RE: [Flightgear-devel] Spitfire - new release
Andy Ross wrote: Sent: 12 August 2004 19:58 To: FlightGear developers discussions Subject: Re: [Flightgear-devel] Spitfire - new release OK, Melchior helped to debug this via chat while I was working on cell phone UI bugs at work. :) It turns out to have been a pair of typos in fuel.nas that were causing all the problems. What I *read* wasn't what the code was actually doing, which explains all the confusion. Yes - thanks. I knew that you would come up with a proper solution. Bit more testing next time, Eh? This one, though, isn't fixed: 3. When a tank is empty, the tank is de-selected by fuel.nas. Thus the position of the fuel cock levers on the Spitfire panel do not necessarily reflect the state of the tank. This is really a metaphor collision. The notion of a tank selected as used by the fuel code and FDM isn't quite the same as that of position of the switch in the cockpit. Yes, quite. I'm still working on the best solution. (the magneto switches have traditionally had the same issue). Philosophically speaking, the property magneto should be a child of engine, while magneto-switch is a control property. Never mind, we don't need to go there, and I've worked up a good solution for the magneto switches in Nasal. It might be a better idea to define a different property to drive the fuel cock animation, and use a Nasal binding to synchronize this with the tank selected property only when it changes (basically: make the fuel cocks output only devices). At the moment this is the case, so when fuel.nas changes the selected state (and I understand why it needs to do this) the fuel cock levers are left behind, and no longer represent the state of selection of the tanks. An alternative is for the fuel cocks to accurately represent the state of selection. However, this would mean that they would move by themselves, which I don't particularly favour right now. I think a more complex solution might be necessary for proper realism. I can't quite see my way through this one yet. Anyway, thanks again for providing a proper solution to these problems Regards, Vivian ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
Re: [Flightgear-devel] Spitfire - new release
Vivian Meazza wrote:
This is, I believe, due to a bug at line 67 of the script
~/data/nasal/fuel.nas which improperly sets the tank property
kill-when-empty.
Haven't we already been here and thrown out this explanation? Here is
line 67:
if(t.getBoolValue(kill-when-empty)) { outOfFuel = 1; }
The property is *read* here, not written.
Can someone else reproduce this issue (the tank's kill-when-empty
property being set mysteriously) with another aircraft?
Andy
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Re: [Flightgear-devel] Spitfire - new release
OK, Melchior helped to debug this via chat while I was working on cell phone UI bugs at work. :) It turns out to have been a pair of typos in fuel.nas that were causing all the problems. What I *read* wasn't what the code was actually doing, which explains all the confusion. This one, though, isn't fixed: 3. When a tank is empty, the tank is de-selected by fuel.nas. Thus the position of the fuel cock levers on the Spitfire panel do not necessarily reflect the state of the tank. This is really a metaphor collision. The notion of a tank selected as used by the fuel code and FDM isn't quite the same as that of position of the switch in the cockpit (the magneto switches have traditionally had the same issue). It might be a better idea to define a different property to drive the fuel cock animation, and use a Nasal binding to synchronize this with the tank selected property only when it changes (basically: make the fuel cocks output only devices). Andy ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
RE: [Flightgear-devel] Spitfire
-Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Bernie Bright Sent: 27 July 2004 05:41 To: FlightGear developers discussions Subject: Re: [Flightgear-devel] Spitfire Vivian Meazza wrote: Ampere K. Hardraade wrote Sent: 26 July 2004 03:13 To: FlightGear developers discussions Subject: Re: [Flightgear-devel] Spitfire To create smoke, we will need two things: smoke emitter and smoke object. [snip] Good analysis. How much of this already exists, either in the context of 3d clouds or AI? plib.ssgAux has a particle system that can simulate smoke. Attach one to an animation object and there you have it. Any takers? Someone (David Megginson?) mentioned the particle system when the subject of smoke was brought up some time ago. Can you point me at some more detail? Regards, Vivian ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
Re: [Flightgear-devel] Spitfire
Vivian Meazza wrote: plib.ssgAux has a particle system that can simulate smoke. Attach one to an animation object and there you have it. Any takers? Someone (David Megginson?) mentioned the particle system when the subject of smoke was brought up some time ago. It may have been me but nothing ever came of it. Can you point me at some more detail? What I am proposing is to derive a new class from SGAnimation that contains a ssgaParticleSystem object. The aircraft xml file specifies the object's location wrt the airframe reference point and color/type of smoke etc. Individual particles are updated every frame according to the laws of physics. Some experimentation will be involved to determine the best number and size of particles. You can view the ssgaParticleSystem documentation and examples at the plib website, http://plib.sourceforge.net/ssgAux/index.html. I don't think the SGAnimation class hierarchy is documented but there are plenty of derived classes to get ideas from. This could be a good first project for someone getting involved with flightgear. It is relatively small and self-contained and provides some exposure to plib, simgear and flightgear. Plus it has obvious visual feedback. Bernie ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
RE: [Flightgear-devel] Spitfire
Ampere K. Hardraade wrote Sent: 26 July 2004 03:13 To: FlightGear developers discussions Subject: Re: [Flightgear-devel] Spitfire To create smoke, we will need two things: smoke emitter and smoke object. The smoke emitter will allow the user to set the following properties: - X, Y, Z coordinate relative to the aircraft. This is the location at which the smoke objects will be created. - vector at which the smoke is emitted. - initial velocity of the smoke relative to the aircraft. - radius of the smoke. - temperature of the smoke (useful when velocity is zero). - density/opacity of the smoke. - illumination value of the smoke in RGB. - color of the smoke. - time it takes for the smoke to become visible. - rate at which the smoke will dessipate. - time it takes for the smoke to lose illumination. - a boolean variable to control the state of the smoke emitter. When the smoke emitter is enabled, it will keep creating new smoke objects. These new smoke objects will have the following properties: - current X, Y, Z coordinates relative to the world. - velocity relative to the world. - current raidus. - time until it becomes visible. - current density. - current illumination. Unlike the smoke emitter, these properties will be completely isolated from the user. In addition, it also needs several functions to: - calculate its new velocity. - calculate its velocity relative to the smoke source. - place itself at the new coordinate. - calculate its new radius. - change its own temperature. - change its own density. - change its own illumination. - determine what type of smoke it will be (explain later). This way, the smoke can be create and forget. As for the actual visible smoke, it can can takes on several geometries. A few useful ones are: - low poly sphereical. - cylindical (for smoke ring). - dougnut/torus (for a more detail smoke ring). - a simple polygon (for low velocity smoke). Each type of geometry has its own advantages and performance issues. That's why it should be controlled by the smoke object instead of the user. In the lifetime of the smoke, these geometries will expand, change orientation, and eveuntually deform, may even change type, and finally dissipate. For the spitfire, since the smoke won't come out at very high speed during engine start, polygon should be used to represent each smoke object. Now if only some kind soul will implement this. =P To be honest, I would rather want someone to fix the framerate problem before working on eye candy. Regards, Ampere On July 22, 2004 11:06 am, Vivian Meazza wrote: I've implemented a Coffman cartridge starter, and it would be nice to have a cloud of black smoke come out of the exhaust and drift downwind at wind speed before dispersing. I can do the first bit, but not the rest. I have my eye on Fred's bump-mapped 3D clouds. Anyone any ideas on this one? (Forget it could be good advice :-) ). Good analysis. How much of this already exists, either in the context of 3d clouds or AI? Regards, Vivian ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Spitfire
Vivian Meazza wrote: Ampere K. Hardraade wrote Sent: 26 July 2004 03:13 To: FlightGear developers discussions Subject: Re: [Flightgear-devel] Spitfire To create smoke, we will need two things: smoke emitter and smoke object. [snip] Good analysis. How much of this already exists, either in the context of 3d clouds or AI? plib.ssgAux has a particle system that can simulate smoke. Attach one to an animation object and there you have it. Any takers? Bernie ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
Re: [Flightgear-devel] Spitfire
To create smoke, we will need two things: smoke emitter and smoke object. The smoke emitter will allow the user to set the following properties: - X, Y, Z coordinate relative to the aircraft. This is the location at which the smoke objects will be created. - vector at which the smoke is emitted. - initial velocity of the smoke relative to the aircraft. - radius of the smoke. - temperature of the smoke (useful when velocity is zero). - density/opacity of the smoke. - illumination value of the smoke in RGB. - color of the smoke. - time it takes for the smoke to become visible. - rate at which the smoke will dessipate. - time it takes for the smoke to lose illumination. - a boolean variable to control the state of the smoke emitter. When the smoke emitter is enabled, it will keep creating new smoke objects. These new smoke objects will have the following properties: - current X, Y, Z coordinates relative to the world. - velocity relative to the world. - current raidus. - time until it becomes visible. - current density. - current illumination. Unlike the smoke emitter, these properties will be completely isolated from the user. In addition, it also needs several functions to: - calculate its new velocity. - calculate its velocity relative to the smoke source. - place itself at the new coordinate. - calculate its new radius. - change its own temperature. - change its own density. - change its own illumination. - determine what type of smoke it will be (explain later). This way, the smoke can be create and forget. As for the actual visible smoke, it can can takes on several geometries. A few useful ones are: - low poly sphereical. - cylindical (for smoke ring). - dougnut/torus (for a more detail smoke ring). - a simple polygon (for low velocity smoke). Each type of geometry has its own advantages and performance issues. That's why it should be controlled by the smoke object instead of the user. In the lifetime of the smoke, these geometries will expand, change orientation, and eveuntually deform, may even change type, and finally dissipate. For the spitfire, since the smoke won't come out at very high speed during engine start, polygon should be used to represent each smoke object. Now if only some kind soul will implement this. =P To be honest, I would rather want someone to fix the framerate problem before working on eye candy. Regards, Ampere On July 22, 2004 11:06 am, Vivian Meazza wrote: I've implemented a Coffman cartridge starter, and it would be nice to have a cloud of black smoke come out of the exhaust and drift downwind at wind speed before dispersing. I can do the first bit, but not the rest. I have my eye on Fred's bump-mapped 3D clouds. Anyone any ideas on this one? (Forget it could be good advice :-) ). ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
RE: [Flightgear-devel] Spitfire
To create smoke, we will need two things: smoke emitter and smoke object. I really hope you can do this. Smoke and fire are important for the X-15, too. :-) Jon ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Spitfire
I hope so too, but the fact is: I'm not a programmer. Regards, Ampere On July 25, 2004 10:53 pm, Jon Berndt wrote: I really hope you can do this. Smoke and fire are important for the X-15, too. ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
RE: [Flightgear-devel] Spitfire
Hi Vivian Vivian Meazza writes I've implemented a Coffman cartridge starter, and it would be nice to have a cloud of black smoke come out of the exhaust and drift downwind at wind speed before dispersing. I can do the first bit, but not the rest. I have my eye on Fred's bump-mapped 3D clouds. Anyone any ideas on this one? (Forget it could be good advice :-) ). No sounds like a good idea there were/are quite a few aircraft that use cartridge start the canberra bomber and the sea venom come to mind.Also it could be arranged to simulate the dirty black smoke that came out of the commercial aircraft of the 60's,70's and 80's Regards, Vivian Cheers Innis _ ½ Price FOXTEL Digital Installation On-Line Limited Offer: http://ninemsn.com.au/share/redir/adTrack.asp?mode=clickclientID=225referral=Hotmail_tagline_July04URL=http://ad.au.doubleclick.net/clk;9412514;9681905;p?http://www.foxtel.com.au/2231.htm ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
RE: [Flightgear-devel] Spitfire
I wrote Sent: 16 July 2004 09:41 To: 'FlightGear developers discussions' Subject: RE: [Flightgear-devel] Spitfire Erik Hofman wrote Sent: 16 July 2004 08:44 To: FlightGear developers discussions Subject: Re: [Flightgear-devel] Spitfire Vivian Meazza wrote: Back up with an upgraded machine - 2.8 Mhz P4, 512 Ram, Gforce 5200. I've rebuilt Cywin, and FGFS-CVS. I've just copied the latest version of the Spitfire from FGFS-0.9.4, where it was working, after a fashion, to FGFS-CVS. All the files. Now it won't fly, as David pointed out. Back to the drawing board! I already started to wonder if the Spitfire was more of a hype than anything else (and even started to wonder if I was such a lousy pilot) :-D You didn't try it in 0.9.4 then? It's really easy to fly, but a little difficult to get off the ground neatly, possible though. Landing's a doddle, providing that there's no crosswind. Spitfires were NOT designed for runways. Anyway, it now works in CVS, and I'm tackling the sound right now. Let me know how you get on, and we'll leave a judgment on lousy pilots 'til later :-) I've sent an updated version of the Spitfire MkIIa to Eric for CVS. It's almost finished now: just some cockpit details and pilot animation to do. I'd be grateful for any feedback you might have, but remember that it's still using legacy propeller/engine code. Still, it flies well enough to have some fun with, I think. I've implemented a Coffman cartridge starter, and it would be nice to have a cloud of black smoke come out of the exhaust and drift downwind at wind speed before dispersing. I can do the first bit, but not the rest. I have my eye on Fred's bump-mapped 3D clouds. Anyone any ideas on this one? (Forget it could be good advice :-) ). Regards, Vivian ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
RE: [Flightgear-devel] Spitfire
I wrote Sent: 15 July 2004 22:16 To: 'FlightGear developers discussions' Subject: RE: [Flightgear-devel] Spitfire I wrote Sent: 09 July 2004 09:53 To: 'FlightGear developers discussions' Subject: RE: [Flightgear-devel] Spitfire David Megginson wrote Sent: 09 July 2004 00:24 To: FlightGear developers discussions Subject: Re: [Flightgear-devel] Spitfire Vivian Meazza wrote: There should also be a version with the legacy code, and that does fly (or rather, does for me), although the performance is a bit down. I don't think that there is an error in the code, but I'll double check with the legacy version Thanks. It's a beautiful model, by the way. Thanks for that - I have an upgraded version with a more accurate cockpit nearly ready to go. There is a real Spitfire based at my home airport -- I actually gave up my parking place for it during our Fly Day a couple of weeks ago. It's normally over on the south field, but I love watching it take off when it's at our end of the airport. If only the plane had an extra seat ... I've tested the CVS version (legacy propeller/engine code) under FGFS 0.9.4 (windows version). Flies OK. 'Evidence' attached. I can't test under CVS source code: frame rate too slow on my computer, which I will upgrade in the very near future. Perhaps that will solve the problem, or, more likely, since I'm doing it myself, I'll lose all the data and take 2 weeks to recover! Back up with an upgraded machine - 2.8 Mhz P4, 512 Ram, Gforce 5200. I've rebuilt Cywin, and FGFS-CVS. I've just copied the latest version of the Spitfire from FGFS-0.9.4, where it was working, after a fashion, to FGFS-CVS. All the files. Now it won't fly, as David pointed out. Back to the drawing board! Regards Vivian Solved (I think) Replace this line in spitfire.xml control-input axis=/controls/engines/engine[0]/propeller-pitch control=PROPPITCH src0=0 src1=1 dst0=0.2 dst1=0.95 / with this one control-input axis=/controls/engines/engine[0]/propeller-pitch control=PROPPITCH src0=0 src1=1 dst0=0.2 dst1=0.8 / I don't know why. I suppose something has changed in the cvs version of YASim. Andy could explain perhaps. I'll send a revised model into Curt for cvs later, when I have reached a suitable point in my upgrade to the cockpit. Probably after the weekend. Regards Vivian ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Spitfire
