Re: [Flightgear-devel] YF-23/yasim: how to climb to 163000 ft
Joacim Persson wrote:
> #1 (below) is a call to localWind for the thruster calculations, only the
> thruster
> altitude is NAN.
>
> "_global_ground" are all NAN:s too. But I think by then, my insane turns had
> become insane loopings. (Hard to tell with the view flipping around like
> that.) I can't see where the NAN value of _global_ground came from, from a
> stack backtrace, so the lead ends there.
>
Hi Joacim,
to find the line, where the NAN is generated you can easily switch on
the floating point exceptions while the FDM is calculating.
e.g. for windows:
file model.cpp in FDM/YASim:
add
#include
#include
and change the function void Model::iterate():
void Model::iterate()
{
_clearfp();_controlfp(
0|_EM_INEXACT|_EM_INVALID|_EM_UNDERFLOW/*|_EM_OVERFLOW|_EM_DENORMAL*/,
_MCW_EM );
initIteration();
initRotorIteration();
_body.recalc(); // FIXME: amortize this, somehow
_integrator.calcNewInterval();
_clearfp(); // always call _clearfp before enabling/unmasking a FPU
exception
_controlfp( _MCW_EM , _MCW_EM );
}
for an other compiler it should be similar (in bootstrap.cxx you can
find some examples).
Maik
Maik
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Re: [Flightgear-devel] YF-23/yasim: how to climb to 163000 ft
On Tue, 8 Aug 2006, Lee Elliott wrote:
> I think there's now a patch in for the engine problem - don't
> know if it fixes everything though.
Well it changed the behaviour somewhat. No more negative FF et al values.
It still accelerates like mad in extreme turns but now we get a SIGSEGV
clue. I got this SIGSEGV three times in a row in the same manner as for the
negative FF effect, so it seems to be reproducable.
#1 (below) is a call to localWind for the thruster calculations, only the
thruster
altitude is NAN. The altitude comes from the lines just
before the for-loop. (yasim::Model::initIteration, Model.cpp line 100 and on)
// Need a local altitude for the wind calculation
float lground[4];
_s->planeGlobalToLocal(_global_ground, lground);
float alt = Math::abs(lground[3]);
"_global_ground" are all NAN:s too. But I think by then, my insane turns had
become insane loopings. (Hard to tell with the view flipping around like
that.) I can't see where the NAN value of _global_ground came from, from a
stack backtrace, so the lead ends there.
On the other hand it's perfectly reasonable that altitude becomes a NAN
under those circumstances -- the aircraft bloody should disintegrate under
that kind of stress. So maybe it isn't a bug after all, rather a realistic
simulation of a massive structural failure due to severe overspeed and
exceeded G limit. ;) ("Altitude?" ...of debris and fumes you mean?)
Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 16384 (LWP 9871)]
0x0825a3b8 in yasim::Turbulence::getTurbulence (this=0xa806678, loc=0x0,
alt=nan(0x40),
up=0xbfffed60, turbOut=0xbfffedb0) at Turbulence.cpp:100
100 static inline float c2fu(unsigned char c) { return (c+0.5)*(1.0/256); }
(gdb) bt
#0 0x0825a3b8 in yasim::Turbulence::getTurbulence (this=0xa806678, loc=0x0,
alt=nan(0x40),
up=0xbfffed60, turbOut=0xbfffedb0) at Turbulence.cpp:100
#1 0x0824fcb5 in yasim::Model::localWind (this=0x9c1222c, pos=0xbfffee40,
s=0x9c1223c,
out=0xbfffee30, alt=nan(0x40)) at Model.cpp:544
#2 0x0824e923 in yasim::Model::initIteration (this=0x9c1222c) at Model.cpp:111
#3 0x0824eb00 in yasim::Model::iterate (this=0x9c1222c) at Model.cpp:163
#4 0x08244baa in yasim::FGFDM::iterate (this=0x9c12228, dt=0.0083377) at
FGFDM.cpp:92
#5 0x0823dab7 in YASim::update (this=0xa92fae0, dt=0.01524188350679) at
YASim.cxx:217
#6 0x080520bd in fgUpdateTimeDepCalcs () at main.cxx:163
#7 0x08052cb6 in fgMainLoop () at main.cxx:488
#8 0x08087492 in GLUTidle () at fg_os.cxx:124
#9 0x400a5929 in __glutRegisterEventParser () from /usr/X11R6/lib/libglut.so.3
#10 0x400a60ad in glutMainLoop () from /usr/X11R6/lib/libglut.so.3
#11 0x0805582b in fgMainInit (argc=2, argv=0xb464) at main.cxx:1021
#12 0x08051a86 in main (argc=2, argv=0xb464) at bootstrap.cxx:203
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Re: [Flightgear-devel] YF-23/yasim: how to climb to 163000 ft
