Re: [Flightgear-devel] FG/Opengc Interface
Andy Ross writes: The effect is happening because the aircraft isn't consuming fuel. If you take off at full tanks, you never get any lighter. A real aircraft would have burned off a big chunk of its fuel store in the climb, and would have an easier time of it. As a workaround, try starting /sim/fuelfraction at 0.5 or so, to simulate an early-to-mid-flight cruise condition. It should climb much better. Fuel consumption in YASim will get done RSN, I promise. That's a good point. I remember reading an article where the author sat in an A340 cockpit on a London-Vancouver flight; it wasn't until around Greenland that the plane had burned enough fuel that it could climb to full cruising altitude. All the best, David -- David Megginson [EMAIL PROTECTED] ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] FG/Opengc Interface
David Megginson [EMAIL PROTECTED] said: Andy Ross writes: The effect is happening because the aircraft isn't consuming fuel. If you take off at full tanks, you never get any lighter. A real aircraft would have burned off a big chunk of its fuel store in the climb, and would have an easier time of it. As a workaround, try starting /sim/fuelfraction at 0.5 or so, to simulate an early-to-mid-flight cruise condition. It should climb much better. Fuel consumption in YASim will get done RSN, I promise. That's a good point. I remember reading an article where the author sat in an A340 cockpit on a London-Vancouver flight; it wasn't until around Greenland that the plane had burned enough fuel that it could climb to full cruising altitude. Yes agreed. And probably with a 747-400 it is only those longer flights like London-Vancouver that get filled to the brim with fuel. Andy, is the aircraft otherwise considered filled to capacity (passenger/cargo) in the fdm? Best, Jim ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] FG/Opengc Interface
Jim Wilson wrote: Yes agreed. And probably with a 747-400 it is only those longer flights like London-Vancouver that get filled to the brim with fuel. Andy, is the aircraft otherwise considered filled to capacity (passenger/cargo) in the fdm? Um... I'm not sure. :) The configured empty weight is 400k lbs, but I didn't record where I got that number. I'd assume that this is really the empty weight, not including payload. YASim has a weight tag that can be used to provide software control over payload via the properties system, which would obviously be the right way to do this. I guess I'll assume that I did the right thing... The issue of flat-rating the engines has been nagging me, too. I strongly suspect this is at least part of the effect; does anyone have numbers that would support this? Implementing this would be really easy; analagous to the way the turbocharger waste gate gets handled in the piston engine model. It would also be a spiffy way of handling the supersonic over-speed behavior the engine model has at high speeds (the mach compression of the intake air is modelled, but the losses due to intake geometry are not). Andy -- Andrew J. RossNextBus 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
Re: [Flightgear-devel] FG/Opengc Interface
On Mon, 25 Feb 2002 08:33:03 -0500, David Megginson [EMAIL PROTECTED] wrote in message [EMAIL PROTECTED]: Andy Ross writes: The effect is happening because the aircraft isn't consuming fuel. If you take off at full tanks, you never get any lighter. A real aircraft would have burned off a big chunk of its fuel store in the climb, and would have an easier time of it. As a workaround, try starting /sim/fuelfraction at 0.5 or so, to simulate an early-to-mid-flight cruise condition. It should climb much better. Fuel consumption in YASim will get done RSN, I promise. That's a good point. I remember reading an article where the author sat in an A340 cockpit on a London-Vancouver flight; it wasn't until around Greenland that the plane had burned enough fuel that it could climb to full cruising altitude. ..another point you guys may be aware of, is that some jets (military only?) tank _cold_ (40-50 Centigrades below zero) fuel, this allows burning off fuel as it expands on heating up to tank temperature, so these jets arrive at mission target altitude with still full tanks. -- ..med vennlig hilsen = with Kind Regards from Arnt... ;-) Scenarios always come in sets of three: best case, worst case, and just in case. ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] FG/Opengc Interface