Vivian Meazza wrote: Back up with an upgraded machine - 2.8 Mhz P4, 512 Ram, Gforce 5200. I've rebuilt Cywin, and FGFS-CVS. I've just copied the latest version of the Spitfire from FGFS-0.9.4, where it was working, after a fashion, to FGFS-CVS. All the files. Now it won't fly, as David pointed out. Back to the drawing board! I already started to wonder if the Spitfire was more of a hype than anything else (and even started to wonder if I was such a lousy pilot) :-D Erik ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
RE: [Flightgear-devel] Spitfire
Erik Hofman wrote Sent: 16 July 2004 08:44 To: FlightGear developers discussions Subject: Re: [Flightgear-devel] Spitfire Vivian Meazza wrote: Back up with an upgraded machine - 2.8 Mhz P4, 512 Ram, Gforce 5200. I've rebuilt Cywin, and FGFS-CVS. I've just copied the latest version of the Spitfire from FGFS-0.9.4, where it was working, after a fashion, to FGFS-CVS. All the files. Now it won't fly, as David pointed out. Back to the drawing board! I already started to wonder if the Spitfire was more of a hype than anything else (and even started to wonder if I was such a lousy pilot) :-D You didn't try it in 0.9.4 then? It's really easy to fly, but a little difficult to get off the ground neatly, possible though. Landing's a doddle, providing that there's no crosswind. Spitfires were NOT designed for runways. Anyway, it now works in CVS, and I'm tackling the sound right now. Let me know how you get on, and we'll leave a judgment on lousy pilots 'til later :-) Regards Vivian ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
RE: [Flightgear-devel] Spitfire
I wrote Sent: 09 July 2004 09:53 To: 'FlightGear developers discussions' Subject: RE: [Flightgear-devel] Spitfire David Megginson wrote Sent: 09 July 2004 00:24 To: FlightGear developers discussions Subject: Re: [Flightgear-devel] Spitfire Vivian Meazza wrote: There should also be a version with the legacy code, and that does fly (or rather, does for me), although the performance is a bit down. I don't think that there is an error in the code, but I'll double check with the legacy version Thanks. It's a beautiful model, by the way. Thanks for that - I have an upgraded version with a more accurate cockpit nearly ready to go. There is a real Spitfire based at my home airport -- I actually gave up my parking place for it during our Fly Day a couple of weeks ago. It's normally over on the south field, but I love watching it take off when it's at our end of the airport. If only the plane had an extra seat ... I've tested the CVS version (legacy propeller/engine code) under FGFS 0.9.4 (windows version). Flies OK. 'Evidence' attached. I can't test under CVS source code: frame rate too slow on my computer, which I will upgrade in the very near future. Perhaps that will solve the problem, or, more likely, since I'm doing it myself, I'll lose all the data and take 2 weeks to recover! Back up with an upgraded machine - 2.8 Mhz P4, 512 Ram, Gforce 5200. I've rebuilt Cywin, and FGFS-CVS. I've just copied the latest version of the Spitfire from FGFS-0.9.4, where it was working, after a fashion, to FGFS-CVS. All the files. Now it won't fly, as David pointed out. Back to the drawing board! Regards Vivian ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Spitfire
Ampere K. Hardraade wrote: Mwhaha... http://www.alexisparkinn.com/photogallery/Videos/ohmygodSpitfire pass.wmv Does anyone have a copy of it ? Martin. -- Unix _IS_ user friendly - it's just selective about who its friends are ! -- ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Spitfire
Hi Guys Of course you could do what I did with the P51 I could not fly just make a quick FDM in JSBSIM with aeromatic. I know thats not the fix but hey it flys Cheers Innis From: David Megginson writes Andy Ross wrote: I know Vivian has had trouble getting it working with the gear ratio stuff on the engine. This (along with tuning the p51d) has been on my list for ages, but I've been swamped with work and homeowner concerns recently. I'm still alive, I promise. :) I don't think it's an engine problem, though -- if I start in the air with a bit of velocity, I should be able to control the plane even if the engine is shut off. All the best, David ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel _ Get a Credit Card - 60 sec online response: http://ad.au.doubleclick.net/clk;8097459;9106288;b?http://www.anz.com/aus/promo/qantas5000ninemsn [AU only] ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
RE: [Flightgear-devel] Spitfire
David Megginson wrote Sent: 09 July 2004 00:24 To: FlightGear developers discussions Subject: Re: [Flightgear-devel] Spitfire Vivian Meazza wrote: There should also be a version with the legacy code, and that does fly (or rather, does for me), although the performance is a bit down. I don't think that there is an error in the code, but I'll double check with the legacy version Thanks. It's a beautiful model, by the way. Thanks for that - I have an upgraded version with a more accurate cockpit nearly ready to go. There is a real Spitfire based at my home airport -- I actually gave up my parking place for it during our Fly Day a couple of weeks ago. It's normally over on the south field, but I love watching it take off when it's at our end of the airport. If only the plane had an extra seat ... I've tested the CVS version (legacy propeller/engine code) under FGFS 0.9.4 (windows version). Flies OK. 'Evidence' attached. I can't test under CVS source code: frame rate too slow on my computer, which I will upgrade in the very near future. Perhaps that will solve the problem, or, more likely, since I'm doing it myself, I'll lose all the data and take 2 weeks to recover! Regards Vivian attachment: fgfs-screen-002.jpg___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Spitfire
On Thu, 08 Jul 2004 16:36:56 -0400 David Megginson [EMAIL PROTECTED] wrote: Can anyone actually fly the Spitfire model in CVS? fgfs --aircraft=spitfireIIa The elevators seem to have no effect at all. On the ground, the plane starts nosing down as soon as it gets to around 30 kt, and after an in-air start, it just dives. I wonder if there's something wrong in the YASim config file. Confirmed. Also, at least for me, I have the same problem as with some other aircraft like the Cessna, in that the volume settings are out of whack, resulting in choppy broken audio and lots of WARNING: Volume larger than 1.0 for configuration for 'engine2' Oops AL error in sample set_volume()! 2.15 for /home/cmetzler/Projects/FlightGear-0.9/data//Aircraft/Spitfire/Sounds/merlin_rpm4_1.wav type messages. -c -- Chris Metzler [EMAIL PROTECTED] (remove snip-me. to email) As a child I understood how to give; I have forgotten this grace since I have become civilized. - Chief Luther Standing Bear pgp5jfBkWKwWh.pgp Description: PGP signature ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Spitfire
On Thu, 08 Jul 2004 16:36:56 -0400 David Megginson [EMAIL PROTECTED] wrote: Can anyone actually fly the Spitfire model in CVS? fgfs --aircraft=spitfireIIa The elevators seem to have no effect at all. On the ground, the plane starts nosing down as soon as it gets to around 30 kt, and after an in-air start, it just dives. I wonder if there's something wrong in the YASim config file. Confirmed. Also, at least for me, I have the same problem as with some other aircraft like the Cessna, in that the volume settings are out of whack, resulting in choppy broken audio and lots of WARNING: Volume larger than 1.0 for configuration for 'engine2' Oops AL error in sample set_volume()! 2.15 for /home/cmetzler/Projects/FlightGear-0.9/data//Aircraft/Spitfire/Sounds/merlin_rpm4_1.wav type messages. -c -- Chris Metzler [EMAIL PROTECTED] (remove snip-me. to email) As a child I understood how to give; I have forgotten this grace since I have become civilized. - Chief Luther Standing Bear pgpSPeLMSUzR5.pgp Description: PGP signature ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Spitfire
David Megginson wrote: Can anyone actually fly the Spitfire model in CVS? I wonder if there's something wrong in the YASim config file. I know Vivian has had trouble getting it working with the gear ratio stuff on the engine. This (along with tuning the p51d) has been on my list for ages, but I've been swamped with work and homeowner concerns recently. I'm still alive, I promise. :) Andy ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Spitfire
Andy Ross wrote: I know Vivian has had trouble getting it working with the gear ratio stuff on the engine. This (along with tuning the p51d) has been on my list for ages, but I've been swamped with work and homeowner concerns recently. I'm still alive, I promise. :) I don't think it's an engine problem, though -- if I start in the air with a bit of velocity, I should be able to control the plane even if the engine is shut off. All the best, David ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
RE: [Flightgear-devel] Spitfire
Andy Ross wrote: I know Vivian has had trouble getting it working with the gear ratio stuff on the engine. This (along with tuning the p51d) has been on my list for ages, but I've been swamped with work and homeowner concerns recently. I'm still alive, I promise. :) I don't think it's an engine problem, though -- if I start in the air with a bit of velocity, I should be able to control the plane even if the engine is shut off. All the best, David With the new propeller/engine code, YASim doesn't work quite right. It's there so that Andy can tinker when he has time... There should also be a version with the legacy code, and that does fly (or rather, does for me), although the performance is a bit down. I don't think that there is an error in the code, but I'll double check with the legacy version Sorry about the sound, haven't got around to fixing it up, but since the engine rpm are all wrong, there didn't seem to be any urgency. We'll get there by and by, please bear with us. Regards Vivian ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Spitfire
Vivian Meazza wrote: There should also be a version with the legacy code, and that does fly (or rather, does for me), although the performance is a bit down. I don't think that there is an error in the code, but I'll double check with the legacy version Thanks. It's a beautiful model, by the way. There is a real Spitfire based at my home airport -- I actually gave up my parking place for it during our Fly Day a couple of weeks ago. It's normally over on the south field, but I love watching it take off when it's at our end of the airport. If only the plane had an extra seat ... All the best, David ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Spitfire
Mwhaha... http://www.alexisparkinn.com/photogallery/Videos/ohmygodSpitfire pass.wmv Regards, Ampere On July 8, 2004 07:23 pm, David Megginson wrote: I love watching it take off when it's at our end of the airport. If only the plane had an extra seat ... All the best, David ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Spitfire
I think this problem occurs with the F16 in 0.9.4 as well when the fuel tanks are full. Regards, Ampere On July 8, 2004 04:36 pm, David Megginson wrote: Can anyone actually fly the Spitfire model in CVS? fgfs --aircraft=spitfireIIa The elevators seem to have no effect at all. On the ground, the plane starts nosing down as soon as it gets to around 30 kt, and after an in-air start, it just dives. I wonder if there's something wrong in the YASim config file. All the best, David ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Spitfire
Ampere K. Hardraade wrote: Mwhaha... http://www.alexisparkinn.com/photogallery/Videos/ohmygodSpitfirepass.wmv Yes, I've seen that clip -- it's pretty funny (scary, actually). Fortunately, the one based at CYOW tends to stick to the runway. All the best, David ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
RE: [Flightgear-devel] Spitfire model
Hi, I've forwarded the current state-of-play Spitfire model to Curt for release in CVS. The model is also available here: http://myweb.tiscali.co.uk/vmeazza/FlightGear/spitfire.tar.gz There are 2 versions: spitfireIIa with legacy YASim propeller/engine code, and spitfireIIa-mod1 with the current propeller/engine code. Only spitfireIIa flies, spitfireIIa-mod1 only allows you to taxi, and that barely. The POH is here: http://home.clara.net/wolverine/BOB/misc/Spit_Hurri_Manuals.zip You might also need this http://myweb.tiscali.co.uk/vmeazza/FlightGear/spitfire_key_bindings.pdf The model should operate as advertised! The sound remains a mess right now, and until the YASim propeller/engine gearing problem is solved, I can't progress it There are also unresolved errors in the -set.xml file: controls engines engine n=0 magneto-switch type=bool1/magneto-switch magneto-switch type=bool1/magneto-switch magnetos3/magnetos /engine /engines /controls I then try to access it elsewhere. This works: binding commandnasal/command script setprop(controls/engines/engine/magneto-switch[0],1); /script /binding But this doesn't: binding commandnasal/command script setprop(controls/engines/engine/magneto-switch[1],1); /script /binding I have left this code in so that the problem can be investigated, but I can work around it. I hope that we can resolve the YASim propeller/engine gearing problem soon. Regards Vivian ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
RE: [Flightgear-devel] Spitfire Performance Testing
Andy Ross wrote Vivian Meazza wrote: Now the bad news - the new propeller/engine code does not seem to work for me. These are the input data: Nothing looks wrong from reading it. Can you post the whole file so I can test? Thanks. This is the whole file. It worked(ish) with the old propeller/engine code. ?xml version=1.0? !-- YASim aerodynamic model for a Spitfire IIa The reference datum for measurements is the nose. -- !-- Weight of everything but fuel (4873 empty) -- airplane mass=5200 !-- Approach configuration -- approach speed=75 aoa=13 control-setting axis=/controls/engines/engine[0]/throttle value=0.1/ control-setting axis=/controls/engines/engine[0]/mixture value=1.0/ control-setting axis=/controls/engines/engine[0]/propeller-pitch value=0.2/ control-setting axis=/controls/engines/engine[0]/boost value=0.25/ control-setting axis=/controls/flight/flaps value=1.0/ control-setting axis=/controls/gear/gear-down value=1/ solve-weight idx=0 weight=180/ /approach !-- Cruise configuration -- cruise speed=308 alt=17500 control-setting axis=/controls/engines/engine[0]/throttle value=1.00/ control-setting axis=/controls/engines/engine[0]/mixture value=1.00/ control-setting axis=/controls/engines/engine[0]/propeller-pitch value=1.0/ control-setting axis=/controls/engines/engine[0]/boost value=1/ control-setting axis=/controls/flight/flaps value=0.0/ control-setting axis=/controls/gear/gear-down value=0/ solve-weight idx=0 weight=180/ /cruise !-- pilot's eyepoint -- cockpit x=-3.86 y=0 z=0.55/ fuselage ax=0.0 ay=0.0 az=0.0 bx=-9.13 by=0.0 bz=0.0 width=0.95 taper=0.38 midpoint=0.4 / !-- NACA airfoil section 2213 stall aoa not available flap drag not available -- wing x=-2.99 y=0.77 z=-0.81 taper=0.3 incidence=2 twist=-2.0 length=4.580 chord=2.845 sweep=0 camber=0.0569 dihedral=6 effectiveness=1.25 stall aoa=20 width=4 peak=1.5/ flap0 start=0.00 end=0.437 lift=1.4 drag=1.6/ flap1 start=0.437 end=0.90 lift=1.3 drag=1.3/ control-input axis=/controls/flight/flaps control=FLAP0/ control-output control=FLAP0 prop=/surface-positions/flap-pos-norm/ control-speed control=FLAP0 transition-time=5/ control-input axis=/controls/flight/aileron control=FLAP1 split=true/ Bcontrol-output control=FLAP1 side=left prop=/surface-positions/left-aileron-pos-norm/ control-output control=FLAP1 side=right prop=/surface-positions/right-aileron-pos-norm/ /wing !-- tailplane -- hstab x=-8.22 y=0.25 z=0.0 taper=0.639 effectiveness=2 length=1.215 chord=1.246 sweep=5 stall aoa=21 width=4 peak=1.5/ flap0 start=0.0 end=1 lift=1.7 drag=1.5/ control-input axis=/controls/flight/elevator control=FLAP0/ control-input axis=/controls/flight/elevator-trim control=FLAP0/ control-output control=FLAP0 prop=/surface-positions/elevator-pos-norm/ /hstab !-- tail -- vstab x=-8.52 y=0 z=-0.29 taper=0.386 length=1.65 chord=0.994 sweep=5 stall aoa=20 width=4 peak=1.5/ flap0 start=0 end=1 lift=1.4 drag=1.4/ control-input axis=/controls/flight/rudder square=true control=FLAP0 invert=true/ control-input axis=/controls/flight/rudder-trim control=FLAP0 invert=true/ control-output control=FLAP0 prop=/surface-positions/rudder-pos-norm min=1 max=-1/ /vstab !-- stub wing left -- vstab x=-2.99 y=0.32 z=-0.81 taper=0 incidence=2 twist=0 chord=2.845 sweep=0 camber=0.0569 dihedral=-90 length=0.503 stall aoa=20 width=4 peak=1.5/ flap0 start=0.00 end=1 lift=1.4 drag=1.6/ control-input axis=/controls/flight/flaps control=FLAP0/ control-output control=FLAP0 prop=/surface-positions/flap-pos-norm/ control-speed control=FLAP0 transition-time=5/ /vstab !-- stub wing right -- vstab x=-2.99 y=-0.32 z=-0.81 taper=0 incidence=2 twist=0 chord=2.845 sweep=0 camber=0.0569 dihedral=90 length=0.503 stall aoa=20 width=4 peak=1.5/ flap0 start=0.00 end=1 lift=1.4 drag=1.6/ control-input axis=/controls/flight/flaps control=FLAP0/ control-output control=FLAP0 prop=/surface-positions/flap-pos-norm/ control-speed control=FLAP0 transition-time=5/ /vstab !-- radiator wing right -- vstab x=-3.23 y=-0.51 z=1.02 taper=0 incidence=0 twist=0 chord=1.114 sweep=0 camber=0.0 dihedral=84 length=0.63 stall aoa=20 width=4 peak=1.5/ flap0 start=0.00 end=1 lift=1.4 drag=1.4/ control-input axis=/controls/engines/engine/cowl-flaps-norm control=FLAP0/ control-output control=FLAP0 prop=/engines/engine/cowl-flaps-norm/ control-speed control=FLAP0 transition-time=3 / /vstab !-- propeller and engine -- !-- moment = radius(m)* propeller mass(kg)/2 - equation provided by Andy Ross -- !-- cruise-rpm documented gear ratio of
Re: [Flightgear-devel] Spitfire Performance Testing
Rick aked himself: (Or do I remember seeing film with the canopy open during the approach?) Yes. It makes landing easier to open the canopy and look around the big engine in front :). :) Nice job Vivian :) Yes, indeed! Rick Bye bye, Wolfram. ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Spitfire Performance Testing
