Both Cm due to pitch rate and Cm due to alpha rate are legitimate. More sophisticated models will have both.
-----Original Message----- From: flying.toaster [mailto:flying.toas...@voila.fr] Sent: Sunday, February 01, 2009 2:35 AM To: development issues; flightgear-devel Subject: Re: [Jsbsim-devel] X-15 issue identified Regarding the pull up issue, it seems fixed (partially) now. My first assumption regarding atmosphere was definitely wrong (even though the JSBSsim atmosphere feels better now and the FG atmosphere is still wrong above 60kft). I have looked into the Cmalpha values and it was only fixed to a single value, when the actual value varied with mach number and alpha itself according to Nasa flight test reports. I fixed the table and I could fly the whole profile from Smiths ranch to Edwards with a 7g pullout with 700KIAS maximum (should be within qbar limits), and attitude control using rockets in the upper part of the trajectory. My landing was only spoiled by a "Warning:: Picked up error in TriangleIntersect" error on the console that brought FG to its knees :) Now I guess I still have to examine closely the rest of derivatives to make sure it fits. I am particularly annoyed by the aerodynamic coefficient attached to the pitch rate rather than the alpha rate since pitch is a geometric (inertial) rather than aerodynamic value. I have also a hard time understanding why the CMmach ( I understand it is there to model the shift in aerodynamic center) varies with altitude ... I guess it is all explained in NASA's reports. Anyway still got a lot of work to do to make the X-15 release-able, but I can guarantee it is fun to fly ... ____________________________________________________ Écoutez en un clic votre musique préférée et découvrez de nouveaux titres en affinité avec vos goûts sur http://musiline.voila.fr ---------------------------------------------------------------------------- -- This SF.net email is sponsored by: SourcForge Community SourceForge wants to tell your story. http://p.sf.net/sfu/sf-spreadtheword _______________________________________________ Jsbsim-devel mailing list jsbsim-de...@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/jsbsim-devel _______________________________________________ The JSBSim Flight Dynamics Model project http://www.JSBSim.org _______________________________________________ ------------------------------------------------------------------------------ This SF.net email is sponsored by: SourcForge Community SourceForge wants to tell your story. http://p.sf.net/sfu/sf-spreadtheword _______________________________________________ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
