From: Maik J. <mj...@gm...> - 2006-06-23 21:42:46
|
Hello all, after a long period of absence on business and family I now want to fix some of the "missings" in the helicopter simulation. But first I have to say thank you to all of you, because of the great development of flightgear in the last three years. And a very big thank you to Melchior for the great Bo105. The first thing I started to work is the co-work with yasim. I was not able to set up yasim correctly. Therefore the fuselage and the stabs were not producing any aerodynamic forces. (Therefore it was necessary, that the rotor itself produces extremely large drag to avoid to high maximum speed of the helicopter. This was the cause for the unrealistic low descent rate.) Now I found how to setup yasim correctly. This is the base for calculation of downwash effects on stabs and fuselage. With this change the bo105 feels significantly different (and I hope more realistic; but all my knowledge is based on model helicopters and theoretical consideration.) Furthermore I have included the air-pressure to the calculations. The bo now does not any longer climb to unlimited heights. Now I want to add/fix - ground effect - more realistic calculation on power-consumption. Autorotation and co-operation with the yasim engines is my aim (Is there any rotation-speed-controller in yasim?) - translational lift - comments to the source - downwash effects on fuselage and stabs - vortex state With these points the helicopter simulation should obtain much more realism. Is there any other helicopter (3D-model) in preparation? @Melchior: is it possible to add an instrument, which shows the lateral movement of the helicopter or the direction of the translation? With this it is much easier to find the correct setting for the pedals. On real helicopters I saw such a instrument realized in two different ways: one was measuring the diefference of the air-pressure on the right and the left side of the heli, but I do not remember how the instrument self looked like. The other was a simple piece of string on the outside of the cockpit. (There is a small bug in the movement of the blades. Due to gyro effects the rotor reacts (about) 90° delayed. If you put the stick forward, the left blade will decrease incidence). Best regards, Maik Maik Justus schrieb: > Hi > > Maik Justus wrote: > >> The helicopter simulation is not finished yet. I will describe later, >> which functions/ effects are totally missing or simplified. > > > Here it is: > > Missing: > -Downwash > -Effect on stabs > -Effect on rotor itself > -Effect on ground (ground effect) > -Engine (The needed power is calculated, but very simplified (i.e. a > autorotation is not possible now) , but the rotor now accelerates in 5 > sec and hold than the revolution for every circumstances) > -Fuel consumption > -Garbage collection to the source > -Comments in the source > > Unrealistic: > -Translational lift > -Teetering (I am not sure, which effect the teetering has. If I try to > calculate it, I get some discrepancies) > -Lift and drag from the Rotor blades is very simplified. To use > realistic values of a realistic airfoil should be not very complicate > (and then the needed power would be realistic and autorotation should > be possible) > -The rotor is simulated at only 4 points. To use many points along the > rotor blades is much better. > > And maybe much more, which I forgot to mention here ;-) > > > The bo105.xml contain only more or less realistic rotors. The fuselage > and the stabs are still missing. (the same for bell206like.xml, > ch47like.xml and as350like.xml). (I am not sure if the stabs are > working correct without the solver. I tried to use fixed values if you > specify no wing and hstab, but maybe there is a bug. In the > ch47like.xml the vstab seems to have no effect at all) > > > All the best, > Maik > > P.S.: I would be very thankful if someone would correct my english in > the README.yasim.... > > > > > > > _______________________________________________ > Flightgear-devel mailing list > Fli...@fl... > http://mail.flightgear.org/mailman/listinfo/flightgear-devel > |
From: Melchior F. <mf...@ao...> - 2006-06-23 22:12:54
|
