The New Fokker 50 Thread

[HeliFlyer]

Hi FokkerCharlie,

very nice you are still working on this aircraft

I posted on the FG developers mailing list and asked if there is any experienced aircraft developer who can help to solve your (two) problems.
I'll keep my fingers crossed.

Regards
Georg EDDW

[Jester]

For the nav issue: add a <bias>0.0001</bias> to each digit's animation, that should fix it (idea stolen from the kx165)

[erik]

All contributions continue to be welcome, particularly textures, which I am a bit rubbish at and take me ages. I spent some time a while ago trying to find a way to get the engine management working, but it looks like a limitation with JSBSim (turboprops not really modelled properly) will prevent me doing that as I had hoped

What exactly is it that is missing or wrong with the turbine code of JSBSim?
Unles you are expecting a fully simulated turbine engine then maybe it's just a matter of adding a few lines of code to get what you want. Or maybe some of it is already present but not obvious to find.

Erik

[FokkerCharlie]

Hi Erik

When I asked on the JSBSim devel-list about this subject, I was advised to the effect that turboprops were essentially modelled as jets, with their thrust tables modified.

I had hoped to find a prop pitch property, which could be related (by means of the type of prop in question) to thrust, RPM and torque. That would entail making a fairly detailed model of the prop, but might not be too onerous a task with a bit of trial-and-error. Controlling the prop pitch is how RPM is governed in most ac, of course, so a model like this would be useful in plenty of FG models.

I have seen some chat about prop properties, so I suspect that I am a little behind the times.

If I have missed something, I'd love to hear it- this part of the model is fundamental to making a good F-50!

Thoughts on this subject welcome as always...

Charlie

[erik]

Looking at the code (and assuming that propeller pitch is used to compensate for propeller efficiency loss) I think this might just be a matter of exposing the proper value to the property tree. I will look into this today or tomorrow.

Updat: It turned out I was loking at the wrong code, I'll add the computations to the flight control section instead.

Erik

[erik]

It's turning out to be more difficutl than I hoped, static horsepower isn't sufficient for the equation of efficiency which basically means I'd have toe rewriting much of the code

Erik

[FokkerCharlie]

Yes, I thought that it might be quite an undertaking to get the prop aspect of JSBSim fixed! I will revisit the issue later on, or find a workaround.

Jester- your 'bias' suggestion worked a treat, VMT!

Charlie

[jentron]

I took the engtm601.xml model I found in your Engines/ folder and correctly modified it to yield 2550 horsepower. I coupled it to a modified RAF 6 prop I'm working up for a 2000 hp engine and flew your Fokker 50 for a few minutes. While it wasn't 100% convincing, it did work. I could control RPM via pitch and there was a torque readout.

If you can provide some data on the real prop I may be able to fine tune the engine/prop combination. I know nothing about the Fokker50... Some data points like speed, prop rpm, engine power, and thrust at different points in the flight envelope would be helpful. As well as physical data on the prop... size, weight, number of blades.

Copy these files to Engines/ and edit the FDM to use them.
http://www.jentronics.com/fgfs/temp/PW125BX.xml
http://www.jentronics.com/fgfs/temp/prop_RAF-6-mod.xml

[FokkerCharlie]

Hi Jentron

Very interested to hear that you have had some success in this area. I have not had time to play with your .xml files yet, but I will do so this week. In the meantime, some facts about the Dowty-Rotol prop:

Diameter 12 feet
6 blades
Weight I am not certain of, but one of the company engineers estimates it as 100kg (total for all blades), not including the spinner or governor mechanics. Sounds about right to me, it's composite...
Speed is an interesting one. Controlled by the Prop Electronic Control (PEC), which sets 100% (=1200RPM) for takeoff, initial climb, approach and go-around. Also for Max Continuous Thrust (for use when 1 engine failed). 85% at other times. 62.5% in ground-idle range. Hydraulics change pitch.

I'll get back with some thrust points in the envelope- all the data I have is in terms or torque, which I am assured relates closely to thrust!

Cheers
Charlie

[erik]

I was wondering, is there any work under way for the 3d model?
If not I wanted to split up the 3d models for the cockpit and the fuselage (like I did for the F-16 model) which would make it much easier for multiple developer to work on both at the same time.

After that I wanted to combine all liveries to just one 3d model and multiplayer liveries support which makes it mucht easier to support liveries on the long run.

For this to work I would need to get the latest model and have nobody work on it until I'm finished.
One way to accomplish this is to move development over to CVS.

Any thoughts?

Erik

[FokkerCharlie]

Hi Erik

Good to hear that the F50 will benefit from your attention! The uploaded version of the aircraft is pretty much the latest one. There are minor changes made here, I will upload again this week. As far as I know, nobody is working on the external/fuselage model.

Currently, the fuselage is a separate model (in fact several of these, for each different livery. I am sure that your changes will improve this situation) to the cockpit, which includes other separate models as instruments, so as long as you keep the position of the aircraft the same, there should be no problem modifying the fuselage in particular. If you wish to modify the cockpit structure, the same applies. I am sure that it could do with a fair bit of refinement, as it was the first modelling that I did!

Committing to CVS is absolutely fine with me, probably the best way ahead all round. I would like to keep adding to the model, but at the moment, my time is a little limited.

If you advise what you are looking at improving first, I will be happy to share all the extra resources that I have here (photos, measurements etc).

Charlie

[erik]

For now I will be working on what's available already. I noticed the VLM version is the most advanced, so I'll upgrade the others to use that model. After that I will probably try to add texturing for the wing and horizontal stabilizer.
All this should take a bit of time and afterwards nobody will notice the difference

Erik

[FokkerCharlie]

All worthwhile stuff, Erik.

If you have not started modifications yet, here is the latest and greatest:
[url]
http://myweb.tiscali.co.uk/charlesnet/f ... kker50.zip[/url]

Charlie

[erik]

I did already start modifying the model. Luckily the cockpit was already a separate model so any changes you made there will be kept. I've the VLM livery and Denim livery almost ready now so I don't expect it to take much longer (hopefully it will be finished this weekend).

Erik

[MaverickAlex]

i would be interested in any developments with regards the engines. As the Dash8 i am developing uses the similar powered PW123 engines.
The FDM i am using is Yasim from DHC6 just adapted for use.