On Friday 14 May 2004 08:30, Erik Hofman wrote: Jim Wilson wrote: Vivian Meazza said: Nearly there: http://myweb.tiscali.co.uk/vmeazza/FlightGear/spitfireIIa-1.jpg http://myweb.tiscali.co.uk/vmeazza/FlightGear/spitfireIIa-2.jpg Great progress...very nice! Very nice indeed! Thirded - or is that fourthed? Very nice model Vivian. LeeE ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Spitfire Performance Testing
On Friday 14 May 2004 23:44, Rick Ansell wrote: On Fri, 14 May 2004 22:48:19 +0100 Vivian Meazza [EMAIL PROTECTED] wrote: -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Rick Ansell Sent: 14 May 2004 21:30 To: FlightGear developers discussions snip I don't recall a jettison function: it had to moved to the rear by hand in an emergency. Aerodynamic forces tended to keep it closed. There are many stories of pilots only managing to escape at the last minute, and I suspect quite a few didn't make it. I'm fairly certain it existed, at least in later versions. There was also an escape drill for a jammed canopy: Undo seat straps. Crouch on seat with back against canopy. Push stick forward as hard and sharply as you can. 'You will now be clear of the aircraft' :) Ah - the old 'kiss-your-ass goodbye' pose:) Using -ve G to throw the pilot out probably worked well if the a/c was in reasonably controlled flight. Might have been more difficult to do if it was tumbling though. A moot point if the pilot can choose but... I'm fairly sure that on ops and current displays the canopy was/is closed on take-off, but I may be mistaken. On ops getting airborne and into the climb as rapidly as possible curtosy of the reduced drag of a closed canopy would take precedence over safety. Dreams It would be nice if the extra drag 'with the top down' was represented /Dreams ignore me, I'm just remembering a spring day a few years ago, sat on the edge of a cornfield at the foot of the Downs, late summer sunshine, a lone Spitfire cavorting in the crystal blue overhead... ...alone in the office watching a Spitfire in the golden twilight, low level over Farnborough airfield... Rick Not quite as poetic, but yesterday evening while sitting in the pub garden, I saw an AN-124 on approach to Stanstead, for the second time - saw another one earlier this year, and for the second time I was too intent on watching it to remember to get the camera out for a few quick snaps:) LeeE ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
RE: [Flightgear-devel] Spitfire Performance Testing
Andy Ross wrote: Sent: 13 May 2004 23:38 To: FlightGear developers discussions Subject: Re: [Flightgear-devel] Spitfire Performance Testing Vivian Meazza wrote: As you can see, it flies. The engine/propeller combination is a horrid bodge in YASim. Very unrealistic performance. Looking forward to resolving that issue. I actually thought it was resolved. Did the recent changes not work for you? I can only fix bugs that are reported. :) First the good news - Cygwin compiles at last - thanks, I think, to Normans latest files. Now the bad news - the new propeller/engine code does not seem to work for me. These are the input data: propeller x=-1.2 y=0 z=0.0 mass=2000 moment=30 radius=1.638 cruise-speed=308 cruise-rpm=1360 cruise-power=1140 cruise-alt=15000 takeoff-power=1120 takeoff-rpm=1300 gear-ratio = 0.477 piston-engine eng-power=1140 eng-rpm=2850 displacement=1649 turbo-mul=3.5 wastegate-mp=48/ /propeller YASim finds a solution which seems reasonable, but the engine idles 445 rpm, and does not accelerate beyond 1485 rpm when throttle = 1. Thrust is 388 lbs - way too low. The model does not fly. Have I misinterpreted the input data requirements? Regards Vivian ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Spitfire Performance Testing
Vivian Meazza wrote: Now the bad news - the new propeller/engine code does not seem to work for me. These are the input data: Nothing looks wrong from reading it. Can you post the whole file so I can test? Thanks. Andy ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
RE: [Flightgear-devel] Spitfire Performance Testing
Andy wrote -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Andy Ross Sent: 13 May 2004 23:38 To: FlightGear developers discussions Subject: Re: [Flightgear-devel] Spitfire Performance Testing Vivian Meazza wrote: As you can see, it flies. The engine/propeller combination is a horrid bodge in YASim. Very unrealistic performance. Looking forward to resolving that issue. I actually thought it was resolved. Did the recent changes not work for you? I can only fix bugs that are reported. :) Sorry, Andy, I've missed the changes. What did you? Actually, I haven't been able to make Cygwin work readily (source of much frustration), so I made the decision to concentrate my efforts on the 3d model, and return to the YASim issue later. Of course, I'm very keen to test your modified program, so now - back to Cygwin. Vivian ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Spitfire Performance Testing
Jim Wilson wrote: Vivian Meazza said: Nearly there: http://myweb.tiscali.co.uk/vmeazza/FlightGear/spitfireIIa-1.jpg http://myweb.tiscali.co.uk/vmeazza/FlightGear/spitfireIIa-2.jpg Great progress...very nice! Very nice indeed! Erik ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Spitfire Performance Testing
On Fri, 14 May 2004 09:30:37 +0200 Erik Hofman [EMAIL PROTECTED] wrote: Jim Wilson wrote: Vivian Meazza said: Nearly there: http://myweb.tiscali.co.uk/vmeazza/FlightGear/spitfireIIa-1.jpg http://myweb.tiscali.co.uk/vmeazza/FlightGear/spitfireIIa-2.jpg Great progress...very nice! Very nice indeed! Very, very, nice! No doubt you will model the canopy closed in future - it was opened in flight under anything but emergency circumstances. It might be nice if it moved in a reasonably realistic way: Open when static on ground (pilot boarding, briefing etc.) Slides forward to the 'slightly open' position adopted by pilots to take advantage of the cooling slipstream from the prop on engine start. Fully closed just before take-off (throttle advanced beyond x%) Slides forward to 'slightly open' again when 'weight on wheels', speed less than y Fully open with 'weight on wheels' and engine stop. (Or do I remember seeing film with the canopy open during the approach?) Fully open or jettisoned in flight under certain circumstances (pilot departed, or preparing to do so - in which case control,input should be disabled!) I know opinions differ on this subject but this is one aircraft that could benefit from the eventual addition of a pilot - the highly visible cockpit makes his presence part of the 'visual signature' of the aircraft. The choice of Bonedome or Helmet and Goggles will depend on whether you wish to represent a modern display aircraft or the historical item. Do we have access to a suitable sound file for the very distinctive Merlin song? :) Nice job Vivian :) Rick ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
RE: [Flightgear-devel] Spitfire Performance Testing
-Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Rick Ansell Sent: 14 May 2004 21:30 To: FlightGear developers discussions Subject: Re: [Flightgear-devel] Spitfire Performance Testing On Fri, 14 May 2004 09:30:37 +0200 Erik Hofman [EMAIL PROTECTED] wrote: Jim Wilson wrote: Vivian Meazza said: Nearly there: http://myweb.tiscali.co.uk/vmeazza/FlightGear/spitfireIIa-1.jpg http://myweb.tiscali.co.uk/vmeazza/FlightGear/spitfireIIa-2.jpg Great progress...very nice! Very nice indeed! Very, very, nice! No doubt you will model the canopy closed in future - it was opened in flight under anything but emergency circumstances. It might be nice if it moved in a reasonably realistic way: Open when static on ground (pilot boarding, briefing etc.) Slides forward to the 'slightly open' position adopted by pilots to take advantage of the cooling slipstream from the prop on engine start. Fully closed just before take-off (throttle advanced beyond x%) Slides forward to 'slightly open' again when 'weight on wheels', speed less than y Fully open with 'weight on wheels' and engine stop. (Or do I remember seeing film with the canopy open during the approach?) Fully open or jettisoned in flight under certain circumstances (pilot departed, or preparing to do so - in which case control,input should be disabled!) POH calls for the canopy to be locked open for take-off and landing so that in the event of inverting, (not uncommon) the pilot could escape more easily. The door opens a little to what the POH describes as half-cocked to lock the canopy in the rear position. It will be under operator control, so you will be able to please yourself. I don't recall a jettison function: it had to moved to the rear by hand in an emergency. Aerodynamic forces tended to keep it closed. There are many stories of pilots only managing to escape at the last minute, and I suspect quite a few didn't make it. I know opinions differ on this subject but this is one aircraft that could benefit from the eventual addition of a pilot - the highly visible cockpit makes his presence part of the 'visual signature' of the aircraft. The choice of Bonedome or Helmet and Goggles will depend on whether you wish to represent a modern display aircraft or the historical item. Helmet and Goggles, I think. The aircraft modelled is the one operated by the Battle of Britain Memorial Flight, so it could be either. Do we have access to a suitable sound file for the very distinctive Merlin song? Yes - a genuine recording, and all the other sounds - undercarriage, flaps etc (pneumatic) :) Nice job Vivian :) Ta Vivian ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Spitfire Performance Testing
On Fri, 14 May 2004 22:48:19 +0100 Vivian Meazza [EMAIL PROTECTED] wrote: -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Rick Ansell Sent: 14 May 2004 21:30 To: FlightGear developers discussions snip I don't recall a jettison function: it had to moved to the rear by hand in an emergency. Aerodynamic forces tended to keep it closed. There are many stories of pilots only managing to escape at the last minute, and I suspect quite a few didn't make it. I'm fairly certain it existed, at least in later versions. There was also an escape drill for a jammed canopy: Undo seat straps. Crouch on seat with back against canopy. Push stick forward as hard and sharply as you can. 'You will now be clear of the aircraft' :) A moot point if the pilot can choose but... I'm fairly sure that on ops and current displays the canopy was/is closed on take-off, but I may be mistaken. On ops getting airborne and into the climb as rapidly as possible curtosy of the reduced drag of a closed canopy would take precedence over safety. Dreams It would be nice if the extra drag 'with the top down' was represented /Dreams ... ignore me, I'm just remembering a spring day a few years ago, sat on the edge of a cornfield at the foot of the Downs, late summer sunshine, a lone Spitfire cavorting in the crystal blue overhead... ...alone in the office watching a Spitfire in the golden twilight, low level over Farnborough airfield... Rick ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
RE: [Flightgear-devel] Spitfire Performance Testing
Erik Hofman wrote (some time ago) Sent: 01 May 2004 08:42 To: FlightGear developers discussions Subject: Re: [Flightgear-devel] Spitfire Performance Testing Vivian Meazza wrote: Thanks, Eric, that link was already a primary source. It's all coming together nicely. Just finishing texturing, a little more animation to do, and about half the 3d instruments. You'll be glad to know that the model is under 5000 vertices so far. I have bodged the engine, and it flies delightfully, but we await Andy's revised engine for proper realism. About 2 or 3 weeks should see it done. This is all wonderful news. I can hardly wait to try it! Thanks for putting all this time into it. Nearly there: http://myweb.tiscali.co.uk/vmeazza/FlightGear/spitfireIIa-1.jpg http://myweb.tiscali.co.uk/vmeazza/FlightGear/spitfireIIa-2.jpg Just the 3d cockpit to do now - it has a basic blind flying panel, but the instruments are borrowed from elsewhere, and are not all the right type. Another 10 days or so to complete. As you can see, it flies. The engine/propeller combination is a horrid bodge in YASim. Very unrealistic performance. Looking forward to resolving that issue. Regards Vivian ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
RE: [Flightgear-devel] Spitfire Performance Testing
Vivian Meazza said: Erik Hofman wrote (some time ago) Sent: 01 May 2004 08:42 To: FlightGear developers discussions Subject: Re: [Flightgear-devel] Spitfire Performance Testing Vivian Meazza wrote: Thanks, Eric, that link was already a primary source. It's all coming together nicely. Just finishing texturing, a little more animation to do, and about half the 3d instruments. You'll be glad to know that the model is under 5000 vertices so far. I have bodged the engine, and it flies delightfully, but we await Andy's revised engine for proper realism. About 2 or 3 weeks should see it done. This is all wonderful news. I can hardly wait to try it! Thanks for putting all this time into it. Nearly there: http://myweb.tiscali.co.uk/vmeazza/FlightGear/spitfireIIa-1.jpg http://myweb.tiscali.co.uk/vmeazza/FlightGear/spitfireIIa-2.jpg Great progress...very nice! Best, Jim ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
RE: [Flightgear-devel] Spitfire Propeller vs. YASim
-Original Message- From: Vivian Meazza Sent: 04 May 2004 7:38 pm To: 'FlightGear developers discussions' Subject: RE: [Flightgear-devel] Spitfire Propeller vs. YASim Richard Bytheway wrote Sent: 04 May 2004 10:42 To: FlightGear developers discussions Subject: RE: [Flightgear-devel] Spitfire Propeller vs. YASim I had already shown by some pretty simple math that at 2850 rmp the tips of a 1.65m radius propeller would be supersonic and therefore highly improbable, but we now know that the data of hp, gear ratio, rpm etc all tie together. Thanks Vivian Meazza I have a memory from years back of being told that the reason the Spitfire had such a distinctive sound was that the propellor tips _were_ supersonic. Maybe it was just heresay. Richard I think it is possible that the propeller tips went supersonic in the corners of the flight envelope of some of the later versions. However, the math seems to show that in most circumstances they were not. It seems unlikely that this could explain the distinctive sound when heard from the ground. Here are some calculations on propeller rpm. The propeller the tip speed should be as high as possible with the only limitation being that the tip should not get into the region of aerodynamic compressibility. Typically a figure of Mach 0.85 is used as the magic number that should not be exceeded. (This makes some allowance for the speed increase as the air passes over the aerofoil curved surface and the increase in air velocity caused by the propeller operation.) If we take 8000 ft as the operating altitude then Mach 1 = 1085 ft/sec (approx) Assuming that the forward velocity of the aircraft is 300 mph = 440 ft/sec Then the maximum rotational velocity may be calculated by Pythagoras: Max Rotational Velocity = ((M *1085)^2 - (V)^2)^0.5 where M is the designed Mach Number (0.85) and V is the aircraft forward velocity = ((0.85*1085)^2 -(440)^2)^0.5 = 810.52 ft/sec RPM at Max rotational velocity is given by: RPM = Max rotational velocity*60/(PI * D) Where D is the propeller diameter (ft) = 810.52*60/(PI * 10.75) = 1439.98 rpm At 3000 rpm the propeller rpm is 1431 rpm, but the Merlin only did this when the throttle was through the gate, and the Boost Control Valve Cutout was operated. This was allowed for 5 minutes. We can calculate the Max Rotational Velocity @ 1431 rpm Max rotational velocity (PI * D) = (RPM/60) * (PI * D) = (1431/60) * (PI * 10.75) = 805 ft/sec We can also calculate the Mach Number (M) of the tip by rearranging and substituting M = ((805^2+440^2)^0.5)/1085 = 0.8459 I hope that all the maths are correct. I think all this shows that under normal operating conditions, and observing the normal operating limit of 2850 rpm, it is unlikely that the propeller tips would exceed M1. Regards Vivian Very clear, thanks, Richard ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
RE: [Flightgear-devel] Spitfire Propeller vs. YASim
I had already shown by some pretty simple math that at 2850 rmp the tips of a 1.65m radius propeller would be supersonic and therefore highly improbable, but we now know that the data of hp, gear ratio, rpm etc all tie together. Thanks Vivian Meazza I have a memory from years back of being told that the reason the Spitfire had such a distinctive sound was that the propellor tips _were_ supersonic. Maybe it was just heresay. RIchard ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Spitfire Propeller vs. YASim
Richard Bytheway wrote: I have a memory from years back of being told that the reason the Spitfire had such a distinctive sound was that the propellor tips _were_ supersonic. Maybe it was just heresay. That probably was for the Harvard. Erik ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Spitfire Propeller vs. YASim
Richard Bytheway wrote: I have a memory from years back of being told that the reason the Spitfire had such a distinctive sound was that the propellor tips _were_ supersonic. Maybe it was just heresay. I don't know about the Spitfire, but I understand that's the case with many floatplanes -- you can usually tell when a plane flying overhead is a floatplane without looking up. All the best, David ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
RE: [Flightgear-devel] Spitfire Propeller vs. YASim
Richard Bytheway said: I had already shown by some pretty simple math that at 2850 rmp the tips of a 1.65m radius propeller would be supersonic and therefore highly improbable, but we now know that the data of hp, gear ratio, rpm etc all tie together. At higher altitudes? IIRC when working on the p51d I figured just below 600mph was the speed of the propellor tips. The merlin had a slightly higher max rpm figure (3000) at that point. Best, Jim ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
RE: [Flightgear-devel] Spitfire Propeller vs. YASim
