On 11/22/2007 12:59 PM, Jon S. Berndt wrote: > .... What happens if > the combined moment on the vehicle and the translational force causes only > one gear to go past its ability to hold traction on the ground?
Well, that's pretty far down on the priority list, but since you asked: That happens sometimes. It happens more often than I would like, but it happens. For example, suppose the student pilot applies the brakes too much and/or unevenly. The result is that the aircraft turns like crazy. This is a good recipe for a ground-loop. This is particularly nasty because the instructor's options are limited. The instructor cannot un-apply the brakes. (This stands in unpleasant contrast to, say, the student pulling on the yoke; the instructor at least has a fighting chance of pushing on the yoke so as to overpower the student.) Much higher on the priority list are -- parking with the parking brake set and not slipping under ordinary non-extreme conditions. -- Weathervaning (yaw and roll) during taxi and during the initial takeoff run. > When you > start programming this to take care of the general case, it just gets out of > hand. Maybe it would help to talk to the CDM guys instead of the FDM guys. http://www.google.com/search?q=car-dynamics-model http://www.google.com/search?q=car-dynamics-model+nascar I reckon the car-dynamics guys have a pretty good model of static friction and quasi-static rolling friction. After all, that is their raison d'être. Whatever they've got is surely more than good enough for our purposes. > it did occur to me that it should be possible to use one set > of data to do gear modeling, and another set to report values (such as > sideslip) for instrumentation. That's a very reasonable compromise for the interim. The airspeed vector (i.e. relative wind vector) exposed via the public interface (i.e. the property tree) should be the honest-to-goodness airspeed, including nature's wind, even while parked. If the FDM finds it convenient to use some notion of "pseudo-wind" as part of a scheme to avoid modeling the ground/tire interaction, then that should be kept strictly separate ... and maybe kept private, internal to the FDM. ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2005. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