* Maik Justus -- Friday 23 June 2006 23:42: > Hello all, Woohoo ... welcome back! :-) > now want to fix some of the "missings" in the helicopter simulation. Wow, excellent news. Bah, who needs sliced bread ... > And a very big thank you to Melchior for the great Bo105. You are welcome. It progresses slowly, because I'm always busy with C++ coding and other stuff. There's still a lot to do, controls, instruments, pilots, textures, ... > - ground effect Look into Mathias' ground cache. This should make it quite easy to get the necessary altitudes quickly. > With these points the helicopter simulation should obtain much more > realism. > > Is there any other helicopter (3D-model) in preparation? Yes, there is an R22, and Josh works on a CH53. Both not in CVS. )The R22 probably won't ever.) > @Melchior: is it possible to add an instrument, which shows the lateral > movement of the helicopter or the direction of the translation? Probably yes. Have to look. We've had someone post a photo of what we identified as drift indicator. (Josh?) > (There is a small bug in the movement of the blades. Due to > gyro effects the rotor reacts (about) 90° delayed. If you put the stick > forward, the left blade will decrease incidence). In the animation only, and With the CVS version? There was a bug that I fixed after the 0.9.10 release, I think. Or an FDM bug? m. |
From: Melchior F. <mf...@ao...> - 2006-06-23 22:23:52
|
* Melchior FRANZ -- Saturday 24 June 2006 00:12: > Yes, there is an R22, and Josh works on a CH53. Both not in CVS. )The > R22 probably won't ever.) The R22 is available here: http://www.geocities.com/flightgearproject/ Don't know if it still works with current cvs, though. m. |
From: Melchior F. <mf...@ao...> - 2006-06-23 22:40:05
|
* Maik Justus -- Saturday 24 June 2006 00:29: > Melchior FRANZ schrieb: > > Look into Mathias' ground cache. This should make it quite easy to > > get the necessary altitudes quickly. > I will have a look on this. Is this used in yasim? Yes. It's use to get "cheap" terrain intersections for the gear. > > Yes, there is an R22, and Josh works on a CH53. Both not in CVS. )The > > R22 probably won't ever.) > > > good (more helicopters) and bad (not in cvs) I'm confident that the CH53 will be submitted for cvs. :-) > > In the animation only, and With the CVS version? There was a bug that > > I fixed after the 0.9.10 release, I think. Or an FDM bug? > > > Yes, only in animation. I think the bug is in the 0.9.10 release and in > the cvs version Oh, whoops. Then it worked before, and it's my "fix" that broke it?! I'll look into it and send you a (reverse) patch for testing. m. |
From: Josh B. <jba...@at...> - 2006-06-23 22:54:49
|
Melchior FRANZ wrote: >>> Yes, there is an R22, and Josh works on a CH53. Both not in CVS. )The >>> R22 probably won't ever.) >>> >> good (more helicopters) and bad (not in cvs) > > I'm confident that the CH53 will be submitted for cvs. :-) Yes, the Sea Stallion will be in CVS as soon as I hack up a GPL FDM for it. I am missing a lot of data for that, and may need some help grokking the format as well. Anyone have any friends in a Marine HLH squadron? I also want to get some basic flight instruments in, as it currently only exists as the cockpit section with a radio stack. Don't look behind you, you won't see any engines! Josh |
From: Maik J. <mj...@gm...> - 2006-06-23 22:30:02
|
Hi Melchior, Melchior FRANZ schrieb: > * Maik Justus -- Friday 23 June 2006 23:42: > >> Hello all, >> > ... > >> - ground effect >> > > Look into Mathias' ground cache. This should make it quite easy to > get the necessary altitudes quickly. > > > I will have a look on this. Is this used in yasim? > >> With these points the helicopter simulation should obtain much more >> realism. >> >> Is there any other helicopter (3D-model) in preparation? >> > > Yes, there is an R22, and Josh works on a CH53. Both not in CVS. )The > R22 probably won't ever.) > > good (more helicopters) and bad (not in cvs) > > > >> @Melchior: is it possible to add an instrument, which shows the lateral >> movement of the helicopter or the direction of the translation? >> > > Probably yes. Have to look. We've had someone post a photo of what we > identified as drift indicator. (Josh?) > > > > >> (There is a small bug in the movement of the blades. Due to >> gyro effects the rotor reacts (about) 90° delayed. If you put the stick >> forward, the left blade will decrease incidence). >> > > In the animation only, and With the CVS version? There was a bug that > I fixed after the 0.9.10 release, I think. Or an FDM bug? > Yes, only in animation. I think the bug is in the 0.9.10 release and in the cvs version > m. > > Using Tomcat but need to do more? Need to support web services, security? > Get stuff done quickly with pre-integrated technology to make your job easier > Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo > http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642 > _______________________________________________ > Flightgear-devel mailing list > Fli...@li... > https://lists.sourceforge.net/lists/listinfo/flightgear-devel > > > Maik |
