On Wed, 2002-03-13 at 04:22, David Megginson wrote: > 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?
Making the cg location (relative to the structural reference point) available to flightgear is no problem. Keep in mind, however, that JSBSim modelers are free to choose what reference point they want to use, it doesn't necessarily have to be anything familiar (such as Cessna's firewall reference point). This could result in some models having wacky view problems. > > > All the best, > > > David > > -- > David Megginson > [EMAIL PROTECTED] > > > _______________________________________________ > Flightgear-devel mailing list > [EMAIL PROTECTED] > http://mail.flightgear.org/mailman/listinfo/flightgear-devel -- Tony Peden [EMAIL PROTECTED] We all know Linux is great ... it does infinite loops in 5 seconds. -- attributed to Linus Torvalds _______________________________________________ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
