Menu
▾
▴
RE: [Jsbsim-devel] C-172 Performance --- More comments
|
From: Bill G. <bi...@ao...> - 2004-10-14 19:00:47
|
Bravo! Bill > -----Original Message----- > From: jsb...@li... > [mailto:jsb...@li...] On Behalf > Of Gregory Pierson > Sent: Thursday, October 14, 2004 12:19 PM > To: jsb...@li... > Subject: Re: [Jsbsim-devel] C-172 Performance --- More comments > > > David > > > > No offense, but this attitude will doom JSBSim to failure. > > > > When you start using excuses to lower the quality of your > input data, doesn' t it invalidate all the high quality > equations in JSBSim all of you have worked so hard on? > > > > Realistically, 90% of JSBSim's input parameters effect less > than +/- 1% of the aircraft's performance. So why use them then? > > > > Both Ron and myself have created a lot of FS flight models. > We found it really does pay off if you try to carry as high a > precision as possible. The end product will really show this > when your user flies it. We've also seen products with a "we > don't need that much precision" that have been total disasters. > > > > Ron and myself go to extreme lengths to make the input data > as accurate as possible. The people that fly our FS aircraft > can tell the difference. If I release a P-51 that does 436mph > instead of 437 at 25,000ft the users will scream. My > competition uses Cessna stability derivatives for all their > fighters, we try to calculate the aircraft's true stability > derivatives. The users can and do feel the difference. But > the real pay dirt is when they fly against each other online > and start complaining about the same issues the real pilots > experienced when flying these aircraft. > > > > The point I'm trying to make is the JSBSim developers need to > aim high. If they want JSBSim to gain wider acceptance, > possibly create a cottage industry for JSBSim consultants or > used in a retail product, their attitude has to always be to > go that extra mile with their data. > > > > Just my two cents from the cheap seats > > > > Gregoryp > > > > > > ----- Original Message ----- > From: "David Megginson" <dav...@gm...> > To: <jsb...@li...> > Sent: Thursday, October 14, 2004 4:28 AM > Subject: Re: [Jsbsim-devel] C-172 Performance --- More comments > > > > On Wed, 13 Oct 2004 21:12:00 -0500, Ron Freimuth > > <ron...@at...> > wrote: > > > > > As far as 'accuracy goes', I'd disagree that ones flight model > doesn't > > > have to be that accurate, 'since real AC vary all over > the place'. > Seems > > > to me that a good flight model should represent the ideal > AC. One > > > fresh > out > > > of the factory. Not one misrigged, with inaccurate instruments, > > > etc. Ideally, a pilot could compare an accurate PC AC > with what he > > > flies. > And > > > see how much has real AC has deteriorated from a factory fresh > > > model. > > > > My point was slightly different -- I'm suggesting that we try to > > choose an appropriate precision for our sample. For example, my > > height probably changes by as much as 5 mm from morning to > evening, so > > there's no point measuring it to within 0.0001 mm, or even > 0.1 mm. Two > > brand-new planes straight off the assembly line are still going to > > handle differently, so even in the best case, there's no point > > measuring more accurately than the likely variation between them. > > > > As a pilot, you must notice this problem with flight training -- > > student pilots have to plan a cross-country predicting our exact > > cross-wind correction, to the degree, our exact groundspeed, to the > > knot, and our exact ETA at each checkpoint, to the second. That's > > good practice in using the E6B, of course, and it's a good > reminder to > > be aware of winds aloft for fuel management, but it has > very little to > > do with actually flying a plane cross-country. I've never seen the > > winds aloft *exactly* the same as forecast, and as you > mentioned, the > > plane becomes lighter as it goes anyway, so your TAS at the > end of a > > 3-4 hour leg is going to be a few knots higher than your TAS at the > > start. > > > > > > All the best, > > > > > > David > > > > -- > > http://www.megginson.com/ > > > > > > ------------------------------------------------------- > > This SF.net email is sponsored by: IT Product Guide on > > ITManagersJournal Use IT products in your business? Tell us > what you > > think of them. Give us Your Opinions, Get Free ThinkGeek Gift > > Certificates! Click to find out > more > > http://productguide.itmanagersjournal.com/guidepromo.tmpl > > _______________________________________________ > > Jsbsim-devel mailing list > > Jsb...@li... > > 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: IT Product Guide on > ITManagersJournal Use IT products in your business? Tell us > what you think of them. Give us Your Opinions, Get Free > ThinkGeek Gift Certificates! Click to find out more > http://productguide.itmanagersjournal.com/guid> epromo.tmpl > > _______________________________________________ > > Jsbsim-devel mailing list > Jsb...@li... > https://lists.sourceforge.net/lists/listinfo/jsbsim-devel > _______________________________________________ > The JSBSim Flight Dynamics Model project > http://www.JSBSim.org _______________________________________________ > > |
