Re: [Flightgear-devel] Help with B-29
Vivian Meazza wrote: The attached diff models the output of a gear-driven supercharger. I've used a 3rd order polynomial which matches the few examples I have been able to find, giving near-linear output up to the max-power rpm of the engine, with a little tail-off below this point, and a larger one above. More importantly, it produces realistic results. Cool. Can you resend the patch as a cvs diff -uw output for readability, and remove the unrelated changes? Are there any sources for the curve you are fitting to? I'm not completely unwilling to stick magic numbers into the source code where they produce acceptable behavior; I just want to put a comment in explaining where the blame lies. :) Andy ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
RE: [Flightgear-devel] Help with B-29
Andy Ross wrote: Vivian Meazza wrote: The attached diff models the output of a gear-driven supercharger. I've used a 3rd order polynomial which matches the few examples I have been able to find, giving near-linear output up to the max-power rpm of the engine, with a little tail-off below this point, and a larger one above. More importantly, it produces realistic results. Cool. Can you resend the patch as a cvs diff -uw output for readability, and remove the unrelated changes? Are there any sources for the curve you are fitting to? I'm not completely unwilling to stick magic numbers into the source code where they produce acceptable behavior; I just want to put a comment in explaining where the blame lies. :) Well, first I thought of using some real maths based on this lot: http://www.teknett.com/pwp/drmayf/turbocal.htm Then I found this: http://www.turbotechnics.com/supercharger/expo.htm The supercharger described is a smaller (much) version of that fitted to the Merlin, but it has the same arrangement of throttle ahead of the compressor. I'm very familiar with the engine - it is the same as the one in my track car (un-supercharged). The supercharger output described is pretty much linear up to the maximum rpm at 7000 rpm. It tails off a bit before that. I reasoned that the Rolls Royce engineers would have gone for pretty much the same output shape. I also wanted to take into account the surge boundary for later use when we model the so-called 'boost control cut-out' so I added a more rapid fall-off in output beyond the maximum power rpm. I did some curve matching, and came up with a suitable 3rd order polynomial. It's a very good fit up to max power; thereafter ... I'll look into that issue later in the context of the boost control cut-out. It probably doesn't matter too much. Not too much magic in the numbers. As to the throttle equation - it's a hack but it works - the P51d and the Hurricane are easier to land. This is pure voodoo except that 750-850 rpm seems to be the chosen idle speed for most piston engines. Big - slower, small - faster. I'd like to do better. It might be possible to put a lower limit on omega in PropEngine.cxx. Meanwhile, I attach a revised diff using -u - w. Hope this all makes sense Regards Vivian YASim.diff Description: Binary data ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
RE: [Flightgear-devel] Help with B-29
Andy Ross wrote: Vivian Meazza wrote: However (and there's always a however), I can't land the thing. Closing the throttle and pulling back the propeller pitch control doesn't reduce the power enough. I reasoned that there was too much boost with the throttle closed, (currently set at 10%, AFAICS). 10% of the supercharger output at sea level before the wastegate is a big number Yeah, that's a good point. The idle tuning of the engine was done before turbocharging was added, and doesn't really map well to the new regime. As a near-term workaround, you can always pull the mixture way back to reduce power to near-zero. I'm wary of adding a magic number to the configuration files for this, though. I wonder if there's a saner way of calculating an appropriate idle power dynamically from the input values... I can't find one right now. Empirically, piston engines in general seem to be set to idle at around 750-850 rpm, although I have read just one report of a Merlin idling at 600. 750-850 rpm implies a minimum throttle setting of about 6%. This number works fine in practice. The attached diff includes a hack which works for all YASim piston engines currently in the inventory. It would be better if we could close the throttle, and then let the idle function settle at 750-850 rpm. Perhaps you can come up with a more elegant solution? A related issue that stands to be fixed is that the current code doesn't really model a gear-driven supercharger properly. With a centrifugal compressor like this, the output pressure gain is a direct funcition of RPM. The existing code tries to model an exhaust-driven turbo charger by simply multiplying the input MP by the turbo-mul factor, which isn't the same thing. The behavior will match at maximum power output, but be off in the middle and at the low end. The attached diff models the output of a gear-driven supercharger. I've used a 3rd order polynomial which matches the few examples I have been able to find, giving near-linear output up to the max-power rpm of the engine, with a little tail-off below this point, and a larger one above. More importantly, it produces realistic results. One other 'however': the property mp-inhg seems to be bound to the supercharger output before the wastegate is applied. Really? PistonEngine.cpp:112 looks like it is setting the current MP based on the turbo output. Maybe there's a different bug somewhere (units conversion, maybe?) I may be misinterpreting the code, but PistonEngine.cpp:114 _mp *= _throttle; seems to be modifying the turbo output incorrectly, and thus the output to the property browser. This line may be redundant? In any case, it's the pressure after the 'wastegate' i.e. 'mp' which we need for the cockpit gauge, either in inhg absolute (US) or psi-gauge (UK). The attached diff provides the output pressure ( _mp) and the manifold pressure (mp). Regards, Vivian YASim.diff Description: Binary data ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
RE: [Flightgear-devel] Help with B-29
Andy Ross wrote: I wrote: Jim Wilson wrote: 4) Fixed rpm/power numbers under the prop tags. They need to be scaled back according to the gear ratio. Someone with a better understanding of mech engineering might be able to explain why the BHP on the prop shaft is reduced by a factor of 0.35 when that's the gear ratio, or maybe that is wrong and there is something going on in the YASim calcs. Yeah, that's a bug. Power is power. If the prop wants to sync X horsepower at Y RPM, then the engine ought to be defined as producing the same X hp at Y/gear-ratio RPM. Let me take a look. Indeed, there was yet another spot I missed when adding the gear-ratio stuff. The torque conversion from propeller side to engine side worked correctly during solution, but not at runtime. This is fixed now, so you should be able to use real numbers in your propeller tags. FWIW, I also took the opportunity to re-visit the P-51D configuration that I promised (long ago) to hack at. Attached is a version that should perform more realistically. The biggest change is that I reduced the cruise speed (360-310) to represent what a typical aircraft should be able to achieve with 50% fuel. The resulting aircraft is a *lot* less slick (it produces almost three times as much parasite drag), and should perform more realistically at low altitudes. You should still be able to hit the textbook numbers with a stripped aircraft and empty tanks. Also, there is a syntax fix: the piston-engine tag should be a subtag of the propeller tag. Putting it immediately after the propeller definition works only due to a lucky interaction with the way the parser stores its current object pointer. It doesn't clear the value when it sees /propeller, so you can get away with putting the engine at any point in the file before the next tag that sets a current object. I haven't flown this enough to say whether it's worth checking in. Let me know if anyone tries it and likes it. I'm currently developing the YASim config for the Hawker Hurricane model. I took the P51d config and plugged in some authoritative numbers for the Merlin XX. Mirabile dictu, it worked right out of the box. The model takes off and flies well (very well, I think), with the performance closely matching the published figures. It can't quite reach the service ceiling, but perhaps the standard atmosphere ain't quite what it was in 1941, or perhaps I need to pump up the supercharger a bit :-). The wastegate opens and closes when it should, and the 2 speed supercharger works correctly. Good work, Andy. However (and there's always a however), I can't land the thing. Closing the throttle and pulling back the propeller pitch control doesn't reduce the power enough. I reasoned that there was too much boost with the throttle closed, (currently set at 10%, AFAICS). 10% of the supercharger output at sea level before the wastegate is a big number - I set it 3% (based on nothing more than a WAG) and it works well. Perhaps we can make this parameter settable with a default value of 10%? One other 'however': the property mp-inhg seems to be bound to the supercharger output before the wastegate is applied. Useful for development, but not for the input to the manifold pressure gauge. Locally, I've added a parameter for manifold pressure after the wastegate. If no one objects, I can send Erik the required changes in the next week or so. Regards Vivian ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
Re: [Flightgear-devel] Help with B-29
Vivian Meazza wrote: However (and there's always a however), I can't land the thing. Closing the throttle and pulling back the propeller pitch control doesn't reduce the power enough. I reasoned that there was too much boost with the throttle closed, (currently set at 10%, AFAICS). 10% of the supercharger output at sea level before the wastegate is a big number Yeah, that's a good point. The idle tuning of the engine was done before turbocharging was added, and doesn't really map well to the new regime. As a near-term workaround, you can always pull the mixture way back to reduce power to near-zero. I'm wary of adding a magic number to the configuration files for this, though. I wonder if there's a saner way of calculating an appropriate idle power dynamically from the input values... A related issue that stands to be fixed is that the current code doesn't really model a gear-driven supercharger properly. With a centrifugal compressor like this, the output pressure gain is a direct funcition of RPM. The existing code tries to model an exhaust-driven turbo charger by simply multiplying the input MP by the turbo-mul factor, which isn't the same thing. The behavior will match at maximum power output, but be off in the middle and at the low end. One other 'however': the property mp-inhg seems to be bound to the supercharger output before the wastegate is applied. Really? PistonEngine.cpp:112 looks like it is setting the current MP based on the turbo output. Maybe there's a different bug somewhere (units conversion, maybe?) Andy ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
RE: [Flightgear-devel] Help with B-29
