Re: [Flightgear-devel] YASim solution solution?
OK, I've examined the jet code a bit more closely, and it actually looks pretty good to me. Attached is a graph of available thrust vs. speed and altitude for the engines as modelled on the 747-400. I threw together a little program that looped over the Jet object, and played with gnuplot's really nifty contour feature a bit. (Apologies for the binary attachment -- it's only 9k, which puts it right at the border of acceptability, IMHO). This may or may not have anything to do with the jet code, but with the 747-yasim, I cannot slow the plane below about 280kt in level flight at 3000ft ASL with throttles at minimum and full flaps, which makes the plane rather hard to land... This is just an observation, I'm not a pilot, please forgive me if I'm talking total nonsense... Andras === Major Andras e-mail: [EMAIL PROTECTED] www:http://andras.webhop.org/ === ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] DC-3 takeoff roll: partial solution
You started up the engines, firewalled the throttle, let the RPMs stablize, released the brakes, and the aircraft pitched *up*??? That's clearly unphysical. Why ? The nose pitches down with power and brake application. So, releasing the brakes makes the nose pitch up. Not immediately, the aircraft pitches up after rolling for a few seconds. I think the main problem really is the rapid increase in airspeed, which is unnatural, and doesn't occur if both engines are used. Actually, it diverges for some reason, I just made another test and ended up with an aircraft at 35 deg, some roll to the right, and 1346kt! This is a few seconds after turning one engine on, running it at full speed, and releasing the brakes. No flaps, all controls centred. Andras === Major Andras e-mail: [EMAIL PROTECTED] www:http://andras.webhop.org/ === ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] DC-3 ground handling. Fixed?
Andy, Bingo. This is a bug in the propeller code; I apparently introduced a FPU explosion when the thing is going backwards. It has nothing to do with the aero or ground modelling, so I was looking in the wrong place. I'll get this fixed. (I'm pretty sure it used to work -- I remember doing hammerhead stalls in the A-4 when testing). Sorry I only realized this just before I actually mentioned it. I used to test in a from-the-back view, in which the window goes black when the divergence happens, I had to test it again with the normal out-of-the-cockpit view to see the 1000kt+. Really? When I tried it, I couldn't turn against the tail wheel at all, even with full braking applied. The tail wheel didn't move until 50 kts or so when it lifted; then the plane became squirrely, as might be expected. Under what conditions did you see that behavior? If it's sliding at speed, are you absolutely sure that's wrong? I can confirm this, the plane moves straight whatever you do as long as the tailwheel stays on the ground. This is definitely far closer to reality than the free swinging we had before. Modeling skidding and sliding friction would be more realistic, but not that important. Thanks for sorting this out so quickly, I will investigate the problems more thoroughly next time... Andras === Major Andras e-mail: [EMAIL PROTECTED] www:http://andras.webhop.org/ === ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] DC-3 ground handling. Fixed?
OK, I found an explosion case in the propeller code which could be triggered by a propeller turning backwards very slowly. That's pretty much consistent with a aircraft with a stopped engine, so I'm hopefully this is it. It's been checked in (this was obvious enough to check in based on code inspection only), so see if this fixes your problem. It does. I make no promises about actually getting off the ground successfully on one engine, however. :) I managed to do it (once), but I wouldn't like to be a passenger on that plane. Also, I can't reproduce the spinning problem, seems like your prop patch did the job. Thanks a lot! Andras === Major Andras e-mail: [EMAIL PROTECTED] www:http://andras.webhop.org/ === ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] DC-3 takeoff roll: partial solution
Andy, CAUTION: THE TAIL WHEEL LOCK MUST BE LOCKED DURING TAKE OFF AND LANDING. Sounds like good advice to me. I'm not at home right now; can someone remove the castering setting from the dc3.xml file and try it? If this is the solution, then I'll add a property-based control for castering tonight. Works, but isn't perfect. At least I can take off now, but if I try to use only one engine, the aircraft soon pitches up and crashes with the front wheels still on the ground, the tail stuck on the tarmac. Two engines work fine, though. Andras === Major Andras e-mail: [EMAIL PROTECTED] www:http://andras.webhop.org/ === ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] DC-3 takeoff roll: partial solution
Andy, I just made two recordings of flights with the DC3, but can't play them back because fgfs segfaults. I can put them on the web if that helps (maybe even to debug the segfault...). Andras === Major Andras e-mail: [EMAIL PROTECTED] www:http://andras.webhop.org/ === ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] DC-3 takeoff roll: partial solution
but if I try to use only one engine, the aircraft soon pitches up and crashes with the front wheels still on the ground, the tail stuck on the tarmac. Two engines work fine, though. But here you've lost me. Normally, the aircraft state with all three wheels on the ground is not called a crash. :) Sorry, sorry, that should have read tail stuck IN the ground. Attached screenshot taken within 3sec after releasing brakes, after this, the plane pitches up even more, and fgfs hangs, moaning about terrain intersections. Maybe it's the two fronts wheels taking off rather than the tailwheel being buried, but in any case airspeed builds up much too quickly. Sorry for the confusion. Andras === Major Andras e-mail: [EMAIL PROTECTED] www:http://andras.webhop.org/ === attachment: dc3-1engine.jpg
Re: [Flightgear-devel] DC-3 takeoff roll: partial solution
but if I try to use only one engine, the aircraft soon pitches up and crashes with the front wheels still on the ground, the tail stuck on the tarmac. Two engines work fine, though. But here you've lost me. Normally, the aircraft state with all three wheels on the ground is not called a crash. :) Sorry, sorry, that should have read tail stuck IN the ground. Attached screenshot taken within 3sec after releasing brakes. Sorry for the confusion. Andras === Major Andras e-mail: [EMAIL PROTECTED] www:http://andras.webhop.org/ === attachment: dc3-1engine.jpg
