dave perry wrote: > Laurence Vanek wrote: > >> I believe, however, that something else is going on with the A/P during >> ILS approach. I do not get the behavior you report on approach. The A/P >> begins to make large over corrections about one mile out, to the point >> where I need to disable the A/P & make the approach manually using the >> HSI. Not good if in poor IMC conditions with no visual refs. until at DH >> (~200 ft). >> >> > I get this behavior with any non zero turbulence even with the 0.3 > scaling. If I open the Weather menu and the Weather Conditions sub menu > and make sure all the turbulence tabs are slid all the way to the left > and then click on apply, the SenecaII settles down and follows the ILS > down to the runway. You cannot just use the fgrun advanced options > weather tab to zero the turbulence as it does not really zero the > turbulence. Make sure the property > /environment/turbulence/magnitude-norm is '0' (double). With fgrun > advanced weather turbulence set to zero, this property will still be > 0.00067 ... which is enough to cause the oscillations on my system. > > One more interesting result. Since I beleive that the AP is chasing even very small turbulence and the aileron inputs are causing the adverse yaw out of phase with the turbulence, I tried using "auto-coordination" with 0.05 turbulence value. The AP flew the SenecaII right down the LOC/GS. There was continuous control movements and the ball was biased off to one side (see the note on the double sense - I had not yet recompiled with the 2nd sense removed). The point here is that with the rudder outputs from the auto-coordination to correct the adverse yaw, the out of phase yaw oscillations were gone.
Conclusions: 1. We know that Jon is going to rework the JSBSim turbulence which should help a lot. 2. Even after that, the adverse-aileron yaw needs to be toned down a lot in JSBSim models to achieve more realistic response in low power cruse such as one has when flying an instrument approach. For the upcoming release, can we modify the JSBSim in fgfs to turn off turbulence modeling? For the upcoming release, should we select a scaling factor for the adverse-aileron yaw in the c172p and SenecaII that result in the performance more similar to the pa28-161 and pa24-250 respectively? -Dave Perry ------------------------------------------------------------------------- SF.Net email is sponsored by: The Future of Linux Business White Paper from Novell. From the desktop to the data center, Linux is going mainstream. Let it simplify your IT future. http://altfarm.mediaplex.com/ad/ck/8857-50307-18918-4 _______________________________________________ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
