Ron Freimuth writes: > One thing MS developers have is access to a lot of real pilots. > Who can at least give some idea if an AC 'feels right'. All the > way to 747's.
That's harder than you might think: how a plane feels to the pilot depends as much on control loading as on responsiveness. For example, let's say that we're modelling a small plane (no hydraulics or fly-by-wire), and we know that with 25% up elevator deflection the nose pitches up at an initial rate of 4 degrees/second after an initial delay of 0.1 seconds -- we test our coefficients, and the behaviour of our model is exactly the same. A pilot familiar with that plane is almost certainly going to find it very unstable in the pitch axis, and complain that the nose bounces up and down too much. In the real plane, the dynamic pressure from the relative wind tends to hold the control surfaces in one spot, and it takes a bit of effort to move them from where they want to be (a *lot* of effort for a big deflection). A home-computer joystick or yoke might have a little spring in it, but in general, it's going to be far too easy for the computer user to create an elevator deflection, and the plane's going to feel unstable. There are two solutions to this problem (other than building a full, force-feedback console). One is to exaggerate the coefficients to make the nose more stable than it should be, but that sort-of sucks. The better solution -- which I stole from Andy Ross -- is to square the joystick axes (preserving sign), so that small joystick movements are less sensitive than large ones: -1.0 => -1.00 -0.5 => -0.25 0.0 => 0.00 0.5 => 0.25 1.0 => 1.00 Now, the pilot will have to move the joystick 50% of the way just to get a 25% elevator deflection, and a 10% joystick deflection will result in only a 1% elevator deflection, so the plane will seem more stable. This is still far from perfect, but it's better. > Further, they are good at scanning Flight Manuals that might be > hard to obtain otherwise. ;) We also have airline employees with > access for photographing cockpits etc. By hook and crook I also > managed to obtain a couple of Boeing Performance Engineering Manuals on > jet transports. One contains proprietary data on drags, lift, and > turbine matrices. We're in a different situation. I work from time to time as a consultant to a major aircraft manufacturer, helping to design and implement the system that produces their manuals (AMM, SRM, FIM/FRM, etc.), and at least one other developer is an employee of the same major manufacturer; we have other developers working with other aerospace companies as well. Obviously, we're not in any position to play with data that even gives the *appearance* of having been obtained illegally: our information has to be above suspicion. > I'll point more of the engineers fooling with MSFS to > sci.aeronautics. One works for 'a big AC company' and has copied > several aerodynamics books from their library. Classics such as > one by Whittle on turbines. I think I might start reading sci.aeronautics. Thanks. All the best, David -- David Megginson, [EMAIL PROTECTED], http://www.megginson.com/ _______________________________________________ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
