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AirWayMan

Aircraft Conversion and ver 1_1_22

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ok first I had to replicate what I had done in ver 1_1_15 since I neglected to save the project build folder (a mistake I wont make again  :P).

Now I have a working Piper Cub build (flyable and all) but if I import/convert with ver 1_1_22 I don't have any visible textures and the engine wont run, I can however build in 1_1_22 the project I imported/converted with ver 1_1_15 and it works fine.

 

The Cessna appears to remain the same no matter which ver I use, giving me a visible model that runs (meaning the engine is running) but is not flyable (the flight dynamics are way off)

 

I am looking into editing the Cessna flight dynamics now, I had hoped to simply replace these files with the ones from the piper to give me a working version to start with (then I could work backward) but keep getting a bad build so may take some time to figure out what all the entries actually do.

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First flight in Cessna !!

 

https://onedrive.live.com/redir?resid=93EF7AF58A9E9F26!119&authkey=!AOKJLoLSmkl-rNk&v=3&ithint=photo%2cjpg

 

although it flies a LOT like a Piper Cub     hehe

 

replaced all the simData files from piper and now adding the Cessna files back a couple at a time to narrow down

if I can locate 1-2 files I will start replacing data, chunks at a time, see if I can get it closer.

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More Success, I have gotten all the Cessna files back in the build with only 1 edit - some balance issues but not bad still.

So here it is - I found this in the aircraft cfg;

reference_datum_position     =  3.6, 0, 0       // (feet) distance from FlightSim Reference position: (1/4 chord, centerline, waterline)
empty_weight_CG_position     = -3.0, 0, 0       // (feet) longitudinal, lateral, vertical distance from specified datum

and in the BaseProperties.simData:

    <DatumOffsetFromModelCenter>
      <Position>
        <LongitudinalOffset>3.6</LongitudinalOffset>
        <LateralOffset>0</LateralOffset>
        <VerticalOffset>0</VerticalOffset>
      </Position>
    </DatumOffsetFromModelCenter>
    <MassProperties>
      <Mass>51.28357</Mass>
      <CenterOfGravityFromDatum>
        <Position>
          <LongitudinalOffset>-3.0</LongitudinalOffset>
          <LateralOffset>0</LateralOffset>
          <VerticalOffset>0</VerticalOffset>
        </Position>
      </CenterOfGravityFromDatum>

where it appears the converter just grabs the CG from the second line of the cfg BUT I believe it needs the difference between the 2.

 

By changing this one line here

      <CenterOfGravityFromDatum>
        <Position>
          <LongitudinalOffset>-3.0</LongitudinalOffset>

to

      <CenterOfGravityFromDatum>
        <Position>
          <LongitudinalOffset>0.6</LongitudinalOffset>

I get a flyable aircraft - it still has some balance problems and wont quite 'trim out' yet but still looking thru the files to see what else may refer to an ambiquous data point rather than the actual datum position I'm guessing the converter uses.

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Your changes don't make sense to me.  The FSX cfg states the CoG is relative to the datum.  I checked in Flight and it is adding the CoG to the Datum, so you essentially just changed the CoG to 4.2, instead of it being at 0.6 which is what it would have been with -3.  I'll try to look into it and see how the FSX version is used.

 

FSX is using it relative to the datum, so the CoG should be at 0.6, so I think the conversion is working properly.  Maybe it is supposed to be in meters instead of feet, but most of the aircraft stuff is in imperial.

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I'm sure you are right, it just seemed to me that the first line states "distance from FlightSim Reference position"  then maybe the CG was being give from that point "distance from specified datum"

while the converter might still be using the FlightSim Reference Position as the starting point for the -3.0 value.

But I'm just guessing so please don't waste your valuable time on my assumptions.

I'm just messing around and filling in missing data now but still cant get the aircraft to balance out yet, it 'noses up' badly after takeoff even after moving the CG forward, so likely it is something else any way.

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No problem. I like ideas as i have definitely made mistakes before.  I think the "FlightSim reference position" is basically just the origin in the model.

 

If there are problems in Flight then i would guess it is an aerodynamics issue.

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Looking closer into the Aerodynamics.simData I found the location of "Lift" isn't set also the wingchord was wrong.

 

aircraft.cfg:

[airplane_geometry]

wing_root_chord         = 4.9                   //Feet

wing_pos_apex_lon       = -2.4                  //Feet, longitudinal distance from reference point, negative going aft
wing_pos_apex_vert      = 0.0                   //Feet, vertical distance from reference point, positive going up

 so edited those here Aerodynamics.simData:

    <ReferenceWingChord>4.9</ReferenceWingChord>

  </Aero.AirplaneAerodynamicGeometry>
  <Aero.AerodynamicCenter Type="Lift">
    <Position>
      <LongitudinalOffset>-2.4</LongitudinalOffset>
      <LateralOffset>0</LateralOffset>
    </Position>

and the rudder:

vtail_pos_lon           = -16.2                 //Feet, longitudinal distance from reference point, negative going aft
vtail_pos_vert          = 1.5                   //Feet, vertical distance from reference point, positive going up

 

  <Aero.AerodynamicCenter Type="Side">
    <Position>
      <LongitudinalOffset>-16.2</LongitudinalOffset>
      <VerticalOffset>1.5</VerticalOffset>

 

cant find any reference to the Horizontal Stabelizer (TailFin) in the Aerodynamics.simData (May be part of the problem)

 

this helped a lot but still having to move the CG forward some (@ -0.5 atm) to get hands off flight

 

in addition I did add some missing data to StaticProperties.simData

Most importantly was MaxTakeoffWeight & MaxLandingWeight taken from cfg max_gross_weight, likely most of this stuff is just used for missions but its nice to see the range and such in Hanger view  :P

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Thanks!