Richard Bytheway wrote Sent: 04 May 2004 10:42 To: FlightGear developers discussions Subject: RE: [Flightgear-devel] Spitfire Propeller vs. YASim I had already shown by some pretty simple math that at 2850 rmp the tips of a 1.65m radius propeller would be supersonic and therefore highly improbable, but we now know that the data of hp, gear ratio, rpm etc all tie together. Thanks Vivian Meazza I have a memory from years back of being told that the reason the Spitfire had such a distinctive sound was that the propellor tips _were_ supersonic. Maybe it was just heresay. Richard I think it is possible that the propeller tips went supersonic in the corners of the flight envelope of some of the later versions. However, the math seems to show that in most circumstances they were not. It seems unlikely that this could explain the distinctive sound when heard from the ground. Here are some calculations on propeller rpm. The propeller the tip speed should be as high as possible with the only limitation being that the tip should not get into the region of aerodynamic compressibility. Typically a figure of Mach 0.85 is used as the magic number that should not be exceeded. (This makes some allowance for the speed increase as the air passes over the aerofoil curved surface and the increase in air velocity caused by the propeller operation.) If we take 8000 ft as the operating altitude then Mach 1 = 1085 ft/sec (approx) Assuming that the forward velocity of the aircraft is 300 mph = 440 ft/sec Then the maximum rotational velocity may be calculated by Pythagoras: Max Rotational Velocity = ((M *1085)^2 - (V)^2)^0.5 where M is the designed Mach Number (0.85) and V is the aircraft forward velocity = ((0.85*1085)^2 -(440)^2)^0.5 = 810.52 ft/sec RPM at Max rotational velocity is given by: RPM = Max rotational velocity*60/(PI * D) Where D is the propeller diameter (ft) = 810.52*60/(PI * 10.75) = 1439.98 rpm At 3000 rpm the propeller rpm is 1431 rpm, but the Merlin only did this when the throttle was through the gate, and the Boost Control Valve Cutout was operated. This was allowed for 5 minutes. We can calculate the Max Rotational Velocity @ 1431 rpm Max rotational velocity (PI * D) = (RPM/60) * (PI * D) = (1431/60) * (PI * 10.75) = 805 ft/sec We can also calculate the Mach Number (M) of the tip by rearranging and substituting M = ((805^2+440^2)^0.5)/1085 = 0.8459 I hope that all the maths are correct. I think all this shows that under normal operating conditions, and observing the normal operating limit of 2850 rpm, it is unlikely that the propeller tips would exceed M1. Regards Vivian ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
RE: [Flightgear-devel] Spitfire Propeller vs. YASim
Wolfram Kuss Spitfire Mk IIA Ah - surprising! Here is an email Rick Fuelcock sent me a short while ago. I hope it helps. Sorry for the poor formating. --- snip - Rather than send you the GBE code , I will direct you to the site where I got it: http://www.aeromech.usyd.edu.au/aero/propeller/prop1.html Just click on program 1 at the bottom of the page. Program 2 (right below) is mathlab code for the implementation without the bells and whistles. I have been playing around with program 1, and have obtained very encouraging results. I keyed in a Spitfire prop with radius 1.55 m and a blade area of 0.98m^3. The program only let's you design a simple blade with a straight, symetrical taper. Rather than complicate things, I just kept the cord constant at .210 the radius to give a total area of .327m^3 per blade. Not knowing anything for sure about the blade angle at a given radius, I just used the default pitch of 0.5, where: pitch = 2pi * r tan theta and theta is the geometric angle of the blade at r. The model also lets you tilt the whole blade +/- any desired angle setting. Assuming the max speed of the Spitfire to be 154.7 m/s, I toyed with angle setting until I obtained a max prop efficiency at angle setting 19.45, J value of 2.09, which corresponds to a true airspeed of 154.7 m/sec for a 1.55 m radius prop, engine running at 3000 rpm and gear ratio 0.477. The model produced a theoretical efficiency of about 85%, with Cq = 0.071. Next, I calculated the torque, using the formula Q=Cq * rho * n^2 * D^4, where n is prop rotation in revolutions per second ( the code converts this to radians) and D is prop diameter. I assumed rho of 0.5 Kg/m^3, an altitude of about 15,000 feet. I than multiplied the torque by angular velocity in radians per second, to get the power (watts) needed to counteract the torque of the prop. This worked out to 865 KW, which converts to 1159 HP. This is about 10% hiigher than what the Merlin could actually put out at the shaft, but it's pretty damn good. Remember, the model is known to be about 5% to 10% too optimistic in predicting performance, so if you take this into account, the prediction is nearly spot on! --- snip - Regards Vivian Bye bye, Wolfram. Why surprising? The choice was made with _impeccable_ logic: Eric Hoffman found the POH on the net, and I found some accurate 3d drawings in a book in my local bookshop. The math is helpful. At first glance some of the input data are a little off, but it shows the proposal, briefly made during the discussion on the performance of YASim, that 2850 was the propeller rpm, not the engine rpm at cruise cannot be sustained. I had already shown by some pretty simple math that at 2850 rmp the tips of a 1.65m radius propeller would be supersonic and therefore highly improbable, but we now know that the data of hp, gear ratio, rpm etc all tie together. Thanks Vivian Meazza ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Spitfire Propeller vs. YASim
Spitfire Mk IIA Ah - surprising! Here is an email Rick Fuelcock sent me a short while ago. I hope it helps. Sorry for the poor formating. --- snip - Rather than send you the GBE code , I will direct you to the site where I got it: http://www.aeromech.usyd.edu.au/aero/propeller/prop1.html Just click on program 1 at the bottom of the page. Program 2 (right below) is mathlab code for the implementation without the bells and whistles. I have been playing around with program 1, and have obtained very encouraging results. I keyed in a Spitfire prop with radius 1.55 m and a blade area of 0.98m^3. The program only let's you design a simple blade with a straight, symetrical taper. Rather than complicate things, I just kept the cord constant at .210 the radius to give a total area of .327m^3 per blade. Not knowing anything for sure about the blade angle at a given radius, I just used the default pitch of 0.5, where: pitch = 2pi * r tan theta and theta is the geometric angle of the blade at r. The model also lets you tilt the whole blade +/- any desired angle setting. Assuming the max speed of the Spitfire to be 154.7 m/s, I toyed with angle setting until I obtained a max prop efficiency at angle setting 19.45, J value of 2.09, which corresponds to a true airspeed of 154.7 m/sec for a 1.55 m radius prop, engine running at 3000 rpm and gear ratio 0.477. The model produced a theoretical efficiency of about 85%, with Cq = 0.071. Next, I calculated the torque, using the formula Q=Cq * rho * n^2 * D^4, where n is prop rotation in revolutions per second ( the code converts this to radians) and D is prop diameter. I assumed rho of 0.5 Kg/m^3, an altitude of about 15,000 feet. I than multiplied the torque by angular velocity in radians per second, to get the power (watts) needed to counteract the torque of the prop. This worked out to 865 KW, which converts to 1159 HP. This is about 10% hiigher than what the Merlin could actually put out at the shaft, but it's pretty damn good. Remember, the model is known to be about 5% to 10% too optimistic in predicting performance, so if you take this into account, the prediction is nearly spot on! --- snip - Regards Vivian Bye bye, Wolfram. ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Spitfire Performance Testing
Vivian Meazza wrote: Thanks, Eric, that link was already a primary source. It's all coming together nicely. Just finishing texturing, a little more animation to do, and about half the 3d instruments. You'll be glad to know that the model is under 5000 vertices so far. I have bodged the engine, and it flies delightfully, but we await Andy's revised engine for proper realism. About 2 or 3 weeks should see it done. This is all wonderful news. I can hardly wait to try it! Thanks for putting all this time into it. Erik ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
RE: [Flightgear-devel] Spitfire Performance Testing
Erik Hofman wrote Sent: 30 April 2004 22:37 To: FlightGear developers discussions Subject: [Flightgear-devel] Spitfire Performance Testing Hi, It just occurred to me I had this link in my bookmarks, just when you think you've seen all information about the spitfire: http://www.fourthfightergroup.com/eagles/spittest.html Erik Thanks, Eric, that link was already a primary source. It's all coming together nicely. Just finishing texturing, a little more animation to do, and about half the 3d instruments. You'll be glad to know that the model is under 5000 vertices so far. I have bodged the engine, and it flies delightfully, but we await Andy's revised engine for proper realism. About 2 or 3 weeks should see it done. Vivian ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
RE: [Flightgear-devel] Spitfire Hurricane manuals
On 4/19/04 at 11:12 PM Vivian Meazza wrote: All you ever wanted to know about a Merlin with 2 speed, 2 stage supercharging is here: http://www.unlimitedexcitement.com/Pride%20of%20Pay%20n%20Pak/Rolls-Royce%2 0 Merlin%20V-1650%20Engine.htm Except exactly how the boost contol valve worked :-) Nice link! I've found a reference describing the BCV mechanism (Thrust for Flight by W. Thomson), apparently it consisted of a stack of metal aneroids that contract under increased pressure. This makes perfect sense - it would measure absolute pressure, and I believe is similar to the mechanism used in many barometers. Cheers - Dave This message has been scanned but we cannot guarantee that it and any attachments are free from viruses or other damaging content: you are advised to perform your own checks. Email communications with the University of Nottingham may be monitored as permitted by UK legislation. ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Spitfire Hurricane manuals
On Wed, 28 Apr 2004 12:26:42 +0100, David wrote in message [EMAIL PROTECTED]: On 4/19/04 at 11:12 PM Vivian Meazza wrote: All you ever wanted to know about a Merlin with 2 speed, 2 stage supercharging is here: http://www.unlimitedexcitement.com/Pride%20of%20Pay%20n%20Pak/Rolls- Royce%2 0 Merlin%20V-1650%20Engine.htm Except exactly how the boost contol valve worked :-) Nice link! I've found a reference describing the BCV mechanism (Thrust for Flight by W. Thomson), apparently it consisted of a stack of metal aneroids that contract under increased pressure. This makes perfect sense - it would measure absolute pressure, and I believe is similar to the mechanism used in many barometers. ..search these for aneroid. http://naca.larc.nasa.gov/index.cgi?method=searchlimit=25offset=0mode=simpleorder=DESCkeywords=supercharger+stage http://www.cebudanderson.com/viewfromtheline.htm http://www.dallasjournal.com/articlesview.php?ID=295 http://www.aircadets.org/pdf/acp33vol3.pdf http://www.unlimitedexcitement.com/Griffon Budweiser/Rolls-Royce Griffon Engine.htm http://www.home.aone.net.au/shack_one/rolls.htm -- ..med vennlig hilsen = with Kind Regards from Arnt... ;-) ...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 [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Spitfire Propeller vs. YASim
Andy Ross said: Vivian Meazza wrote: Here are some calculations on propeller rpm. [...] We can see that 2850 is unlikely to be the rpm of a 10.75 diameter propeller Yeah, you're right. This is a real bug. I was playing with it this morning, and we're hitting an edge case in the propeller solver. The propeller as defined is actually fine. It sinks the right amount of power and generates appropriate thrust at the specified cruise RPM. The problem is that (due to a deficiency in the model) the torque required to turn the propeller are *lower* RPMs increases faster than the engine torque does*. So while the engine and propeller are matched at cruise; the combination can't get there because it can't accelerate the prop at low speeds. The end result is that this breaks the stabilize step in the solver, which tries to iteratively solve for the steady state RPM for an engine/prop before running the aero FDM. Mathematically, the current propeller model has two minima, and it's picking the wrong one. The spitfire is hitting the condition because of the high gear ratio, recent changes in the engine code which reduce available power at low speeds (to get idle speeds right), and a miscalbration quirk in the manual pitch handling (setting 0.5 for manual pitch doesn't produce the same results as a non-variable propeller). I'm not quite sure what the right thing to do here is. One trick would be to jigger the stabilize routine so it starts from an RPM within the right range, but that's going to be really hard to maintain over time. Let me think about it... Any ideas on this yet? I caught a little bit of this thread before heading to NY and have been sitting on the edge of my seat ever since :-) It is an issue with the p51-d as well, of course. It'd really be nice to finally get that one right. Best, Jim ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
RE: [Flightgear-devel] Spitfire Propeller vs. YASim
Wolfram Kuss asked I did not see the original thread. What Spitfire version are you speaking about? Spitfire Mk IIA Regards Vivian ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Spitfire Propeller vs. YASim
I did not see the original thread. What Spitfire version are you speaking about? Bye bye, Wolfram. ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
RE: [Flightgear-devel] Spitfire Propeller vs. YASim
Andy Ross [Starting a new thread. The reply nesting level in my mozilla window was getting freaky.] Vivian Meazza wrote: The engine I'm trying to specify developed 1140 HP at engine revolutions of 2850 rpm at a boost pressure of 9 psi. It was fitted with 1:0.477 reduction gearing, which I think means that the propeller turned at 1360 rpm. Hrm, 1360 RPM is very slow for a cruise value, just over idle speed for a smaller plane. Likewise, 2850 RPM really isn't that fast for a piston engine. It's at the top end of ungeared engines like a Lycoming O-360 or whatnot, but not really very fast for four stroke engines as a whole (my Saturn redlines at 6000, for example). Is it possible that the 2850 number is a *propeller* RPM at max power? Then you'd get a max power engine speed of 5975, which seems plausible to me and avoids the problems with solving for a propeller which cruises at a pitch where normal props would be windmilling. Does anyone have good info on whether the cockpit engine speed gauge in a Spitfire (which is presumably what most sources will quote for RPM) reads engine or propeller speed? Andy I pondered that question for quite a while before I decided to use that data. And I agree that the max engine rpm sounds low when compared to modern engines, particularly modern automotive engines. Propeller rpm seems impossibly low, and I wondered if I am misinterpreted the meaning of the published gear ratio of 1:0.477. All documents that I have seen quote the max engine of the Merlin as 3000 (2850 is the max cruise). Similarly, all the POH (Hurricane/Spitfire/p51d) quote the cockpit instrument as engine rpm Compare the 2 engines Bore 5.4 in, Stroke 6 in, Displacement 1,649 cu in (27 litres). Max rpm 3000 Bore 3.38 in, Stroke 3.46 in, Displacement 180.75 cu in (2.962 litres) max rpm 6000 This is a rough formula derived for automotive applications. A piston speed of 3500 fpm is usually quoted as an estimate for non-high performance modern engines. RPM limit = (Piston speed (fpm) * 6) / stroke (in) If we take the Saturn data, and re-arranging, we get: Piston Speed = 6000*3.4/6 = 3460 fps We can see that the Saturn complies with this paradigm. Now taking the Merlin data: RPM Limit = 3500 * 6/6 = 3500 rpm We can say that it is highly unlikely that the Merlin engine would have been capable of achieving the 6290 rpm required if the max rpm were quoted as propeller rpm. This would call for a piston speed of: Piston Speed = 6290 * 6/6 = 6290 fps 4000 is usually quoted as the maximum for high performance engines, although the modern F1 engine exceeds this, 4000 would be a reasonable limit for a 1930's engine I think it is safe to assume that the rpm quoted for the engine rpm for the Merlin is indeed the engine rpm. I believe the low propeller rpm was to do with tip speeds approaching or exceeding Mach 1 at high aircraft speeds. I will research that next. Regards Vivian ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
RE: [Flightgear-devel] Spitfire Propeller vs. YASim
