I wrote > > Jim Wilson wrote > > > > > I can see a difference, but it is still broken. No matter > > what the setting, now the engine RPM is either way to high or > > way to low. > > > > 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 > > flies like it has the glide ration of a 30m soaring plane. > > Any help is appreciated. > > > > Jim, it's a super model, and deserves to fly well. Once we > get the Merlin > sorted for the Spitfire, we should be able to fix up the > p51d. It's a bit > hard to separate the various effects at the moment. >
PS - here's a quick fix - I think your stall AoA was too close to your approach AoA, which was forcing a wheel landing rather than a 3 point. The wing should stall before the tail, so I adjusted the incidences, and I think the engine/prop mass position and the prop action point were the wrong way round. Anyway, until the engine bug is fixed I can't test it properly, but the stall speed is about right, and it lands well. Won't fly fast enough though. See what you think <?xml version="1.0"?> <!-- ************************************************************************ YASim aerodynamic model for a P-51D mustang Started 2003-04-24 by Jim Wilson This aerodynamic model is based on three-views, unauthoritative performance data, and wild guesses. These sites provided particularly useful information or were simply fun to visit: Performance data: http://www.hq.nasa.gov/office/pao/History/SP-468/app-a2.htm http://www.olympicflightmuseum.com/aircraft_gallery/p51d_mustang.htm http://www.btinternet.com/~lee_mail/P51.html http://www.sprucegoose.org/pdfs/planes/P51Mustang.pdf Weight and balance: http://www.p51.wjackparker.com/P51_Additional_reference_material/x_maintenan ce.htm http://www.nzfpm.co.nz/aircraft/p51d.htm http://www.wpafb.af.mil/museum/engines/eng33.htm Three-view: http://members.optushome.com.au/gjmustang/docs/3-View.html (Note: I have local copies if this url becomes un-available) The reference datum for measurements is the nose. ************************************************************************ --> <!-- Weight of everything but fuel (7010 empty) --> <airplane mass="7190"> <!-- Approach configuration --> <approach speed="87" aoa="13"> <control-setting axis="/controls/engines/engine[0]/throttle" value="0.2"/> <control-setting axis="/controls/engines/engine[0]/mixture" value="1.0"/> <control-setting axis="/controls/engines/engine[0]/propeller-pitch" value="0.5"/> <control-setting axis="/controls/flight/flaps" value="1.0"/> <control-setting axis="/controls/gear/gear-down" value="1"/> </approach> <!-- Cruise configuration --> <cruise speed="380" alt="25000"> <control-setting axis="/controls/engines/engine[0]/throttle" value="1.00"/> <control-setting axis="/controls/engines/engine[0]/mixture" value="1.00"/> <control-setting axis="/controls/engines/engine[0]/propeller-pitch" value="1.0"/> <control-setting axis="/controls/engines/engine[0]/boost" value="1.0"/> <control-setting axis="/controls/flight/flaps" value="0.0"/> <control-setting axis="/controls/gear/gear-down" value="0"/> </cruise> <!-- pilot's eyepoint --> <cockpit x="-4.495" y="0" z="0.689"/> <fuselage ax="0.0" ay="0.0" az="0.0" bx="-9.9" by="0.0" bz="0.0" width="0.94" taper="0.38"/> <!-- stall aoa not available flap drag not available --> <wing x="-3.96" y="0.55" z="-0.60" taper="0.466" incidence="2" length="5.16" chord="2.845" sweep="-3.5" dihedral="5" camber="0.1"> <stall aoa="20" width="4" peak="1.5"/> <flap0 start="0.024" end="0.543" lift="1.2" drag="1.8"/> <flap1 start="0.543" end="0.945" lift="1.3" drag="1.4"/> <control-input axis="/controls/flight/flaps" control="FLAP0"/> <control-output control="FLAP0" prop="/surface-positions/flap-pos-norm"/> <control-speed control="FLAP0" transition-time="5"/> <control-input axis="/controls/flight/aileron" control="FLAP1" split="true"/> <control-input axis="/controls/flight/aileron-trim" control="FLAP1" split="true"/> </wing> <hstab x="-8.62" y="0.18" z="0.34" taper="0.639" effectiveness="3.5" length="1.834" chord="1.256" sweep="0" incidence="0"> <stall aoa="20" width="4" peak="1.5"/> <flap0 start="0.0" end="1.8" lift="1.65" drag="1.2"/> <control-input axis="/controls/flight/elevator" control="FLAP0"/> <control-input axis="/controls/flight/elevator-trim" control="FLAP0"/> <control-output control="FLAP0" prop="/surface-positions/elevator-pos-norm"/> </hstab> <!