On Tuesday 08 August 2006 12:08, Joacim Persson wrote: > On Tue, 8 Aug 2006, Lee Elliott wrote: > > Thanks for posting this observation - this is clearly a bit > > wacky (not that accelerating w/o +energy wasn't) - can you > > reproduce it? > > Now that I tested it again, I saw however that the FF number > didn't fall over from a high number to a negative, but > decreased to zero first. Same goes for N1. But it happens > quite suddenly. > > KSFO "Fair weather", Noon. 2D mini-panel on. Full throttle (no > AB, no flaps or slats). Take-off. Gear up and climb to 1000'. > Bank 90° and pull the stick all the way back. After a while > the engine sound suddenly changes to a low thunder and not > only FF goes negative, but so does N1 and EGT. (I don't think > N2 did though) Tank fills up and overfills quickly. FF is > *very* negative. The number runs off-screeen. If you get too > much altitude the phenomenon stops. Stay low; below 5000', at > 1000' or so ...without crashing into anything -- which isn't > that easy to avoid in 70G mach 3 turns. If you ease off > throttle, you get the reported phenomenon with insane speed > instead. (mach 8 and 300G). AoA seems to stay at about 16°. > > Apparently the "magical energy" doesn't come from increased > mass -- FF is near zero (and positive) with zero throttle and > mass doesn't increase. My guess is that this is a bug in the > yasim jet engine code somewhere. One of these one-liners that > are so hard to find. ;) But at least it's easy to reproduce. I think there's now a patch in for the engine problem - don't know if it fixes everything though. LeeE - Using Tomcat but need to do more? Need to support web services, security? Get stuff done quickly with pre-integrated technology to make your job easier Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642 ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] YF-23/yasim: how to climb to 163000 ft
On Tue, 8 Aug 2006, Lee Elliott wrote: Thanks for posting this observation - this is clearly a bit wacky (not that accelerating w/o +energy wasn't) - can you reproduce it? Now that I tested it again, I saw however that the FF number didn't fall over from a high number to a negative, but decreased to zero first. Same goes for N1. But it happens quite suddenly. KSFO "Fair weather", Noon. 2D mini-panel on. Full throttle (no AB, no flaps or slats). Take-off. Gear up and climb to 1000'. Bank 90° and pull the stick all the way back. After a while the engine sound suddenly changes to a low thunder and not only FF goes negative, but so does N1 and EGT. (I don't think N2 did though) Tank fills up and overfills quickly. FF is *very* negative. The number runs off-screeen. If you get too much altitude the phenomenon stops. Stay low; below 5000', at 1000' or so ...without crashing into anything -- which isn't that easy to avoid in 70G mach 3 turns. If you ease off throttle, you get the reported phenomenon with insane speed instead. (mach 8 and 300G). AoA seems to stay at about 16°. Apparently the "magical energy" doesn't come from increased mass -- FF is near zero (and positive) with zero throttle and mass doesn't increase. My guess is that this is a bug in the yasim jet engine code somewhere. One of these one-liners that are so hard to find. ;) But at least it's easy to reproduce.- Using Tomcat but need to do more? Need to support web services, security? Get stuff done quickly with pre-integrated technology to make your job easier Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] YF-23/yasim: how to climb to 163000 ft
On Monday 07 August 2006 18:36, Melchior FRANZ wrote: > * Lee Elliott -- Monday 07 August 2006 02:16: > > Can you reproduce it while under control of the A/P? That > > should help me reproduce it here. > > Didn't try. It's really easy to reproduce when you follow the > instructions. I don't think the AP is involved in any way. > > m. Hi M, it wasn't that I thought that the A/P might be involved in the problem but just that it would make it easier to reproduce. It's just that scripted flights are more consistent. LeeE - Using Tomcat but need to do more? Need to support web services, security? Get stuff done quickly with pre-integrated technology to make your job easier Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642 ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] YF-23/yasim: how to climb to 163000 ft
