Andy Ross > David Megginson wrote: > > I've been spending a bit of time on the PA-28 model in > YASim, and one > > problem is that the engine idles far too fast sitting still on the > > ground (around 1000 rpm, instead of 600-650 rpm). Is there > any simple > > parameter I can tune to slow it down a bit? > > Not really. The propeller torque near zero airspeed is just > too low right now. I'm really happy with the way the > existing propeller model works under normal cases; it works > backwards from an efficiency curve to come up with a model > that produces good physics for simple inputs without going > wacky in some important regime. It's not good with edge > cases, though. > > One option would be to port another engine/propeller model > onto the existing yasim::Thruster interface. This might not > follow the "solution from known performance" idiom, but for > the case of a single aircraft can probably be tuned to work better. > > Short term, we could try to hack in a "idle speed" or > "minimum torque coefficient" or somesuch too, although even > that is probably going to be difficult. > > > What do we need to do to get YASim to publish convincing values for > > these properties for piston engines? > > /engines/engine[*]/oil-pressure-psi > > /engines/engine[*]/oil-temperature-degf > > /engines/engine[*]/fuel-pressure-psi > > I'm not quite sure what convincing values for these > properties would be. The pressures are pump-driven and are, > or should be, static under normal conditions, right? The oil > temperature can probably be driven by a low-pass-filtered > output power. Maybe a tiny bit of YASim-specific Nasal glue > is what's required here.
So far as oil-pressure-psi is concerned a normalised number increasing with rpm should do the trick - we can then set max/min values. Oil temperature hmmmm - a function of OAT and rpm and any movable cowling - too engine specific - too difficult? > > Once YASim is running, it takes control of the > > /consumables/fuel/tank[*]/level-gal_us property (as well as the > > associated weight property) and will not accept changes. > To simulate > > refueling, either in the ground or on the air, it would be > nice to be > > able to change these values dynamically inside a FlightGear session. > > This one is much easier to fix. I proposed a Nasal-driven > fuel system a few months back, and still have half-finished > YASim support for it sitting in my build tree. The basic > idea is that YASim merely exports an ever-increasing > "consumed fuel" number for each engine. The Nasal code then > poll this at some sane frequency (maybe 3 Hz), inspects > configuration, subtracts the fuel from the appropriate tanks, > sets engine out-of-fuel flags, and finally resets the > consumed fuel numbers to zero. YASim then just reads the > fuel quantities for mass calculation only. > > The best part is that this can be done portably. The > consumed fuel properties will be missing for non-YASim > aircraft and the script can simply disable itself. And for > the future, arbitrarily complicated fuel flow schemes can be > implemented entirely in Nasal with no FDM support needed. That's very sophisticated. All I need is the ability to set fuel values, but this would be very interesting. > I'll try to get this working tonight. Thank you Regards Vivian Meazza _______________________________________________ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