-- rudder has to be able to counteract aileron drag --> <vstab x="-9.30" y="0" z="-0.37" taper="0.432" effectiveness="3.5" length="1.971" chord="2.65" sweep="25" incidence="-0.58"> <stall aoa="15" width="4" peak="1.5"/> <flap0 start="0" end="1" lift="1.3" drag="1.2"/> <control-input axis="/controls/flight/rudder" square="true" control="FLAP0" invert="true"/> <control-input axis="/controls/flight/rudder-trim" control="FLAP0" invert="true"/> <control-output control="FLAP0" prop="/surface-positions/rudder-pos-norm" min="1" max="-1"/> </vstab> <!-- moment calculated using formula submitted by Donald Simon: MOI = # of Blades * (8.2*(10^-5))*(D^5), slug-ft^2 then converted to kg-m^2 and finally square root to kg-m for torque value --> <!-- wastegate setting should not apply. set here so that calculations would approximate. YASim doesn't model gear supercharger. Have read various figures (turbo-mul) 4.0 to 5.8 for running the second stage blower. Fixing this would probably give more reasonable performance at lower altitude --> <!-- cruise-rpm roughly estimated from documented gear ratio of 0.479 --> <propeller x="-1.25" y="0" z="0" radius="1.75" mass="2000" moment="35" eng-power="1590" eng-rpm="3000" turbo-mul="4.0" wastegate-mp="61" cruise-alt="21400" cruise-power="1370" cruise-speed="380" cruise-rpm="2900" manual-pitch="true" > <actionpt x="-0.75" y="0" z="0"/> <control-input axis="/controls/engines/engine[0]/throttle" control="THROTTLE"/> <control-input axis="/controls/engines/engine[0]/starter" control="STARTER"/> <control-input axis="/controls/engines/engine[0]/magnetos" control="MAGNETOS"/> <control-input axis="/controls/engines/engine[0]/mixture" control="MIXTURE"/> <control-input axis="/controls/engines/engine[0]/propeller-pitch" control="PROPPITCH" src0="0" src1="1" dst0="0.40" dst1="0.82"/> <control-input axis="/controls/engines/engine[0]/boost" control="BOOST"/> </propeller> <!-- Tail wheel --> <!-- tail wheel "steerable" in p-51d (in stick back locked position it actually should be limited to 6deg +/-) --> <gear x="-7.90" y="0" z="-0.96" compression="0.2"> <control-input axis="/controls/flight/rudder" control="STEER" square="true" src0="-1.0" src1="1.0" dst0="0.5" dst1="-0.5"/> </gear> <!-- left main --> <gear x="-2.79" y="1.81" z="-2.20" compression="0.4" spring="0.7" damp="3.0"> <control-input axis="/controls/gear/brake-left" control="BRAKE"/> <control-input axis="/controls/gear/brake-parking" control="BRAKE" split="true"/> <control-input axis="/controls/gear/gear-down" control="EXTEND"/> <control-speed control="EXTEND" transition-time="6"/> <control-output control="EXTEND" prop="/gear/gear[0]/position-norm"/> </gear> <!-- right main --> <gear x="-2.79" y="-1.81" z="-2.20" compression="0.4" spring="0.7" damp="3.0"> <control-input axis="/controls/gear/brake-right" control="BRAKE"/> <control-input axis="/controls/gear/brake-parking" control="BRAKE" split="true"/> <control-input axis="/controls/gear/gear-down" control="EXTEND"/> <control-speed control="EXTEND" transition-time="6"/> <control-output control="EXTEND" prop="/gear/gear[1]/position-norm"/> </gear> <!-- Guess on wing tank positions --> <tank x="-3.50" y="1.0" z="-0.61" capacity="726"/> <tank x="-3.50" y="-1.0" z="-0.61" capacity="726"/> <tank x="-6.50" y="0" z="0" capacity="671"/> <!-- pilot --> <ballast x="-4.495" y="0" z="0.689" mass="180"/> <!-- armament --> <!-- Had too much weight I think...disable until stall speed fixed <ballast x="-3.20" y="0.7" z="-0.60" mass="800"/> <ballast x="-3.20" y="-0.7" z="-0.60" mass="800"/> --> <!-- prop --> <!-- <ballast x="0.1" y="0" z="0.0" mass="200"/> --> </airplane> _______________________________________________ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel