"Jon S. Berndt" <jonsber...@comcast.net> wrote: >> From: Martin Spott [mailto:martin.sp...@mgras.net]
>> BUT, basically, I'd say this is not the point at all - these are >> interesting theoretical approaches to the problem, but for the 'real' >> user who's getting veered off the apron while he is simply doing a >> proper run-up at a windy location, this is entirely irrelevant. > > If this is truly the case, and if it is due to a gear modeling fidelity > issue, then I agree. But, the kind of problem you describe would be a > different issue. Since wind effects are only ramped in as velocity > increases, the example you describe above should not happen with JSBSim. I just put the default Cessna at EDLN RWY 13 with parking brake applied, the wind is 11009KT. It took approx. three and a half minutes to let the aircraft slip backwards by the length of a main gear cover. And, _no_, don't even think of it ;-)) it's definitely _not_ a proper solution to work around such a case by clamping the aircaft to a fixed position as long the brakes are applied :-) >> Just for the sake of completeness: Think of a scenario on the carrier, >> you're approaching the catapult from behind .... oh, too far, you're >> idling the engine, letting the wind blow you backwards while you're >> slowly manoeuvering your aircraft right into the catapult position >> solely by nose wheel steering. That's what I call proper simulation of >> tire ground reactions. FlightGear _could_ do that - it they didn't >> depend decisions made at JSBSim. > JSBSim also does not (quite yet) do blade element modeling, so it's not easy > to do a proper snap roll. Nor do we model multiple articulated landing gear > struts. Nor do we ... As far as I can tell, nobody's asking JSBSim to do "blade element modeling" - to my opinion this is mostly a buzzword. Being able to fly an aircraft by table lookups derived from real life flight test data is quite an appealing approach. Instead, I'm talking about what I'd call a 'misfeature' to which a proper fix had already been submitted (years ago) and I'm convinced that you may apply as many workarounds, filters, whatever you like to the current gear/ground simulation, there'll be always a relevant corner case which remains uncaught as long as you stick to the current approach of gear modelling. I know that the patch which had been submitted to you uses a fundamentally different approach at modelling the tire/surface reactions and forces, but to my understanding this is by far the best way to get rid of the perpetually arising discussions about ground handling. > Apart from that, do you have a specific proposal in mind? My proposal is either to develop a copy of the FDM inside FlightGear and to focus primarily on FlightGear's needs (and to try getting a copy of the respective patch) or to have the changes applied to JSBSim's code tree and to later merge this into FlightGear. > We should move this to a new thread. Feel free to do that. From my point everything's been said - the sole purpose why I've actually been jumping into this discussion has been to dissect and/or explain the background which has led to the current situation wrt. gear/tire/surface modelling in JSBSim. I actually knew about it for a long time but I wanted to hear both sides. Cheers, Martin. -- Unix _IS_ user friendly - it's just selective about who its friends are ! -------------------------------------------------------------------------- ------------------------------------------------------------------------------ Create and Deploy Rich Internet Apps outside the browser with Adobe(R)AIR(TM) software. With Adobe AIR, Ajax developers can use existing skills and code to build responsive, highly engaging applications that combine the power of local resources and data with the reach of the web. Download the Adobe AIR SDK and Ajax docs to start building applications today-http://p.sf.net/sfu/adobe-com _______________________________________________ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel