Jim Wilson wrote: > It'd be great if someone else could look at the P51D fdm. I'm > lost. Flight dynamics is neither my area of expertise or > interest. The only reason I did it in the first place is I had a > 3D model that Jon supposedly had a JSBsim config for that never > materialized. > > In short, the major issues are with the propeller rpm (as Vivian > noted) and probably more significant, the thing still flys like > it has the glide ration of a 30m soaring plane. Any help is > appreciated.
OK, I'll give it a shot. Most of your problems are due, I suspect, to the manual propeller stuff. This gets tricky: I notice you used a "maximum/fast" propeller pitch for the cruise solution, which is presumably a maximum level speed value. But 380 knots at ~1300 RPM is actually a very *low* advance ratio, and requires a coarse pitch, not a fine one. Add that to the fact that YASim allows for a non-physically large range of pitch travel and things can get wacky. An automatic pitch governor takes care of this for you, but for a manual lever you're stuck doing all the tuning. Maybe a good idea would be to export the equivalent manual settings as a property from a governor, so you could lift values from there... The issue with the glide ratio may be due to bad data. You have the cruise value at 380 (195.5 m/s) ktas and ~1300 horsepower (968500 W). With those values, the Mustang is being forced by fundamental physics to cruise on just 1100 pounds of thrust (4953 N). For an aircraft with an weight of 8000 pounds, that's *really* slick. Could a production mustang really cruise at 380 knots with 50% fuel, or is that more of a theoretical maximum and/or record attempt made with a stripped aircraft? (To the peanut gallery: please don't tell us all about the oil cooler again. :)) I played with Vivian's number for the spitfire, and they came out much saner; with about double the drag coefficient. Andy _______________________________________________ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
