xml and model.xml documentation

Postby Necolatis » Fri Jul 31, 2015 8:48 am

Well, the model xml is fairly well documented on the wiki. Basically you do 3 things in there: animations, shaders and loading/placing of models. Many pages on the wiki documents that. For example look here: http://wiki.flightgear.org/Category:Modeling

As for the -set.xml it is really just a list of properties. So if you want to understand that you should go find pages on the property system. For example: http://wiki.flightgear.org/PropertyList_XML_files

Code: Select all
<engine file="nk-8-2u">


This seems to be from JSBsim, not model or -set xml files. It load the engine from the file nk-8-2u.xml.

Code: Select all
<engine n="0">


This is from a propertylist xml file, maybe a -set.xml. It refers to the property engine[0], but is really taken out of context, so hard to explain it. What you should look for is where in the xml file you found it. If it was inside a <engines> tags, then it refers to engines/engine[0] in the property tree, IE. the first engine on the aircraft.
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Re: -set.xml and model.xml documentation

Postby CaptB » Fri Jul 31, 2015 9:27 am

Let me describe the situation.

I am trying to make a somewhat realistic APU for the A330, since the APU is an engine I wanted to add a generic APU engine to those that were already defined in the XML file, however I wanted my particular engine file "apu.xml" to be used and I did not how.

The first thing that comes to mind is to look in the wiki on how to use the <engine> tag within the xml, maybe make a search for something like add engine, model.xml -set.xml or <engine> but this returns nothing of interest.

I found exactly one <engine> reference in the JSBSim Reference Manual which did not tell me how to use two different engine definitions on one aircraft.

Of course I somewhat found out how by looking around,especially the TU154, but your avrage new would be aircraft dev will not.

I think it should be possible to get a simple answer to wiki queries like that, maybe in a howto? This is not a request, I would try to do it myself, just kindly requesting oppinions.
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Re: -set.xml and model.xml documentation

Postby Necolatis » Fri Jul 31, 2015 9:40 am

Ah, yes. if you would explain in the wiki how to add multiple engines and such, would be nice.

I think it should go into the top of this document: http://wiki.flightgear.org/JSBSim_Engines
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Re: -set.xml and model.xml documentation

Postby Richard » Fri Jul 31, 2015 6:55 pm

CaptB wrote in Fri Jul 31, 2015 9:27 am:I am trying to make a somewhat realistic APU for the A330, since the APU is an engine I wanted to add a generic APU engine to those that were already defined in the XML file, however I wanted my particular engine file "apu.xml" to be used and I did not how.


A JSBSim system is much more suited to the implementation of an APU;

For reference I made a JT9D model based on the data in CR-1756. see https://github.com/Zaretto/fg-aircraft/ ... s/jt9d.xml

Obviously the difficulty bit is getting enough data to produce a realistic APU model; however although the APU is a jet engine internally an APU simulation is more focused around the outputs (RPM, EGT, Bleeds, Hyds, Electrics, Indicators) and not so much of a need for a gas generator model or simulation of the N1, N2 etc.

My knowledge is based on an AiResearch GTCP 331-200
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Re: -set.xml and model.xml documentation

Postby CaptB » Sat Aug 01, 2015 1:33 pm

Thanks for the example. The problem is I have no data, since honeywell does not supply anything, hence the "generic" part, but I seem to have hit a wall anyway...
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Re: -set.xml and model.xml documentation

Postby japreja » Sat Sep 19, 2015 4:40 am

CaptB wrote in Sat Aug 01, 2015 1:33 pm:Thanks for the example. The problem is I have no data, since honeywell does not supply anything, hence the "generic" part, but I seem to have hit a wall anyway...


If you have problems with finding data through normal search engines try ntrs.nasa.gov, here is a simple ntrs search on honeywell that returns over 5,000 results specific to honeywell reports. When honeywell, and companies like them, gather data it will most likely be submitted to NASA for research. Most of the results will most likely be unwanted so you might want to read the NTRS documentation on advanced searches to pinpoint the data you are interested in.
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Re: -set.xml and model.xml documentation

Postby wlbragg » Sat Sep 19, 2015 5:29 am

CaptB wrote in Fri Jul 31, 2015 9:27 am:I found exactly one <engine> reference in the JSBSim Reference Manual which did not tell me how to use two different engine definitions on one aircraft.

The newly revamped c172p is using two "switchable" engine definitions, maybe that would have some good examples as to how it might work.
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Re: -set.xml and model.xml documentation

Postby Thorsten » Sat Sep 19, 2015 7:25 am

The Space Shuttle has 51 different engines defined (different thrust, different ISP, different orientation,...) - should provide plenty of examples.
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