Andy Ross wrote Vivian Meazza wrote: However (and there's always a however), I can't land the thing. Closing the throttle and pulling back the propeller pitch control doesn't reduce the power enough. I reasoned that there was too much boost with the throttle closed, (currently set at 10%, AFAICS). 10% of the supercharger output at sea level before the wastegate is a big number Yeah, that's a good point. The idle tuning of the engine was done before turbocharging was added, and doesn't really map well to the new regime. As a near-term workaround, you can always pull the mixture way back to reduce power to near-zero. Unfortunately, the Hurricane had/has automatic mixture control! I'm wary of adding a magic number to the configuration files for this, though. I wonder if there's a saner way of calculating an appropriate idle power dynamically from the input values... That would be good ... if we knew or could deduce the HP. Meanwhile, it's quite easy to tune the minimum output using the so called 'magic number' A related issue that stands to be fixed is that the current code doesn't really model a gear-driven supercharger properly. With a centrifugal compressor like this, the output pressure gain is a direct funcition of RPM. The existing code tries to model an exhaust-driven turbo charger by simply multiplying the input MP by the turbo-mul factor, which isn't the same thing. The behavior will match at maximum power output, but be off in the middle and at the low end. Working on it right now. BTW the Merlin had a Roots type displacement compressor. I'm looking at some representative pressure ratio curves wrt rpm. I'm testing out a supercharger which varies output with engine rpm, modified by throttle. One other 'however': the property mp-inhg seems to be bound to the supercharger output before the wastegate is applied. Really? PistonEngine.cpp:112 looks like it is setting the current MP based on the turbo output. Maybe there's a different bug somewhere (units conversion, maybe?) The property is bound to the variable _mp, while the wastegate is applied to the variable mp. If the property is bound to mp, it gives the right output. The problem is entirely in the binding - the turbo code works correctly. Regards, Vivian ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
Re: [Flightgear-devel] Help with B-29
On Thu, 7 Apr 2005 19:16:08 +0100, Vivian wrote in message [EMAIL PROTECTED]: Andy Ross wrote Vivian Meazza wrote: However (and there's always a however), I can't land the thing. Closing the throttle and pulling back the propeller pitch control doesn't reduce the power enough. I reasoned that there was too much boost with the throttle closed, (currently set at 10%, AFAICS). 10% of the supercharger output at sea level before the wastegate is a big number Yeah, that's a good point. The idle tuning of the engine was done before turbocharging was added, and doesn't really map well to the new regime. As a near-term workaround, you can always pull the mixture way back to reduce power to near-zero. ..how about solving for idle static thrust? Unfortunately, the Hurricane had/has automatic mixture control! ..??? The only ones I'm aware of had such fancy gear, is the Axis side, look for kommandogerat, was used in all frontline piston powered WWII Luftwaffe fighters. I'm wary of adding a magic number to the configuration files for this, though. I wonder if there's a saner way of calculating an appropriate idle power dynamically from the input values... That would be good ... if we knew or could deduce the HP. Meanwhile, it's quite easy to tune the minimum output using the so called 'magic number' A related issue that stands to be fixed is that the current code doesn't really model a gear-driven supercharger properly. With a centrifugal compressor like this, the output pressure gain is a direct funcition of RPM. The existing code tries to model an exhaust-driven turbo charger by simply multiplying the input MP by the turbo-mul factor, which isn't the same thing. The behavior will match at maximum power output, but be off in the middle and at the low end. Working on it right now. BTW the Merlin had a Roots type displacement compressor. ..this is the big ass clutch-housing-and-gearbox like thing down the rear end of the Merlins? ..ahem; http://www.enginehistory.org/merlin_xx.htm , specificly http://www.enginehistory.org/ModelEngines/Hares/Merlin XX/2i.jpg http://www.enginehistory.org/ModelEngines/Hares/Merlin XX/2j.jpg http://www.enginehistory.org/ModelEngines/Hares/Merlin XX/2k.jpg ..looks centrifugal, no? ;o) I'm looking at some representative pressure ratio curves wrt rpm. I'm testing out a supercharger which varies output with engine rpm, modified by throttle. One other 'however': the property mp-inhg seems to be bound to the supercharger output before the wastegate is applied. Really? PistonEngine.cpp:112 looks like it is setting the current MP based on the turbo output. Maybe there's a different bug somewhere (units conversion, maybe?) The property is bound to the variable _mp, while the wastegate is applied to the variable mp. If the property is bound to mp, it gives the right output. The problem is entirely in the binding - the turbo code works correctly. -- ..med vennlig hilsen = with Kind Regards from Arnt... ;o) ...with a number of polar bear hunters in his ancestry... Scenarios always come in sets of three: best case, worst case, and just in case. ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
Re: [Flightgear-devel] Help with B-29
On Thu, 7 Apr 2005 21:37:31 +0200, Arnt wrote in message [EMAIL PROTECTED]: On Thu, 7 Apr 2005 19:16:08 +0100, Vivian wrote in message [EMAIL PROTECTED]: Andy Ross wrote Working on it right now. BTW the Merlin had a Roots type displacement compressor. ..apologies all, I hit the wrong button as I was gonna wipe out... : ..this is the big ass clutch-housing-and-gearbox like thing down the rear end of the Merlins? ...before putting this right under Vivian's compressor line, and found the end result in message[EMAIL PROTECTED] a fair bit embarrasing. ;o) ..ahem; http://www.enginehistory.org/merlin_xx.htm , specificly http://www.enginehistory.org/ModelEngines/Hares/Merlin XX/2i.jpg http://www.enginehistory.org/ModelEngines/Hares/Merlin XX/2j.jpg http://www.enginehistory.org/ModelEngines/Hares/Merlin XX/2k.jpg ..looks centrifugal, no? ;o) -- ..med vennlig hilsen = with Kind Regards from Arnt... ;o) ...with a number of polar bear hunters in his ancestry... Scenarios always come in sets of three: best case, worst case, and just in case. ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
RE: [Flightgear-devel] Help with B-29
Arnt Karlsen wrote Andy Ross wrote Vivian Meazza wrote: However (and there's always a however), I can't land the thing. Closing the throttle and pulling back the propeller pitch control doesn't reduce the power enough. I reasoned that there was too much boost with the throttle closed, (currently set at 10%, AFAICS). 10% of the supercharger output at sea level before the wastegate is a big number Yeah, that's a good point. The idle tuning of the engine was done before turbocharging was added, and doesn't really map well to the new regime. As a near-term workaround, you can always pull the mixture way back to reduce power to near-zero. ..how about solving for idle static thrust? If we knew the static idle thrust that would be a good way to go. I was considering solving for idle rpm, which we do know. If I can't, Andy will come up with a way, I'm sure. Unfortunately, the Hurricane had/has automatic mixture control! ..??? The only ones I'm aware of had such fancy gear, is the Axis side, look for kommandogerat, was used in all frontline piston powered WWII Luftwaffe fighters. Surprised me too. Seems unlikely: the Spitfire had a manual mixture lever. I'm going by the Pilot's Notes para 19: Throttle. The throttle lever works is a slot in the decking shelf on the left-hand side of the cockpit. The take-off position is gated. There is a friction adjuster on the inboard end of the lever spindle. The mixture control is fully automatic and there is no pilot's control lever. I can't identify a lever in any of the contemporary photos that I have access to, but I can't be absolutely certain - they are pretty blurred. Wishful thinking by the author of the Notes? Possibly, but I'm going to stick with the reference, unless anyone can come up with an amended version. I'm wary of adding a magic number to the configuration files for this, though. I wonder if there's a saner way of calculating an appropriate idle power dynamically from the input values... That would be good ... if we knew or could deduce the HP. Meanwhile, it's quite easy to tune the minimum output using the so called 'magic number' A related issue that stands to be fixed is that the current code doesn't really model a gear-driven supercharger properly. With a centrifugal compressor like this, the output pressure gain is a direct funcition of RPM. The existing code tries to model an exhaust-driven turbo charger by simply multiplying the input MP by the turbo-mul factor, which isn't the same thing. The behavior will match at maximum power output, but be off in the middle and at the low end. Working on it right now. BTW the Merlin had a Roots type displacement compressor. ..this is the big ass clutch-housing-and-gearbox like thing down the rear end of the Merlins? Yes ..ahem; http://www.enginehistory.org/merlin_xx.htm , specificly http://www.enginehistory.org/ModelEngines/Hares/Merlin XX/2i.jpg http://www.enginehistory.org/ModelEngines/Hares/Merlin XX/2j.jpg http://www.enginehistory.org/ModelEngines/Hares/Merlin XX/2k.jpg ..looks centrifugal, no? ;o) Yes - bit of brain fade there - I interpreted one of my references incorrectly, but on closer reading I was quite wrong. I read 2 impellors and assumed that meant Roots type, which has 2, but of course they are on the same shaft and centrifugal, giving 2 compressor stages. (And 2 speed, but that's another story) Thank you for pointing it out. Regards, Vivian ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
Re: [Flightgear-devel] Help with B-29
I wrote: Jim Wilson wrote: 4) Fixed rpm/power numbers under the prop tags. They need to be scaled back according to the gear ratio. Someone with a better understanding of mech engineering might be able to explain why the BHP on the prop shaft is reduced by a factor of 0.35 when that's the gear ratio, or maybe that is wrong and there is something going on in the YASim calcs. Yeah, that's a bug. Power is power. If the prop wants to sync X horsepower at Y RPM, then the engine ought to be defined as producing the same X hp at Y/gear-ratio RPM. Let me take a look. Indeed, there was yet another spot I missed when adding the gear-ratio stuff. The torque conversion from propeller side to engine side worked correctly during solution, but not at runtime. This is fixed now, so you should be able to use real numbers in your propeller tags. FWIW, I also took the opportunity to re-visit the P-51D configuration that I promised (long ago) to hack at. Attached is a version that should perform more realistically. The biggest change is that I reduced the cruise speed (360-310) to represent what a typical aircraft should be able to achieve with 50% fuel. The resulting aircraft is a *lot* less slick (it produces almost three times as much parasite drag), and should perform more realistically at low altitudes. You should still be able to hit the textbook numbers with a stripped aircraft and empty tanks. Also, there is a syntax fix: the piston-engine tag should be a subtag of the propeller tag. Putting it immediately after the propeller definition works only due to a lucky interaction with the way the parser stores its current object pointer. It doesn't clear the value when it sees /propeller, so you can get away with putting the engine at any point in the file before the next tag that sets a current object. I haven't flown this enough to say whether it's worth checking in. Let me know if anyone tries it and likes it. Andy ?xml version=1.0? !