From: Mathias <Mat...@gm...> - 2006-06-26 05:42:20
|
On Saturday 24 June 2006 00:29, Maik Justus wrote: > >> - ground effect > > > > Look into Mathias' ground cache. This should make it quite easy to > > get the necessary altitudes quickly. > > I will have a look on this. Is this used in yasim? Yes it is. There is an api in FGInterface which can be used to get agl values in a sma= ll=20 environment from the aircraft. There is just a small cache containing the=20 scenery triangles a few meters around the aircraft. =46eel free to ask if there are some problems. Greetings Mathias =2D-=20 Mathias Fr=C3=B6hlich, email: Mat...@gm... |
From: Josh B. <jba...@at...> - 2006-06-23 22:51:06
|
Maik Justus wrote: >> Missing: >> -Downwash >> -Effect on stabs >> -Effect on rotor itself >> -Effect on ground (ground effect) >> -Engine (The needed power is calculated, but very simplified (i.e. a >> autorotation is not possible now) , but the rotor now accelerates in 5 >> sec and hold than the revolution for every circumstances) >> -Fuel consumption >> -Garbage collection to the source >> -Comments in the source >> >> Unrealistic: >> -Translational lift >> -Teetering (I am not sure, which effect the teetering has. If I try to >> calculate it, I get some discrepancies) >> -Lift and drag from the Rotor blades is very simplified. To use >> realistic values of a realistic airfoil should be not very complicate >> (and then the needed power would be realistic and autorotation should >> be possible) >> -The rotor is simulated at only 4 points. To use many points along the >> rotor blades is much better. >> >> And maybe much more, which I forgot to mention here ;-) >> >> Great! I have been waiting for someone to come back and rescue the helo code from stagnation. I have a CH-53E model in the early stages, though I haven't done anything with the FDM config, I just borrowed a non-GPL and extremely alpha one from someone else. I like your todo list. I would just suggest one more thing. If you look at a helo from behind, the rotor disk will be canted slightly to one side in straight and level flight. The side force offsets the side force of the tail rotor to prevent sideslip. In FG, instead of the rotor disk being tilted to the left a few degrees, the whole aircraft is. I'm not sure how the rotor hub is modeled, but I think that it is transferring too much pitch/roll torque. In a RL teetering system for instance, the rotor does not transmit any pitch/roll torque to the mast at all until the hinge reaches its limits, it just tugs it fore and back and side to side. Once the hinge reaches its limits (mast bumping), it becomes damaged. There also the possibility of a body strike, as with most fully articulated hubs. I'm not sure how this works in fully articulated, elastomeric and rigid hubs, but I would assume that the former only transmits that kind of torque based on the moment arm of the section of rotor inside the flapping hinge. The latter two, I guess transmit quite a lot since the flapping hinges are actually flexible sections of the hub. Anyway, if the rotor was free to pitch and roll correctly, I think that the helos would be a lot easier and more realistic to fly. Specifically, sudden control inputs would not cause violent rocking of the airframe, but rather violent rocking of the rotor disk with smooth movement of the airframe. It would also allow some very pretty animations of the rotor disks. And welcome back! http://video.google.com/videoplay?docid=9158894674372480270&q=helicopter+refueling+accident Josh |
From: Martin S. <Mar...@mg...> - 2006-06-23 23:04:41
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Josh Babcock wrote: > I like your todo list. I would just suggest one more thing. If you look > at a helo from behind, the rotor disk will be canted slightly to one > side in straight and level flight. The side force offsets the side force > of the tail rotor to prevent sideslip. In FG, instead of the rotor disk > being tilted to the left a few degrees, the whole aircraft is. This might very well be a phenomenon that's unique to helicopters which are based on this hingeless rotor concept, aircraft and rotor mostly move as one entity. They vary significantly from the typical Bell rotor style: http://www.christoph31.de/cgi-bin/MasterFrameReunion.cgi?http%3A//www.christoph31.de/foto/details.php%3Fimage_id%3D590%26 Martin. -- Unix _IS_ user friendly - it's just selective about who its friends are ! -------------------------------------------------------------------------- |
