Jim Wilson wrote: > Actually I tried all the way up to 80,000lbs and still ran into > problems in the 25000ft range. There is a little uncertaintly in just > what I'm observing. Basically there is a steady decrease in > attainable airspeed.
I found one bug. There was a property name typo* in David's changes that hooked the global environment into YASim. This resulted in all temeratures at runtime (but not at solution time) being exactly 0 degrees C. This is far too warm for the flight levels, which resulted in an air density that was significantly lower than it should have been. Effectively, the airplane was performing as it it were at a higher altitude than it was. This improves things a bit, as does the increase of thrust to 63737 pounds (we should probably check that number in, btw). I did discover, however, that the airplane has a very sensitive "back of the power curve" behavior. I had it trimmed for climb at about 230 kias (about 7 degrees of AoA), and topped out at a service ceiling of FL220. Gently easing down on the trim, I had it climbing at 500fpm again at 260 kias and 4 degrees. Then I had to go to bed, so I didn't get a complete set of numbers. But certainly "climbing too slow" is part of the problem here. You need to keep the AoA down to avoid burning all your thrust working against induced drag. Does anyone have good, hard climb numbers for this plane? I mean stuff like: "At NNN pounds gross weight, XXX feet MSL and YYY knots TAS, the 747-400 can climb at ZZZ feet per minute." My suspicion is that we're being bitten by a combination of bad performance numbers being fed to YASim, and bad pilot climb technique. Andy * "degC" instead of "degc". Norman, you can fire away at the lack of symbol safety in the property system. This is one circumstance where it's deserved. :) -- 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