On Monday 07 August 2006 11:50, Joacim Persson wrote: > On Fri, 4 Aug 2006, Curtis L. Olson wrote: > > Based on my understanding of YASim, this has to be some sort > > of bug in the core yasim code since it's getting energy from > > nowhere. Might be some sort of numerical/roundoff issue, > > perhaps some of the code in YAsim makes > > assumptions/simplifications that start to break down at > > extremely high alpha angles? > > I've seen the fuel flow meter (2D panel on) go *negative* at > supersonic speed and extremely high G turns (like 50G and > beyond) at low altitude. It actually fills up the tank. ;) So > it do seem to be some sort of type/typecast mixup. (Magically > add mass at speed and you increase kinetic energy.) Thanks for posting this observation - this is clearly a bit wacky (not that accelerating w/o +energy wasn't) - can you reproduce it? LeeE - Using Tomcat but need to do more? Need to support web services, security? Get stuff done quickly with pre-integrated technology to make your job easier Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642 ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] YF-23/yasim: how to climb to 163000 ft
* Lee Elliott -- Monday 07 August 2006 02:16: > Can you reproduce it while under control of the A/P? That should > help me reproduce it here. Didn't try. It's really easy to reproduce when you follow the instructions. I don't think the AP is involved in any way. m. - Using Tomcat but need to do more? Need to support web services, security? Get stuff done quickly with pre-integrated technology to make your job easier Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642 ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] YF-23/yasim: how to climb to 163000 ft
On Fri, 4 Aug 2006, Curtis L. Olson wrote: > Based on my understanding of YASim, this has to be some sort of bug in > the core yasim code since it's getting energy from nowhere. Might be > some sort of numerical/roundoff issue, perhaps some of the code in YAsim > makes assumptions/simplifications that start to break down at extremely > high alpha angles? I've seen the fuel flow meter (2D panel on) go *negative* at supersonic speed and extremely high G turns (like 50G and beyond) at low altitude. It actually fills up the tank. ;) So it do seem to be some sort of type/typecast mixup. (Magically add mass at speed and you increase kinetic energy.) - Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys -- and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] YF-23/yasim: how to climb to 163000 ft
On Friday 04 August 2006 15:26, Melchior FRANZ wrote: > * Curtis L. Olson -- Friday 04 August 2006 15:34: > > I will point out that while it's possible to force the YF-23 > > into this extreme state, if you fly it in a more normal > > range, it behaves pretty normally. > > Not for me. I actually noticed the problems during "normal" > flight. I chased the KA6 and, because (unlike in real life) > there's no indication how far it's still away, I was a tad too > fast when I noticed it coming nearer and nearer. I tried to > fly some narrow curves, but unlike in all other fgfs aircraft, > this didn't decelerate, but *accelerate*. > > Of course, I'm not a pilot, and in real life there'd be a FCS > with g-limiter, and my body would warn me earlier, too, but > that's no excuse. Unfortunately, we don't have a single > halfway modern fighter in fgfs, that is not totally broken. > The F16 is pathetic and unusable since JSBSim 2.0. The > hunter/seahawk work nicely, but aren't exactly modern. > > > So personally I think the YF-23 is a pretty fun plane to > > fly, even if it isn't 100% perfect. > > Sorry, no offense to Lee -- it's still very well done 3D model > wise, but I find it a bit embarrassing to show off in the > NTPS. I'm not even sure if this is an old bug or if it's > caused by later YASim changes. I don't remember ever having > seen such unrealistic behavior, and I used to fly the YF23 a > lot at times. > > m. Hi Melchior, been out or watching Tintin movies all weekend but I have been following this thread. I haven't flown the YF-23 for a long time but I spent ages on it when I first did it and don't recall ever seeing this behaviour. This isn't to say that it doesn't happen of course - I seem to be the only person who has problems with the weather/altitude settings behaving randomly. Anyway, I just checked the output from the stand-alone solver and there doesn't seem to be anything suspicious in it: Solution results: Iterations: 530 Drag Coefficient: 14.044194 Lift Ratio: 160.218765 Cruise AoA: 0.343368 Tail Incidence: -0.639466 Approach Elevator: -0.593619 CG: -1.609, 0.000, 0.369 Drag's a bit low and the lift is a bit high but you've got to remember that it is a low drag design and the wing is huge - it's defined up to the center-line. I can't see anything there that gives any clues about accelerating without putting energy in. Can you reproduce it while under control of the A/P? That should help me reproduce it here. LeeE - Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys -- and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] YF-23/yasim: how to climb to 163000 ft