 

Doing a second look through the code and noticing there is an error with the ReferenceWingChord calculation. I believe this parameter is supposed to be the mean wing chord, which is different than wing_root_chord, so I think your fix is wrong, but I did notice I was missing a *2 so it was half of what it should have been.

 

As far as I can tell for wing_pos_apex_lon and wing_pos_apex_vert, they aren't really used in FSX, and are not the lift aerodynamic center, however FSX seems to calculate some default value for the aerodyanmic center if it isn't specified in the .air file, but I'm not doing that in my conversion, so I'm guessing that is what is happening for the Cessna, and why they are coming through as 0.

 

Aerodynamic center for the side should always be 0 to match FSX, so i think your changes broke that here.

 

As for horizontal stabilizer, are there particular variables from FSX aircraft.cfg that aren't being used?

 

StaticProperties are just used for the UI i believe. Do you have a list of values from the aircraft.cfg that need to be converted?

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  I believe this parameter is supposed to be the mean wing chord, which is different than wing_root_chord

 

this is true the root chord is the widest point (measured at the base of the wing) and the mean chord is an average over a tapered wing but in the case of the Cessna these 2 would be real close to the same.

 

wing_pos_apex_lon and wing_pos_apex_vert, they aren't really used in FSX, and are not the lift aerodynamic center

the 'apex' would be the highest point of the airfoil, while not exactly the center of lift it again would be real close (a lot closer than zero  :P  anyway)

 

Aerodynamic center for the side should always be 0 to match FSX

this one I'm not sure about, I was assuming it was a reference to the rudder as it asks for long and vert offsets only - no lat offset - by using the rudder offset from the cfg file it does cause the aircraft to turn better on the ground but still may be wrong as you suggest.

 

As for horizontal stabilizer, are there particular variables from FSX aircraft.cfg that aren't being used?

Just the same ones I used for wing apex position plus a few more for size

[airplane_geometry]

htail_area              = 28.0                  //Square feet
htail_span              = 10.5                  //Feet
htail_pos_lon           = -13.1                 //Feet, longitudinal distance from reference point, negative going aft
htail_pos_vert          = 0.0                   //Feet, vertical distance from reference point, positive going up
htail_incidence         = 0.0                   //Degrees
htail_sweep             = 10.0                   //Degrees, horizontal tail leading edge

of course the tailfin does give 'some' lift (not much) but more important it 'distributes' (thru forward motion forces) lift to the aft

 

first some notes here, not all aircraft leave the Lift value blank, the Extra300S for instance fills this in

(from what I have no idea) but it isn't from any cfg number I can find.

 

 

StaticProperties are just used for the UI i believe. Do you have a list of values from the aircraft.cfg that need to be converted?          

Yea I thought the same here, so I just added what I could find here for the Hanger view (also may have some effect on missions Like the MaxTakeoffWeight & SeatingCapacity) There are only a few from aircraft.cfg that I added:

 

max_gross_weight   I added as   MaxTakeoffWeight & MaxLandingWeight

full_flaps_stall_speed    added to  StallSpeedVs0

flaps_up_stall_speed   added to  StallSpeedVs1

 

I added a few more but these either came from the Definition section or google

like ServiceCeiling, RateOfClimb, GlideRatio etc

 

Another note here: its possible to remove sections in StaticProperties.simData with no apparent ill effects, I removed a couple sections that reffered to waterlanding distance just to see if it broke things, all it did I could see was remove these values from the Info tab in Hanger view.

 

so far all I'm changing to get them to fly is the Lift in Aerodynamics and the CG in BaseProperties (Oh and editing the textures to fix the glass alpha problem), by manually adjusting these a little at a time I can get a 'fairly' stable aircraft but obviously it isn't right - another note here is the trim doesn't seem to have any effect, likely its because I'm screwing with the CG so throwing of the balance to far for trim to be noticeable.

Edited by AirWayMan

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Well dang, I just tried some more aircraft with ver 1_1_22 and then again with ver 1_1_15 - found another aircraft that doesn't render the model at all when I import it with ver 1_1_22 but does render imported with ver 1_1_15 :(

Guess I will go back and try some more with 1_1_15 to see if I can get the couple (at least 2) that I tried that did the same thing  :P

Both the Piper and the Beach Baron render only if imported/converted with ver 1_1_15

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Can you put the .15 and .22 converted aircraft into a zip file and share it?  I can take a look at what the differences are.

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sent you a pm  :)   hope it helps

 

just looked thru it, at first glance I noticed the interior model file is a different size but may be more differences.

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