-- YASim aerodynamic model for a P-51D mustang Started 2003-04-24 by Jim Wilson This aerodynamic model is based on three-views, unauthoritative performance data, and wild guesses. These sites provided particularly useful information or were simply fun to visit: Performance data: http://www.hq.nasa.gov/office/pao/History/SP-468/app-a2.htm http://www.olympicflightmuseum.com/aircraft_gallery/p51d_mustang.htm http://www.btinternet.com/~lee_mail/P51.html http://www.sprucegoose.org/pdfs/planes/P51Mustang.pdf Weight and balance: http://www.p51.wjackparker.com/P51_Additional_reference_material/x_maintenance.htm http://www.nzfpm.co.nz/aircraft/p51d.htm http://www.wpafb.af.mil/museum/engines/eng33.htm Three-view: http://members.optushome.com.au/gjmustang/docs/3-View.html (Note: I have local copies if this url becomes un-available) The reference datum for measurements is the nose. -- !-- Weight of everything but fuel (7010 empty) -- airplane mass=7125 !-- Approach configuration -- approach speed=87 aoa=13 control-setting axis=/controls/engines/engine[0]/throttle value=0.3/ control-setting axis=/controls/engines/engine[0]/mixture value=1.0/ control-setting axis=/controls/engines/engine[0]/propeller-pitch value=0.5/ control-setting axis=/controls/flight/flaps value=1.0/ control-setting axis=/controls/gear/gear-down value=1/ /approach !-- Cruise configuration -- !-- 360ktas is often quoted as the top speed for a mustang, but that - is almost certainly for a stripped aircraft. In this cruise - condition, we are carrying about 1100 lbs of fuel that the - record-setting aircraft was (probably) not. Since drag goes - (very roughly) as the square of both weight and speed, a 14% - increase in weight should come out to a proportional reduction - in maximum speed, thus this value. This results in an aircraft - that is much less slippery in descents. -- cruise speed=310 alt=25000 control-setting axis=/controls/engines/engine[0]/throttle value=1.00/ control-setting axis=/controls/engines/engine[0]/mixture value=0.65/ control-setting axis=/controls/engines/engine[0]/propeller-pitch value=1.0/ control-setting axis=/controls/engines/engine[0]/boost value=1.0/ control-setting axis=/controls/flight/flaps value=0.0/ control-setting axis=/controls/gear/gear-down value=0/ /cruise !-- pilot's eyepoint -- cockpit x=-4.495 y=0 z=0.689/ fuselage ax=0.0 ay=0.0 az=0.0 bx=-9.9 by=0.0 bz=0.0 width=0.94 taper=0.38/ !-- stall aoa not available flap drag not available -- wing x=-3.96 y=0.55 z=-0.60 taper=0.466 incidence=1.0 length=5.16 chord=2.845 sweep=-3.5 dihedral=5 camber=0.1 stall aoa=16 width=4 peak=1.5/ flap0 start=0.024 end=0.543 lift=1.2 drag=1.8/ flap1 start=0.543 end=0.945 lift=1.3 drag=1.4/ control-input axis=/controls/flight/flaps
Re: [Flightgear-devel] Help with B-29
On Saturday 19 March 2005 23:55, Josh Babcock wrote: [snip...] Is the sweep supposed to be the LE or the .25% chord? Josh The sweep in YASim is measured at the chord mid-point. At least that's what I've been using:) It corresponds with the wing location definition and I vaguely remember this topic coming up a long time ago. LeeE ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
Re: [Flightgear-devel] Help with B-29
Lee Elliott wrote: On Saturday 19 March 2005 23:55, Josh Babcock wrote: [snip...] Is the sweep supposed to be the LE or the .25% chord? Josh The sweep in YASim is measured at the chord mid-point. At least that's what I've been using:) It corresponds with the wing location definition and I vaguely remember this topic coming up a long time ago. LeeE ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d Thanks. I think I was originally assuming something like that. I'll change the numbers back to what they should be, not that it will make a whole lot of difference until I can get the segfaults to stop. Josh ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
Re: [Flightgear-devel] Help with B-29
From: Andy Ross snip FWIW, I also took the opportunity to re-visit the P-51D configuration that I promised (long ago) to hack at. Attached is a version that snip Also, there is a syntax fix: the piston-engine tag should be a subtag of the propeller tag. Putting it immediately after the propeller definition works only due to a lucky interaction with the way the parser stores its current object pointer. It doesn't clear the value when it sees /propeller, so you can get away with putting the engine at any point in the file before the next tag that sets a current object. I haven't flown this enough to say whether it's worth checking in. Let me know if anyone tries it and likes it. This looks good. I just added it to CVS. Actually the pubs I've seen say 380 is the top speed, so I had backed it off a little with the 360. Some suggestions on how to figure these values might be good YASim Howto material. The p51d (as it was) was not making the 360 anyway, so 310 looks good and makes sense. The test flight I took was still falling well short of the 310kias (maxed @ 260) so I will do a little more testing and let you know. Many thanks for the adjustments. Best regards, Jim ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
Re: [Flightgear-devel] Help with B-29
Jim Wilson wrote: From: Andy Ross snip FWIW, I also took the opportunity to re-visit the P-51D configuration that I promised (long ago) to hack at. Attached is a version that snip Also, there is a syntax fix: the piston-engine tag should be a subtag of the propeller tag. Putting it immediately after the propeller definition works only due to a lucky interaction with the way the parser stores its current object pointer. It doesn't clear the value when it sees /propeller, so you can get away with putting the engine at any point in the file before the next tag that sets a current object. I haven't flown this enough to say whether it's worth checking in. Let me know if anyone tries it and likes it. This looks good. I just added it to CVS. Actually the pubs I've seen say 380 is the top speed, so I had backed it off a little with the 360. Some suggestions on how to figure these values might be good YASim Howto material. The p51d (as it was) was not making the 360 anyway, so 310 looks good and makes sense. The test flight I took was still falling well short of the 310kias (maxed @ 260) so I will do a little more testing and let you know. Many thanks for the adjustments. Note that the speed you give to YAsim is true speed, not indicated airspeed. This can make a big difference up at altitude. Also, you have to pay close attention to the weight YAsim solves at versus the weight you test fly at. Curt. -- Curtis Olsonhttp://www.flightgear.org/~curt HumanFIRST Program http://www.humanfirst.umn.edu/ FlightGear Project http://www.flightgear.org Unique text:2f585eeea02e2c79d7b1d8c4963bae2d ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
Re: [Flightgear-devel] Help with B-29
From: Curtis L. Olson Note that the speed you give to YAsim is true speed, not indicated airspeed. This can make a big difference up at altitude. Also, you have to pay close attention to the weight YAsim solves at versus the weight you test fly at. Hi Curt, Yes, I know. The test flight was at low altitude so I didn't even have to convert. Actually low altitude can also be a factor. I've been messing with the YASim model quite a bit over the last year or two. Like I said I'll do some more tests before bringing it up any problems. My guess is it'll probably work out. Right now I'm running greps on a hard disk device... which...ahem, some folks might know what that means I did earlier tonight :-) Thanks, Jim ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
Re: [Flightgear-devel] Help with B-29
Jim Wilson wrote: 4) Fixed rpm/power numbers under the prop tags. They need to be scaled back according to the gear ratio. Someone with a better understanding of mech engineering might be able to explain why the BHP on the prop shaft is reduced by a factor of 0.35 when that's the gear ratio, or maybe that is wrong and there is something going on in the YASim calcs. Yeah, that's a bug. Power is power. If the prop wants to sync X horsepower at Y RPM, then the engine ought to be defined as producing the same X hp at Y/gear-ratio RPM. Let me take a look. It seems that is what you have to do to get a solution that works. In any case YASim should at least do some sanity checking here to avoid the endless loop thing. Indeed. The problem is that simply exiting the loop in stabilizeThrust() isn't enough to tell you what the problem is. Andy ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
Re: [Flightgear-devel] Help with B-29
Hi guys I guess the only thing that needs to be remembered is the prop tip must never become supersonic so work out the prop dia and what rpm keeps it near supersonic and that will be close to the prop rpm. Cheers Innis From: Arnt Karlsen [EMAIL PROTECTED] Reply-To: FlightGear developers discussions flightgear-devel@flightgear.org To: FlightGear developers discussions flightgear-devel@flightgear.org Subject: Re: [Flightgear-devel] Help with B-29 Date: Sat, 19 Mar 2005 06:24:26 +0100 On Fri, 18 Mar 2005 11:14:45 -0800, Andy wrote in message [EMAIL PROTECTED]: Josh Babcock wrote: OK, here's the file: http://home.comcast.net/~jrbabcock/superfort/b29-yasim.xml Some random notes, before I start running it: The inbord and outboard engines don't match. Your inbord ones are defined to produce 2200 HP at 1000 RPM (which is *monster* engine), while your outboard ones get 2200 at 2900 RPM (a little over 1/3 the power of the others). The inboard ones look typoed to me. I see that all your propellers have a gear-ratio=0.35 setting. This is almost certainly wrong. The B-29 used big cylinder radials, and as far as I know no one ever made one of these with with a gearing system ..no? Those late and post WWII big ass corncobs were all geared, to stay as small as possible. ;o) (no point, as pistons that size can't be made to move much faster). Note also that this doesn't match your (outboard) engine settings. You have a propeller that wants to sink 1800 HP at 2200 RPM. But at that speed the engine would be turning at a shaft-melting 6285 RPM. The props also have buggy settings for their controller levers. The are power-calibrated at 2200 RPM, which matches the engine settings you have. But the max-rpm value is only 1200, so the governor will never allow them to turn that fast. ..those B-29 props was spun at 910 rpm by 2200 T/O and military ponies spinning the crank shaft at 2600 rpm. http://www.wpafb.af.mil/museum/research/bombers/b3-30.htm http://www.google.com/search?num=100q=B-29+R-3350+rpm+%22gear+ratio%22ie=UTF-8oe=UTF-8 I'll try these changes as soon as I get a chance and see what happens. Andy ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d -- ..med vennlig hilsen = with Kind Regards from Arnt... ;o) ...with a number of polar bear hunters in his ancestry... Scenarios always come in sets of three: best case, worst case, and just in case. ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
Re: [Flightgear-devel] Help with B-29
Arnt Karlsen wrote: ..what had me wondering is the eng-rpm in the turbine-engine section, where these word of wisdom appears: ;o) And what would you propose? Turbine RPM is almost never quoted in real units, but in percentages. Where is appropriate, the documentation tells you to specify engine RPM. Where it is not appropriate, it tells you to use shaft RPM. It even explains why. Seriously, if you want a change, ask for it. All you are doing right now is nitpicking and pissing me off. So, let me ask this just once, nicely, before I start yelling: is there an *actual* change to the YASim parser or documentation that you would like to see? Andy ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