Hi Jon, I think it makes sense to clamp the integrated value in any PID regulator. Due to the fact, that for a PID-regulator the output is clamped, the integrator should be clamped to a value, which is sufficient for reaching the maximum allowed output (even if the D-part is working against the I-Part). the below mentioned change would reduce the problem, but due to the not exactly 1G load for any runway in the world, the problem would still occur after longer times on the runway. Maik Jon S. Berndt wrote: >>> One way to reproduce: >>> >>> - start fgfs with --aircraft=f16-3d >>> - apply parking brakes >>> - wait 10 minutes >>> - fly and die (elevator pulls *strongly* up) >>> >>> m. >>> > > I think I see at least one problem. The pitch channel integrates load factor > error. Sitting on the runway, I see that a normal 1G load, multiplied by a > 0.125 gain, and that is getting integrated. I believe that the load factor > to be integrated on the runway should be zero - that is, in trimmed flight > the integrator should not have any error to integrate. I'm looking into > that, now. > > Jon > - Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys -- and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] YF-23/yasim: how to climb to 163000 ft
> > One way to reproduce: > > > > - start fgfs with --aircraft=f16-3d > > - apply parking brakes > > - wait 10 minutes > > - fly and die (elevator pulls *strongly* up) > > > > m. I think I see at least one problem. The pitch channel integrates load factor error. Sitting on the runway, I see that a normal 1G load, multiplied by a 0.125 gain, and that is getting integrated. I believe that the load factor to be integrated on the runway should be zero - that is, in trimmed flight the integrator should not have any error to integrate. I'm looking into that, now. Jon - Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys -- and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] YF-23/yasim: how to climb to 163000 ft
* Jon S. Berndt -- Saturday 05 August 2006 13:21: > Now, if I can get OpenGL to work with my new video card, I can > help debug this one... :-( You can use the new stopwatch dialog under the Debug menu. My personal record for surviving an F16 flight after 10 minute parking is around 25 seconds. There's no way to counter the elevator. You quickly make a half loop and ... pull the ejection seat handle. m. - Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys -- and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] YF-23/yasim: how to climb to 163000 ft
> One way to reproduce: > > - start fgfs with --aircraft=f16-3d > - apply parking brakes > - wait 10 minutes > - fly and die (elevator pulls *strongly* up) > > m. Thank you. Now, if I can get OpenGL to work with my new video card, I can help debug this one... :-( - Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys -- and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] YF-23/yasim: how to climb to 163000 ft
* Melchior FRANZ -- Saturday 05 August 2006 08:00: > (I and others can *always* reliably reproduce.) One way to reproduce: - start fgfs with --aircraft=f16-3d - apply parking brakes - wait 10 minutes - fly and die (elevator pulls *strongly* up) m. - Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys -- and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] YF-23/yasim: how to climb to 163000 ft
* Jon S. Berndt -- Saturday 05 August 2006 01:31: > By saying "the F-16 is pathetic", that tells me nothing about what > problems you are having. Sorry, but this wasn't meant as a bug report. I've told Erik twice about the problem already. He said he couldn't easily reproduce it. (I and others can *always* reliably reproduce.) > By the way, there is a bug report about a possible integrator windup problem > with the F-16. Yes, that's exactly the problem. It makes the F16 unflyable after a few minutes. All PIDs seem to be concerned, but it starts with the yaw channel PID. The rudder starts pulling more and more to the right, until one loses control. If I replace that channel PID settings by the definition of the 737 (as Dave suggested), then that rudder breakage doesn't happen, but one gets the same problem on the elevator. m. - Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys -- and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] YF-23/yasim: how to climb to 163000 ft
