[Sorry for the delay. I was out of town last week.] David Megginson wrote: > What can we do to prevent the over-eager wing drop in YASim? Is > there something we can change in the config files, or is it a C++ > code problem?
Barring bugs, this is a pure configuration problem. It sounds like there are two issues with the model. The first is that the asymmetry in wing stalls is too high, and that the stalls themselves are too viscious. The second is that it is too easy to put the aircraft into a stall in the first place. The second is the easiest to explain. From your description, it sounds like full elevator in the real plane puts the aircraft at an AoA just barely past the stall -- you feel the buffet, but don't lose much lift. This makes an awful lot of design sense to me, I'm sure they intended it that way. My guess is that the YASim elevator is capable of pulling the AoA well past stall, so you get nastier behavior. Try modifying the "flap" setting on the hstab (the effectiveness of the stabilizor flaps) until full elevator is just barely enough to acheive stall AoA. You are helped in this because (I think) the "approach" configuration in the file actually represents a stall. The solver prints out the elevator required to trim for approach in the solution report, make this as close to 1.0 as you can. This might be enough to fix your problem -- you could still get a viscious asymettric stall with violent control input, but gentle motion of the yoke wouldn't be able to pull the nose high enough. The problem with the stalls themselves should be fixeable with the stall subtag on the wing. There is a "width" parameter that controls the sharpness of the lift curve peak. It's roughly twice the radius of curvature of the top of the peak, in degrees (not exactly, because I'm using a cubic interpolant, but close enough). It's currently set to six, which I would think would be pretty gentle. But you could try a higher value and see what you get. Is it possible I have a unit bug in there? Another tunable you could play with is the "peak" number. This controls how high the "normal" lift peak is in relation to the more fundamental one at 45° generated by the underlying surface model. Setting this value higher results in a sharper lift drop past the stall. Lower values produce more gentle curves. I have *no* idea what the right value for this is; I haven't seen any data on wing lift though the full 360° of AoA. :) Andy -- Andrew J. Ross NextBus Information Systems Senior Software Engineer Emeryville, CA [EMAIL PROTECTED] http://www.nextbus.com "Men go crazy in conflagrations. They only get better one by one." - Sting (misquoted) _______________________________________________ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
