> > Hello David, I like your PA-28 very much, but I can't resist to note
> > that there is one 'feature' that is really annoying (I must admit that
> > this word is a bit too strong in this context !):
> > At least in the outside views the aircraft rotate around its nose.
> > It's difficult to tell if the cockpit view is correct but there are
> > signs that it suffers from the same effect (this effect already existed
> > before your recent changes). It would make the aircraft even prettier
> > if this would get fixed.
>
> Thanks. I skipped most of the recent discussion on this point --
> was there
> any consensus on how to set the aerodynamic centre point for a 3D model?
Yes. JSBSim now features an item in our configuration file format that
specifies the location of the VRP (Visual Reference Point) in the structural
frame for the aircraft. The structural frame, as you may recall, is the
frame in which the empty weight CG, gear locations, etc. are given in the
JSBSim config file. The VRP is taken to be the forward most point on the
aircraft -- assumed in almost all cases I can think of as being the tip of
the nose - not including pitot tubes, etc. This would be the tip of the prop
hub in the case of prop aircraft.
As an example (not necessarily quantitatively correct) consider what I have
done with the experimental C-172:
AC_CGLOC 41.0 0.0 36.5
<!-- Pilot -->
AC_POINTMASS 180.0 36.0 -14.0 24.0
<!-- Co-pilot -->
AC_POINTMASS 180.0 36.0 14.0 24.0
AC_EYEPTLOC 37.0 0.0 48.0
AC_VRP -10.0 0.0 0.0
The above suggests that datum for the structural frame is nearer the pilot
than the VRP.
This is in JSBSim CVS, but the aircraft have not had their VRP set, yet. I
also do not think the modeling rendering code has been set up to use this,
yet.
Jon
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