> Unfortunately, we don't have a single halfway modern fighter > in fgfs, that is not totally broken. The F16 is pathetic and unusable > since JSBSim 2.0. The hunter/seahawk work nicely, but aren't exactly > modern. I tested several aircraft with FlightGear and JSBSim 0.9.11 with the v2.0 configuration file format (JSBSim-ML v2.0). It worked fine for me, but I didn't run it through too many hoops. If you go to the JSBSim web site, there is a "Bugs" button you can press and enter information on what problems you hare having. By saying "the F-16 is pathetic", that tells me nothing about what problems you are having. I'd like to hear specifics. Unfortunately, for the past few months I have been unable to run OpenGL apps, and am still waiting on eVGA and nVidia to resolve the issue. All that we have to go on are user reports. Don't just complain about a problem: be part of the solution. Here's the URL, www.sf.net/tracker/?atid=119399&group_id=19399&func=browse By the way, there is a bug report about a possible integrator windup problem with the F-16. I'll try and come up with a test for the F-16 that I can run as a scripted, standalone test with JSBSim, and investigate (since I can't run Flightgear now). Jon - Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys -- and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] YF-23/yasim: how to climb to 163000 ft
* Curtis L. Olson -- Friday 04 August 2006 16:58: > For what it's worth, the NTPS is using their own flight dynamics model > and are looking out the window sans-3d cockpit, so they are just seeing > the outside world + hud. Ahh, good. In that case it's anything but urgent. m. - Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys -- and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] YF-23/yasim: how to climb to 163000 ft
Melchior FRANZ wrote: > Sorry, no offense to Lee -- it's still very well done 3D model wise, > but I find it a bit embarrassing to show off in the NTPS. I'm not > even sure if this is an old bug or if it's caused by later YASim > changes. I don't remember ever having seen such unrealistic behavior, > and I used to fly the YF23 a lot at times. > For what it's worth, the NTPS is using their own flight dynamics model and are looking out the window sans-3d cockpit, so they are just seeing the outside world + hud. Curt. -- Curtis Olsonhttp://baron.flightgear.org/~curt HumanFIRST Program http://www.humanfirst.umn.edu/ FlightGear Project http://www.flightgear.org Unique text:2f585eeea02e2c79d7b1d8c4963bae2d - Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys -- and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] YF-23/yasim: how to climb to 163000 ft
* Melchior FRANZ -- Friday 04 August 2006 16:26: > Unfortunately, we don't have a single halfway modern fighter > in fgfs, that is not totally broken. No, wait. There's the harrier, and maybe the f15 is good, too (though without model). m. :-) - Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys -- and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] YF-23/yasim: how to climb to 163000 ft
* Curtis L. Olson -- Friday 04 August 2006 15:34: > I will point out that while it's possible to force the YF-23 into this > extreme state, if you fly it in a more normal range, it behaves pretty > normally. Not for me. I actually noticed the problems during "normal" flight. I chased the KA6 and, because (unlike in real life) there's no indication how far it's still away, I was a tad too fast when I noticed it coming nearer and nearer. I tried to fly some narrow curves, but unlike in all other fgfs aircraft, this didn't decelerate, but *accelerate*. Of course, I'm not a pilot, and in real life there'd be a FCS with g-limiter, and my body would warn me earlier, too, but that's no excuse. Unfortunately, we don't have a single halfway modern fighter in fgfs, that is not totally broken. The F16 is pathetic and unusable since JSBSim 2.0. The hunter/seahawk work nicely, but aren't exactly modern. > So personally I think the YF-23 is a pretty fun plane to fly, > even if it isn't 100% perfect. Sorry, no offense to Lee -- it's still very well done 3D model wise, but I find it a bit embarrassing to show off in the NTPS. I'm not even sure if this is an old bug or if it's caused by later YASim changes. I don't remember ever having seen such unrealistic behavior, and I used to fly the YF23 a lot at times. m. - Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys -- and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] YF-23/yasim: how to climb to 163000 ft