Vivian Meazza wrote Andy Ross [Starting a new thread. The reply nesting level in my mozilla window was getting freaky.] Vivian Meazza wrote: The engine I'm trying to specify developed 1140 HP at engine revolutions of 2850 rpm at a boost pressure of 9 psi. It was fitted with 1:0.477 reduction gearing, which I think means that the propeller turned at 1360 rpm. Hrm, 1360 RPM is very slow for a cruise value, just over idle speed for a smaller plane. Likewise, 2850 RPM really isn't that fast for a piston engine. It's at the top end of ungeared engines like a Lycoming O-360 or whatnot, but not really very fast for four stroke engines as a whole (my Saturn redlines at 6000, for example). Is it possible that the 2850 number is a *propeller* RPM at max power? Then you'd get a max power engine speed of 5975, which seems plausible to me and avoids the problems with solving for a propeller which cruises at a pitch where normal props would be windmilling. Does anyone have good info on whether the cockpit engine speed gauge in a Spitfire (which is presumably what most sources will quote for RPM) reads engine or propeller speed? Andy I believe the low propeller rpm was to do with tip speeds approaching or exceeding Mach 1 at high aircraft speeds. I will research that next. Regards Vivian Here are some calculations on propeller rpm. The propeller the tip speed should be as high as possible with the only limitation being that the tip should not get into the region of aerodynamic compressibility. Typically a figure of Mach 0.85 is used as the magic number that should not be exceeded. (This makes some allowance for the speed increase as the air passes over the aerofoil curved surface and the increase in air velocity caused by the propeller operation.) If we take 8000 ft as the operating altitude then Mach 1 = 1085 ft/sec (approx) Assuming that the forward velocity of the aircraft is 300 mph = 440 ft/sec Then the maximum rotational velocity may be calculated by Pythagoras: Max Rotational Velocity = ((M *1085)^2 - (V)^2)^0.5 -(1) where M is the designed Mach Number (0.85) and V is the aircraft forward velocity = ((0.85*1085)^2 -(440)^2)^0.5 = 810.52 ft/sec RPM at Max rotational velocity is given by: RPM = Max rotational velocity*60/(PI * D) -(2) Where D is the propeller diameter (ft) = 810.52*60/(PI * 10.75) = 1420 rpm Thus we can see that 1360 rpm is more appropriate for this application than 2850 We can also calculate the Max Rotational Velocity @ 2850 Max rotational velocity (PI * D) = (RPM/60) * (PI * D) = (2850/60) * (PI * 10.75) = 1604 ft/sec We can also calculate the Mach Number of the tip by rearranging and substituting in (1) M = ((1604^2+440^2)^0.5)/1085 where M is the Mach Number of the tip = 1.5329 We can see that 2850 is unlikely to be the rpm of a 10.75 diameter propeller Well, I hope I've got the math right! Please pick holes in it. Regards Vivian ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Spitfire Propeller vs. YASim
Vivian Meazza wrote: Here are some calculations on propeller rpm. [...] We can see that 2850 is unlikely to be the rpm of a 10.75 diameter propeller Yeah, you're right. This is a real bug. I was playing with it this morning, and we're hitting an edge case in the propeller solver. The propeller as defined is actually fine. It sinks the right amount of power and generates appropriate thrust at the specified cruise RPM. The problem is that (due to a deficiency in the model) the torque required to turn the propeller are *lower* RPMs increases faster than the engine torque does*. So while the engine and propeller are matched at cruise; the combination can't get there because it can't accelerate the prop at low speeds. The end result is that this breaks the stabilize step in the solver, which tries to iteratively solve for the steady state RPM for an engine/prop before running the aero FDM. Mathematically, the current propeller model has two minima, and it's picking the wrong one. The spitfire is hitting the condition because of the high gear ratio, recent changes in the engine code which reduce available power at low speeds (to get idle speeds right), and a miscalbration quirk in the manual pitch handling (setting 0.5 for manual pitch doesn't produce the same results as a non-variable propeller). I'm not quite sure what the right thing to do here is. One trick would be to jigger the stabilize routine so it starts from an RPM within the right range, but that's going to be really hard to maintain over time. Let me think about it... Andy ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
RE: [Flightgear-devel] Spitfire Hurricane manuals
Andy wrote Vivian Meazza wrote: However, eng-power should be the un-supercharged max power, so I reduced eng-power value, No no, I was wrong. Use the superchared value, the eng-power gets corrected before solving to assume max sea level manifold density (i.e. with boost and wastegate applied). Is it possible that reduction gearing reduces engine revs for a given propeller rpm? I thought it was the other way around. You are correct. The gear-ratio value is multiplied by the engine RPM to get the propeller RPM. Typical PSRUs will have a value less than 1.0. Andy OK, I'll try again, this time with the supercharged power figures. Thank goodness - they are the only good power values available! Vivian ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
RE: [Flightgear-devel] Spitfire Hurricane manuals
Andy Ross Vivian Meazza wrote: However, eng-power should be the un-supercharged max power, so I reduced eng-power value, No no, I was wrong. Use the superchared value, the eng-power gets corrected before solving to assume max sea level manifold density (i.e. with boost and wastegate applied). Is it possible that reduction gearing reduces engine revs for a given propeller rpm? I thought it was the other way around. You are correct. The gear-ratio value is multiplied by the engine RPM to get the propeller RPM. Typical PSRUs will have a value less than 1.0. Andy This converges (1): eng-power=1140 eng-rpm=2850 turbo-mul=2 wastegate-mp=48 cruise-alt=17500 cruise-power=1140 cruise-speed=308 cruise-rpm=5975 takeoff-power=900 takeoff-rpm=5000 manual-pitch=true gear-ratio = 0.477 As does this (2): eng-power=1140 eng-rpm=2850 turbo-mul=2 wastegate-mp=48 cruise-alt=17500 cruise-power=1140 cruise-speed=308 cruise-rpm=2850 takeoff-power=900 takeoff-rpm=2000 manual-pitch=true gear-ratio = 0.477 This does not (3): eng-power=1140 eng-rpm=2850 turbo-mul=2 wastegate-mp=48 cruise-alt=17500 cruise-power=1140 cruise-speed=308 cruise-rpm=1360 takeoff-power=900 takeoff-rpm=1200 manual-pitch=true gear-ratio = 0.477 I ran FGFS using (2). From the property browser, at throttle = 1 engine rpm = 6779. I note that 6779 * 0.477 = 3233.6 This also converges nicely (4): eng-power=1140 eng-rpm=2850 turbo-mul=2 wastegate-mp=48 cruise-alt=17500 cruise-power=1140 cruise-speed=308 cruise-rpm=2850 takeoff-power=900 takeoff-rpm=2650 manual-pitch=true gear-ratio = 1 I now ran FGFS using (4). At throttle = 1 from property browser engine rpm = 3233.8 I conclude from the foregoing that the gear ratio is being applied incorrectly by YASim. I think that the correct input data is at (3) above. Sign wrong somewhere? Vivian ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Spitfire Hurricane manuals
Vivia Meazza wrote: As does this (2): cruise-speed=308 cruise-rpm=2850 This does not (3): cruise-speed=308 cruise-rpm=1360 Again, these are *wildly* different propoellers you are specifying. The second one is going to end up with four (!) times the force coefficient. In general, multiplying any number in the configuration file by a factor of two and expecting the aircraft to perform similarly just isn't going to work. Is there another typo? What are you trying to accomplish? Andy ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Spitfire Hurricane manuals
Vivian, Are you aware of this data I once sent to the list: http://baron.flightgear.org/pipermail/flightgear-flightmodel/2003-March/002130.html Erik ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
RE: [Flightgear-devel] Spitfire Hurricane manuals
Andy Ross tried again! Vivian Meazza wrote: As does this (2): cruise-speed=308 cruise-rpm=2850 This does not (3): cruise-speed=308 cruise-rpm=1360 Again, these are *wildly* different propoellers you are specifying. The second one is going to end up with four (!) times the force coefficient. In general, multiplying any number in the configuration file by a factor of two and expecting the aircraft to perform similarly just isn't going to work. Is there another typo? What are you trying to accomplish? Andy The engine I'm trying to specify developed 1140 HP at engine revolutions of 2850 rpm at a boost pressure of 9 psi. It was fitted with 1:0.477 reduction gearing, which I think means that the propeller turned at 1360 rpm. Thus, if I have understood all of the various emails correctly, leads to a specification file: eng-power=1140engine power output = 1140 HP eng-rpm=2850 @ 2850 rpm (supercharged) turbo-mul=2 Turbo multiplication factor = 2 wastegate-mp=48 Boost Control Valve = 48 in Hg absolute cruise-alt=17500 Cruise altitude = 17500 ft cruise-speed=308 cruise speed at cruise altitude = 308 kts cruise-power=1140 Power absorbed by propeller at cruise = 1140 HP cruise-rpm=1360 Propeller cruise rpm 2850 * 0.477 = 1360 rpm takeoff-power=900 take off numbers takeoff-rpm=1200 manual-pitch=true gear-ratio = 0.477reduction gear of 1:0.477 I'm reasonably confident that the numbers are in accordance with the published data for the engine. This results in a YASIM output; Iterations: 1 Drag Coefficient: 1000.00 Lift Ratio: 1.00 Cruise AoA: 0.00 Tail Incidence: -0.0 Approach Elevator: 0.00 CG: -2.528, 0.000, -0.270 FGFS locks up attempting to run with these settings, not unexpectedly. I made an alternative assumption as an experiment: that cruise-rpm was the engine rpm at cruise - 2850. They are also about the lowest values for which YASim converges. With these settings, YASim converges with these results: Iterations: 2320 Drag Coefficient: 6.279826 Lift Ratio: 360.380524 Cruise AoA: 0.770977 Tail Incidence: -0.8144328 Approach Elevator: 0.939014 CG: -2.523, 0.000, -0.276 FGFS runs with this input, but when throttle = 1 engine rpm = 6928, which is as expected for a propeller rpm of 2850 and a gear ratio of 0.477. I had hoped to see the engine rpm stay constant, and the propeller rpm to drop, but, as I say, I was just experimenting. Apart from the engine rpm the model performs well with these settings. I think we have to assume that either the published engine parameters are outside YASim's calculations in some way, or that I still have some fundamental misunderstanding of what goes where in the file. Sorry to be a nuisance with all these queries, and thank you for your patience and help. Regards Vivian ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
RE: [Flightgear-devel] Spitfire Hurricane manuals
Andy Ross wrote Vivian Meazza wrote: With these values eng-power=1140 eng-rpm=2850 cruise-power=2850 cruise-rpm=1359 takeoff-power=1100 takeoff-rpm=1359 YASim appears go into a loop and provides no output. These settings don't make much sense in combination. The eng setting is a maximum power (at standard sea level) for the engine without supercharging. In this case, the normally aspirated engine develops 1140 HP at max RPM. The cruise numbers are used to fix the propeller's maximum efficiency peak. The propeller you are using wants to sink 2850 HP (more than double max sea level power) at less than half (!) of the engine's max RPM. Even with 4x supercharging (which sounds kinda high to me, but I'm not an expert), that's just not going to work. Are you working from POH numbers for this engine that might be typoed or misinterpreted? The takeoff values correspond to the power and RPM developed by the aircraft at max throttle and zero airspeed. It's there because propellers have funny, non-linear behavior in the very low pitch regime (when the blades are partially stalled). The default model produces strange results here, so the FDM allows you specify a clamp to match real-world behavior. It's not important to the solver, or for in-flight performance. I'll look into the apparent infinite loop behavior. Andy The numbers are correct, it's how I've interpreted them and where I've put them that is the problem :-) The eng setting: the documentation that I am using (readme YASim) indicates that it is the brake horsepower at cruise I presumed that this was A. The supercharged output. The un-supercharged output is un-measured and would only be a rough guess. B. At the cruise altitude. The power output at any other altitude is somewhat different. Does the model understand variations of power with altitude? Now that I know that it is the un-supercharged number, I think I can adjust the number empirically to give a reasonable value. The cruise numbers - typo here I'm afraid: 1140 HP would be the right number. I've changed these so many times . 4x was just grabbed out of the air, but since the Boost Control Valve is open in the real aircraft up to 25000 ft or so, this didn't seem to matter. I was going to adjust this number in due course to try to model the proper boost curve. The takeoff values. Are these the power absorbed by the propeller at propeller rpm, or the engine output at engine rpm, super- or un-supercharged? Finally, I've had some difficulty understanding the concept of using absolute pressure for the Boost Control Valve (BCV). In the real world a BCV comprises, in principle, a plate exposed to manifold pressure on one side and to the local atmospheric pressure on the other and held closed by a spring which opens at the designed boost pressure (in this case 9 psi adjustable by the pilot to allow 12.5 psi for up to 5 mins), and is thus corrected for altitude. I've been scratching through the code, and can't confirm that YASim models this behaviour. Perhaps I don't need to bother? And I haven't even tackled the constant speed propeller! I suppose that we should update the documentation to reflect these misinterpretations. Thanks for your help. We'll have a Spitfire with a Merlin engine yet! Vivian Meazza ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
RE: [Flightgear-devel] Spitfire Hurricane manuals
On 4/19/04 at 9:24 AM Vivian Meazza wrote: Finally, I've had some difficulty understanding the concept of using absolute pressure for the Boost Control Valve (BCV). In the real world a BCV comprises, in principle, a plate exposed to manifold pressure on one side and to the local atmospheric pressure on the other and held closed by a spring which opens at the designed boost pressure (in this case 9 psi adjustable by the pilot to allow 12.5 psi for up to 5 mins), and is thus corrected for altitude. I've been scratching through the code, and can't confirm that YASim models this behaviour. Perhaps I don't need to bother? My understanding of it is that at rated throttle position, the boost control attempts to maintain sea-level-ambient-pressure + 9psi boost, approximately 42inHg manifold absolute pressure (MAP), regardless of altitude. This is well within the supercharger rating at sea-level, since its designed for altitude, and the BCV is controlling the pressure. As the plane climbs, the BCV maintains the 42 inHg MAP (if the rated-boost throttle position is maintained) until an altitude is reached at which the full supercharger output is being used to maintain 42in, and from then on MAP falls as height is gained. Thus the BCV is attempting to maintain an absolute pressure, not local-pressure + boost. I don't know how it works though - I had assumed it would have a sealed sea-level-ambient-pressure chamber at one side and MAP at the other, but that's just a guess. Can anyone clarify the function of the Boost cut-out EMERGENCY control mentioned in the manual. The name implies that it cuts the boost completely in an engine emergency. However, the text implies that it overrides the BCV for extra emergency boost: If it is desired in an emergency to override the automatic boost control, this control can be cut-out by pushing forward the small red-painted lever (14) at the forward end of the throttle quadrant. The lever is sealed as a check against inadvertant operation. Can anyone confirm either one or other of the possible functions of this? Cheers - Dave This message has been scanned but we cannot guarantee that it and any attachments are free from viruses or other damaging content: you are advised to perform your own checks. Email communications with the University of Nottingham may be monitored as permitted by UK legislation. ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Spitfire Hurricane manuals
Vivian Meazza wrote: The takeoff values. Are these the power absorbed by the propeller at propeller rpm, or the engine output at engine rpm, super- or un-supercharged? Un-supercharged. And the equations are solved such that both power values are the same. Basically, don't sweat this one; it affects performance only at the very start of the takeoff roll. Leave it out until you get things working, and then start fiddling with it to get the initial RPM right. Finally, I've had some difficulty understanding the concept of using absolute pressure for the Boost Control Valve (BCV). In the real world a BCV comprises [...] and is thus corrected for altitude. Actually, everything I've read indicates that wastegate designs are calibrated to absolute pressure, not relative pressure (which makes sense, obviously, because what you are trying to regulate is the force on the engine parts, not the overpressure in the manifold which is a non-critical structural part). Measuring absolute pressure is mechanically more difficult but not impossible. It doesn't have to be as simple as a single spring valve. I suppose that we should update the documentation to reflect these misinterpretations. Roger. See if what's there now makes more sense. Andy ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
RE: [Flightgear-devel] Spitfire Hurricane manuals
-Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of David Luff Sent: 19 April 2004 09:52 To: FlightGear developers discussions Subject: RE: [Flightgear-devel] Spitfire Hurricane manuals On 4/19/04 at 9:24 AM Vivian Meazza wrote: Finally, I've had some difficulty understanding the concept of using absolute pressure for the Boost Control Valve (BCV). In the real world a BCV comprises, in principle, a plate exposed to manifold pressure on one side and to the local atmospheric pressure on the other and held closed by a spring which opens at the designed boost pressure (in this case 9 psi adjustable by the pilot to allow 12.5 psi for up to 5 mins), and is thus corrected for altitude. I've been scratching through the code, and can't confirm that YASim models this behaviour. Perhaps I don't need to bother? My understanding of it is that at rated throttle position, the boost control attempts to maintain sea-level-ambient-pressure + 9psi boost, approximately 42inHg manifold absolute pressure (MAP), regardless of altitude. This is well within the supercharger rating at sea-level, since its designed for altitude, and the BCV is controlling the pressure. As the plane climbs, the BCV maintains the 42 inHg MAP (if the rated-boost throttle position is maintained) until an altitude is reached at which the full supercharger output is being used to maintain 42in, and from then on MAP falls as height is gained. Thus the BCV is attempting to maintain an absolute pressure, not local-pressure + boost. I don't know how it works though - I had assumed it would have a sealed sea-level-ambient-pressure chamber at one side and MAP at the other, but that's just a guess. This seems to be correct. This is from a contemporary test of a Spitfire MkIIa: http://www.fourthfightergroup.com/eagles/p7280speed.gif Can anyone clarify the function of the Boost cut-out EMERGENCY control mentioned in the manual. The name implies that it cuts the boost completely in an engine emergency. However, the text implies that it overrides the BCV for extra emergency boost: If it is desired in an emergency to override the automatic boost control, this control can be cut-out by pushing forward the small red-painted lever (14) at the forward end of the throttle quadrant. The lever is sealed as a check against inadvertant operation. I think it was also known as the Boost Control Cut-out. These documents explain that your latter interpretation is correct: http://www.fourthfightergroup.com/eagles/spit1-12lbs.jpg http://www.fourthfightergroup.com/eagles/ap1590b.jpg http://www.fourthfightergroup.com/eagles/dowding1.jpg http://www.fourthfightergroup.com/eagles/dowding2.jpg Can anyone confirm either one or other of the possible functions of this? Cheers - Dave Regards Vivian ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Spitfire Hurricane manuals
