Jim Wilson writes: > It's still a little weird with a steep roll angle. Found an > article on quarternions. It seems that they can be used to solve > the problem of the rotation being off center.
Actually what we need to know is the center of gravity (CG) for each plane, or maybe the aero reference point -- I'm not sure which. The FDMs already know this: if they could publish the offset, in meters, from each plane's the reference point, we could use that to get the center point for all rotations. For example, as you mentioned earlier, the reference point for a Cessna 172 is on the floor right by the firewall (i.e. behind the rudder pedals). The centre of gravity, according to the JSBSim config file, is 41.0 inches back and 36.5 inches up from that. We could hardcode it for each model, but I think getting the value from the FDM is better: the CG can move around, depending on how the plane is loaded, and eventually the FDMs will model that movement. For example, if I've been draining all my fuel from the left wing tank so that it's empty and the right wing tank is full, my CG is no longer going to be right on the Y-axis. FDM guys? All the best, David -- David Megginson [EMAIL PROTECTED] _______________________________________________ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