Melchior FRANZ wrote: > * Lee Elliott -- Friday 04 August 2006 01:05: > >> Just a thought - what sort of speed are we talking here? AFAIK >> YASim doesn't 'do' trans/supersonic - might this be a factor? >> > > We are talking about accelerating from 300 kts to 2000 kts with > zero throttle. I doubt that this has anything to do with trans/supersonic. > I can fly from New York to London with no throttle. (At some point > you should probably actually read this thread. :-) > I will point out that while it's possible to force the YF-23 into this extreme state, if you fly it in a more normal range, it behaves pretty normally. So personally I think the YF-23 is a pretty fun plane to fly, even if it isn't 100% perfect. Based on my understanding of YASim, this has to be some sort of bug in the core yasim code since it's getting energy from nowhere. Might be some sort of numerical/roundoff issue, perhaps some of the code in YAsim makes assumptions/simplifications that start to break down at extremely high alpha angles? I'm just throwing out wild guesses here, but there's nothing you can do in a yasim config file to create energy out of nothing. All the physics is handled deep in the yasim code. Curt. -- Curtis Olsonhttp://baron.flightgear.org/~curt HumanFIRST Program http://www.humanfirst.umn.edu/ FlightGear Project http://www.flightgear.org Unique text:2f585eeea02e2c79d7b1d8c4963bae2d - Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys -- and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] YF-23/yasim: how to climb to 163000 ft
* Lee Elliott -- Friday 04 August 2006 01:05: > Just a thought - what sort of speed are we talking here? AFAIK > YASim doesn't 'do' trans/supersonic - might this be a factor? We are talking about accelerating from 300 kts to 2000 kts with zero throttle. I doubt that this has anything to do with trans/supersonic. I can fly from New York to London with no throttle. (At some point you should probably actually read this thread. :-) m. - Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys -- and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] YF-23/yasim: how to climb to 163000 ft
On Tuesday 01 August 2006 22:50, Melchior FRANZ wrote: > * Lee Elliott -- Tuesday 01 August 2006 23:40: > > Again, IIRC, the real (Y)F-23 could (was intended) get to > > > > >65000ft so with the YASim YF-23 under weight and too > > > powerful > > > > it's able to climb just a bit too high:) > > That's a minor problem. The bigger problem is that it > *accelerates* in very narrow turns, and even with no throttle > at all. And you can fly straight down with 1000 kt, and > shortly before touch-down pitch up and fly straight up again. > Doesn't seem to have enough mass/inertia. (Yes, the g-load > would kill me anyway, so I shouldn't bother. :-) > > m. Just a thought - what sort of speed are we talking here? AFAIK YASim doesn't 'do' trans/supersonic - might this be a factor? In the sub-sonic regime I was able to achieve some interesting high-AoA manuevours and almost a cobra & hook out of the YF-23. With the large lift area and power, combined with the "V" hstab configuration this seemed reasonable - the "v" hstab configuration should produce less drag in high-AoA than 'flat' hstabs (this might be a problem with the SU-37 I'm working on but perhaps playing with idrag might help). Then again, I might have given the 'wing' a much too high stall aoa... I've seen a quote, apparently from a high-ranking USAF? officer, who said that YF-23 technology (in terms of the airframe design/configuration philosophy) was being made use of. Didn't state where though, of course. I've also seen some drawings of a variable-sweep version of a YF-23 type recon aircraft but this might just be a case of one false rumour re-enforcing another LeeE - Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys -- and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] YF-23/yasim: how to climb to 163000 ft
