Curtis L. Olson writes: > >Jon S Berndt writes: >> On Wed, 3 Apr 2002 22:54:01 -0000 >> "Jim Wilson" <[EMAIL PROTECTED]> wrote: >> >> >Ok, so are you saying that the lon/lat/alt values that >> >the fdm outputs are at the origin already adjusted for cg? >> >> JSBSim gives the lat/lon/alt of the CURRENT CG - NOT the >> origin of the structural frame. > >This means that currently as the CG moves (i.e. loading baggage, fuel, >people, etc.) the aircraft and the view point will move as well. >This is probably too small to normally notice and we typically aren't >changing the CG over time, but this does seem like something that >needs to be straightened out. Whatever the FDM's are returning for >position, it does need to be a fixed point relative to the airframe.
FWIW I think the whole problem here stems from an old misunderstanding that although is a quite reasonable one is unfortunately mistaken ie CG has been considerd by some to be Center of Gravity and by others as Center of Geometry and its usage has gotten mixed up When we weren't changing the mass of the plane this made no difference but now that we are this needs to be cleared up I should have pointed this out at the time we started 'burning fuel' but I was well just 'burning' at the assumption that default behaviour could be changed ar will with out 'group' discussion. < which BTW would have led very quickly to exposing this CG confusion > FWIW My take on this is that all we need is a 'fixed' position ie 'Center of Geometry' returned by the FDM. This fixed position can be anywhere on the AirFrame and it needs to be described more exactly in the individual model's configuration file so as the Viewer part of the program can do it's thing Ciao Norman _______________________________________________ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
