Lee Elliott <[EMAIL PROTECTED]> said:
> The B-52 is proving quite a tricky one to get right. Some of the > characteristics almost seem mutaully exclusive and it can be hard to > reconcile them. For example, I found max speeds of 554 kts @ 21000 ft and > 495 kts at 46500 ft but I can't get a working solution that'll climb that > high. Another characteristic is the take-roll & clearence for a fifty ft > obstacle these are 7000ft & 9100ft respectively, which is difficult to > reconcile with the speed and alt ratings. Yet another 'unusual' > characteristic are the flaps. These are pretty big but only have two > positions - fully deployed (35deg) or fully retracted, with no in-between > settings and can tend to produce huge pitch changes, which is the last thing > you want in a relatively under-powered a/c like the B-52 at low speed. > > In other words, I dunno why it's not stalling properly. > Try this (diffs to current CVS version): http://www.spiderbark.com/fgfs/b52.diff For some reason YASim isn't going to work with an approach AoA of 0.5...even if that is the correct figure. I'm not sure if the angle is supposed to include the wing incidence (which is considerable toward the tips). Set cruise close to where you want the ceiling and use full throttle. The way the solver works these aren't exactly real cruise figures but more like max performance figures. Also IIRC the approach help approximate stalls. My quick calcs show 26.0m for wing length. The aircraft has a 56m wingspan. I messed with a few other wing values...to get it closer to what it should be. Experiment with individual changes to see the results. IIRC you should target about 10 (5-20) for drag coefficient. 200 or less for LR and near -0.9 or so for approach elevator. I decreased stall AoA and width for the hstab. And finally I increased the thrust of the engines to 17,000lb max (B-52H). This configuration gets closer...about 34000ft. You might want to just overstate the thrust a little (think I read somewhere that they've actually used up to 8x22,000lb engines), as it doesn't seem anything else is really incorrect. Also, be careful to decrease vertical speed as you get higher. It is very easy to get behind the power curve at high altitude. Best, Jim _______________________________________________ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
