Curtis L. Olson wrote: > I have a lot of problems flying it well from the mouse. It doesn't > seem to respond well to elevator input ... you get an initial "bump" > and then pitch oscillations ... I don't know if that's realistic or > not. I'm sure Andy can provide a suitable explanation for why it does > this from a physics perspective, but I don't think the real airplane > behaves like this in real life.
I'm not sure I understand. A given stick position corresponds very closely to a given angle of attack. If you change the stick position, the aircraft will "seek" to the new AoA. If you change the stick position very rapidly, it will seek rapidly, overshoot, and oscillate. This is pretty normal behavior for all aircraft; but some "baby" (mostly military) consumer simulators aren't like this -- they map stick position to pitch *rate*, which is unphysical. Well, not quite unphysical: rather, coming up with a control system that did this would require gyros and fancy computers. The A-4 doesn't have those -- stick positions in traditional aircraft act like trim settings, they select for AoA. The differences from other YASim aircraft are that the A-4, as modelled, has a lot of elevator authority. So if you just yank the stick back, you'll end up in a nasty pitch oscillation with the nose tipping up well past 20 degrees. Just don't do that. Be gentle, and the aircraft won't oscillate. The added elevator authority is needed to effect high AoA combat maneuvers, but you can't use it all at once. Yanking on the stick in a 172 works just fine -- you're only transiting through a 5-10 degrees of pitch. Yanking the stick back on the A-4 tries to rotate the aircraft by 20-30 degrees, and is much less forgiving. I rather like this property, honestly. I've never tried to fly it with the mouse, but I could easily believe it would be difficult. But flown correctly, the aircraft moves smoothly and does nice things. You just can't yank it around the sky like a 172 -- I'm fairly confident that this is true of the real aircraft, too. Here's a really quick overview of my flight ops procedures in the current A-4, for those who want to try it. These are culled from tidbits I've found on the web, in books and on my own experience with YASim. They certainly shouldn't be taken as official Navy procedures. :) Takeoff: + No flaps. Full throttle. + At 145-160 knots*, apply about 1/2 elevator and raise the nose to 15-20 degrees. The aircraft will lift off. + Gear up. + Do not try to climb yet. Accelerate to ~300 knots** with no more than 5 degrees of climb, and then pull the nose up to 20 degrees or so. Trying to climb while slow requires high AoA's and bleeds energy rapidly. [* Depending on gross weight. I have a trial version at home that models the external stores, absolutely refuses to leave the ground sustainably at less than 210 knots when fully loaded, and handles like a royal pig. Dunno if this is correct or not, but it makes physical sense and is awfully fun to fly. You can map joystick buttons to "drop" the bombs and actually feel them release.] [** Military jets don't usually follow FAA speed regulations. They aren't built to fly that slow.] Landing: + Fly over the field at ~350 knots and ~1000ft AGL. + Chop throttle. Roll into a level, 2G turn to the downwind leg, decelerating to ~200 knots or so. This is called the "brake", because the aircraft will only decelerate quickly at high AoAs. Trying to line up for an approach at 350 knots and fly it like a civilian plane is a recipe for an overshoot. + Drop gear. Add full flaps gradually as the aircraft decelerates to 13.5 degrees AoA. The Navy doesn't fly approaches to speed, they track AoA. Add throttle to keep the aircraft level at 600-1000 ft. AGL. Try to get the aircraft trimmed at 10-12 degrees or so, to avoid having to push on the stick during final. + Turn onto final in one 180 degree turn, and land. Be *very* careful with the throttle. The aircraft decelerates quickly as you reduce thrust, and you can rapidly find yourself falling out of the sky at 110 kias. If you see speed dropping past 130 knots, jam the throttle to full. I find that at 20% fuel, the aircraft needs about 40-50% throttle to sustain 130 knots at 13.5 degrees. But speed management on the approach is really hard. It's really easy to get trapped in a throttle oscillation between too fast (pushing on the nose to keep the aircraft from balooning) and too slow (yikes! help! eject!). It may be that the flap drag is overmodelled. Another possibiliy is that the engines are spooling too slowly. I know that real skyhawks usually fly the approach with speed brakes out, so that the throttle is at a higher setting and can spool faster to maximum thrust. YASim doesn't have speedbrakes yet (although adding them would be really simple if someone wants them). 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