On Mon, 25 Feb 2002 16:17:29 -0500, David Megginson [EMAIL PROTECTED] wrote in message [EMAIL PROTECTED]: Arnt Karlsen writes: ..another point you guys may be aware of, is that some jets (military only?) tank _cold_ (40-50 Centigrades below zero) fuel, this allows burning off fuel as it expands on heating up to tank temperature, so these jets arrive at mission target altitude with still full tanks. You wouldn't want to do that with civil jets -- imagine a 747's wing tanks exploding because it got stuck in an hour-long line for takeoff and the fuel heated up too soon. ..well, I'm only 99% sure about military only. ;-) -- ..med vennlig hilsen = with Kind Regards from Arnt... ;-) Scenarios always come in sets of three: best case, worst case, and just in case. ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] FG/Opengc Interface
Certainly not, when it's gross weight is 800k lbs. :) The weight you quote is close to the zero-fuel weight, which is typical for landing. By default, YASim will top your tanks off at startup. The plane in this condition will indeed have a very high approach speed. Try setting the /sim/fuel-fraction property to something like 0.2 for a reasonable approach configuration. DUH!! (sound of slapping) I knew that! ;-) I should find that fuel property and send it across to the displays. Your problems with the lack of elevator authority seem real, though. You could try tuning the effectiveness property of the hstab definition, like so: hstab ... effectiveness=2 !-- Give it 2x as much force per surface area -- I'm not sure what the AoA produced by max back-yoke in a 747 is. It looks like the YASim model tops out at around 16 degrees, which is probably not enough. Heavies are not my forte either, but a little more complexity and avionics to work on. the idea is to learn, so pick your favorite and enjoy. Any thoughts on my query regards gear/flap actuation times? And how to access the same. Regards John W. ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] FG/Opengc Interface
John Wojnaroski [EMAIL PROTECTED] said: Certainly not, when it's gross weight is 800k lbs. :) The weight you quote is close to the zero-fuel weight, which is typical for landing. By default, YASim will top your tanks off at startup. The plane in this condition will indeed have a very high approach speed. Try setting the /sim/fuel-fraction property to something like 0.2 for a reasonable approach configuration. DUH!! (sound of slapping) I knew that! ;-) IIRC the 747-400 comes down pretty fast anyway. I think you're looking at 195 KIAS range for final dropping down to 175 KIAS (with full flaps) at the outer marker. But note again, this is from memory. Still, there is no way that pig flies at 150. The biggest problem I saw with that model was the issue it had with climbing (ran out of climb speed at too low an alititude). IIRC it should climb at least 500fpm even above 30,000. Has that problem been addressed? Best, Jim ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] FG/Opengc Interface
Hi, IIRC the 747-400 comes down pretty fast anyway. I think you're looking at 195 KIAS range for final dropping down to 175 KIAS (with full flaps) at the outer marker. But note again, this is from memory. Still, there is no way that pig flies at 150. The biggest problem I saw with that model was the issue it had with climbing (ran out of climb speed at too low an alititude). IIRC it should climb at least 500fpm even above 30,000. Has that problem been addressed? It still appears to be underpowered, tops out at around FL230 @ 315KIAS. I've got some very good performance numbers and an authoritative source, but just a little reticent to mess around with someone else's code and design plus, like most of us, a limited time budget and other priorities... But I will make the changes suggested by Andy and report back on the results. ATM, it is good enough to drive the displays which is my focus for now, but it would be nice to have the capability to shoot a more representative descent, approach, and landing. Regards John W. ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] FG/Opengc Interface
Jim Wilson wrote: IIRC the 747-400 comes down pretty fast anyway. I think you're looking at 195 KIAS range for final dropping down to 175 KIAS (with full flaps) at the outer marker. But note again, this is from memory. Still, there is no way that pig flies at 150. The biggest problem I saw with that model was the issue it had with climbing (ran out of climb speed at too low an alititude). IIRC it should climb at least 500fpm even above 30,000. Has that problem been addressed? I looked at it, and essentially decided that it's Not A Bug. :) It's fairly easy to verify via properties that the engines are producing an appropriate thrust. At altitude, the available thrust decreases roughly with the air density, which is exactly what you should see. The effect is happening because the aircraft isn't consuming fuel. If you take off at full tanks, you never get any lighter. A real aircraft would have burned off a big chunk of its fuel store in the climb, and would have an easier time of it. As a workaround, try starting /sim/fuelfraction at 0.5 or so, to simulate an early-to-mid-flight cruise condition. It should climb much better. Fuel consumption in YASim will get done RSN, I promise. You could also try tweaking the maximum thrust a little; it may be that the real engines are flat-rated below some altitude, and have more thrust available than their rating would suggest. As before, reference to real documentation would be great; I'm a code jockey, not a research goon. :) Andy -- Andrew J. RossNextBus 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
