Hello,
Just to report that this parameter in the flight_model.cfg file has currently no effect at all on the flight model.
I don’t know if it’s supposed to be this way, but it’s a shame as it prevents from adjusting lift at high speeds.
Hopefully this gets fixed ASAP.
It would be informative if the SDK documented which parameters were used uniquely or shared by the two Flight Models ( Classic & Modern).
ie It could be that “Lift_coef_mach_table” is only used by the Classic Flight Model ??
It could be but in that case the Modern flight model wouldn’t take into account the increase in lift with increasing Mach…
Which is what your original post said is happening …
Just to report that this parameter in the flight_model.cfg file has currently no effect at all on the flight model.
Replying to myself, the table works but only accepts scalar lower than 1.
So after a bit of testing, it can be used in conjunction with cruise_lift_scalar to modulate the L/D ratio for different Mach numbers.
cruise_lift_scalar will also scale up the drag by the same amount, and the lift_coef_mach_table can be used to decrease the lift, thus allowing for lower L/D ratio.
thanks for this useful testing. So to use it you’d get the max L/D right at whatever speed that should be, set the mach parameter to 1 for that speed, and tweak the mach parameters lower at faster and slower speeds?
it’s hard to see how that would work with ‘normal’ polar curve that the flight sim already models, i.e. above some speed the drag already increases faster than the lift so the L/D decreases anyway. Although FSX has always had a big problem for gliders (I’ve modelled a lot of them) that the L/D (hence glide ratio) always improves as you slow down, until you reach the stall (sim power pilots/developers in my experience have never noticed this, and find it hard to believe) - maybe the mach table is ideal to address this for speeds below max L/D.
I actually realized after that you can also tune the drag coefficient at zero lift vs the Mach number using the drag_coef_zero_lift_mach_tab parameter. So we can completely modulate the L/D ratio for different Mach numbers. In the case of gliders, the MN range might be too small to see an effect, but you can try. I’m focusing on the big birds (747 mainly).
Maybe some developers don’t notice this because this problem only applies to gliders?
I haven’t designed any glider FDEs, but getting Vimd right is one of the basic important values for a a high quality FDE and I can’t remember that achieving this was a significant problem.
I didn’t use the Mach table to establish this speed.
Why would this be limited to gliders only?? Once an aircraft has lost power to its’ engine/s it is in essence, a glider and the same rules that apply to gliders apply everywhere else. Perhaps they aten’t as visible, but that doesnt mean they arent there, and if you want to build a high quality FDE they need to be included regardless if that FDE is for a glider, or an A380
The reason why this might not work as designed with gliders is due to usually the very high aspect ratio wings.
If it’s FSX, MSFS or x-plane, flight model design work best with more ‘conventional’ designs.