Beechcraft KingAir 350

[jwocky]

Okay, everybody relaxes! I was over the weekend without internet due to thunderstorms. I try to catch up on some work today and tomorrow, I keep Wednesday for the KingAir and see, what's up with it. As of yet, everything sounds more or less like a list of small things easy to fix.

[LesterBoffo]

Also, the gear position seems to be wrong, it rotates around a wrong point when on ground, but I don't understand the coordinate system of jsb

JSBsim or YAsim has nothing to do with where the animation points rotate, translate, etc. Those are all coded in the animation file, in decimals of meters. If you can open the Beech KingAir's 3d file in a program, say like AC3D or Blender, you should be able to isolate and identify exactly where the pivot points are.

[jwocky]

Yeah, does the plane rotate around the wrong point -> gear position in JSB
or does the wheel rotate around the wrong point -> position in model file.

If it is the JSB file:
1.) get the positions of the gears (nose and left main gear) out of Blender. Blender gives you metric positions.
2.) search "Nose" in the JSB file, that brings you right where the gears are defined
3.) replace unit="in" against unit="m" in all three gears
4.) enter the positions in metric as you got them from Blender (and the right main gear has the same position as the left, only the sign on the y-axis changes from - to +)

chances are, you get away with this easy solution unless, the GC ends up suddenly far ahead and she sits on the butt. Then you have to rebalance her on the ground a little.

[LesterBoffo]

Also,, if you do take JWocky's advice and change the JSBsim neasurements from inches to meters, please remember to properly scale the new X-Y-Z entries changed by dividing the inches of each bogey or contact point by 39.3701

[D-ECHO]

@LesterBoffo @jwocky Thanks,
the plane rotates around the wrong point, I've messed enough with animations and FDMs to seperate these things.
And @jwocky I've tried this earlier but the plane ended up tilting backwards and then flying into the air, is this a problem of CG?

[bomber]

Why does the plane turn left? There is no p-factor on multi-engine props.... is there?

Josh

Yes there is... it's only on planes fitted with contra rotating props like the p38 that there's no P

To stop this open the left engine throttle a little infront of the right engine.

[LesterBoffo]

@LesterBoffo @jwocky Thanks,
the plane rotates around the wrong point, I've messed enough with animations and FDMs to seperate these things.
And @jwocky I've tried this earlier but the plane ended up tilting backwards and then flying into the air, is this a problem of CG?

Engine mass positions, fuel mass positions, both can be estimated along with internal cargo and pilot/crew weights, any and all possible masses should all be reflected accurately in the FDM file. You can also calculate the position of the landing gear's bogey-points by using a 3D program..

[D-ECHO]

This is what I could produce with coordinates from blender...

Code: Select all

   <metrics>
      <wingarea  unit="FT2">  310.00 </wingarea>
      <wingspan  unit="FT" >   57.95 </wingspan>
      <wing_incidence>          6.00 </wing_incidence>
      <chord     unit="FT" >    5.85 </chord>
      <htailarea unit="FT2">   68.00 </htailarea>
      <htailarm  unit="FT" >   18.45 </htailarm>
      <vtailarea unit="FT2">   24.85 </vtailarea>
      <vtailarm  unit="FT" >   23.33 </vtailarm>

      <location name="AERORP" unit="IN">
         <x> 0.0 </x>
         <y>   0.00 </y>
         <z>   0.00 </z>
      </location>

      <location name="EYEPOINT" unit="IN">
         <x>  44.79 </x>
         <y> -24.00 </y>
         <z>  65.00 </z>
      </location>

      <location name="VRP" unit="IN">
         <x>0</x>
         <y>0</y>
         <z>0</z>
      </location>
   
   </metrics>

   <mass_balance>
      <ixx unit="SLUG*FT2">     26392 </ixx>
      <iyy unit="SLUG*FT2">     20469 </iyy>
      <izz unit="SLUG*FT2">     46381 </izz>

      <emptywt unit="LBS" >      9885 </emptywt>
      <location name="CG" unit="M">
         <x> -2.29977</x>
         <y>   0.00 </y>
         <z> -0.57938 </z>
      </location>

      <pointmass name="Payload">
         <description> 1305 LBS + full (3810 LBS) fuel should bring model up to entered max weight</description>
         <weight unit="LBS">    652.5 </weight>
         <location name="POINTMASS" unit="IN">
            <x> 338.52 </x>
            <y>   0.00 </y>
            <z> -14.00 </z>
         </location>
      </pointmass>
   
   </mass_balance>

   <ground_reactions>

      <contact type="BOGEY" name="NOSE">
         <location unit="M">
            <x>  -6.64082 </x>
            <y>   0.00 </y>
            <z> -1.81689 </z>
         </location>
         <static_friction>  0.80 </static_friction>
         <dynamic_friction> 0.50 </dynamic_friction>
         <rolling_friction> 0.02 </rolling_friction>
         <spring_coeff unit="LBS/FT">       4500.00 </spring_coeff>
         <damping_coeff unit="LBS/FT/SEC">  7500.00 </damping_coeff>
         <max_steer unit="DEG"> 45.00 </max_steer>
         <brake_group>NONE</brake_group>
         <retractable>1</retractable>
      </contact>