I wrote (incorrectly): The eng setting is a maximum power (at standard sea level) for the engine without supercharging. Never mind the last part. The code *does* correctly handle the boost setting, and assumes that it is at maximum (in most cases, the wastegate setting) at the specified power. Andy ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Spitfire Hurricane manuals
Andy Ross said: These settings don't make much sense in combination. The eng setting is a maximum power (at standard sea level) for the engine without supercharging. In this case, the normally aspirated engine develops 1140 HP at max RPM. That needs to be clarified in the docs (the part about without supercharging). I know it should be obvious, but the way the solver works with other values it is reasonable to assume the max power is max power, not max power w/o supercharger. Also IIRC the only specs available for the Merlin were with the supercharger. Possibly there are some older models that could be used, but I'm not sure if there was one that went into production w/o at least turbo. In any case this sheds some light on a few problems I had modeling the p51d. Best, Jim ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
RE: [Flightgear-devel] Spitfire Hurricane manuals
David Luff said: Can anyone clarify the function of the Boost cut-out EMERGENCY control mentioned in the manual. The name implies that it cuts the boost completely in an engine emergency. However, the text implies that it overrides the BCV for extra emergency boost: If it is desired in an emergency to override the automatic boost control, this control can be cut-out by pushing forward the small red-painted lever (14) at the forward end of the throttle quadrant. The lever is sealed as a check against inadvertant operation. Can anyone confirm either one or other of the possible functions of this? Cheers - Dave That quote actually makes sense to some degree. The term I've seen used is war emergency power which is basically just used to escape a bad under fire situation. You are given 7 minutes of it IIRC. But the automatic boost control I do not understand. The supercharger is described as two staged, but what you are suggesting is that each stage is automatically and continuously adjusted through some sort of relief to maintain sea level pressure. In contrast, my take was the second stage kicked in automatically at a particular altitude or ambient pressure (note this is manual in our p51d model). The purpose being to step up the pressure to make it possible to maintain normal sea level operating conditions (a gross adjustment that is). The p51d cockpit comes with a manifold/throttle lever, so I guess my questions is, if I am wrong, how does such an automatic control work? I have access to a real live p51d pilot via email so if we can get questions together I can probably forward them and get some answers. Note however I will be out of town for a few days starting tomorrow, so there could be a delay. Best, Jim ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Spitfire Hurricane manuals
Jim Wilson writes: David Luff said: Can anyone clarify the function of the Boost cut-out EMERGENCY control mentioned in the manual. The name implies that it cuts the boost completely in an engine emergency. However, the text implies that it overrides the BCV for extra emergency boost: If it is desired in an emergency to override the automatic boost control, this control can be cut-out by pushing forward the small red-painted lever (14) at the forward end of the throttle quadrant. The lever is sealed as a check against inadvertant operation. Can anyone confirm either one or other of the possible functions of this? Cheers - Dave That quote actually makes sense to some degree. The term I've seen used is war emergency power which is basically just used to escape a bad under fire situation. You are given 7 minutes of it IIRC. But the automatic boost control I do not understand. The supercharger is described as two staged, but what you are suggesting is that each stage is automatically and continuously adjusted through some sort of relief to maintain sea level pressure. To maintain sea-level-pressure *plus* a certain boost level mandated by the throttle position - eg 29.92 + ~13 = ~42inHg for the 9psi (~13inHg) rated boost (throttle position just before the take-off position gate) of the Merlin XII. In contrast, my take was the second stage kicked in automatically at a particular altitude or ambient pressure (note this is manual in our p51d model). The purpose being to step up the pressure to make it possible to maintain normal sea level operating conditions (a gross adjustment that is). The p51d cockpit comes with a manifold/throttle lever, so I guess my questions is, if I am wrong, how does such an automatic control work? I have access to a real live p51d pilot via email so if we can get questions together I can probably forward them and get some answers. Note however I will be out of town for a few days starting tomorrow, so there could be a delay. I think the engine described in the manuals (Merlin XII) was fitted with a single speed supercharger, whereas the engine in the p51d (Merlin 61 or Packard equivalent) had a two-speed supercharger. For each speed of the Merlin 61 the automatic boost control would try to maintain a given absolute pressure (I think). I've got a graph of power vs. altitude for a typical WWII 2 speed supercharger in a book somewhere. The power rises slightly from sea level to about 1 ft as the exhaust backpressure drops. It then starts to drop more steeply as the boost from the first speed reaches it's limit. The after a small drop the switch to the second speed is made, and the power rises slightly again with altitude until the second stage boost limit is reached, at which point it drops off steadily with altitude. Note that the switchover altitude is higher than that at which peak 1st speed power is made after the power has dropped off slightly - this is because the higher supercharger speed at speed 2 requires more engine power to drive it and the switch is made at the crossover of the two powers. Thus there are actually two local maxima in the power vs. altitude trace. I had wondered about your Ctrl-b to switch over - all the references I can find have it as automatic. Note also that the Merlin 61 is often described as having 2-speed, 2-stage supercharging. In this case the supercharger is phyically made of two separate stages. However, this is an engineering issue transparent to the pilot. It is the 2 supercharger drive speeds that are switched by the switchover valve, and within each of those discreet speeds the automatic boost control attempts to maintain constant MAP. I *think* - I'm quite open to correction on all these points! You can take it from this that supercharging in JSBSim is fairly imminent BTW ;-) And I'll have to take my leave from this discussion shortly - I'm imminently off to the expo... Cheers - Dave ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
RE: [Flightgear-devel] Spitfire Hurricane manuals
David Luff said Jim Wilson writes: David Luff said: Can anyone clarify the function of the Boost cut-out EMERGENCY control mentioned in the manual. The name implies that it cuts the boost completely in an engine emergency. However, the text implies that it overrides the BCV for extra emergency boost: If it is desired in an emergency to override the automatic boost control, this control can be cut-out by pushing forward the small red-painted lever (14) at the forward end of the throttle quadrant. The lever is sealed as a check against inadvertant operation. Can anyone confirm either one or other of the possible functions of this? Cheers - Dave That quote actually makes sense to some degree. The term I've seen used is war emergency power which is basically just used to escape a bad under fire situation. You are given 7 minutes of it IIRC. But the automatic boost control I do not understand. The supercharger is described as two staged, but what you are suggesting is that each stage is automatically and continuously adjusted through some sort of relief to maintain sea level pressure. To maintain sea-level-pressure *plus* a certain boost level mandated by the throttle position - eg 29.92 + ~13 = ~42inHg for the 9psi (~13inHg) rated boost (throttle position just before the take-off position gate) of the Merlin XII. In contrast, my take was the second stage kicked in automatically at a particular altitude or ambient pressure (note this is manual in our p51d model). The purpose being to step up the pressure to make it possible to maintain normal sea level operating conditions (a gross adjustment that is). The p51d cockpit comes with a manifold/throttle lever, so I guess my questions is, if I am wrong, how does such an automatic control work? I have access to a real live p51d pilot via email so if we can get questions together I can probably forward them and get some answers. Note however I will be out of town for a few days starting tomorrow, so there could be a delay. I think the engine described in the manuals (Merlin XII) was fitted with a single speed supercharger, whereas the engine in the p51d (Merlin 61 or Packard equivalent) had a two-speed supercharger. For each speed of the Merlin 61 the automatic boost control would try to maintain a given absolute pressure (I think). I've got a graph of power vs. altitude for a typical WWII 2 speed supercharger in a book somewhere. The power rises slightly from sea level to about 1 ft as the exhaust backpressure drops. It then starts to drop more steeply as the boost from the first speed reaches it's limit. The after a small drop the switch to the second speed is made, and the power rises slightly again with altitude until the second stage boost limit is reached, at which point it drops off steadily with altitude. Note that the switchover altitude is higher than that at which peak 1st speed power is made after the power has dropped off slightly - this is because the higher supercharger speed a t speed 2 requires more engine power to drive it and the switch is made at the crossover of the two powers. Thus there are actually two local maxima in the power vs. altitude trace. I had wondered about your Ctrl-b to switch over - all the references I can find have it as automatic. Note also that the Merlin 61 is often described as having 2-speed, 2-stage supercharging. In this case the supercharger is phyically made of two separate stages. However, this is an engineering issue transparent to the pilot. It is the 2 supercharger drive speeds that are switched by the switchover valve, and within each of those discreet speeds the automatic boost control attempts to maintain constant MAP. I *think* - I'm quite open to correction on all these points! You can take it from this that supercharging in JSBSim is fairly imminent BTW ;-) And I'll have to take my leave from this discussion shortly - I'm imminently off to the expo... Cheers - Dave All you ever wanted to know about a Merlin with 2 speed, 2 stage supercharging is here: http://www.unlimitedexcitement.com/Pride%20of%20Pay%20n%20Pak/Rolls-Royce%20 Merlin%20V-1650%20Engine.htm Except exactly how the boost contol valve worked :-) Regards Vivian Meazza ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
RE: [Flightgear-devel] Spitfire Hurricane manuals
Andy Ross wrote Vivian Meazza wrote: The takeoff values. Are these the power absorbed by the propeller at propeller rpm, or the engine output at engine rpm, super- or un-supercharged? Un-supercharged. And the equations are solved such that both power values are the same. Basically, don't sweat this one; it affects performance only at the very start of the takeoff roll. Leave it out until you get things working, and then start fiddling with it to get the initial RPM right. Finally, I've had some difficulty understanding the concept of using absolute pressure for the Boost Control Valve (BCV). In the real world a BCV comprises [...] and is thus corrected for altitude. Actually, everything I've read indicates that wastegate designs are calibrated to absolute pressure, not relative pressure (which makes sense, obviously, because what you are trying to regulate is the force on the engine parts, not the overpressure in the manifold which is a non-critical structural part). Measuring absolute pressure is mechanically more difficult but not impossible. It doesn't have to be as simple as a single spring valve. I suppose that we should update the documentation to reflect these misinterpretations. Roger. See if what's there now makes more sense. Andy I think I might be getting somewhere. First I started with these values: eng-power=1140 eng-rpm=2850 turbo-mul=4 wastegate-mp=48 cruise-alt=17500 cruise-power=1140 cruise-speed=308 cruise-rpm=2850 takeoff-power=900 takeoff-rpm=2500 manual-pitch=true gear-ratio = 0.477 AS before, YASim converges nicely However, eng-power should be the un-supercharged max power, so I reduced eng-power value, while holding all others constant. YASim only converged with a eng-power = 1130. This cannot be the un-supercharged max power? I then set eng-pwr to 1140, and tried reducing turbo-mul. YASim only converged with turbo-mul =3.5 I next set turbo-mul to 4, and tried reducing cruise-rpm. YASim only converged with cruise-rpm 2820. I then tried increasing cruise-rpm. YASim only converges with cruise-rpm 6799. Is it possible that reduction gearing reduces engine revs for a given propeller rpm? I thought it was the other way around. So assuming this to be the case, I set cruise-rpm to 5975, and repeated the above sequence. YASim converges when: eng-power =575 turbo-mul =0.0001 In each case the other value is set with the initial value as above. Now, assuming a turbo-mul value of 2 as a reasonable guess, and 750 HP as the un-supercharged output, we get this: eng-power=750 eng-rpm=2850 turbo-mul=2 wastegate-mp=48 cruise-alt=17500 cruise-power=1140 cruise-speed=308 cruise-rpm=5975 takeoff-power=725 takeoff-rpm=5000 manual-pitch=true gear-ratio = 0.477 YASim converges nicely. Problem solved? Regards Vivian Meazza ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Spitfire Hurricane manuals
While I remember, if a YASim a/c only has one tank, the second tank - tank[1] - seems to be set with a 'nan' level. Doesn't stop the a/c engine from starting or running but it screws up the tot fuel figure. Setting the level for tank[1] to zero via the property browser sorts it ok. LeeE ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Spitfire Hurricane manuals
Lee Elliott wrote: While I remember, if a YASim a/c only has one tank, the second tank - tank[1] - seems to be set with a 'nan' level. Doesn't stop the a/c engine from starting or running but it screws up the tot fuel figure. Setting the level for tank[1] to zero via the property browser sorts it ok. Hrm... The initialization conditions for the first two tanks were a little touchy (there are still some hardwired assumptions about 2 tanks in the code), but I was pretty sure I got it all figured out. Which aircraft is showing this problem? Andy ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Spitfire Hurricane manuals
On Tuesday 20 April 2004 01:58, Andy Ross wrote: Lee Elliott wrote: While I remember, if a YASim a/c only has one tank, the second tank - tank[1] - seems to be set with a 'nan' level. Doesn't stop the a/c engine from starting or running but it screws up the tot fuel figure. Setting the level for tank[1] to zero via the property browser sorts it ok. Hrm... The initialization conditions for the first two tanks were a little touchy (there are still some hardwired assumptions about 2 tanks in the code), but I was pretty sure I got it all figured out. Which aircraft is showing this problem? Andy I'm getting it on the ComperSwift - afaik it only has a single 15 gal tank. It looks like a hardwired sort of issue but as I said it's easily fixed by specifying 0 for the level in the browser (don't need to set the tanks as un-selected now:) LeeE ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Spitfire Hurricane manuals
Vivian Meazza wrote: YASim crashes, or perhaps, fails to converge, just by attempting to run with takeoff-power=1100 takeoff-rpm=1360 Crashing and solution failure ought to be easily distinguished. :) Maybe the recent logging changes have hidden the failure message, I'll take a look. Try running the command line yasim program on your XML file. It will give you a solution (and print the report) result much faster than a full fgfs invocation. I'll take a look at the file as soon as I can. Andy ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
RE: [Flightgear-devel] Spitfire Hurricane manuals
