> 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. 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
