Hello fellow developers. I present a topic that is for me central to (sailplane, piston, turboprop) airplane and ask for your experiences and ideas. The topic is aerodynamics, specific the difference between zero-lift drag coefficient and maximum lift-drag ratio.
As you may know, zero-lift drag coefficient CD,0 is controlled by drag_coef_zero_lift and parasite_drag_scalar. Maximum lift-drag ratio (L/D)max is measured by Aircraft Editor, Debug, SimPolar VhVs. I found no good documentation about the correlation between CD,0 and (L/D)max. I assume that for MSFS 2020 the 3D model of the airplane and CD,0 determine (L/D)max.
In MSFS 2020 my experience is that CD,0 = drag_coef_zero_lift * parasite_drag_scalar. That is you can set parasite_drag_scalar to 1 and only “adjust” drag_coef_zero_lift for the (L/D)max you want. Or you set drag_coef_zero_lift to the manufacturer value - if you have it - and use parasite_drag_scalar for adjustment.
Now the important detail: What (L/D)max value is the best for MSFS 2020? My information is that the Cessna 172 has a (L/D)max of 11.6. The Asobo C172 model has a measured (L/D)max of 12.0. That is the Asobo model is near to reality. But on the other hand: reality has propeller drag and reality has ground effect that - in my understanding - increase the drag.
My questions to my fellow developers:
1.) Do you think that a realistic (manufacturer data) (L/D)max value is necessary?
2.) Because MSFS 2020 has today (version 1.13.16.0) no propeller drag a (L/D)max of say 90% or 80% of manufacturer value is an acceptable workaround for “realistic airplane behavior within the limitations of the simulation”.
I wait for your comments. And if you want to see how my ideas about (L/D)max work out, see my flight level mods at MSFS 2020 sailplane
This is a (L/D)max chart I found on ch7-6
