RE: CG placing

> I am modeling an R/C UAV, 2.2m span and 6.5 kg
> the METRICS file looks like this:
>     AC_CGLOC     28.3 0.0 0.0
>     AC_AERORP    28.3 0.0 0.0
>     AC_EYEPTLOC  17.0 0.0 15.0
>     AC_VRP       28.3 0.0 0.0
> and the undercarriage is:
> AC_GEAR NOSE_LG     10.0   0.0  -10.0
> AC_GEAR LEFT_MLG   37.5 -17.8  -10.0
> AC_GEAR RIGHT_MLG 37.5  17.8  -10.0
>
> the model.xml file links directly to the .ac model
> and the .ac model in AC3D has the origin (0,0,0) at the center of gravity.
>
> When I launch FG with the aircraft on the runway, it spins around like a
> bouncy ball and ends-up about 3m below ground....

It looks like you are doing the correct thing. There is a problem when modeling landing
gear forces when at rest. Careful selection of spring and damping coefficients is needed
to prevent the aircraft from turning into a bouncy ball. But, it does require some work to
get the right values. Also, even with the best values, there will still be some (maybe a
lot) of jittering. This is one area where we have known for some time that we need to do
some work on the FDM.

Jon


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