On Wednesday 02 August 2006 00:03, Josh Babcock wrote: > Lee Elliott wrote: > > dearth of good info on the YF-23 when I originally did it. > > I > > Should you find a moment, I feel that I should point this out: > http://www.flight-manuals-on-cd.com/YFN.html > > Josh Ta for that - I might have a look into it when I get back to the YF-23. LeeE - Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys -- and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] YF-23/yasim: how to climb to 163000 ft
Lee Elliott wrote: > dearth of good info on the YF-23 when I originally did it. I Should you find a moment, I feel that I should point this out: http://www.flight-manuals-on-cd.com/YFN.html Josh - Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys -- and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] YF-23/yasim: how to climb to 163000 ft
On Tuesday 01 August 2006 22:50, Melchior FRANZ wrote: > * Lee Elliott -- Tuesday 01 August 2006 23:40: > > Again, IIRC, the real (Y)F-23 could (was intended) get to > > > > >65000ft so with the YASim YF-23 under weight and too > > > powerful > > > > it's able to climb just a bit too high:) > > That's a minor problem. The bigger problem is that it > *accelerates* in very narrow turns, and even with no throttle > at all. And you can fly straight down with 1000 kt, and > shortly before touch-down pitch up and fly straight up again. > Doesn't seem to have enough mass/inertia. (Yes, the g-load > would kill me anyway, so I shouldn't bother. :-) > > m. Hmm... I don't remember it ever behaving like that but I haven't flown it for ages. I'll have to take a look at it. LeeE - Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys -- and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] YF-23/yasim: how to climb to 163000 ft
* Lee Elliott -- Tuesday 01 August 2006 23:40: > Again, IIRC, the real (Y)F-23 could (was intended) get to > >65000ft so with the YASim YF-23 under weight and too powerful > it's able to climb just a bit too high:) That's a minor problem. The bigger problem is that it *accelerates* in very narrow turns, and even with no throttle at all. And you can fly straight down with 1000 kt, and shortly before touch-down pitch up and fly straight up again. Doesn't seem to have enough mass/inertia. (Yes, the g-load would kill me anyway, so I shouldn't bother. :-) m. - Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys -- and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] YF-23/yasim: how to climb to 163000 ft
I think this is resulting from a combination of factors. The YASim YF-23, as currently defined, probably doesn't weigh enough and the engines are a bit too powerful, both due to a dearth of good info on the YF-23 when I originally did it. I suspect that this means that it can get to > 74000ft at which point, IIRC, YASim stops calculating altitude effects with the result that once you're above 74000ft you can carry on climbing. Again, IIRC, the real (Y)F-23 could (was intended) get to >65000ft so with the YASim YF-23 under weight and too powerful it's able to climb just a bit too high:) I do want update the YF-23 some time soon but I'm already pretty busy with two updates and a new aircraft so it'll have to wait a bit. LeeE On Monday 31 July 2006 05:44, JD Fenech wrote: > Is this some sort of bug in the model? It strikes me as > something that would either be a tightly held performance spec > on the part of the US Gov't, or a glaring flaw somewhere... > > Stefan Seifert wrote: > > Melchior FRANZ wrote: > >> $ fgfs --aircraft=YF-23 --airport=knuq > >> --disable-real-weather-fetch > >> > >> - full throttle > >> - climb to 8000 ft > >> - 90 degree bank > >> - pull stick fully back > >> amazingly: you don't bleed off speed, but *accelerate* > >> - at ~1630 kt (after that the speed decreases) 0 degree > >> bank and 90 degree pitch up > >> - climb to 163000 ft in no time > > > > If you really want to travel to other planets I suggest just > > pulling the throttle to zero when you reach the speed limit, > > while still rotating. This gives you the extra boost you > > need for interplanetary travel. > > > > Nine - Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys -- and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] YF-23/yasim: how to climb to 163000 ft