Andy Ross wrote: Sent: 18 April 2004 19:04 To: FlightGear developers discussions Subject: Re: [Flightgear-devel] Spitfire Hurricane manuals Vivian Meazza wrote: YASim crashes, or perhaps, fails to converge, just by attempting to run with takeoff-power=1100 takeoff-rpm=1360 Crashing and solution failure ought to be easily distinguished. :) Maybe the recent logging changes have hidden the failure message, I'll take a look. Try running the command line YASim program on your XML file. It will give you a solution (and print the report) result much faster than a full fgfs invocation. I'll take a look at the file as soon as I can. Andy Thank you for drawing my attention to that utility. Using these values: propeller x=-1.10 y=0 z=0 radius=1.638 moment=37.15 mass=2000 eng-power=1140 eng-rpm=2850 turbo-mul=4.0 wastegate-mp=28 cruise-alt=17500 cruise-power=2850 cruise-speed=308 cruise-rpm=2850 takeoff-power=1100 takeoff-rpm=2850 manual-pitch=true gear-ratio = 0.477 YASim converges nicely. With these values propeller x=-1.10 y=0 z=0 radius=1.638 moment=37.15 mass=2000 eng-power=1140 eng-rpm=2850 turbo-mul=4.0 wastegate-mp=28 cruise-alt=17500 cruise-power=2850 cruise-speed=308 cruise-rpm=1359 takeoff-power=1100 takeoff-rpm=1359 manual-pitch=true gear-ratio = 0.477 YASim appears go into a loop and provides no output. The only way out is to shut down Cygwin. Vivian ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Spitfire Hurricane manuals
On Sunday 18 April 2004 22:46, Vivian Meazza wrote: Andy Ross wrote: Sent: 18 April 2004 19:04 To: FlightGear developers discussions Subject: Re: [Flightgear-devel] Spitfire Hurricane manuals Vivian Meazza wrote: YASim crashes, or perhaps, fails to converge, just by attempting to run with takeoff-power=1100 takeoff-rpm=1360 Crashing and solution failure ought to be easily distinguished. :) Maybe the recent logging changes have hidden the failure message, I'll take a look. Try running the command line YASim program on your XML file. It will give you a solution (and print the report) result much faster than a full fgfs invocation. I'll take a look at the file as soon as I can. Andy Thank you for drawing my attention to that utility. Using these values: propeller x=-1.10 y=0 z=0 radius=1.638 moment=37.15 mass=2000 eng-power=1140 eng-rpm=2850 turbo-mul=4.0 wastegate-mp=28 cruise-alt=17500 cruise-power=2850 cruise-speed=308 cruise-rpm=2850 takeoff-power=1100 takeoff-rpm=2850 manual-pitch=true gear-ratio = 0.477 YASim converges nicely. With these values propeller x=-1.10 y=0 z=0 radius=1.638 moment=37.15 mass=2000 eng-power=1140 eng-rpm=2850 turbo-mul=4.0 wastegate-mp=28 cruise-alt=17500 cruise-power=2850 cruise-speed=308 cruise-rpm=1359 takeoff-power=1100 takeoff-rpm=1359 manual-pitch=true gear-ratio = 0.477 YASim appears go into a loop and provides no output. The only way out is to shut down Cygwin. Vivian I've experienced similar 'looping' behaviour when trying to get propellers working properly. Don't know why though - never seems to happen with jet aircraft. Just taking a quick look at the propeller definitions above, it looks as though you're specifying the eng-rpm value for the cruise-power entry in both cases (2850) - what happens if you use 1100? (this being the same value you use for the takeoff-power - the takeoff-rpm and the cruise-rpm match in the definition) LeeE ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Spitfire Hurricane manuals
Vivian Meazza wrote: With these values eng-power=1140 eng-rpm=2850 cruise-power=2850 cruise-rpm=1359 takeoff-power=1100 takeoff-rpm=1359 YASim appears go into a loop and provides no output. These settings don't make much sense in combination. The eng setting is a maximum power (at standard sea level) for the engine without supercharging. In this case, the normally aspirated engine develops 1140 HP at max RPM. The cruise numbers are used to fix the propeller's maximum efficiency peak. The propeller you are using wants to sink 2850 HP (more than double max sea level power) at less than half (!) of the engine's max RPM. Even with 4x supercharging (which sounds kinda high to me, but I'm not an expert), that's just not going to work. Are you working from POH numbers for this engine that might be typoed or misinterpreted? The takeoff values correspond to the power and RPM developed by the aircraft at max throttle and zero airspeed. It's there because propellers have funny, non-linear behavior in the very low pitch regime (when the blades are partially stalled). The default model produces strange results here, so the FDM allows you specify a clamp to match real-world behavior. It's not important to the solver, or for in-flight performance. I'll look into the apparent infinite loop behavior. Andy ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
RE: [Flightgear-devel] Spitfire Hurricane manuals
Andy Ross wrote Vivian Meazza wrote: How do we set the reduction gearing ratio? Set the gear-ratio attribute of the propeller tag. This is the reduction ratio, so typical values will be less than 1.0. Can we do a constant speed propeller? The min-rpm and max-rpm attributes define the range of the blue lever. These are the speeds to which the propeller will seek; it may not be able to achieve them in practice. The documentation for these was, er, wrong. I'll fix that. And can we set the handedness of the propeller to RH? Sure thing. Use a negative moment value. :) No joke: that will have exactly the effect of a counter-rotating engine. The DC-3 uses this trick for the starboard engine, for example. I'll add some documentation for that as well. Andy I have almost finished the Spitfire model. Texturing, animation and a 3d cockpit remain to do. However, I am having some difficulty with the engine reduction gear ratio. I've used using the following numbers which give a reasonable solution in YASim. propeller x=-1.10 y=0 z=0 radius=1.638 moment=37.15 mass=2000 eng-power=1140 eng-rpm=2850 turbo-mul=4.0 wastegate-mp=18.32 cruise-alt=17500 cruise-power=1100 cruise-speed=308 cruise-rpm=2850 takeoff-power=1100 takeoff-rpm=2850 manual-pitch=true actionpt x=-0.75 y=0 z=0/ control-input axis=/controls/engines/engine[0]/propeller-pitch control=PROPPITCH src0=0 src1=1 dst0=0.1 dst1=0.6/ /propeller The model flies reasonably well, with the following output data when throttle = 1: max-hp = 1140.491452 mp-osi = 26.050 - does the wastegate work? - is this psi? power-pct = 105.863353 prop-thrust = 1314.603118 rpm = 3014.603118 I've kept to manual pitch control for now. I've tried this, although I would think, incorrectly: propeller x=-1.10 y=0 z=0 radius=1.638 moment=37.15 mass=2000 eng-power=1140 eng-rpm=2850 turbo-mul=4.0 wastegate-mp=18.32 cruise-alt=17500 cruise-power=1100 cruise-speed=308 cruise-rpm=2850 takeoff-power=1100 takeoff-rpm=2850 manual-pitch=true gear-ratio = 0.477 actionpt x=-0.75 y=0 z=0/ control-input axis=/controls/engines/engine[0]/propeller-pitch control=PROPPITCH src0=0 src1=1 dst0=0.1 dst1=0.6/ /propeller The model still flies reasonably well, with the following output data when throttle = 1: max-hp = 1140.491452 mp-osi = 29.729 - does the wastegate work? - is this psi? power-pct = 222.856 prop-thrust = 1375.645173 rpm = 6176.318088 - this is wrong Finally, I tried this: propeller x=-1.10 y=0 z=0 radius=1.638 moment=37.15 mass=2000 eng-power=1140 eng-rpm=2850 turbo-mul=4.0 wastegate-mp=18.32 cruise-alt=17500 cruise-power=1100 cruise-speed=308 cruise-rpm=1360 takeoff-power=1100 takeoff-rpm=2850 manual-pitch=true gear-ratio = 0.477 control-input axis=/controls/engines/engine[0]/propeller-pitch control=PROPPITCH src0=0 src1=1 dst0=0.1 dst1=0.6/ /propeller The model does not fly, failing to accelerate (insufficient prop thrust), with the following output data when throttle = 1: max-hp = 1140.491452 mp-osi = 29.729 power-pct = 225.856 - wrong prop-thrust = 659.082929 - wrong rpm = 6232.318088 - even more wrong I've tried increasing pitch, to no avail. I've tried takeoff-power=1100 takeoff-rpm=1360 - then YASim crashes What is the obvious mistake that I am making? Regards Vivian Meazza ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Spitfire Hurricane manuals
Vivian Meazza wrote: wastegate-mp=18.32 [...] mp-osi = 26.050 - does the wastegate work? - is this psi? The units are absolute pressure in inches of mercury (I honestly don't know what the -osi suffix means). The wastegate should indeed work. However, it is an overpressure release valve. It cannot suck a vacuum in the manifold if ambient pressure is already higher than its setting. :) Typical values for the wastegate are going to be significantly higher than one atmosphere (== ~28 Hg), but I'm sure that varies with supercharger design. Probably some aircraft don't have them at all. The model does not fly, failing to accelerate (insufficient prop thrust), with the following output data when throttle = 1: Outside the wastegate setting (which is a noop in this case) nothing looks clearly incorrect. Can you post the whole file so I can try it? I've tried increasing pitch, to no avail. I've tried takeoff-power=1100 takeoff-rpm=1360 - then YASim crashes That's clearly a bug; no configuration should be causing crashes*. Can you be more specific about how to reproduce it? Andy * Well, not quite: you can crash YASim by mapping a property to an incorrect object -- THROTTLE on a wing, for example. It should check for validity at parse time, but doesn't. ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
RE: [Flightgear-devel] Spitfire Hurricane manuals
Andy Ross replied Vivian Meazza wrote: wastegate-mp=18.32 [...] mp-osi = 26.050 - does the wastegate work? - is this psi? The units are absolute pressure in inches of mercury (I honestly don't know what the -osi suffix means). The wastegate should indeed work. However, it is an overpressure release valve. It cannot suck a vacuum in the manifold if ambient pressure is already higher than its setting. :) Typical values for the wastegate are going to be significantly higher than one atmosphere (== ~28 Hg), but I'm sure that varies with supercharger design. Probably some aircraft don't have them at all. The model does not fly, failing to accelerate (insufficient prop thrust), with the following output data when throttle = 1: Outside the wastegate setting (which is a noop in this case) nothing looks clearly incorrect. Can you post the whole file so I can try it? I've tried increasing pitch, to no avail. I've tried takeoff-power=1100 takeoff-rpm=1360 - then YASim crashes That's clearly a bug; no configuration should be causing crashes*. Can you be more specific about how to reproduce it? Andy * Well, not quite: you can crash YASim by mapping a property to an incorrect object -- THROTTLE on a wing, for example. It should check for validity at parse time, but doesn't. Osi - ounces per sq in :-) more likely a typo for psi. I'm just going to try the wastegate (or, more strictly, boost control valve) using absolute pressure. Slightly odd, that, manifold pressures are usually referred to as overpressure. YASim crashes, or perhaps, fails to converge, just by attempting to run with takeoff-power=1100 takeoff-rpm=1360 Thanks for the quick response. Vivian Meazza ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
RE: [Flightgear-devel] Spitfire Hurricane manuals
Andy Ross wrote Vivian Meazza wrote: wastegate-mp=18.32 [...] mp-osi = 26.050 - does the wastegate work? - is this psi? The units are absolute pressure in inches of mercury (I honestly don't know what the -osi suffix means). The wastegate should indeed work. However, it is an overpressure release valve. It cannot suck a vacuum in the manifold if ambient pressure is already higher than its setting. :) Typical values for the wastegate are going to be significantly higher than one atmosphere (== ~28 Hg), but I'm sure that varies with supercharger design. Probably some aircraft don't have them at all. The model does not fly, failing to accelerate (insufficient prop thrust), with the following output data when throttle = 1: Outside the wastegate setting (which is a noop in this case) nothing looks clearly incorrect. Can you post the whole file so I can try it? Here's the whole file as requested: ?xml version=1.0? !-- YASim aerodynamic model for a Spitfire IIa The reference datum for measurements is the nose. -- !-- Weight of everything but fuel (4873 empty) -- airplane mass=5200 !-- Approach configuration -- approach speed=75 aoa=13 control-setting axis=/controls/engines/engine[0]/throttle value=0.2/ control-setting axis=/controls/engines/engine[0]/mixture value=1.0/ control-setting axis=/controls/engines/engine[0]/propeller-pitch value=0.2/ control-setting axis=/controls/engines/engine[0]/boost value=0.25/ control-setting axis=/controls/flight/flaps value=1.0/ control-setting axis=/controls/gear/gear-down value=1/ /approach !-- Cruise configuration -- cruise speed=308 alt=17500 control-setting axis=/controls/engines/engine[0]/throttle value=0.90/ control-setting axis=/controls/engines/engine[0]/mixture value=1.00/ control-setting axis=/controls/engines/engine[0]/propeller-pitch value=1.0/ control-setting axis=/controls/engines/engine[0]/boost value=1/ control-setting axis=/controls/flight/flaps value=0.0/ control-setting axis=/controls/gear/gear-down value=0/ /cruise !-- pilot's eye point -- cockpit x=-3.86 y=0 z=0.55/ fuselage ax=0.0 ay=0.0 az=0.0 bx=-9.13 by=0.0 bz=0.0 width=0.94 taper=0.38 midpoint=0.4 / !-- stall aoa not available flap drag not available -- wing x=-2.99 y=0.77 z=-0.81 taper=0.3 incidence=2 twist=-2.0 length=4.576 chord=2.845 sweep=-3.5 dihedral=6 stall aoa=20 width=4 peak=1.5/ flap0 start=0.00 end=0.437 lift=1.3 drag=1.8/ flap1 start=0.437 end=0.90 lift=1.2 drag=1.2/ control-input axis=/controls/flight/flaps control=FLAP0/ control-output control=FLAP0 prop=/surface-positions/flap-pos-norm/ control-speed control=FLAP0 transition-time=5/ control-input axis=/controls/flight/aileron control=FLAP1 split=true/ control-input axis=/controls/flight/aileron-trim control=FLAP1 split=true/ /wing !-- tailplanee -- hstab x=-8.22 y=0.25 z=0.0 taper=0.639 effectiveness=2 length=1.215 chord=1.246 sweep=5 stall aoa=24 width=4 peak=1.5/ flap0 start=0.0 end=1 lift=1.65 drag=1.5/ control-input axis=/controls/flight/elevator control=FLAP0/ control-input axis=/controls/flight/elevator-trim control=FLAP0/ control-output control=FLAP0 prop=/surface-positions/elevator-pos-norm/ /hstab !-- tail -- vstab x=-8.52 y=0 z=-0.29 taper=0.386 effectiveness=2 length=1.598 chord=0.994 sweep=5 stall aoa=15 width=4 peak=1.5/ flap0 start=0 end=1 lift=1.65 drag=1.5/ control-input axis=/controls/flight/rudder square=true control=FLAP0 invert=true/ control-input axis=/controls/flight/rudder-trim control=FLAP0 invert=true/ control-output control=FLAP0 prop=/surface-positions/rudder-pos-norm min=1 max=-1/ /vstab !-- wastegate setting should not apply. set here so that calculations would approximate. YASim doesn't model gear supercharger. Have read various figures (turbo-mul) 4.0 to 5.8 for running the second stage blower. Fixing this would probably give more reasonable performance at lower altitude -- !-- moment = radius(m)* propeller mass(kg)/2 - equation provided by Andy Ross -- !-- cruise-rpm documented gear ratio of 0.479 min-rpm=600 max-rpm=3000-- propeller x=-1.10 y=0 z=0 radius=1.638 moment=37.15 mass=2000 eng-power=1140 eng-rpm=2850 turbo-mul=4.0 wastegate-mp=48.2454 cruise-alt=17500 cruise-power=1100 cruise-speed=308 cruise-rpm=2850 takeoff-power=1100 takeoff-rpm=2850 manual-pitch=true gear-ratio = 0.477 actionpt x=-0.75 y=0 z=0/ control-input axis=/controls/engines/engine[0]/throttle control=THROTTLE/ control-input
RE: [Flightgear-devel] Spitfire Hurricane manuals
Jonathan Richards On Wednesday 31 Mar 2004 11:09 am, Vivian Meazza wrote: snip I now have the Spitfire IIa model well underway. I have all the drawings and data I need (far too much probably). I've rather lost the bubble on the recent changes to the piston engine simulation in YASim: Vivian The pictures here http://www.raf.mod.uk/news/limage_bbmf.html appeared on our intranet and I thought you might find them useful. 'Desert Spitfire' clearly has a four-bladed propeller, while 'Spitfire Head-On' is equally clearly three-bladed. There's some good detailed views for modellers, though. Regards Jonathan Great pics. They're sure to come in useful. Not sure about the Desert Spitfire - I think it ought to have the sand filter under the nose. Thanks Vivian Meazza ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Spitfire Hurricane manuals
On Wednesday 31 Mar 2004 11:09 am, Vivian Meazza wrote: snip I now have the Spitfire IIa model well underway. I have all the drawings and data I need (far too much probably). I've rather lost the bubble on the recent changes to the piston engine simulation in YASim: Vivian The pictures here http://www.raf.mod.uk/news/limage_bbmf.html appeared on our intranet and I thought you might find them useful. 'Desert Spitfire' clearly has a four-bladed propeller, while 'Spitfire Head-On' is equally clearly three-bladed. There's some good detailed views for modellers, though. Regards Jonathan ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Spitfire Hurricane manuals
On Thu, 1 Apr 2004 08:47:15 +0100, Vivian wrote in message [EMAIL PROTECTED]: Arnt Karlsen wrote On Wed, 31 Mar 2004 13:32:39 -0800, Andy wrote in message [EMAIL PROTECTED]: Vivian Meazza wrote: Thanks for all that: all looks good - the documentation has got a bit astern of station. Could you explain a bit more about the turbo attribute when used for a supercharger? Actually, the existing turbo-mul implementation is *more* like a supercharger than a real turbo. YASim models the boost as a simply multiplication factor on the input manifold pressure. If it's set to 2.0, then the engine sees twice the static pressure, etc... Real turbochargers don't have linear boost-vs-RPM curves, and tend to lag ..you mean lead? On pouring gas, the first thing to happen is the extra fuel spins up _only_ the turbo, which then promptly feeds engine more air etc as soon as that turbo is spun up. I don't think so. Turbo-lag is well known. The throttle opens, more fuel goes to the engine, which produces more exhaust gas which then speeds up the turbo-charger which increases air flow to the engine, hence the increase in inlet pressure lags the increase in engine rpm. ..for automobiles, I can agree, you floor it, then it hops. For the geared supercharger, you need to move all the iron around first. ..another thing is the sizing policy, in the air, you want good cruise performance and good altitude performance, and you don't wanna fry a dump valve if you can design it away. In an automobile, you need that dump valve and a giant turbine to turn that wee compressor, to get that marketing butt kick, and you get away with it because you cruise town at 5% between burnouts. (With stickshift, you don't.) ..for WWII combat planes, I can see compromises coming here. ..a geardriven supercharger is geared to the entire engine, and moves with the entire engine, and that too has to move around faster, before it can feed any more air. Whilst that is technically true, the increase in engine rpm brings an instantaneous increase in supercharger rpm and an instantaneous increase in output pressure. The only lag is caused in the ducting, which is usually kept as short as possible. For a supercharger, any lag can be ignored for practical purposes. ..this lag could easily be evaluated graphing rpm and manifold pressure etc against time. (in time) engine power by a little bit. A gear-driven supercharger is going to be closer to that ideal. Andy Regards Vivian Meazza -- ..med vennlig hilsen = with Kind Regards from Arnt... ;-) ...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 [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