Re: [Flightgear-devel] Help with B-29
Jim Wilson wrote: From: Josh Babcock snip Yeah, I'm still messing around and I don't really understand what I'm doing. The .35 gear ratio came straight out of the POH, and I think I recall seeing a cutaway photo of this engine with a gearbox behind the propeller. The engine rpms should be 2900, I'm not sure how that 1000 got in there. The weird controller lever setting are me grasping at straws. Should the prop rpm figures be in prop rpm or engine rpm? I took some of the engine figures and multiplied by .35 whet I set some of those. Hi Josh, I'm not sure what Andy is talking about, which may not mean he's wrong. What I can say for certain, is that if the props are indeed 16.25' in diameter, then 1000 rpm or so would have to be the max. That would make the gear ratio of 0.35 about right. In short, assuming the data you've provided is accurate (it sounds right), your max-rpm under engine should be 2900. Your gear ratio 0.35. And the prop max-rpm should be 1015 (2900 * 0.35). I haven't tried the file yet, this is just based on a quick look at it and the dicussion so far. Best regards, Jim Wilson ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d Yeah, I have been reviewing this, and I think I understand how the definition works. I'm getting pretty much the same numbers based on the 2900 and .35 which I got out of the POH and several internet sources on the cyclone engines. I have a more appropriate yasim file now, but I still can't get it to solve, so I wonder if there is another problem somewhere else? Maybe I have screwed up the aero data and it is producing way too much drag. Here's the latest: http://home.comcast.net/~jrbabcock/superfort/b29-yasim.2.xml Everyone, thanks for all the help so far, it is very appreciated, Josh ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
Re: [Flightgear-devel] Help with B-29
Yeah, I have been reviewing this, and I think I understand how the definition works. I'm getting pretty much the same numbers based on the 2900 and .35 which I got out of the POH and several internet sources on the cyclone engines. I have a more appropriate yasim file now, but I still can't get it to solve, so I wonder if there is another problem somewhere else? Maybe I have screwed up the aero data and it is producing way too much drag. Here's the latest: http://home.comcast.net/~jrbabcock/superfort/b29-yasim.2.xml Everyone, thanks for all the help so far, it is very appreciated, Josh Not sure if I started with the latest or not, but this one solves: http://www.spiderbark.com/fgfs/b29-yasim.xml This is what I changed: 1) Added fuselage length. 2) Increased wing length to something closer to correct length. 3) Probably adjusted a couple other less significant numbers that seemed wrong (wing sweep angle maybe?). 4) Fixed rpm/power numbers under the prop tags. They need to be scaled back according to the gear ratio. Someone with a better understanding of mech engineering might be able to explain why the BHP on the prop shaft is reduced by a factor of 0.35 when that's the gear ratio, or maybe that is wrong and there is something going on in the YASim calcs. It seems that is what you have to do to get a solution that works. In any case YASim should at least do some sanity checking here to avoid the endless loop thing. Solution results: Iterations: 1220 Drag Coefficient: 3.398360 Lift Ratio: 417.065216 Cruise AoA: 1.252508 Tail Incidence: 3.132050 Approach Elevator: 0.268476 CG: -10.439, 0.000, -0.137 This solution isn't quite right. I had to knock down your cruise speed and altitude, but at least you've got something to go back to while tweaking. BTW I don't know much about the B-29, but did you do that airspeed in KIAS? 365 @ 25000 sounds a bit high. Best regards, Jim Wilson ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
Re: [Flightgear-devel] Help with B-29
Jim Wilson wrote: Yeah, I have been reviewing this, and I think I understand how the definition works. I'm getting pretty much the same numbers based on the 2900 and .35 which I got out of the POH and several internet sources on the cyclone engines. I have a more appropriate yasim file now, but I still can't get it to solve, so I wonder if there is another problem somewhere else? Maybe I have screwed up the aero data and it is producing way too much drag. Here's the latest: http://home.comcast.net/~jrbabcock/superfort/b29-yasim.2.xml Everyone, thanks for all the help so far, it is very appreciated, Josh Not sure if I started with the latest or not, but this one solves: http://www.spiderbark.com/fgfs/b29-yasim.xml This is what I changed: 1) Added fuselage length. 2) Increased wing length to something closer to correct length. 3) Probably adjusted a couple other less significant numbers that seemed wrong (wing sweep angle maybe?). 4) Fixed rpm/power numbers under the prop tags. They need to be scaled back according to the gear ratio. Someone with a better understanding of mech engineering might be able to explain why the BHP on the prop shaft is reduced by a factor of 0.35 when that's the gear ratio, or maybe that is wrong and there is something going on in the YASim calcs. It seems that is what you have to do to get a solution that works. In any case YASim should at least do some sanity checking here to avoid the endless loop thing. Solution results: Iterations: 1220 Drag Coefficient: 3.398360 Lift Ratio: 417.065216 Cruise AoA: 1.252508 Tail Incidence: 3.132050 Approach Elevator: 0.268476 CG: -10.439, 0.000, -0.137 This solution isn't quite right. I had to knock down your cruise speed and altitude, but at least you've got something to go back to while tweaking. BTW I don't know much about the B-29, but did you do that airspeed in KIAS? 365 @ 25000 sounds a bit high. Best regards, Jim Wilson ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d Many thanks, I will make these changes (I already caught the fuse snafu, I put that in by accident recently) As for the figures, they are the same ones that I keep seeing everywhere. Actually, the max altitude is more like 32000. Part of the reason that we beat Japan so badly once we got in range is that they simply didn't have anything that could catch and/or reach the superfort. Josh ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
Re: [Flightgear-devel] Help with B-29
Jim Wilson wrote: Yeah, I have been reviewing this, and I think I understand how the definition works. I'm getting pretty much the same numbers based on the 2900 and .35 which I got out of the POH and several internet sources on the cyclone engines. I have a more appropriate yasim file now, but I still can't get it to solve, so I wonder if there is another problem somewhere else? Maybe I have screwed up the aero data and it is producing way too much drag. Here's the latest: http://home.comcast.net/~jrbabcock/superfort/b29-yasim.2.xml Everyone, thanks for all the help so far, it is very appreciated, Josh Not sure if I started with the latest or not, but this one solves: http://www.spiderbark.com/fgfs/b29-yasim.xml This is what I changed: 1) Added fuselage length. 2) Increased wing length to something closer to correct length. 3) Probably adjusted a couple other less significant numbers that seemed wrong (wing sweep angle maybe?). 4) Fixed rpm/power numbers under the prop tags. They need to be scaled back according to the gear ratio. Someone with a better understanding of mech engineering might be able to explain why the BHP on the prop shaft is reduced by a factor of 0.35 when that's the gear ratio, or maybe that is wrong and there is something going on in the YASim calcs. It seems that is what you have to do to get a solution that works. In any case YASim should at least do some sanity checking here to avoid the endless loop thing. Solution results: Iterations: 1220 Drag Coefficient: 3.398360 Lift Ratio: 417.065216 Cruise AoA: 1.252508 Tail Incidence: 3.132050 Approach Elevator: 0.268476 CG: -10.439, 0.000, -0.137 This solution isn't quite right. I had to knock down your cruise speed and altitude, but at least you've got something to go back to while tweaking. BTW I don't know much about the B-29, but did you do that airspeed in KIAS? 365 @ 25000 sounds a bit high. Best regards, Jim Wilson ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d Is the sweep supposed to be the LE or the .25% chord? Josh ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
Re: [Flightgear-devel] Help with B-29
Josh Babcock wrote: Jim Wilson wrote: Yeah, I have been reviewing this, and I think I understand how the definition works. I'm getting pretty much the same numbers based on the 2900 and .35 which I got out of the POH and several internet sources on the cyclone engines. I have a more appropriate yasim file now, but I still can't get it to solve, so I wonder if there is another problem somewhere else? Maybe I have screwed up the aero data and it is producing way too much drag. Here's the latest: http://home.comcast.net/~jrbabcock/superfort/b29-yasim.2.xml Everyone, thanks for all the help so far, it is very appreciated, Josh Not sure if I started with the latest or not, but this one solves: http://www.spiderbark.com/fgfs/b29-yasim.xml This is what I changed: 1) Added fuselage length. 2) Increased wing length to something closer to correct length. 3) Probably adjusted a couple other less significant numbers that seemed wrong (wing sweep angle maybe?). 4) Fixed rpm/power numbers under the prop tags. They need to be scaled back according to the gear ratio. Someone with a better understanding of mech engineering might be able to explain why the BHP on the prop shaft is reduced by a factor of 0.35 when that's the gear ratio, or maybe that is wrong and there is something going on in the YASim calcs. It seems that is what you have to do to get a solution that works. In any case YASim should at least do some sanity checking here to avoid the endless loop thing. Solution results: Iterations: 1220 Drag Coefficient: 3.398360 Lift Ratio: 417.065216 Cruise AoA: 1.252508 Tail Incidence: 3.132050 Approach Elevator: 0.268476 CG: -10.439, 0.000, -0.137 This solution isn't quite right. I had to knock down your cruise speed and altitude, but at least you've got something to go back to while tweaking. BTW I don't know much about the B-29, but did you do that airspeed in KIAS? 365 @ 25000 sounds a bit high. Best regards, Jim Wilson ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d Is the sweep supposed to be the LE or the .25% chord? Josh ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d OK, it solves with this line: control-input axis=/controls/engines/engine[3]/propeller-pitch control=ADVANCE/ but not this one: control-input axis=/controls/engines/engine[3]/propeller-pitch control=PROPPITCH/ Does ADVANCE mean prop pitch here? Josh ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
Re: [Flightgear-devel] Help with B-29
Josh Babcock wrote:
Josh Babcock wrote:
Jim Wilson wrote:
Yeah, I have been reviewing this, and I think I understand how the
definition works. I'm getting pretty much the same numbers based on
the 2900 and .35 which I got out of the POH and several internet
sources on the cyclone engines. I have a more appropriate yasim file
now, but I still can't get it to solve, so I wonder if there is
another problem somewhere else? Maybe I have screwed up the aero
data and it is producing way too much drag.
