On Mon, 2002-12-16 at 10:26, Erik Hofman wrote: > Tony Peden wrote: > > --- Erik Hofman <[EMAIL PROTECTED]> wrote: > > > >>Jon Berndt wrote: > >> > >>>>Well, to rotate the aircraft realistically the refference point > >>> > >>should > >> > >>>>be known by the 3D modellers, but that aside. > >>> > >>> > >>>The rigid body rotates about the CG, not the aero ref. pt. > >> > >>Even when in motion? > > > > > > In the FDM's (all of them, AFAIK), yes. Always. > > In reality, the aircraft will rotate about the cg in air and some other > > point if any of the gear are touching the ground. During takeoff > > rotation and landing de-rotation, for example, the aircraft will rotate > > about the main gear. > > This confuses me a bit. My gut feeling tels me that the lift generated > on the various parts of the aircraft (fuselage included) would > concentrate the aircrafts rotation around its aero reff. point instead > of CG. Or is this the part where the moving CG comes in place?
No, think about the geometry of the situation. The gear can't go down and won't go up prior to liftoff. So aside from some possible changes in tire compression, the wheel axles do not translate up or down during the rotation or de-rotation. Another way to think about it may be in terms of a lever. The main gear act as the fulcrum about which the tail must produce/relieve enough force to rotate/de-rotate the aircraft. > > Erik > > > _______________________________________________ > Flightgear-devel mailing list > [EMAIL PROTECTED] > http://mail.flightgear.org/mailman/listinfo/flightgear-devel -- Tony Peden <[EMAIL PROTECTED]> _______________________________________________ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
