I am forwarding an exchange from today's users list to the developers list because it raises a significant difference between jsbsim and yasim. These fdms treat turbulence very differently and jsbsim has a very exaggerated adverse-aileron yaw that makes this difference fatal for autopilot ILS approaches even in light turbulence.
-------- Original Message -------- Subject: Re: [Flightgear-users] Seneca II - couple of user comments Date: Sun, 02 Dec 2007 19:10:05 -0700 From: dave perry <[EMAIL PROTECTED]> Reply-To: FlightGear user discussions <[EMAIL PROTECTED]> To: FlightGear user discussions <[EMAIL PROTECTED]> References: <[EMAIL PROTECTED]> Laurence Vanek wrote: > For my money, the Seneca is one of the best done aircraft in FG. Have > been flying it a good deal of late. > > Agreed! <snip> > [2] On localizer during an ILS approach the A/P seems unstable > (increasing roll oscillations) when within ~1 mile of approach end of > runway. Perhaps this requires tweak of A/P controller constants. On a > CAT II or III approach one would still not be able to see the runway at > that distance. I usually disable the A/P at DH point. > I have commented before about the difference between yasim and jsbsim when it comes to two autopilot issues. 1. jsbsim becomes almost uncontrolable with turbulence. Even at 0.1 or certainly at 0.2 turbulence, the c172p will not complete an approach with the kap140. So, make sure you have turbulence at 0. 2. I spent many many hours tweaking the SenecaII autopilot config file. Since jsbsim (in my opinion) has a very exagerated adverse aileron yaw response and most autopilots have aileron but not rudder roll outputs, this creates the oscillations. That is why I put in the menu options for the SenecaII a yaw-damper that may help some. It is a controller that applies rudder to try and keep the ball centered. To see the fdm difference, fly the Senecal II and then the pa24-250 (which has the same autopilot nasal file and very similar autopilot config file) down the same ILS. The pa24-250 with the Century III autopilot will be rock solid all the way to the runway center line even with light to moderate turbulence. The pa24 uses yasim. You can see the same comparison between the jsbsim c172p and the yasim pa28-161 which both have the kap140. <snip> Does anyone know of a jsbsim model with autopilot that will fly an ILS with no oscillation with even very light turbulence? -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-users mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/flightgear-users ------------------------------------------------------------------------- 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
