On Wed, 2002-10-16 at 07:27, Curtis L. Olson wrote: > Tony Peden writes: > > 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. > > Tony, I apologize, I should have been more clear in my original > message. The JSBSim drives the ball in a reasonable way, as does this > other FDM I'm playing with. However, the scaling is about an order of > magnitude different between the two, even though they supposedly > report the accels in the same units and are modeling the same > aircraft. YASim seems to drive the ball yet another order of > magnitude further. It's not so much the behavior, but the range of > motion and scaling. I found it strange since supposedly all three are > reporting body axis accels in ft/sec^2 and it's the same code used in > all three cases to compute ball motion based on these accels.
Well, keep in mind that the accels driving the TC are calculated largely from the aero and propulsion models, so differences of degree between different models should not be surprising. Also, the FDM you are using probably has better aero data driving the lateral-directional dynamics (I'd guess it's based on Cessna flight test data). The lateral-directional terms in the JSBSim c172 are based largely on Roskam's estimates and pilot feedback, not actual data, so it doesn't surprise me that they don't agree. > > 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