From: Josh B. <jba...@at...> - 2006-06-23 23:53:48
|
Martin Spott wrote: > Josh Babcock wrote: > >> I like your todo list. I would just suggest one more thing. If you look >> at a helo from behind, the rotor disk will be canted slightly to one >> side in straight and level flight. The side force offsets the side force >> of the tail rotor to prevent sideslip. In FG, instead of the rotor disk >> being tilted to the left a few degrees, the whole aircraft is. > > This might very well be a phenomenon that's unique to helicopters which > are based on this hingeless rotor concept, aircraft and rotor mostly > move as one entity. They vary significantly from the typical Bell rotor > style: > > http://www.christoph31.de/cgi-bin/MasterFrameReunion.cgi?http%3A//www.christoph31.de/foto/details.php%3Fimage_id%3D590%26 > > Martin. Yeah, this behavior may be appropriate for the bo105, I have a picture of an EC-135 with a semi-rigid rotor in a 1" hover that has that has that same tilt, though it might have just been wiggling as it lifted off. Most of the rotors out there, however, are still fully articulated. There are even a significant number of teetering rotors still flying. Just about every Jet Ranger has one. It is definitely not right for them. As far as I can tell, YASim treats all rotors this way. Josh |
From: Maik J. <mj...@gm...> - 2006-06-24 13:06:43
|
Josh Babcock schrieb: > Martin Spott wrote: > >> Josh Babcock wrote: >> >> >>> I like your todo list. I would just suggest one more thing. If you look >>> at a helo from behind, the rotor disk will be canted slightly to one >>> side in straight and level flight. The side force offsets the side force >>> of the tail rotor to prevent sideslip. In FG, instead of the rotor disk >>> being tilted to the left a few degrees, the whole aircraft is. >>> >> This might very well be a phenomenon that's unique to helicopters which >> are based on this hingeless rotor concept, aircraft and rotor mostly >> move as one entity. They vary significantly from the typical Bell rotor >> style: >> >> http://www.christoph31.de/cgi-bin/MasterFrameReunion.cgi?http%3A//www.christoph31.de/foto/details.php%3Fimage_id%3D590%26 >> >> Martin. >> > > Yeah, this behavior may be appropriate for the bo105, I have a picture > of an EC-135 with a semi-rigid rotor in a 1" hover that has that has > that same tilt, though it might have just been wiggling as it lifted > off. Most of the rotors out there, however, are still fully articulated. > There are even a significant number of teetering rotors still flying. > Just about every Jet Ranger has one. It is definitely not right for > them. As far as I can tell, YASim treats all rotors this way. > > Josh > > I think the simulation is correct at this point. But there is a second source for the tilting of the fuselage. The tail-rotor itself gives some moment to the fuselage, depending on the height where the tail-rotor is connected. (This effect is simulated as well.) I've never calculated the strength of this effect, but I expect it to be not negligible for the Jet Ranger. A UH1 I expect to hover more ore less parallel to the ground (depending on the cg). If we trust the simulation (I do), we can check this by using the bell206-simulation and modify the height of the tail-rotor to be the same as the main-rotor. > In a RL teetering system for > instance, the rotor does not transmit any pitch/roll torque to the mast > at all until the hinge reaches its limits, it just tugs it fore and back > and side to side. This is only correct for rotor heads with the hinge exactly in the center of the head (like Jet Ranger, UH1). If the hinge is not in the center (e. g. CH53), the rotor transmit torque to the mast. The rotor head of the Bo can transmit more torque to the mast, than the mast is designed for. Therefor the Bo has an instrument, which shows the moment on the mast. I have some documentation on the bo105 here. There is a comparison of the bo105 and the bell206. If you put the stick to one side the bell206 needs 1.7s for reaching 63% of the final rotational speed. The sa341 (gazelle) needs 1.2s and the bo105 needs 0.2s. Therefore the bell206 reacts very delayed to any input on the cyclic and the bo reacts instantly. Maik |
From: Josh B. <jba...@at...> - 2006-06-24 13:52:01
|
