YASim Ground Effect Calculation

--===============2109420886432023487==
Content-Type: multipart/alternative; boundary="000000000000b6136c0625673b97"

--000000000000b6136c0625673b97
Content-Type: text/plain; charset="UTF-8"

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

--000000000000b6136c0625673b97
Content-Type: text/html; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable

<div dir=3D"ltr"><div>Hi, I&#39;d like to make a suggestion on how YASim do=
es ground effect. (Am I posting this to the right list?)<br></div><div><br>=
</div><div>My understanding is the existing calculation linearly increases =
lift from 1x at 1 wingspan to 1.15x at 0 wingspans. However, I understand a=
ctual ground effect increases non-linearly as the plane gets deeper.</div><=
div><br></div><div>My suggestion is to non-linearize it, perhaps something =
like follows:<br></div><div><br></div><div>When compiling my own build, I t=
ook src/FDM/YASim/Model.cpp</div><div>existing line 368: fz *=3D (_wingSpan=
 - dist) / _wingSpan;</div><div>and replaced it with: fz *=3D pow( (_wingSp=
an - dist) / _wingSpan, 2.5);</div><div><br></div><div>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 pit=
ch moments with that kind of engine placement. Before, that thing could bal=
loon itself without any flare input from yoke. Now it&#39;s &quot;just&quot=
; light landing and easy to overflare.<br></div><div><br></div><div>Thanks,=
</div><div>Joel<br></div><div><div><br></div></div></div>

--000000000000b6136c0625673b97--


--===============2109420886432023487==
Content-Type: text/plain; charset="us-ascii"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Content-Disposition: inline


--===============2109420886432023487==
Content-Type: text/plain; charset="us-ascii"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Content-Disposition: inline

_______________________________________________
Flightgear-flightmodel mailing list
[email protected]
https://lists.sourceforge.net/lists/listinfo/flightgear-flightmodel

--===============2109420886432023487==--