[Flightgear-devel] [Fwd: Re: [Flightgear-users] Seneca II - couple of user comments]
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
Re: [Flightgear-devel] [Fwd: Re: [Flightgear-users] Seneca II - couple of user comments]
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? For the SenecaII: Yes. I will work on that issue - hopefully today. Torsten - 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
[Flightgear-devel] [Fwd: Re: [Flightgear-users] Seneca II - couple of user comments]
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
Re: [Flightgear-devel] [Fwd: Re: [Flightgear-users] Seneca II - couple of user comments]
I can't answer this at length at the moment, but a couple of months ago I turned off JSBSim turbulence completely because I had some questions about it myself. If you get the FGAtmosphere.cpp file from JSBSim CVS, that should include the newly turned off turbulence. I hope to revisit that in the near future. I have assembled some reference documents to review as time permits. Jon -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of dave perry Sent: Sunday, December 02, 2007 9:45 PM To: FlightGear developers discussions Subject: [Flightgear-devel] [Fwd: Re: [Flightgear-users] Seneca II - couple of user comments] 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 flightgear- [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 - 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
