Flight Model Wing Geometry



  • The flight model wing geometry currently defined in the flight_model.cfg file for this aircraft is incorrect, and appears to be based on the much shorter rectangular shaped wings used in previous PA28 models, prior to the Arrow III. This wing geometry significantly affects the flight characteristics, weight and balance, and overall performance of the aircraft.

    This is the currently defined wing geometry...

    Screenshot 2021-04-16 155853.jpg

    This is what it should actually look like, based on the Arrow III wing specs...

    Screenshot 2021-04-17 054746.jpg

    Fortunately, this can be easily corrected... Here are the required changes to the flight_model.cfg file to correct the wing geometry to match the actual Arrow III specs. This only affects the flight model, and does not affect the external visual model of the aircraft.

    [AIRPLANE_GEOMETRY]
    wing_area =170
    wing_span =35.42 ;32.2
    wing_root_chord =6.09 ;5.3
    wing_camber =1
    wing_dihedral =6.32 ;3.5
    wing_thickness_ratio =0.05
    wing_incidence =2
    wing_twist =-3 ;-0



  • I would STRONGLY advise against anyone changing the wing dihedral. The sim has a nasty tendency to overdo the secondary effect of rudder input and this is worsened by the dihedral angle - in testing it was found that with the correct dihedral angle you could roll the aircraft almost as well as an aileron roll purely on rudder alone. At the setting suggested above, roll almost becomes the primary effect of rudder use.

    Unfortunately, this is a base sim issue, and we have to create an aircraft which flies as well as we can within the limitations and problems presented by the sim. This is just one example of why reading the POH and repeating it perfectly into the sim does not work.

    Having spent an entire morning of this week chasing a major, fundamental problem which should not have been there, was not there through development but has suddenly appeared thanks to 'recommended changes', I have to urge caution: we are walking towards a point where support will be virtually impossible because there is no way of knowing what user-edits have been incorporated, and currently chasing these issues is taking more time which should be spent actually reading the feedback and making corrections.



  • @RetiredMan93231 Maybe the JF team adjusted the geometry parameters on purpose in order to make up for imperfections in the MSFS flight model and by that come closer to the actual physics of that aircraft?



  • @Delta558 said in Flight Model Wing Geometry:

    I would STRONGLY advise against anyone changing the wing dihedral. The sim has a nasty tendency to overdo the secondary effect of rudder input and this is worsened by the dihedral angle - in testing it was found that with the correct dihedral angle you could roll the aircraft almost as well as an aileron roll purely on rudder alone. At the setting suggested above, roll almost becomes the primary effect of rudder use.

    Unfortunately, this is a base sim issue, and we have to create an aircraft which flies as well as we can within the limitations and problems presented by the sim. This is just one example of why reading the POH and repeating it perfectly into the sim does not work.

    Having spent an entire morning of this week chasing a major, fundamental problem which should not have been there, was not there through development but has suddenly appeared thanks to 'recommended changes', I have to urge caution: we are walking towards a point where support will be virtually impossible because there is no way of knowing what user-edits have been incorporated, and currently chasing these issues is taking more time which should be spent actually reading the feedback and making corrections.

    Wow, uh, maybe the XP fans are onto something when discussion happens around MSFS flight physics...or seemingly lack of, if the engine can't even handle standard wing shapes without falling apart.



  • @sluflyer06 I don't think there's anything in the XPlane flight model that makes it inherently better for flight simulation than the FS2020 model. But XPlane does have two things going for it, currently: development time and a developer that is much more open to community input. I bet that XPlane was a buggy mess too 8 months after release.