      <contact type="BOGEY" name="LEFT_MAIN">
         <location unit="M">
            <x> -1.91892 </x>
            <y>-2.77772</y>
            <z> -1.8049 </z>
         </location>
         <static_friction>  0.80 </static_friction>
         <dynamic_friction> 0.50 </dynamic_friction>
         <rolling_friction> 0.02 </rolling_friction>
         <spring_coeff unit="LBS/FT">      15000.00 </spring_coeff>
         <damping_coeff unit="LBS/FT/SEC">  7500.00 </damping_coeff>
         <max_steer unit="DEG">0</max_steer>
         <brake_group>LEFT</brake_group>
         <retractable>1</retractable>
      </contact>

      <contact type="BOGEY" name="RIGHT_MAIN">
         <location unit="M">
            <x> -1.91892 </x>
            <y>-2.77772</y>
            <z> -1.8049 </z>
         </location>
         <static_friction>  0.80 </static_friction>
         <dynamic_friction> 0.50 </dynamic_friction>
         <rolling_friction> 0.02 </rolling_friction>
         <spring_coeff unit="LBS/FT">      15000.00 </spring_coeff>
         <damping_coeff unit="LBS/FT/SEC">  7500.00 </damping_coeff>
         <max_steer unit="DEG">0</max_steer>
         <brake_group>RIGHT</brake_group>
         <retractable>1</retractable>
      </contact>

      <contact type="STRUCTURE" name="LEFT_WING">
         <location unit="M">
            <x> -2.25297 </x>
            <y> -8.83521 </y>
            <z> 0.13229 </z>
         </location>
         <static_friction>  1.00 </static_friction>
         <dynamic_friction> 1.00 </dynamic_friction>
         <spring_coeff unit="LBS/FT">      15000.00 </spring_coeff>
         <damping_coeff unit="LBS/FT/SEC"> 15000.00 </damping_coeff>
      </contact>

      <contact type="STRUCTURE" name="RIGHT_WING">
         <location unit="M">
            <x> -2.25297 </x>
            <y> 8.83521 </y>
            <z> 0.13229 </z>
         </location>
         <static_friction>  1.00 </static_friction>
         <dynamic_friction> 1.00 </dynamic_friction>
         <spring_coeff unit="LBS/FT">      15000.00 </spring_coeff>
         <damping_coeff unit="LBS/FT/SEC"> 15000.00 </damping_coeff>
      </contact>

   </ground_reactions>

   <propulsion>

      <engine file="PW_PT6A-60">
         <location unit="M">
            <x> -4.1969 </x>
            <y>-2.76458 </y>
            <z> -0.25374</z>
         </location>
         <orient unit="DEG">
            <pitch> 0.00 </pitch>
            <roll>  0.00 </roll>
            <yaw>   0.00 </yaw>
         </orient>
         <feed>0</feed>
         <thruster file="Prop_L10">
            <location unit="M">
               <x> -5.45496 </x>
               <y> -2.74939 </y>
               <z> -0.18085 </z>
            </location>
            <orient unit="DEG">
               <pitch> 0.00 </pitch>
               <roll>  0.00 </roll>
               <yaw>   0.00 </yaw>
            </orient>
         </thruster>
      </engine>

      <engine file="PW_PT6A-60">
         <location unit="M">
            <x> -4.1969 </x>
            <y>2.76458 </y>
            <z> -0.25374</z>
         </location>
         <orient unit="DEG">
            <pitch> 0.00 </pitch>
            <roll>  0.00 </roll>
            <yaw>   0.00 </yaw>
         </orient>
         <feed>1</feed>
         <thruster file="Prop_L10">
            <location unit="M">
               <x> -5.45496 </x>
               <y> 2.74939 </y>
               <z> -0.18085 </z>
            </location>
            <orient unit="DEG">
               <pitch> 0.00 </pitch>
               <roll>  0.00 </roll>
               <yaw>   0.00 </yaw>
            </orient>
         </thruster>
      </engine>

      <tank type="FUEL" number="0">
         <location unit="M">
            <x> -1.97584 </x>
            <y>  -5.71787 </y>
            <z> -0.12133 </z>
         </location>
         <capacity unit="LBS"> 1270.00 </capacity>
         <contents unit="LBS"> 635.00 </contents>
      </tank>

      <tank type="FUEL" number="1">
         <location unit="M">
            <x>-1.6858 </x>
            <y>   -2.17981 </y>
            <z> -0.44779 </z>
         </location>
         <capacity unit="LBS"> 786.65 </capacity>
         <contents unit="LBS"> 786.65 </contents>
      </tank>

      <tank type="FUEL" number="2">
         <location unit="M">
            <x>-1.6858 </x>
            <y>   2.17981 </y>
            <z> -0.44779 </z>
         </location>
         <capacity unit="LBS"> 786.65 </capacity>
         <contents unit="LBS"> 786.65 </contents>
      </tank>

      <tank type="FUEL" number="3">
         <location unit="M">
            <x> -1.97584 </x>
            <y>  5.71787 </y>
            <z> -0.12133 </z>
         </location>
         <capacity unit="LBS"> 786.65 </capacity>
         <contents unit="LBS"> 786.65 </contents>
      </tank>

but still the aircraft is falling back

[bomber]

Go to fdm/jsb/interia and look at the CoG x value.

with fuel and payload it might well have shift backwards past allowable distance

[bomber]

ok I've a question what Hz value do you run FG at ?