Andy,
I have added you initial revision to the flightgear tree and have
committed it to CVS. We should probably 'negotiate' where the
aircraft xml files should live in the base package.
Wow, this has been a busy week: a whole new FDM to play with, zillions
of changes to JSBSim, a new twin aircraft, glass cockpit display
interface, sound effects, and I'm sure a few other things I'm
forgetting.
Regards,
Curt.
Andy Ross writes:
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