Here's the latest:
http://home.comcast.net/~jrbabcock/superfort/b29-yasim.2.xml
Everyone, thanks for all the help so far, it is very appreciated,
Josh
Not sure if I started with the latest or not, but this one solves:
http://www.spiderbark.com/fgfs/b29-yasim.xml
This is what I changed:
1) Added fuselage length.
2) Increased wing length to something closer to correct length. 3)
Probably adjusted a couple other less significant numbers that seemed
wrong (wing sweep angle maybe?).
4) Fixed rpm/power numbers under the prop tags. They need to be
scaled back according to the gear ratio. Someone with a better
understanding of mech engineering might be able to explain why the
BHP on the prop shaft is reduced by a factor of 0.35 when that's the
gear ratio, or maybe that is wrong and there is something going on
in the YASim calcs. It seems that is what you have to do to get a
solution that works. In any case YASim should at least do some
sanity checking here to avoid the endless loop thing.
Solution results: Iterations: 1220
Drag Coefficient: 3.398360
Lift Ratio: 417.065216
Cruise AoA: 1.252508
Tail Incidence: 3.132050
Approach Elevator: 0.268476
CG: -10.439, 0.000, -0.137
This solution isn't quite right. I had to knock down your cruise
speed and altitude, but at least you've got something to go back to
while tweaking. BTW I don't know much about the B-29, but did you do
that airspeed in KIAS? 365 @ 25000 sounds a bit high.
Best regards,
Jim Wilson
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Is the sweep supposed to be the LE or the .25% chord?
Josh
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OK, it solves with this line:
control-input axis=/controls/engines/engine[3]/propeller-pitch
control=ADVANCE/
but not this one:
control-input axis=/controls/engines/engine[3]/propeller-pitch
control=PROPPITCH/
Does ADVANCE mean prop pitch here?
Josh
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OK, looks good in yasim, but in fgfs I get this:
[snip]
open(/usr/local/share/FlightGear/data/Aircraft/b29/jim.xml, O_RDONLY) = 15
fstat64(15, {st_mode=S_IFREG|0644, st_size=10371, ...}) = 0
mmap2(NULL, 131072, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) =
0xa53da000
read(15, ?xml version=\1.0\?\n!-- Tacti..., 131072) = 10371
read(15, , 131072)= 0
read(15, , 131072)= 0
close(15) = 0
munmap(0xa53da000, 131072) = 0
--- SIGSEGV (Segmentation fault) @ 0 (0) ---
+++ killed by SIGSEGV +++
Oh woe is me, what's up with the segfaults? Let me know if anyone wants the
whole strace. This looks suspiciously like what the jsbsim one was doing, but my
b29-magic works fine, and the only difference is the fdm file.
Josh
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Re: [Flightgear-devel] Help with B-29
On Sat, 19 Mar 2005 07:45:07 -0800, Andy wrote in message [EMAIL PROTECTED]: Arnt Karlsen wrote: ..what had me wondering is the eng-rpm in the turbine-engine section, where these word of wisdom appears: ;o) And what would you propose? Turbine RPM is almost never quoted in real units, but in percentages. Where is appropriate, the documentation tells you to specify engine RPM. Where it is not appropriate, it tells you to use shaft RPM. It even explains why. ..ah, missed that pie. I agree %'s are more appropriate here, however I feel the 100% rpm figures (that the %'s are calculated from), as such will become useful as we start playing with shaft torque calculations to make things like turbos from shaft driven superchargers and power recovery turbines. Seriously, if you want a change, ask for it. All you are doing right now is nitpicking and pissing me off. So, let me ask this just once, nicely, before I start yelling: is there an *actual* change to the YASim parser or documentation that you would like to see? ..not yet, the docs and source first needs a read, and I some more sleep so the reading gets productive, it's been a while. (Never ever accept round-da-clock-to-meet-everlasting-deadlines just to get your business going.) I stand firm on the B29's R-3350 .35 gear ratio, though. ;o) ..the other change I would like to see in YASim (and the other FDM's too), is running independently like JSBSim can do, so we can simulate one plane with several different networked FDM's to see how they differ in responding to gusts, ice, vortices etc., should help debugging and build better data on modelling new planes. By independently, I mean running YASim, LaRCSim, -UIUC etc outside of FlightGear, I see no need to drag along dead weight, the graphics _is_ the heavy part of FG. -- ..med vennlig hilsen = with Kind Regards from Arnt... ;o) ...with a number of polar bear hunters in his ancestry... Scenarios always come in sets of three: best case, worst case, and just in case. ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
Re: [Flightgear-devel] Help with B-29
Josh Babcock wrote:
Jim Wilson wrote:
It means you've found a bug in the solver. I don't recall it doing
that. Maybe it is just a missing sanity check. Post what you have.
It looks like it's only getting one line into the file. I'll muck with the
first few lines and see what I can do.
Nah, the parser reads the whole file at once. Note the following
lines. It opens the file successfully and stats it to get the size
(which is 10705 bytes). Then it tries to read 10705 bytes from the
file into a 128k buffer, which works in just one syscall.
open(b29-yasim.xml, O_RDONLY) = 3
fstat64(3, {st_mode=S_IFREG|0644, st_size=10705, ...}) = 0
read(3, !-- Tactical Empty Weight 78000..., 131072) = 10705
After that, parsing and solving is 100% CPU work, so strace can't tell
you anything.
I'll give your file a whirl. The only infinte loop condition I'm
aware of at the moment is one where you specify an engine performance
that the solver cannot reach (because of stuff like the throttle being
bound to the wrong property, or not set in the cruise configuration,
etc...) and it iterates forever trying to stabilize the thrust.
Andy
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Re: [Flightgear-devel] Help with B-29
Josh Babcock wrote: OK, here's the file: http://home.comcast.net/~jrbabcock/superfort/b29-yasim.xml Some random notes, before I start running it: The inbord and outboard engines don't match. Your inbord ones are defined to produce 2200 HP at 1000 RPM (which is *monster* engine), while your outboard ones get 2200 at 2900 RPM (a little over 1/3 the power of the others). The inboard ones look typoed to me. I see that all your propellers have a gear-ratio=0.35 setting. This is almost certainly wrong. The B-29 used big cylinder radials, and as far as I know no one ever made one of these with with a gearing system (no point, as pistons that size can't be made to move much faster). Note also that this doesn't match your (outboard) engine settings. You have a propeller that wants to sink 1800 HP at 2200 RPM. But at that speed the engine would be turning at a shaft-melting 6285 RPM. The props also have buggy settings for their controller levers. The are power-calibrated at 2200 RPM, which matches the engine settings you have. But the max-rpm value is only 1200, so the governor will never allow them to turn that fast. I'll try these changes as soon as I get a chance and see what happens. Andy ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
Re: [Flightgear-devel] Help with B-29
Andy Ross wrote: Josh Babcock wrote: OK, here's the file: http://home.comcast.net/~jrbabcock/superfort/b29-yasim.xml Some random notes, before I start running it: The inbord and outboard engines don't match. Your inbord ones are defined to produce 2200 HP at 1000 RPM (which is *monster* engine), while your outboard ones get 2200 at 2900 RPM (a little over 1/3 the power of the others). The inboard ones look typoed to me. I see that all your propellers have a gear-ratio=0.35 setting. This is almost certainly wrong. The B-29 used big cylinder radials, and as far as I know no one ever made one of these with with a gearing system (no point, as pistons that size can't be made to move much faster). Note also that this doesn't match your (outboard) engine settings. You have a propeller that wants to sink 1800 HP at 2200 RPM. But at that speed the engine would be turning at a shaft-melting 6285 RPM. The props also have buggy settings for their controller levers. The are power-calibrated at 2200 RPM, which matches the engine settings you have. But the max-rpm value is only 1200, so the governor will never allow them to turn that fast. I'll try these changes as soon as I get a chance and see what happens. Andy ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d Yeah, I'm still messing around and I don't really understand what I'm doing. The .35 gear ratio came straight out of the POH, and I think I recall seeing a cutaway photo of this engine with a gearbox behind the propeller. The engine rpms should be 2900, I'm not sure how that 1000 got in there. The weird controller lever setting are me grasping at straws. Should the prop rpm figures be in prop rpm or engine rpm? I took some of the engine figures and multiplied by .35 whet I set some of those. Thanks, Josh ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
Re: [Flightgear-devel] Help with B-29