Maik Justus wrote: OK, you are clearly way ahead of me on this. Everything you say makes perfect sense, so I retract my original request. The welcome back still stands though! Josh |
From: Joacim P. <no...@tu...> - 2006-06-24 13:57:55
|
On Fri, 23 Jun 2006, Maik Justus wrote: > Is there any other helicopter (3D-model) in preparation? Hello Maik, I was fiddling with mainly the FDM for the Chinook last winter, and have = a simple 3D for it. (only an untextured exterior fuselage with two non-rota= ting rotors and the four wheels) There is quite extensive documentation on the variou= s ch47 models on the net, D-model in particular. Pilot manuals, tech manuals... thousands of pdf-pages. I also downloaded a few film clips of it flying, including a British crew performing some impressive aerobatic manouvres, to get an idea of how it ought to feel in the simulator too. (The ch-47 fdm in the cvs is apparently a mock-up with 4-blade(!) rotors etc.) Most of the info came from here: http://www.chinook-helicopter.com/ (and yes, the web design of those pages may make you go epileptic, but there's /piles/ of information on the Chinook there) Regarding the stabiliser on the ch47, that's not all there is to it: The real thing has two flight control systems, one for each rotor. If any of them are failed the heli can still be flown, but with a speed limit and according to what chinook pilots have said on the net, only with full concentration. (impossible to fly it and navigate at the same time with both FCS's out of operation.) This is also my experience with the FDM (my version) for it in FG, so perhaps the FDM is correct. ;) Speeding with it is terrifying... It really *do* need an FCS, even in the sim... The FCS varies the lift an= d tilt on the rotors according to speed. This, I noticed, has a great impac= t on stability. But I haven't found the details on the algorithms yet. Ther= e is *some* info on it in the tech manuals but I recall missing some data. AFAIK, the yasim fdm-engine does not simulate rotor blades with twist. Chinook blades are twisted as much as 12=B0. ("for stability reasons") I don't remember in what state I left my ch47 fdm last winter. (was experimenting quite a bit with it) I'll have a look at it later and see i= f I can resurrect something fairly flyable and post the config file here. I= 'm too busy with other things right now to do any serious work on it. |
From: Josh B. <jba...@at...> - 2006-06-24 14:05:34
|
Joacim Persson wrote: > AFAIK, the yasim fdm-engine does not simulate rotor blades with twist. > Chinook blades are twisted as much as 12°. ("for stability reasons") I have read that rotor twist is very important for autorotation operations. Josh |
From: Maik J. <mj...@gm...> - 2006-06-24 20:29:16
|
Hi Josh, yes, it has impact on the autorotation. But I hope that it is possible, to simulate autorotation as a first attempt without it. Most model helicopter have no twist and are able to fly autorotations. Maik Josh Babcock schrieb: > Joacim Persson wrote: > > >> AFAIK, the yasim fdm-engine does not simulate rotor blades with twist. >> Chinook blades are twisted as much as 12°. ("for stability reasons") >> > > I have read that rotor twist is very important for autorotation operations. > > Josh > > Using Tomcat but need to do more? Need to support web services, security? > Get stuff done quickly with pre-integrated technology to make your job easier > Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo > http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642 > _______________________________________________ > Flightgear-devel mailing list > Fli...@li... > https://lists.sourceforge.net/lists/listinfo/flightgear-devel > > > |
From: Josh B. <jba...@at...> - 2006-06-24 20:43:55
|
Maik Justus wrote: > Hi Josh, > > yes, it has impact on the autorotation. But I hope that it is possible, > to simulate autorotation as a first attempt without it. Most model > helicopter have no twist and are able to fly autorotations. > > Maik > > Josh Babcock schrieb: >> Joacim Persson wrote: >> >> >>> AFAIK, the yasim fdm-engine does not simulate rotor blades with twist. >>> Chinook blades are twisted as much as 12°. ("for stability reasons") >>> >> I have read that rotor twist is very important for autorotation operations. >> >> Josh Yes, as long as the blades can pitch below flat. Most helicopters IIRC can't technically do this because the blade angle is measured at the root, but once you subtract the twist it becomes apparent that the blade is overall at a downward pitch. I have also been told that that because the tips have a higher moment arm, the rotor can both produce net lift and maintain RPM at the same time. Josh |
