Designing planes using Simulators

[rutanman]

I wasn't sure where to post this but Modeling Science seemed almost as good as the simulators forum.

I am considering buying a flight simulator (will require a computer upgrade also). I have been looking at the Great Planes Flight Simulator as well as the one made by Phoenix R/C. Although I think that helis are cool, I am mainly a fixed wing pilot.

The Flight Sim that I have had for years is FMS. (Yes, I know - very outdated to say the least, but the price was right and I didn't have to pay extra for extra planes.)

I am thinking about getting a new Flight Sim to not only practice(and learn new) R/C aerobatic skills, but also to experiment with Aircraft Designs (tail sizes, canards, wing loading, etc.) to get a feel for how design choices affect real world flying.(design choices almost on an engineering type level) I am wondering which Simulator would be a better choice for this type of use?

Also, with FMS, I designed my own models using Metasequoia and updated the par file for different flight characteristics. Is it possible to create your own unique planes (shape and texture maps) for use with G3.5 sim? or PhoenixRC sim?

Thanks for the feedback,
Paul D.

[vintage1]

I can only talk about G2..cos I have it.

I did try and add my planes to it, with some limited success.

1/. I could not find a way of modifying the displayed outline.

2/. I was fairly successful at modifying the color scheme.

3/. Although its totally possible to modify wing span/area etc etc, the actual figures I ended up using were nowhere near the ones the plane actually used to fly. CG was about right, but the simulated planes were hugely 'snappier' than the real ones. I ended up having to specify symmetrical or semi-symmetrical airfoils to get them to behave like the actual models did. Other issues like models that would sit there vibrating on the runway before tipping over and crashing before I had even touched the throttle, lead me to believe that the simulator algorithms were pretty crude, and had been 'tweaked' to get the supplied planes to fly right.

I don't actually bother any more..frankly I use Motocalc, a CG calculator and a hefty dose of TLAR to design planes these days.

[ciurpita]

crrc sim was developed using a flight control model from nasa and modified by Dr mark drela. i've read he uses it in his classes at MIT. the source code is available, and is now being worked on as a sourceForge project.
http://crrcsim.sourceforge.net/

i studied this a few years ago, and thought some developer had a long term goal of it being used to model/test new designs. but the parameters modeling the aircraft are not trivial. the following are some notes are wrote describing the aircraft description file
http://ciurpita.tripod.com/rc/crrcSim/crrcSimAirNotes.html

drela also has program for analysing aircraft designs, AVL, and i believe its output can be used as a aircraft description file in crrcSim
http://web.mit.edu/drela/Public/web/avl/

[vintage1]

Linux sim! I like it!

[nmasters]

Flight simulators are pilot training tools, NOT engineering analysis tools. It's quite possible to design an airplane that will fly fine in a simulator but not work at all as hardware. The parameters of the sim model are filled in with numbers that you get from the real airplane or from real analysis code like AVL. If you just tweak the numbers until the sim flys right you may have designed an airplane that works but you may have just created a physically impossible model. You won't know until you either do a real analysis or build the airplane.

[Brandano]

If you are into linux sims and want an accurate flight model you could try FlightGear (http://www.flightgear.org/ , there's a windows version too). It's not a model sim, but a full feature flight sim. You can obviously make your own planes, and someone has already made a SlowStick for it. And there's more than one flight model engine available for it, so it might be possible to find the one closer to your actual needs. Actually, i am trying to model a Wallis autogyro for it (James Bond's "Little Nell") but can't find good elevations for it. Anyone got a link to good drawings I can use to get the scale right?I have plenty of pictures of the real thing, but no accurate drawings

[Sparky Paul]

To use a flight simulator as a design tool you have to know where the numbers for all the flight coefficients come from.
You don't for instance, modify your Cnbeta by 15% without knowing what causes Cnbeta, and what modifying the cause does to all the other parameters.

[yoyoML]

http://www.x-plane.com/

X-Plane is a full-scale flight-sim plus designing tools. The plane designing in X-Plane is much more physics based than tweaking PAR files, it actually takes the 3D model, breaks it down to pieces, and calculates individual parts on the fly. The end result is quite unlikely to be physically impossible. Read the "About X-Plane" on the side bar.

Last time I checked, it came with a 2-stroke RC trainer already. My only concern is that the claimed 15Hz physics frequency isn't really high enough to simulate RC planes, although it feels nowhere as low as that...

[HELModels]

crrc sim was developed using a flight control model from nasa and modified by Dr mark drela. i've read he uses it in his classes at MIT. the source code is available, and is now being worked on as a sourceForge project.
http://crrcsim.sourceforge.net/

i studied this a few years ago, and thought some developer had a long term goal of it being used to model/test new designs. but the parameters modeling the aircraft are not trivial. the following are some notes are wrote describing the aircraft description file
http://ciurpita.tripod.com/rc/crrcSim/crrcSimAirNotes.html

drela also has program for analysing aircraft designs, AVL, and i believe its output can be used as a aircraft description file in crrcSim
http://web.mit.edu/drela/Public/web/avl/

I dont have the knowledge to create the read file needed to get AVL to work its magic, but the CRRCsim is awesome. Thanks for the link. The apogee will stay up indefinitely at Cape Cod :D or until the sim stops responding. :(

[rutanman]

I was hoping to use an r/c flight sim as a very basic - very preliminary design tool. It sounds that even for that the most popular r/c sims are lacking. I am still looking at Xplane, the Crrcsim and the Flightgear simulators - very impressive.

Thanks all for the info. and feedback. Thanks too for the great links. They are awesome.

Greg C., I looked a little deeper into your webpages and was very impressed. I especially liked the info. on wing bending moments and tail design/aircraft stability. So much good info. on your website, I am surprised that I hadn't come across it sooner.

Thanks again,
Paul D.

[flieslikeabeagle]

Linux sim! I like it!
Indeed! And very nice flight physics, too, as something with input from Dr. Mark Drela might be expected to have.

I've run the Linux version of CRRCSIM on both Slackware and Gentoo boxes in the past. Version 0.9.6 had considerably improved graphics and the model aircraft config files had just switched from plain old text to XML (still text but with tags to make it much saner). Version 0.9.7 is supposed to have even better graphics.

I do wish there was a fairly straightforward way to design new models for CRRCSIM, though. It doesn't look easy to master the existing tools.

-Flieslikeabeagle

[othmanskn]

I was hoping to use an r/c flight sim as a very basic - very preliminary design tool. It sounds that even for that the most popular r/c sims are lacking. I am still looking at Xplane, the Crrcsim and the Flightgear simulators - very impressive.

Thanks all for the info. and feedback. Thanks too for the great links. They are awesome.

Greg C., I looked a little deeper into your webpages and was very impressed. I especially liked the info. on wing bending moments and tail design/aircraft stability. So much good info. on your website, I am surprised that I hadn't come across it sooner.

Thanks again,
Paul D.
Try aerofly pro. It comes with 3D design. I believe I could modify some geometries as well as the actual pictures. Can't really remember.
One weakness is that the smallest mass is 10g, which is too high for x-twin, that has a total mass of 20g.