AFAICT, the behavior with JSBSim is reasonable. This is what I see at 93 kias, power for level flight, a left turn makes the ball go left and needs left rudder to recenter. Opposite for right turn.
Same behavior (with similar magnitudes) observed at around 70 kias. At both speeds I did observe asymmetrical behavior, the ball tended to the left a small amount (but still within the vertical lines) in constant heading flight and may have been more sensitive to left turns than right. A power off descent at 70 knots tended to make it symmetric, so I suspect that the propwash effects are causing the aircraft trim at a small slip angle. On Wed, 2002-10-16 at 07:00, Jon Berndt wrote: > I'd tend to pay some attention to McFarland's document, but haven't had a > chance to review it with this in mind. Might get to that today. > > > -----Original Message----- > > From: [EMAIL PROTECTED] > > [mailto:[EMAIL PROTECTED]]On Behalf Of Tony Peden > > Sent: Wednesday, October 16, 2002 8:28 AM > > To: FGFS Devel > > Subject: Re: [Flightgear-devel] TC ball > > > > > > On Tue, 2002-10-15 at 20:12, Curtis L. Olson wrote: > > > FWIW, the turn coordinator ball behaves *very* differently between > > > JSBSim and YASim and another FDM I am playing with. All supposedly > > > return accelerations in body axis in ft/sec squared. > > > > IMO, what we should all be aiming at providing are accels very similar > > to what three body-axis aligned acclerometers mounted at the pilot > > eyepoint would give. The FDMs should provide to the TC only that which > > an airplane would provide, the raw forces or accels. > > > > > > > > > > This means we > > > can't create a single turn coordinator instrument who's ball behaves > > > reasonably well for every FDM. > > > > Well, I tried to compare the two, but got this for the yasim c172: > > > > > YASim solution results: > > Iterations: 404 > > Drag Coefficient: 18.9992 > > Lift Ratio: 87.1639 > > Cruise AoA: -0.124142 > > Tail Incidence: 0.440443 > > Approach Elevator: -1.00013 > > CG: -2.3, -0.0, 0.2 > > YASim SOLUTION FAILURE: > > Insufficient elevator to trim for approach > > [exit] > > > > I just used fgfs --aircraft=c172-yasim, is anything else needed? > > > > > Would it be better to force the FDM's to calculate a ball deflection > > > in degrees/radians, or do we need to investigate why the body axis > > > accelerations are so radically different for 3 different FDM's (who > > > all are trying to model a C172.) > > > > No and yes. > > > > If the FDM's do the work, then they > > > all have to do the failure modeling too. It would be nicer to figure > > > out what's going on ... it seems to be more than a simple coordinate > > > system difference, unless JSBSim/YASim swap X/Y axes or something > > > strange like that. > > > > > > > > > > Regards, > > > > > > Curt. > > > -- > > > Curtis Olson IVLab / HumanFIRST Program FlightGear Project > > > Twin Cities [EMAIL PROTECTED] [EMAIL PROTECTED] > > > Minnesota http://www.menet.umn.edu/~curt > http://www.flightgear.org > > > > _______________________________________________ > > 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 -- 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