Josh Babcock wrote: Andy Ross wrote: Josh Babcock wrote: OK, here's the file: http://home.comcast.net/~jrbabcock/superfort/b29-yasim.xml Some random notes, before I start running it: The inbord and outboard engines don't match. Your inbord ones are defined to produce 2200 HP at 1000 RPM (which is *monster* engine), while your outboard ones get 2200 at 2900 RPM (a little over 1/3 the power of the others). The inboard ones look typoed to me. I see that all your propellers have a gear-ratio=0.35 setting. This is almost certainly wrong. The B-29 used big cylinder radials, and as far as I know no one ever made one of these with with a gearing system (no point, as pistons that size can't be made to move much faster). Note also that this doesn't match your (outboard) engine settings. You have a propeller that wants to sink 1800 HP at 2200 RPM. But at that speed the engine would be turning at a shaft-melting 6285 RPM. The props also have buggy settings for their controller levers. The are power-calibrated at 2200 RPM, which matches the engine settings you have. But the max-rpm value is only 1200, so the governor will never allow them to turn that fast. I'll try these changes as soon as I get a chance and see what happens. Andy ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d Yeah, I'm still messing around and I don't really understand what I'm doing. The .35 gear ratio came straight out of the POH, and I think I recall seeing a cutaway photo of this engine with a gearbox behind the propeller. The engine rpms should be 2900, I'm not sure how that 1000 got in there. The weird controller lever setting are me grasping at straws. Should the prop rpm figures be in prop rpm or engine rpm? I took some of the engine figures and multiplied by .35 whet I set some of those. Thanks, Josh ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d Yeah, there appear to be some planetary gears here, I am not sure if they are for gearing or if they drive some pump or connect to the starter or generator(s). The oil scavenger pump is located in that general area, but that would be a lot of hardware to drive a little gear pump. http://www.enginehistory.org/GjJBrossett/RAFCosford/Wright%20Cyclone%20R-3350%20cutaway%20view.JPG http://www.enginehistory.org/GjJBrossett/RAFCosford/Wright%20Cyclone%20R-3350%20cutaway.JPG Josh ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
Re: [Flightgear-devel] Help with B-29
Arnt Karlsen wrote: ..very good question! Comparing the notes on piston engines and turboprops, is confusing, is the eng-rpm the prop shaft rpm? [...] ..we're back to checking the source, to see what Andy meant here. ;o) Uh, the lines in the README.yasim document read, exactly: eng-power:Maximum BHP of the engine at sea level. eng-rpm: The engine RPM at which eng-power is developed Now, I'm all for fixing the docs where they need to be fixed; but I hardly had to check the source code to tell that eng-rpm represents the engine RPM at which eng-power is developed. Please let me know if you are still confused. Andy ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
Re: [Flightgear-devel] Help with B-29
On Fri, 18 Mar 2005 15:21:35 -0800, Andy wrote in message [EMAIL PROTECTED]: Arnt Karlsen wrote: ..very good question! Comparing the notes on piston engines and turboprops, is confusing, is the eng-rpm the prop shaft rpm? [...] ..we're back to checking the source, to see what Andy meant here. ;o) Uh, the lines in the README.yasim document read, exactly: eng-power:Maximum BHP of the engine at sea level. eng-rpm: The engine RPM at which eng-power is developed Now, I'm all for fixing the docs where they need to be fixed; but I hardly had to check the source code to tell that eng-rpm represents the engine RPM at which eng-power is developed. Please let me know if you are still confused. ..what had me wondering is the eng-rpm in the turbine-engine section, where these word of wisdom appears: ;o) eng-rpm: The engine RPM at which eng-power is developed. Note that this is shaft RPM as seen by the propeller. Don't use a gear-ratio on the enclosing propeller, or else you'll get confused. :) ..not a problem for the B-29, might possibly be for the turbo-prop Guppies. ;o) -- ..med vennlig hilsen = with Kind Regards from Arnt... ;o) ...with a number of polar bear hunters in his ancestry... Scenarios always come in sets of three: best case, worst case, and just in case. ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
Re: [Flightgear-devel] Help with B-29
On Fri, 18 Mar 2005 11:14:45 -0800, Andy wrote in message [EMAIL PROTECTED]: Josh Babcock wrote: OK, here's the file: http://home.comcast.net/~jrbabcock/superfort/b29-yasim.xml Some random notes, before I start running it: The inbord and outboard engines don't match. Your inbord ones are defined to produce 2200 HP at 1000 RPM (which is *monster* engine), while your outboard ones get 2200 at 2900 RPM (a little over 1/3 the power of the others). The inboard ones look typoed to me. I see that all your propellers have a gear-ratio=0.35 setting. This is almost certainly wrong. The B-29 used big cylinder radials, and as far as I know no one ever made one of these with with a gearing system ..no? Those late and post WWII big ass corncobs were all geared, to stay as small as possible. ;o) (no point, as pistons that size can't be made to move much faster). Note also that this doesn't match your (outboard) engine settings. You have a propeller that wants to sink 1800 HP at 2200 RPM. But at that speed the engine would be turning at a shaft-melting 6285 RPM. The props also have buggy settings for their controller levers. The are power-calibrated at 2200 RPM, which matches the engine settings you have. But the max-rpm value is only 1200, so the governor will never allow them to turn that fast. ..those B-29 props was spun at 910 rpm by 2200 T/O and military ponies spinning the crank shaft at 2600 rpm. http://www.wpafb.af.mil/museum/research/bombers/b3-30.htm http://www.google.com/search?num=100q=B-29+R-3350+rpm+%22gear+ratio%22ie=UTF-8oe=UTF-8 I'll try these changes as soon as I get a chance and see what happens. Andy ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d -- ..med vennlig hilsen = with Kind Regards from Arnt... ;o) ...with a number of polar bear hunters in his ancestry... Scenarios always come in sets of three: best case, worst case, and just in case. ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
Re: [Flightgear-devel] Help with B-29
On Tue, 15 Mar 2005 21:24:00 -0600, Dave wrote in message [EMAIL PROTECTED]: FG_PROPELLER NAME=prop IXX 53.2729 DIAMETER 199.2 NUMBLADES 4 GEARRATIO 2.3 ..ahem: 35/100 for the R-3350's in the B-29'ers. ..the R-3350 was built with several different gear ratios, so we need to chk in each case. ..the B-29D used PW R-4360-35's and was AKA B-50. -- ..med vennlig hilsen = with Kind Regards from Arnt... ;o) ...with a number of polar bear hunters in his ancestry... Scenarios always come in sets of three: best case, worst case, and just in case. ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
Re: [Flightgear-devel] Help with B-29
Arnt Karlsen wrote: On Tue, 15 Mar 2005 21:24:00 -0600, Dave wrote in message [EMAIL PROTECTED]: FG_PROPELLER NAME=prop IXX 53.2729 DIAMETER 199.2 NUMBLADES 4 GEARRATIO 2.3 ..ahem: 35/100 for the R-3350's in the B-29'ers. ..the R-3350 was built with several different gear ratios, so we need to chk in each case. ..the B-29D used PW R-4360-35's and was AKA B-50. Right, thanks. It does say .35 in the POH. Now I have a YASim engine question. I'm trying to rebuild the YASim file from scratch to see if I can get it to work. In README.yasim, the line: eng-rpm: The engine RPM at which eng-power is developed what does eng-power mean? Is this the RPM where the engine catches? Josh ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
Re: [Flightgear-devel] Help with B-29
From: Josh Babcock Right, thanks. It does say .35 in the POH. Now I have a YASim engine question. I'm trying to rebuild the YASim file from scratch to see if I can get it to work. In README.yasim, the line: eng-rpm: The engine RPM at which eng-power is developed what does eng-power mean? Is this the RPM where the engine catches? Sometimes published engine specifications will say X hp at Y rpm. If you don't have that then just use the specified maximum rpm, or maximum sustained rpm, or something along those lines. You would not want to use a dive rpm or war/emergency power rpm number. For the Mustang I used 3000 (published max rpm for merlin 1650), but according to specifications you could spin it up to something like 3500+ in a dive without blowing the engine. Best regards, Jim ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
Re: [Flightgear-devel] Help with B-29
Jim Wilson wrote: From: Josh Babcock Right, thanks. It does say .35 in the POH. Now I have a YASim engine question. I'm trying to rebuild the YASim file from scratch to see if I can get it to work. In README.yasim, the line: eng-rpm: The engine RPM at which eng-power is developed what does eng-power mean? Is this the RPM where the engine catches? Sometimes published engine specifications will say X hp at Y rpm. If you don't have that then just use the specified maximum rpm, or maximum sustained rpm, or something along those lines. You would not want to use a dive rpm or war/emergency power rpm number. For the Mustang I used 3000 (published max rpm for merlin 1650), but according to specifications you could spin it up to something like 3500+ in a dive without blowing the engine. Best regards, Jim ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d OK, I get it, I misunderstood the prop RPM settings and got thoroughly confused. The answer to my question was actually on the previous line of the README. Now, what does it mean if yasim sits there for 15 or more minutes at 98% CPU utilization? That's what's happening with my new yasim file. Josh ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
Re: [Flightgear-devel] Help with B-29
From: Josh Babcock OK, I get it, I misunderstood the prop RPM settings and got thoroughly confused. The answer to my question was actually on the previous line of the README. Now, what does it mean if yasim sits there for 15 or more minutes at 98% CPU utilization? That's what's happening with my new yasim file. It means you've found a bug in the solver. I don't recall it doing that. Maybe it is just a missing sanity check. Post what you have. Best regards, Jim ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
Re: [Flightgear-devel] Help with B-29