From: Maik J. <mj...@gm...> - 2006-06-24 20:20:39
|
Hi Joacim, I am surprised how many helicopter types are (more or less) in process. The ch47 simulation is only a proof of concept. It shows, that the rotor simulation is able to simulate this rotor configuration (It has 4-blade rotors, it is much to small, no parameter of the rotor is form the ch47, etc.) Due to the missing drag of stabs and fuselage it is absolutely unrealistic. But this bug is solved and now it feels much better, but it is easy to get into very critical states. I have no information about the flight control systems; the control in the simulation is as it is in the rc models of chinook like helicopters. About the twist you are totally right. This is not simulated up to now. The main rotor is only simulated at one point of the blades. But I add this on my todo list. Maybe it is possible to add the flight control system to the simulation. As more we know about the real thing as easier the simulation will be. Maik Joacim Persson schrieb: > On Fri, 23 Jun 2006, Maik Justus wrote: > >> Is there any other helicopter (3D-model) in preparation? > > Hello Maik, > > I was fiddling with mainly the FDM for the Chinook last winter, and > have a > simple 3D for it. (only an untextured exterior fuselage with two > non-rotating rotors > and the four wheels) There is quite extensive documentation on the > various > ch47 models on the net, D-model in particular. Pilot manuals, tech > manuals... thousands of pdf-pages. I also downloaded a few film clips of > it flying, including a British crew performing some impressive aerobatic > manouvres, to get an idea of how it ought to feel in the simulator too. > (The ch-47 fdm in the cvs is apparently a mock-up with 4-blade(!) rotors > etc.) > > Most of the info came from here: http://www.chinook-helicopter.com/ > (and yes, the web design of those pages may make you go epileptic, > but there's /piles/ of information on the Chinook there) > > Regarding the stabiliser on the ch47, that's not all there is to it: The > real thing has two flight control systems, one for each rotor. If any of > them are failed the heli can still be flown, but with a speed limit and > according to what chinook pilots have said on the net, only with full > concentration. (impossible to fly it and navigate at the > same time with both FCS's out of operation.) > > This is also my experience with the FDM (my version) for it in FG, so > perhaps the FDM is correct. ;) Speeding with it is terrifying... > > It really *do* need an FCS, even in the sim... The FCS varies the lift > and > tilt on the rotors according to speed. This, I noticed, has a great > impact > on stability. But I haven't found the details on the algorithms yet. > There > is *some* info on it in the tech manuals but I recall missing some data. > > AFAIK, the yasim fdm-engine does not simulate rotor blades with twist. > Chinook blades are twisted as much as 12°. ("for stability reasons") > > > I don't remember in what state I left my ch47 fdm last winter. (was > experimenting quite a bit with it) I'll have a look at it later and > see if > I can resurrect something fairly flyable and post the config file > here. I'm > too busy with other things right now to do any serious work on it. > ------------------------------------------------------------------------ > > Using Tomcat but need to do more? Need to support web services, security? > Get stuff done quickly with pre-integrated technology to make your job easier > Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo > http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642 > ------------------------------------------------------------------------ > > _______________________________________________ > Flightgear-devel mailing list > Fli...@li... > https://lists.sourceforge.net/lists/listinfo/flightgear-devel > |
From: Joacim P. <no...@tu...> - 2006-06-24 21:16:34
|