RE: [Flightgear-devel] Spitfire Hurricane manuals
Erik Hofman Sent: 13 March 2004 15:12 To: FlightGear developers discussions Subject: Re: [Flightgear-devel] Spitfire Hurricane manuals Erik Hofman wrote: http://home.clara.net/wolverine/BOB/misc/Spit_Hurri_Manuals.zip To get back to the original subject, this site has an aweful lot of information on WWII warbirds, including performance charts: http://www.rdrop.com/users/hoofj/ I now have the Spitfire IIa model well underway. I have all the drawings and data I need (far too much probably). I've rather lost the bubble on the recent changes to the piston engine simulation in YASim: How do we set the reduction gearing ratio? Can we do a constant speed propeller? And can we set the handedness of the propeller to RH? Regards Vivian Meazza ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Spitfire Hurricane manuals
On Wednesday 31 March 2004 11:09, Vivian Meazza wrote: Erik Hofman Sent: 13 March 2004 15:12 To: FlightGear developers discussions Subject: Re: [Flightgear-devel] Spitfire Hurricane manuals Erik Hofman wrote: http://home.clara.net/wolverine/BOB/misc/Spit_Hurri_Manuals.zip To get back to the original subject, this site has an aweful lot of information on WWII warbirds, including performance charts: http://www.rdrop.com/users/hoofj/ I now have the Spitfire IIa model well underway. I have all the drawings and data I need (far too much probably). I've rather lost the bubble on the recent changes to the piston engine simulation in YASim: How do we set the reduction gearing ratio? Can we do a constant speed propeller? And can we set the handedness of the propeller to RH? Regards Vivian Meazza Hello Vivian, I've used a geared prop in the Comper Swift - it seems to work well except the fuel mixture and flow rates don't seem correct. Can't help you with the CS prop though. Changing the handedness of the prop is easy enough as far as the animation goes but I think there's an assumption that all props rotate the same way as far as prop effects are concerned. LeeE ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Spitfire Hurricane manuals
Vivian Meazza wrote: How do we set the reduction gearing ratio? Set the gear-ratio attribute of the propeller tag. This is the reduction ratio, so typical values will be less than 1.0. Can we do a constant speed propeller? The min-rpm and max-rpm attributes define the range of the blue lever. These are the speeds to which the propeller will seek; it may not be able to achieve them in practice. The documentation for these was, er, wrong. I'll fix that. And can we set the handedness of the propeller to RH? Sure thing. Use a negative moment value. :) No joke: that will have exactly the effect of a counter-rotating engine. The DC-3 uses this trick for the starboard engine, for example. I'll add some documentation for that as well. Andy ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
RE: [Flightgear-devel] Spitfire Hurricane manuals
Andy Ross replied Sent: 31 March 2004 20:43 To: FlightGear developers discussions Subject: Re: [Flightgear-devel] Spitfire Hurricane manuals Vivian Meazza wrote: How do we set the reduction gearing ratio? Set the gear-ratio attribute of the propeller tag. This is the reduction ratio, so typical values will be less than 1.0. Can we do a constant speed propeller? The min-rpm and max-rpm attributes define the range of the blue lever. These are the speeds to which the propeller will seek; it may not be able to achieve them in practice. The documentation for these was, er, wrong. I'll fix that. And can we set the handedness of the propeller to RH? Sure thing. Use a negative moment value. :) No joke: that will have exactly the effect of a counter-rotating engine. The DC-3 uses this trick for the starboard engine, for example. I'll add some documentation for that as well. Thanks for all that: all looks good - the documentation has got a bit astern of station. Could you explain a bit more about the turbo attribute when used for a supercharger? The P51d uses this to calculate the moment: MOI = # of Blades * (8.2*(10^-5))*(D^5), slug-ft^2 then converted to kg-m^2 and finally square root to kg-m for torque value Is this the most up-to-date we have? Thanks again Vivian Meazza ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Spitfire Hurricane manuals
Vivian Meazza wrote: Thanks for all that: all looks good - the documentation has got a bit astern of station. Could you explain a bit more about the turbo attribute when used for a supercharger? Actually, the existing turbo-mul implementation is *more* like a supercharger than a real turbo. YASim models the boost as a simply multiplication factor on the input manifold pressure. If it's set to 2.0, then the engine sees twice the static pressure, etc... Real turbochargers don't have linear boost-vs-RPM curves, and tend to lag (in time) engine power by a little bit. A gear-driven supercharger is going to be closer to that ideal. MOI = # of Blades * (8.2*(10^-5))*(D^5), slug-ft^2 then converted to kg-m^2 and finally square root to kg-m for torque value Is D diameter? That looks like the right relationship (linear dimension to the fifth power) for a moment as a function of size, but I'd be *really* suspicious of using that equation for anything else. The .82 constant is pure fabrication, and will change depending on the shape and density (wood? aluminum? composite?) of any given propeller. A Lockheed Constellation and a Piper Cub sure as hell aren't going to have the same constant. :) Here's (IMHO) a better framework: Think of a propeller blade as a stick, with a constant density along its length. That's not quite right, but for most propellers the non-stickness is concentrated in the thick middle, which makes very little contribution to the moment of inertia. So the MOI is the integral along the blade length (from zero to R -- the propeller radius) of rho*r*dr, where rho (the density) is just propeller-[M]ass / ([N]umber-of-blades * R). So we do the integral for each blade and multiply by N: R M N * INTEGRAL --- * r * dr 0 N * R M, N and R come out as constants (and the N drops out entirely), so we have just a trivial: MR --- * INTEGRAL r * dr R0 Which of course is just (M/R) * (R^2/2) == M*R/2 So multiply your propeller mass (which you might have to guess at) by its radius and divide by two. Much simpler, and no magic constants needed. And you can do it in native units, without looking up what a slug is. :) Andy ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Spitfire Hurricane manuals
On Wed, 31 Mar 2004 13:32:39 -0800, Andy wrote in message [EMAIL PROTECTED]: Vivian Meazza wrote: Thanks for all that: all looks good - the documentation has got a bit astern of station. Could you explain a bit more about the turbo attribute when used for a supercharger? Actually, the existing turbo-mul implementation is *more* like a supercharger than a real turbo. YASim models the boost as a simply multiplication factor on the input manifold pressure. If it's set to 2.0, then the engine sees twice the static pressure, etc... Real turbochargers don't have linear boost-vs-RPM curves, and tend to lag ..you mean lead? On pouring gas, the first thing to happen is the extra fuel spins up _only_ the turbo, which then promptly feeds engine more air etc as soon as that turbo is spun up. ..a geardriven supercharger is geared to the entire engine, and moves with the entire engine, and that too has to move around faster, before it can feed any more air. (in time) engine power by a little bit. A gear-driven supercharger is going to be closer to that ideal. MOI = # of Blades * (8.2*(10^-5))*(D^5), slug-ft^2 then converted to kg-m^2 and finally square root to kg-m for torque value Is D diameter? That looks like the right relationship (linear dimension to the fifth power) for a moment as a function of size, but I'd be *really* suspicious of using that equation for anything else. The .82 constant is pure fabrication, and will change depending on the shape and density (wood? aluminum? composite?) of any given propeller. A Lockheed Constellation and a Piper Cub sure as hell aren't going to have the same constant. :) Here's (IMHO) a better framework: Think of a propeller blade as a stick, with a constant density along its length. That's not quite right, but for most propellers the non-stickness is concentrated in the thick middle, which makes very little contribution to the moment of inertia. So the MOI is the integral along the blade length (from zero to R -- the propeller radius) of rho*r*dr, where rho (the density) is just propeller-[M]ass / ([N]umber-of-blades * R). So we do the integral for each blade and multiply by N: R M N * INTEGRAL --- * r * dr 0 N * R M, N and R come out as constants (and the N drops out entirely), so we have just a trivial: MR --- * INTEGRAL r * dr R0 Which of course is just (M/R) * (R^2/2) == M*R/2 So multiply your propeller mass (which you might have to guess at) by its radius and divide by two. Much simpler, and no magic constants needed. And you can do it in native units, without looking up what a slug is. :) Andy -- ..med vennlig hilsen = with Kind Regards from Arnt... ;-) ...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 [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
RE: [Flightgear-devel] Spitfire Hurricane manuals
Andy Ross wrote Vivian Meazza wrote: Thanks for all that: all looks good - the documentation has got a bit astern of station. Could you explain a bit more about the turbo attribute when used for a supercharger? Actually, the existing turbo-mul implementation is *more* like a supercharger than a real turbo. YASim models the boost as a simply multiplication factor on the input manifold pressure. If it's set to 2.0, then the engine sees twice the static pressure, etc... Real turbochargers don't have linear boost-vs-RPM curves, and tend to lag (in time) engine power by a little bit. A gear-driven supercharger is going to be closer to that ideal. MOI = # of Blades * (8.2*(10^-5))*(D^5), slug-ft^2 then converted to kg-m^2 and finally square root to kg-m for torque value Is D diameter? That looks like the right relationship (linear dimension to the fifth power) for a moment as a function of size, but I'd be *really* suspicious of using that equation for anything else. The .82 constant is pure fabrication, and will change depending on the shape and density (wood? aluminum? composite?) of any given propeller. A Lockheed Constellation and a Piper Cub sure as hell aren't going to have the same constant. :) Here's (IMHO) a better framework: Think of a propeller blade as a stick, with a constant density along its length. That's not quite right, but for most propellers the non-stickness is concentrated in the thick middle, which makes very little contribution to the moment of inertia. So the MOI is the integral along the blade length (from zero to R -- the propeller radius) of rho*r*dr, where rho (the density) is just propeller-[M]ass / ([N]umber-of-blades * R). So we do the integral for each blade and multiply by N: R M N * INTEGRAL --- * r * dr 0 N * R M, N and R come out as constants (and the N drops out entirely), so we have just a trivial: MR --- * INTEGRAL r * dr R0 Which of course is just (M/R) * (R^2/2) == M*R/2 So multiply your propeller mass (which you might have to guess at) by its radius and divide by two. Much simpler, and no magic constants needed. And you can do it in native units, without looking up what a slug is. :) Andy Like the math - D was diameter btw. How about embedding it in YASim? I have an accurate figure for the mass of the propeller. Slug: Unit of mass that is equal to the mass that takes 1 lbf to accelerate at 1 ft/s2 - that's the easy bit. Now on with the model until the next question. Thanks Vivian Meazza ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
RE: [Flightgear-devel] Spitfire Hurricane manuals
Arnt Karlsen wrote On Wed, 31 Mar 2004 13:32:39 -0800, Andy wrote in message [EMAIL PROTECTED]: Vivian Meazza wrote: Thanks for all that: all looks good - the documentation has got a bit astern of station. Could you explain a bit more about the turbo attribute when used for a supercharger? Actually, the existing turbo-mul implementation is *more* like a supercharger than a real turbo. YASim models the boost as a simply multiplication factor on the input manifold pressure. If it's set to 2.0, then the engine sees twice the static pressure, etc... Real turbochargers don't have linear boost-vs-RPM curves, and tend to lag ..you mean lead? On pouring gas, the first thing to happen is the extra fuel spins up _only_ the turbo, which then promptly feeds engine more air etc as soon as that turbo is spun up. I don't think so. Turbo-lag is well known. The throttle opens, more fuel goes to the engine, which produces more exhaust gas which then speeds up the turbo-charger which increases air flow to the engine, hence the increase in inlet pressure lags the increase in engine rpm. ..a geardriven supercharger is geared to the entire engine, and moves with the entire engine, and that too has to move around faster, before it can feed any more air. Whilst that is technically true, the increase in engine rpm brings an instantaneous increase in supercharger rpm and an instantaneous increase in output pressure. The only lag is caused in the ducting, which is usually kept as short as possible. For a supercharger, any lag can be ignored for practical purposes. (in time) engine power by a little bit. A gear-driven supercharger is going to be closer to that ideal. Andy Regards Vivian Meazza ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Spitfire Hurricane manuals
Erik Hofman wrote: http://home.clara.net/wolverine/BOB/misc/Spit_Hurri_Manuals.zip To get back to the original subject, this site has an aweful lot of information on WWII warbirds, including performance charts: http://www.rdrop.com/users/hoofj/ Erik ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Spitfire Hurricane manuals
Sorry I've not had the opportunity to reply to this earlier (holiday away on business). I was responsible for the spitfire model. Unfortunately the commitments of work and trying to have a social life didn't agree with continuing it. I hope to at some stage get some very detailed pictures on a later model spitfire. The model is based on a mkXIV and I have collected many pictures of the spit whilst I modelled it. These wouldn't be of much use in it's current state as all the geometry that's really missing is some ducts. Under wing and centre fuse. I never got as far as putting it into flightgear... but it's GPL'd from my standpoint. I think Jon had some data for the flight model. It is a hope of mine to have a Concorde model. However I find blender a bit backwards compared to what's available at work, and I'm not getting anymore free time than I was before. At work we have a flying spitfire and typhoon. I'm trying to get access to these so I can provide more detailed information on them e.g. photos etc. We also have the last production Concorde (lucky eh..). From my point of view I think the spitfire is a spectacular plane to watch, and I find the rumours about the design origin most interesting. I'll probably see some of you at the expo...thought it'd be a nice break from work. Chris ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Spitfire Hurricane manuals
On Mon, 08 Mar 2004 21:52:04 -0500, David Megginson [EMAIL PROTECTED] wrote: And psychological warfare. From what I've read, the German flight crews were much more frightened of the Spitfires (and British RADAR guidance for interceptions made it look like there were many more planes than the British actually had). Also, I'm not certain about this, but I believe that often the Spits would concentrate on engaging the fighters so that the Hurricanes could get at the bombers. Obviously, the Spits would rack up many fewer kills themselves that way, but I'm not sure how well the BoB would have gone if Britain hadn't been able to deploy a fighter well-matched with the ME-109. From what I've seen on TV and read, the hurricanes usually fared better against cannon equipped aircraft because they have a lot of fabric on their airframe. The cannon rounds would pass straight through many parts of the airframe causing a minimal amount of damage (minimal seems the wrong word to use!). Whereas the spitfires monocoque conventional structure took cannon rounds quite badly in comparison... There was a series of TV documentaries here recently called 'Spitfire Ace' which I thought was very good. I think you can buy the accompanying book from Amazon.co.uk. One of the quotes from a German pilot was with refernce to the 8 browning machine guns on the spitfire...it was something like 'if he gets you at the right distance with all 8 guns you will be caput!'. Whichever way you look at it they were brilliant, brave pilots on both sides. All the best, Matt. ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