Jim Wilson wrote: From: Josh Babcock OK, I get it, I misunderstood the prop RPM settings and got thoroughly confused. The answer to my question was actually on the previous line of the README. Now, what does it mean if yasim sits there for 15 or more minutes at 98% CPU utilization? That's what's happening with my new yasim file. It means you've found a bug in the solver. I don't recall it doing that. Maybe it is just a missing sanity check. Post what you have. Best regards, Jim ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d OK, here's the file: http://home.comcast.net/~jrbabcock/superfort/b29-yasim.xml Here's the strace: http://home.comcast.net/~jrbabcock/superfort/out It looks like it's only getting one line into the file. I'll muck with the first few lines and see what I can do. Here's some output: top - 22:47:44 up 7:58, 11 users, load average: 1.07, 0.45, 0.25 PID PPID UID PR NI VIRT SWAP %CPU %MEM TIME COMMAND 20202 19663 1000 25 0 6136 3544 99.1 0.5 2:31 yasim tower:b29$ time yasim b29-yasim.xml real6m54.660s user6m40.577s sys 0m0.201s ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
Re: [Flightgear-devel] Help with B-29
On Thu, 17 Mar 2005 20:46:32 -0500, Josh wrote in message [EMAIL PROTECTED]: Arnt Karlsen wrote: On Tue, 15 Mar 2005 21:24:00 -0600, Dave wrote in message [EMAIL PROTECTED]: FG_PROPELLER NAME=prop IXX 53.2729 DIAMETER 199.2 NUMBLADES 4 GEARRATIO 2.3 ..ahem: 35/100 for the R-3350's in the B-29'ers. ..the R-3350 was built with several different gear ratios, so we need to chk in each case. ..the B-29D used PW R-4360-35's and was AKA B-50. Right, thanks. It does say .35 in the POH. Now I have a YASim engine question. I'm trying to rebuild the YASim file from scratch to see if I can get it to work. In README.yasim, the line: eng-rpm: The engine RPM at which eng-power is developed what does eng-power mean? ..very good question! Comparing the notes on piston engines and turboprops, is confusing, is the eng-rpm the prop shaft rpm? ..ignoring gear box losses, power is constant thru it, shaft speed in is shaft speed out times the gear ratio and inverse of the torque ratio. ..we're back to checking the source, to see what Andy meant here. ;o) Is this the RPM where the engine catches? Josh -- ..med vennlig hilsen = with Kind Regards from Arnt... ;o) ...with a number of polar bear hunters in his ancestry... Scenarios always come in sets of three: best case, worst case, and just in case. ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
Re: [Flightgear-devel] Help with B-29
On Thu, 17 Mar 2005 21:33:34 -0500, Jim wrote in message [EMAIL PROTECTED]: From: Josh Babcock Right, thanks. It does say .35 in the POH. Now I have a YASim engine question. I'm trying to rebuild the YASim file from scratch to see if I can get it to work. In README.yasim, the line: eng-rpm: The engine RPM at which eng-power is developed what does eng-power mean? Is this the RPM where the engine catches? Sometimes published engine specifications will say X hp at Y rpm. If you don't have that then just use the specified maximum rpm, or maximum sustained rpm, or something along those lines. You would not want to use a dive rpm or war/emergency power rpm number. For the Mustang I used 3000 (published max rpm for merlin 1650), but according to specifications you could spin it up to something like 3500+ in a dive without blowing the engine. ..those big ass corncobs blew much quicker on overspeeding. -- ..med vennlig hilsen = with Kind Regards from Arnt... ;o) ...with a number of polar bear hunters in his ancestry... Scenarios always come in sets of three: best case, worst case, and just in case. ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
Re: [Flightgear-devel] Help with B-29
Josh Babcock wrote: As for the directory, it is Engines, but that doesn't matter, I tried it both ways and it pretty much does the same thing. I just took a closer look at this. I had misread the strace before. Here's what I found that it's doing: This might be a silly question, but are you using a fairly recent version of FlightGear/JSBSim? Erik ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
RE: [Flightgear-devel] Help with B-29
Josh Babcock wrote: As for the directory, it is Engines, but that doesn't matter, I tried it both ways and it pretty much does the same thing. I just took a closer look at this. I had misread the strace before. Here's what I found that it's doing: This might be a silly question, but are you using a fairly recent version of FlightGear/JSBSim? Erik Not a silly question! :-) Version information would help. Josh, I don't recall if you did this already or not, but can you post the B-29 aircraft, engine, and propeller file you got from Aeromatic. It ought to be easy for one of us to figure out if there is a simple error. I've not seen the strace output before that you've been posting so far. Another thing that would help is to change the logging level that FlightGear outputs. I'd like to see the B29 flight model file get read in by FlightGear. By default that is turned off, now, but watching that happen might pinpoint the problem. BTW, on the Boeing B-29 wing, looks like the UIUC airfoil site shows this: Boeing 345 B-29 Superfortress Boeing 117 airfoil (22% @root, 9% @tip). I'll bet that doesn't help a whole lot, but IIRC, the B-17 airfoil was symmetric. Maybe the B-29 wing was, also. Jon ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
Re: [Flightgear-devel] Help with B-29
Ampere K. Hardraade wrote: On March 15, 2005 07:27 am, Josh Babcock wrote: I abandoned the idea of using JSBSim mostly though because I can't find any polar data on the superfort wing. I think DATCOM+can give you the data that you want. Ampere ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d Yes, I would think so to, but from what I have looked at, it has a fairly steep learning curve. Not impossible for me, but pretty time consuming. Josh ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
Re: [Flightgear-devel] Help with B-29
Jon Berndt wrote: Yeah, I actually took a look at that. I have a handle on how to do the XML, I just don't have the expertise to make the actual sound files. The DC3 engine sounds are nice, but they don't quite have that throaty sound that you get from an 18 cyl radial. I found a few recordings, but they are low quality. I suppose I should write to the CAF in Midland and see if they have any recordings of Fifi. That would probably be the best starting point. Josh You could also try Aeromatic at the JSBSim web site: http://www.jsbsim.org/aeromatic.html For giving you a very quick start on a JSBSim flight model. Jon Yes, I actually have. In fact that's where I got the only working flight model that I have. Unfortunately, I couldn't seem to get the engines to work right. I abandoned the idea of using JSBSim mostly though because I can't find any polar data on the superfort wing. I do have cross sections, but it' a lot of work for me to get a fluid dynamics program running to generate the data from the cross sections. I'm also missing some of the geometry info, like twist and hstab incidence. It just seems like the data that I do have is much more suited to YASim. Josh ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
Re: [Flightgear-devel] Help with B-29
Jon Berndt wrote:
Yeah, I actually took a look at that. I have a handle on how to do the XML, I
just don't have the expertise to make the actual sound files. The DC3 engine
sounds are nice, but they don't quite have that throaty sound that you get from
an 18 cyl radial. I found a few recordings, but they are low quality. I suppose
I should write to the CAF in Midland and see if they have any recordings of
Fifi. That would probably be the best starting point.
Josh
You could also try Aeromatic at the JSBSim web site:
http://www.jsbsim.org/aeromatic.html
For giving you a very quick start on a JSBSim flight model.
Jon
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2f585eeea02e2c79d7b1d8c4963bae2d
Jon,
I took another crack at this with aeromatic, but I'm getting the following
segfault from fgfs. It seems that it is looking at the engine file and then
discarding it and looking for an alternative file that doesn't exist. Also,
http://home.comcast.net/~jrbabcock/superfort/b29.xml exists.
Josh
[big snip]
open(/usr/local/share/FlightGear/data/Aircraft/b29/Engines/R-3350.xml,
O_RDONLY) = 9
fstat64(9, {st_mode=S_IFREG|0644, st_size=443, ...}) = 0
mmap2(NULL, 131072, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) =
0xa7b9b000
read(9, ?xml version=\1.0\?\n!--\n Fil..., 131072) = 443
read(9, , 131072) = 0
open(/usr/local/share/FlightGear/data/Aircraft/b29/Engine/R-3350.xml,
O_RDONLY) = -1 ENOENT (No such file or directory)
read(9, , 131072) = 0
close(9)= 0
munmap(0xa7b9b000, 131072) = 0
open(/usr/local/share/FlightGear/data/Aircraft/b29/Engines/R-3350.xml,
O_RDONLY) = 9
fstat64(9, {st_mode=S_IFREG|0644, st_size=443, ...}) = 0
mmap2(NULL, 131072, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) =
0xa7b9b000
read(9, ?xml version=\1.0\?\n!--\n Fil..., 131072) = 443
read(9, , 131072) = 0
open(/usr/local/share/FlightGear/data/Aircraft/b29/Engine/R-3350.xml,
O_RDONLY) = -1 ENOENT (No such file or directory)
read(9, , 131072) = 0
close(9)= 0
munmap(0xa7b9b000, 131072) = 0
open(/usr/local/share/FlightGear/data/Aircraft/b29/Engines/R-3350.xml,
O_RDONLY) = 9
fstat64(9, {st_mode=S_IFREG|0644, st_size=443, ...}) = 0
mmap2(NULL, 131072, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) =
0xa7b9b000
read(9, ?xml version=\1.0\?\n!--\n Fil..., 131072) = 443
read(9, , 131072) = 0
open(/usr/local/share/FlightGear/data/Aircraft/b29/Engine/R-3350.xml,
O_RDONLY) = -1 ENOENT (No such file or directory)
read(9, , 131072) = 0
close(9)= 0
munmap(0xa7b9b000, 131072) = 0
open(/usr/local/share/FlightGear/data/Aircraft/b29/Engines/R-3350.xml,
O_RDONLY) = 9
fstat64(9, {st_mode=S_IFREG|0644, st_size=443, ...}) = 0
mmap2(NULL, 131072, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) =
0xa7b9b000
read(9, ?xml version=\1.0\?\n!--\n Fil..., 131072) = 443
read(9, , 131072) = 0
open(/usr/local/share/FlightGear/data/Aircraft/b29/Engine/R-3350.xml,
O_RDONLY) = -1 ENOENT (No such file or directory)
read(9, , 131072) = 0
close(9)= 0
munmap(0xa7b9b000, 131072) = 0
read(8, , 131072) = 0
read(8, , 131072) = 0
close(8)= 0
munmap(0xa7c0d000, 131072) = 0
--- SIGSEGV (Segmentation fault) @ 0 (0) ---
+++ killed by SIGSEGV +++
FYI:
tower:b29$ cat /usr/local/share/FlightGear/data/Aircraft/b29/Engines/R-3350.xml
?xml version=1.0?
