On Thursday 20 January 2005 16:45, Jim Wilson wrote: > Dave Martin said: > > On Thursday 20 Jan 2005 16:13, Jim Wilson wrote: > > > Dave Martin said: > > > > On Thursday 20 Jan 2005 14:42, Jim Wilson wrote: > > > > getting an aircraft working > > > > > > > > > is about 2 parts theory and 1 part voodoo (the part > > > > > that the basic formulas don't cover). > > > > > > > > "Any sufficiently advanced technology is > > > > indistinguishable from magic" - Sir Arthur C Clarke. > > > > > > Ok wrong word. Let me just say that it seems to lack some > > > magic. Setting up the p51d in Yasim was not my original > > > intention as Jon S. Berdnt was claiming at the time I > > > started the 3D that he had a nearly working JSBSim model. > > > Doing the yasim model was a juggling act that started with > > > geometric specifications, a couple software patch > > > submissions, and then an endless number of tweaks. The > > > "tweaks" were really comprimises that ended up producing > > > something that was sort of close to performance > > > specifications, but not really accurate in any respect. > > > > > > Best, > > > > > > Jim > > > > Thats litterally what I've just been doing with the B1900D > > FDM. > > > > The numbers in the FDM file don't all match up to the > > numbers in the POH but the FDM does now match with the > > *performance* figures in the POH - Which I hope is the right > > thing to aim for. > > The biggest tradeoffs seemed to be in trying to balance high > end performance, (e.g. altitude, speed) against having enough > drag to get reasonable behavior at lower power settings. It > seems pretty common for yasim models to glide too much > (excessive lift/insufficient drag) when cutting the power. > > Best, > > Jim
I've hit that lift/drag issue on just about all the a/c I've done. The degree varies but I mostly put it down to me not being any sort of aerodynamicist. Sometimes I wish for a more dynamic standalone solver so I could tweak the settings and see the results straight away. The gui would be massive though, and I'm not sure how the results could be visualised - a bunch of converging curves perhaps... LeeE _______________________________________________ Flightgear-devel mailing list [email protected] http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
