--- Jon Berndt <[EMAIL PROTECTED]> wrote: > > I may be a little slow (monday morning here), but that does not > tell me > > anything. We are talking about agl not the center of gravity. > > Is that the confusion? > > I'm not sure, but let me jump in here with a somewhat related > comment. Like > I've said before, the FDM naturally solves the rigid body equations > of > motion using the CG of the aircraft as a point of importance. At > least for > JSBSim we always will know where the CG location is in lat/long/alt. > The FDM > can _derive_ where any other point is located. This is important > since the > CG moves, and it can cause small problems when trying to link up the > FDM and > the visual model (hence the VRP "solution"). > > When it comes to AGL (Above Ground Level) we can report the AGL of > the CG > above the local ground elevation. We can (and any FDM can) report the > AGL of > any point on the aircraft, for that matter. So, the hard part is > deciding > where the point of importance is on the aircraft. Apparently, YASim > uses the > landing gear point of contact (?) -- arguably a point of importance > at > landing. We (JSBSim) use the CG -- arguably a point of importance for > the > FDM (since we measure gear contact points) from the CG, and depending > on > whether the gear are retracted or extended. > > For trimming on-ground the AGL value needs to be iterated on until > the > lowest point of the aircraft has a positive AGL value.
Not really. Trimming iterates on altitude and theta until the landing gear are deflected just the right amount to hold the aircraft up. I'd have to > think > about this whole thing a bit more to figure out a logical potential > solution, and I won't have time to do that for the moment, but I'll > throw in > my $0.02 to this discussion as it progresses. It would be nice to > simplify > things a bit. > > Jon > > > _______________________________________________ > Flightgear-devel mailing list > [EMAIL PROTECTED] > http://mail.flightgear.org/mailman/listinfo/flightgear-devel > > __________________________________ Do you Yahoo!? Yahoo! Small Business $15K Web Design Giveaway http://promotions.yahoo.com/design_giveaway/ _______________________________________________ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