!--
File: R-3350.xml
Author: Aero-Matic v 0.7
Inputs:
name: R-3350
type: piston
power: 2200 hp
augmented? no
injected? no
--
FG_PISTON NAME=R-3350
MINMP 6.0
MAXMP 30.0
DISPLACEMENT 3520.00
MAXHP2200.00
CYCLES 2.0
IDLERPM 700.0
MAXTHROTTLE1.0
MINTHROTTLE0.2
/FG_PISTON
___
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2f585eeea02e2c79d7b1d8c4963bae2d
Re: [Flightgear-devel] Help with B-29
open(/usr/local/share/FlightGear/data/Aircraft/b29/Engine/R-3350.xml, The directory should be plural, Engines. Maybe that will fix it. Also, this prop config will give you better thrust. Aero-Matic's prop generator needs some work. xml version=1.0? !-- Generated by Aero-Matic v 0.7, with new CT and CP tables from Aero-Matic v 0.8 Inputs: horsepower: 2200.0 pitch:variable Outputs: linear-blade-inches: 248.59203527064 -- FG_PROPELLER NAME=prop IXX 53.2729 DIAMETER 199.2 NUMBLADES 4 GEARRATIO 2.3 MINPITCH 12 MAXPITCH 40 MINRPM904 MAXRPM 1130 C_THRUST 2 2 12 40 0.0 0.0519 0.0519 2.4 0.0519 0.0519 C_POWER 17 2 12 40 0.0 0.0604 0.1204 0.1 0.0604 0.1204 0.2 0.0575 0.1204 0.3 0.0547 0.1204 0.4 0.0481 0.1204 0.5 0.0396 0.1191 0.6 0.0321 0.1177 0.7 0.0189 0.1151 0.8 0.0075 0.1097 1.0 -0.0226 0.0896 1.2 -0.0660 0.0602 1.4 -0.1226 0.0301 1.6 -0.1811-0.0026 1.8 -0.2415-0.0734 2.0 -0.3019-0.1469 2.2 -0.3623-0.2203 2.4 -0.4227-0.2937 /FG_PROPELLER Dave ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
Re: [Flightgear-devel] Help with B-29
Dave Culp wrote:
open(/usr/local/share/FlightGear/data/Aircraft/b29/Engine/R-3350.xml,
The directory should be plural, Engines. Maybe that will fix it.
Also, this prop config will give you better thrust. Aero-Matic's prop
generator needs some work.
[snip]
Dave,
Thanks for the prop file. I'll try it out, though I may have written that file
from scratch myself, which is probably no better :)
As for the directory, it is Engines, but that doesn't matter, I tried it both
ways and it pretty much does the same thing. I just took a closer look at this.
I had misread the strace before. Here's what I found that it's doing:
brk
brk
open b29.xml
fstat
mmap2 address
some junk
for i = 1 .. 4
Attempt to open the file in Engines
memap2
read from it
close it
munmap
Attempt to open the file in Engine
memap2
read from it
close it
munmap
munmap address
segfault
So it looks like it's choking when it tries to free some memory that it was
using when it started parsing the FDM file, and the engine file has nothing to
do with it.
Thoughts?
Josh
Here's a bigger strace starting before the first mmap2 call:
brk(0) = 0xcb44000
brk(0xcb7) = 0xcb7
open(/usr/local/share/FlightGear/data/Aircraft/b29/b29.xml, O_RDONLY) = 8
fstat64(8, {st_mode=S_IFREG|0644, st_size=12009, ...}) = 0
mmap2(NULL, 131072, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) =
0xa7c3e000THIS ONE**
read(8, FDM_CONFIG NAME=\b29\ VERSION=\..., 131072) = 12009
rt_sigaction(SIGINT, {SIG_IGN}, {SIG_DFL}, 8) = 0
rt_sigaction(SIGQUIT, {SIG_IGN}, {SIG_DFL}, 8) = 0
rt_sigprocmask(SIG_BLOCK, [CHLD], [], 8) = 0
clone(child_stack=0, flags=CLONE_PARENT_SETTID|SIGCHLD,
parent_tidptr=0xbfffed40) = 4875
waitpid(4875, [{WIFEXITED(s) WEXITSTATUS(s) == 0}], 0) = 4875
rt_sigaction(SIGINT, {SIG_DFL}, NULL, 8) = 0
rt_sigaction(SIGQUIT, {SIG_DFL}, NULL, 8) = 0
rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
fstat64(1, {st_mode=S_IFCHR|0620, st_rdev=makedev(136, 2), ...}) = 0
mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) =
0xa7c3d000
write(1, \n, 1) = 1
write(1, \n, 1) = 1
write(1, \33[1mThis aircraft model is a \33[3..., 58) = 58
write(1, \n, 1) = 1
write(1, \33[0mThis aircraft model probably..., 59) = 59
write(1, \n, 1) = 1
write(1, \33[34m\33[1mUse this model for deve..., 66) = 66
write(1, \n, 1) = 1
open(/usr/local/share/FlightGear/data/Aircraft/b29/Engines/R-3350.xml,
O_RDONLY) = -1 ENOENT (No such file or directory)
open(/usr/local/share/FlightGear/data/Aircraft/b29/Engine/R-3350.xml,
O_RDONLY) = 9
fstat64(9, {st_mode=S_IFREG|0644, st_size=434, ...}) = 0
mmap2(NULL, 131072, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) =
0xa7bcc000
read(9, ?xml version=\1.0\?\n!--\n Fil..., 131072) = 434
read(9, , 131072) = 0
read(9, , 131072) = 0
close(9)= 0
munmap(0xa7bcc000, 131072) = 0
open(/usr/local/share/FlightGear/data/Aircraft/b29/Engines/R-3350.xml,
O_RDONLY) = -1 ENOENT (No such file or directory)
open(/usr/local/share/FlightGear/data/Aircraft/b29/Engine/R-3350.xml,
O_RDONLY) = 9
fstat64(9, {st_mode=S_IFREG|0644, st_size=434, ...}) = 0
mmap2(NULL, 131072, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) =
0xa7bcc000
read(9, ?xml version=\1.0\?\n!--\n Fil..., 131072) = 434
read(9, , 131072) = 0
read(9, , 131072) = 0
close(9)= 0
munmap(0xa7bcc000, 131072) = 0
open(/usr/local/share/FlightGear/data/Aircraft/b29/Engines/R-3350.xml,
O_RDONLY) = -1 ENOENT (No such file or directory)
open(/usr/local/share/FlightGear/data/Aircraft/b29/Engine/R-3350.xml,
O_RDONLY) = 9
fstat64(9, {st_mode=S_IFREG|0644, st_size=434, ...}) = 0
mmap2(NULL, 131072, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) =
0xa7bcc000
read(9, ?xml version=\1.0\?\n!--\n Fil..., 131072) = 434
read(9, , 131072) = 0
read(9, , 131072) = 0
close(9)= 0
munmap(0xa7bcc000, 131072) = 0
open(/usr/local/share/FlightGear/data/Aircraft/b29/Engines/R-3350.xml,
O_RDONLY) = -1 ENOENT (No such file or directory)
open(/usr/local/share/FlightGear/data/Aircraft/b29/Engine/R-3350.xml,
O_RDONLY) = 9
fstat64(9, {st_mode=S_IFREG|0644, st_size=434, ...}) = 0
mmap2(NULL, 131072, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) =
0xa7bcc000
read(9, ?xml version=\1.0\?\n!--\n Fil..., 131072) = 434
read(9, , 131072) = 0
read(9, , 131072) = 0
close(9)= 0
munmap(0xa7bcc000, 131072) = 0
Re: [Flightgear-devel] Help with B-29
Josh Babcock wrote: OK, so I've been slowly working on this: http://home.comcast.net/~jrbabcock/superfort/ for quite some time now. I planned on getting it into CVS once it had a reasonable start for a flight model. My problem is that I apparently am genetically incapable of getting a YASim config to converge. I also have no experience creating sounds, and I want this aircraft to have several. For the sound you might want to start by using the DC-3 configuration file. Not exactly what you are looking for, but it would be a nice starting position. Erik ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
Re: [Flightgear-devel] Help with B-29
Erik Hofman wrote: Josh Babcock wrote: OK, so I've been slowly working on this: http://home.comcast.net/~jrbabcock/superfort/ for quite some time now. I planned on getting it into CVS once it had a reasonable start for a flight model. My problem is that I apparently am genetically incapable of getting a YASim config to converge. I also have no experience creating sounds, and I want this aircraft to have several. For the sound you might want to start by using the DC-3 configuration file. Not exactly what you are looking for, but it would be a nice starting position. Erik ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d Yeah, I actually took a look at that. I have a handle on how to do the XML, I just don't have the expertise to make the actual sound files. The DC3 engine sounds are nice, but they don't quite have that throaty sound that you get from an 18 cyl radial. I found a few recordings, but they are low quality. I suppose I should write to the CAF in Midland and see if they have any recordings of Fifi. That would probably be the best starting point. Josh ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
RE: [Flightgear-devel] Help with B-29
Yeah, I actually took a look at that. I have a handle on how to do the XML, I just don't have the expertise to make the actual sound files. The DC3 engine sounds are nice, but they don't quite have that throaty sound that you get from an 18 cyl radial. I found a few recordings, but they are low quality. I suppose I should write to the CAF in Midland and see if they have any recordings of Fifi. That would probably be the best starting point. Josh You could also try Aeromatic at the JSBSim web site: http://www.jsbsim.org/aeromatic.html For giving you a very quick start on a JSBSim flight model. Jon ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
Re: [Flightgear-devel] Help with B-29
Josh Babcock wrote: My problem is that I apparently am genetically incapable of getting a YASim config to converge. XML file? Output? Andy ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
