Re: [Flightgear-flightmodel] YASim Ground Effect Calculation

[Torsten D. <to...@t3...>]

Hi Joel,

you might want to also post this in the flightgear-developers list 
(fli...@li...)
which is much more active that this list.

Torsten


> Hi, I'd like to make a suggestion on how YASim does ground effect. (Am 
> I posting this to the right list?)
>
> My understanding is the existing calculation linearly increases lift 
> from 1x at 1 wingspan to 1.15x at 0 wingspans. However, I understand 
> actual ground effect increases non-linearly as the plane gets deeper.
>
> My suggestion is to non-linearize it, perhaps something like follows:
>
> When compiling my own build, I took src/FDM/YASim/Model.cpp
> existing line 368: fz *= (_wingSpan - dist) / _wingSpan;
> and replaced it with: fz *= pow( (_wingSpan - dist) / _wingSpan, 2.5);
>
> Planes seem to land more reasonably with this change. Especially 
> rear-jets like the Citation X, which are already quite floaty landing 
> due to how power changes affect pitch moments with that kind of engine 
> placement. Before, that thing could balloon itself without any flare 
> input from yoke. Now it's "just" light landing and easy to overflare.
>
> Thanks,
> Joel
>