OK, as promised, I've put together a first release of my "YASim" (sue me, I couldn't think of a better name) FDM for FlightGear. Actually, I promised over on the flightmodel list, for those who aren't subscribed. Basically, this is a rough, first cut of a "different take" on FDM design. It's intended to be very simple to use, producing reasonable results for aircraft of all sorts and sizes, while maintaining simulation plausibility even in odd flight conditions like spins and aerobatics. It's at the point now where one can actually fly the planes around, so I'm itching to show it off.
Those familiar with my posting history should note that, unlike all the other code I've sent around in the past, this is ACTUALLY INTEGRATED with fgfs. You can do stuff with it, like fly planes. :) For those brave enough to try it, the instructions are below. Note that this has been tested only on Linux. It "should" work on cygwin with gcc. Other environments will require tweaking, I'm sure. Make sure your FlightGear source is up to date with the CVS archive. Download the YASim code from: http://www.plausible.org/andy/yasim-0.1.tar.gz Get into your top-level FlightGear source directory (the one containing NEWS, README, INSTALL & such -- *not* the src subdirectory of that) and unpack the tarball. Note that this will clobber the following files. If you have personal changes to them, you will have to merge them in yourself: configure.in src/FDM/Makefile.am src/Main/Makefile.am src/Main/fg_init.cxx Rebuild from scratch: make distclean aclocal automake -a autoconf ./configure <whatever args you use> make make install You will find three aircraft .xml files (Cessna 172, Douglas A-4 Skyhawk, Boeing 747) in the src/FDM/YASim directory. Put them into the Aircraft directory of your fgfsbase tree. This is a bad place, and I'm sure David will find a better home for them. :) Run fgfs with one of the configured aircraft: fgfs --fdm=yasim --aircraft=c172 # Gotta have the skyhawk --aircraft=a4 # And this skyhawk too. :) --aircraft=747 # Big guy You can experiment with different fuel amounts with: --prop:/yasim/fuel-fraction=0.5 # 50% fuel in each tank The cessna doesn't care, of course, but the A-4 and 747 have wildly different performance with different weights. If all goes well, you will be sitting on the runway as usual. Take off, fly, and find bugs. I'll start with a known bugs list: + Not an ounce of documentation exists. The truly adventurous could probably figure most of the configuration stuff out from context and examination of the parser code, but I promise to write some anyway. + The default Cessna panel doesn't work well with the jets. Try the HUDs instead. + The simulator will crash (literally: *(int*)0=0) if one of the gear passes through the ground. This is a debugging aid that has been left in. Sometimes you can do this without trying: stopping hard in the Boeing can force the nose gear into the ground. Tunable gear springs and shocks will show up eventually. The currently (automatically calculated) gear forces are rather stiff, and heavily damped. They feel right for the jets, but the 172 needs more bounce. + The propeller on the Cessna is too hard to turn at low speeds, and RPM (and climb performance) is therefore too low. This is an honestly to goodness design flaw, and needs to be fixed in ways I haven't come up with yet. The cruise performance is vaguely correct, for what it's worth. + For the most part, the engine gauges don't work. The engine models are, as I said, really cheezy. No spooling on the jets, for example. Actually, "third party" engine models, like Mr. Luff's, should be relatively easy to integrate. I haven't looked closely enough to be sure, though. + Lots of features aren't there yet: + P-factor + Prop wash + Turbulence + Supersonic aerodynamics + Takeoff speeds for all the aircraft are higher than I'd expect given the approach settings in their configuration files. I still need to investigate. + Control forces are all over the map. The A-4 stalls really easily, but the 172 needs loads of back stick to get off the runway. Those interested can try playing with the "flap" settings on the tail and the "effectiveness" parameters until they get something they like. Andy -- Andrew J. Ross NextBus Information Systems Senior Software Engineer Emeryville, CA [EMAIL PROTECTED] http://www.nextbus.com "Men go crazy in conflagrations. They only get better one by one." - Sting (misquoted) _______________________________________________ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