Re: [Flightgear-devel] FG/Opengc Interface
I tried downloading OpenGC stuff, but http://opengc.sf.net/ seems to be dead (might be temporarily, though). Is the FG related stuff under that same address (I recall it was integrated, right?) or somewhere else? Try http://www.opengc.org. If the problem persists, I can upload a package to the kingmont site. there is a bit of a glitch with the CVS. In the FMC directory the Makefile.am was moved to the atttic, and a new version is being rejected by CVS. You need to have/install the freetype and ftgl/gltt font libraries also. The build process is not as slick as FG's but getting better... Regards John W. ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] FG/Opengc Interface
John Wojnaroski wrote: On the 747 YASim model, have not been able to slow to a resonable approach speed 150kts and maintain altitude, run out of elevator authority around 184 kts and flap settings seem to have no effect. The numbers I have in my 747 flight manual don't match up with what I'm seeing in the sim. For example, for 450k lbs, landing speed at full flap/slat setting is 128kts. It won't fly at that speed! Certainly not, when it's gross weight is 800k lbs. :) The weight you quote is close to the zero-fuel weight, which is typical for landing. By default, YASim will top your tanks off at startup. The plane in this condition will indeed have a very high approach speed. Try setting the /sim/fuel-fraction property to something like 0.2 for a reasonable approach configuration. Your problems with the lack of elevator authority seem real, though. You could try tuning the effectiveness property of the hstab definition, like so: hstab ... effectiveness=2 !-- Give it 2x as much force per surface area -- I'm not sure what the AoA produced by max back-yoke in a 747 is. It looks like the YASim model tops out at around 16 degrees, which is probably not enough. Or any of the reference landing speeds for that matter. Realize the model is not intended to be *right-on*, but closer would be nice. (Using the 0.7.9 official release) Undeniably. Unfortunately, the only way to get it closer is to have people work on and provide feedback for the models. I'll freely admit that I don't spend much time in the 747 model, because big jets don't push my buttons. Andy -- Andrew J. RossNextBus 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
Re: [Flightgear-devel] FG/Opengc Interface
Andy Ross writes: Undeniably. Unfortunately, the only way to get it closer is to have people work on and provide feedback for the models. I'll freely admit that I don't spend much time in the 747 model, because big jets don't push my buttons. Jim Brennan, could probably rattle off 747 performance numbers all day long for you if you want (or at least know where / how to look them up.) I'm sure hey wouldn't mind seeing the 747 model improved. Regards, Curt. -- Curtis Olson IVLab / HumanFIRST Program FlightGear Project Twin Cities[EMAIL PROTECTED] [EMAIL PROTECTED] Minnesota http://www.menet.umn.edu/~curt http://www.flightgear.org ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] FG/Opengc Interface
On Saturday 23 February 2002 10:24 pm, you wrote: Andy Ross writes: Undeniably. Unfortunately, the only way to get it closer is to have people work on and provide feedback for the models. I'll freely admit that I don't spend much time in the 747 model, because big jets don't push my buttons. Jim Brennan, could probably rattle off 747 performance numbers all day long for you if you want (or at least know where / how to look them up.) I'm sure hey wouldn't mind seeing the 747 model improved. Regards, Curt. There may be stuff already up on ftp.kingmont ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] FG/Opengc Interface
Andy Ross writes: Undeniably. Unfortunately, the only way to get it closer is to have people work on and provide feedback for the models. I'll freely admit that I don't spend much time in the 747 model, because big jets don't push my buttons. Jim Brennan, could probably rattle off 747 performance numbers all day long for you if you want (or at least know where / how to look them up.) I'm sure hey wouldn't mind seeing the 747 model improved. Jim ran off some performance data for me which I posted a while back , but I did not try to mess with the code hoping the authors would do a much better job of tweaking the params. Regards John W. ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