Is this some sort of bug in the model? It strikes me as something that would either be a tightly held performance spec on the part of the US Gov't, or a glaring flaw somewhere... Stefan Seifert wrote: > Melchior FRANZ wrote: > >> $ fgfs --aircraft=YF-23 --airport=knuq --disable-real-weather-fetch >> >> - full throttle >> - climb to 8000 ft >> - 90 degree bank >> - pull stick fully back >> amazingly: you don't bleed off speed, but *accelerate* >> - at ~1630 kt (after that the speed decreases) 0 degree bank and >> 90 degree pitch up >> - climb to 163000 ft in no time >> >> > > If you really want to travel to other planets I suggest just pulling the > throttle to zero when you reach the speed limit, while still rotating. > This gives you the extra boost you need for interplanetary travel. > > Nine > > - > Take Surveys. Earn Cash. Influence the Future of IT > Join SourceForge.net's Techsay panel and you'll get the chance to share your > opinions on IT & business topics through brief surveys -- and earn cash > http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV > ___ > Flightgear-devel mailing list > Flightgear-devel@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/flightgear-devel > > - Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys -- and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] YF-23/yasim: how to climb to 163000 ft
Melchior FRANZ wrote: > $ fgfs --aircraft=YF-23 --airport=knuq --disable-real-weather-fetch > > - full throttle > - climb to 8000 ft > - 90 degree bank > - pull stick fully back > amazingly: you don't bleed off speed, but *accelerate* > - at ~1630 kt (after that the speed decreases) 0 degree bank and > 90 degree pitch up > - climb to 163000 ft in no time > If you really want to travel to other planets I suggest just pulling the throttle to zero when you reach the speed limit, while still rotating. This gives you the extra boost you need for interplanetary travel. Nine - Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys -- and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] YF-23/yasim: how to climb to 163000 ft
* Jeff McBride -- Friday 28 July 2006 15:46: > Actually, sometimes if you get it right (well, I did it once), you can > go a lot faster than that. Yes, you are right. I suggested 8000 ft only as sufficiently high to not rush into the ground immediately, at that high speed. But trying at 1000 ft one can easily accelerate to 3000 kt and more. Very dangerous! Don't try at home, kids! m. - Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys -- and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] YF-23/yasim: how to climb to 163000 ft
> $ fgfs --aircraft=YF-23 --airport=knuq --disable-real-weather-fetch > > - full throttle > - climb to 8000 ft > - 90 degree bank > - pull stick fully back > amazingly: you don't bleed off speed, but *accelerate* > - at ~1630 kt (after that the speed decreases) 0 degree bank and > 90 degree pitch up > - climb to 163000 ft in no time > > m. :-) just tried this on a seneca in reality. Didn't work. Reality could be so disappointing... Torsten - Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys -- and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] YF-23/yasim: how to climb to 163000 ft
Actually, sometimes if you get it right (well, I did it once), you can go a lot faster than that. I managed to get the speed to diverge rapidly up to 5 or 6 digits once and then FG crashed. I wasn't able to do it consistently though. -Jeff On 7/28/06, Melchior FRANZ <[EMAIL PROTECTED]> wrote: > $ fgfs --aircraft=YF-23 --airport=knuq --disable-real-weather-fetch > > - full throttle > - climb to 8000 ft > - 90 degree bank > - pull stick fully back > amazingly: you don't bleed off speed, but *accelerate* > - at ~1630 kt (after that the speed decreases) 0 degree bank and > 90 degree pitch up > - climb to 163000 ft in no time > > m. :-) > > - > Take Surveys. Earn Cash. Influence the Future of IT > Join SourceForge.net's Techsay panel and you'll get the chance to share your > opinions on IT & business topics through brief surveys -- and earn cash > http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV > ___ > Flightgear-devel mailing list > Flightgear-devel@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/flightgear-devel > - Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys -- and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
[Flightgear-devel] YF-23/yasim: how to climb to 163000 ft
$ fgfs --aircraft=YF-23 --airport=knuq --disable-real-weather-fetch - full throttle - climb to 8000 ft - 90 degree bank - pull stick fully back amazingly: you don't bleed off speed, but *accelerate* - at ~1630 kt (after that the speed decreases) 0 degree bank and 90 degree pitch up - climb to 163000 ft in no time m. :-) - Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys -- and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