On Sat, 24 Jun 2006, Maik Justus wrote: > Hi Joacim, > > I am surprised how many helicopter types are (more or less) in process. > The ch47 simulation is only a proof of concept. It shows, that the rotor > simulation is able to simulate this rotor configuration (It has 4-blade > rotors, it is much to small, no parameter of the rotor is form the ch47, > etc.) Due to the missing drag of stabs and fuselage it is absolutely > unrealistic. But this bug is solved and now it feels much better, but it > is easy to get into very critical states. Aha! So that's why I couldn't make it fly with the fuselage in level. It has always flown a bit nose-up at speed, no matter what insane drag values I set for the fuselage. Very confusing. ;) (talking about my 3-blade rotors >50000lbs version here) There is (was?) also an odd bug occuring from time to time, where some kind of torque was wrong or missing and the chinook started spinning like mad at takeoff; as if the torque on one rotor was missing or the cyclic aileron was differing between the rotors. Restarting fgfs usually "fixed" the problem. (I *can* get the same interesting effect by changing certain values on one rotor only, so they produce different torque. But this happens when they numbers are correct too.) Seems like uninitialised memory somewhere perhaps. > I have no information about > the flight control systems; the control in the simulation is as it is in > the rc models of chinook like helicopters. CH47 Theory of Operation, chapter 11. Can be downloaded from: http://www.chinook-helicopter.com/Publications/Publications.html (beware: 47 meg pdf, 500 pages) There is also a bitmapped drawing from Boeing there, containing fuselage measures, CG limits, pylon and rotorblade data etc. For now, I've added a manual longitudal cyclic trim (LCT) on it via the "propeller pitch" control through CYCLICELE on the rotors, but the numbers are guesswork so far. (I have tilt angles numbers for each rotor at various speeds, but I can't set that directly in the fdm.) The AFCS's do more than adjusting LCT. (yaw and pitch stabilisation for instance, which definitely takes a PID-regulator or two. ...or fifty-seven. =) > Maybe it is possible to add the flight control system to the simulation. It can be designed in nasal + a number of PID-regulators. All the necessary tools are already there in FG, so it doesn't affect the heli code in yasim. (Just a lot of work trimming the regulator values. :P) |
From: Maik J. <mj...@gm...> - 2006-06-27 21:51:08
|
Hi Joacim, Joacim Persson schrieb: > There is (was?) also an odd bug occuring from time to time, where some > kind of torque was wrong or missing and the chinook started spinning like > mad at takeoff; as if the torque on one rotor was missing or the cyclic > aileron was differing between the rotors. Restarting fgfs usually "fixed" > the problem. (I *can* get the same interesting effect by changing certain > values on one rotor only, so they produce different torque. But this > happens when they numbers are correct too.) > Seems like uninitialised memory somewhere perhaps. > Your analysis is 100% correct. I found an uninitialized variable which caused this behavior. Maik |
From: Melchior F. <mf...@ao...> - 2006-06-24 22:15:41
|
* Maik Justus -- Friday 23 June 2006 23:42: > @Melchior: is it possible to add an instrument, which shows the lateral > movement of the helicopter or the direction of the translation? Done. There's a GSDI (Ground Speed Drift Indicator) on the right side, under the VSI. The implementation is rather simple, and loosely modeled after a photo. Unfortunately, it is almost impossible to get photos. Seems to be top-secret stuff ... I had another implementation first with direction needle, but thought the current one was better. (?) m. |
From: Melchior F. <mf...@ao...> - 2006-06-25 22:17:59
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* Maik Justus -- Sunday 25 June 2006 23:49: > Is it possible to switch it to a air-speed-drift-indicator? Not the C++ instrument, because it's a GSDI and that's not how these work. But you can open $FG_ROOT/Aircraft/bo105/Instruments/gsdi/gsdi.xml and replace the two properties "instrumentation/gsdi/drift-[uv]-kt" with "velocities/[uv]Body-fps". m. |
From: Maik J. <mj...@gm...> - 2006-06-25 22:52:24
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Hello Melchior, Very good. Thank you. Maik Melchior FRANZ schrieb: > * Maik Justus -- Sunday 25 June 2006 23:49: > >> Is it possible to switch it to a air-speed-drift-indicator? >> > > Not the C++ instrument, because it's a GSDI and that's not how these > work. But you can open $FG_ROOT/Aircraft/bo105/Instruments/gsdi/gsdi.xml > and replace the two properties "instrumentation/gsdi/drift-[uv]-kt" > with "velocities/[uv]Body-fps". > > m. > > Using Tomcat but need to do more? Need to support web services, security? > Get stuff done quickly with pre-integrated technology to make your job easier > Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo > http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642 > _______________________________________________ > Flightgear-devel mailing list > Fli...@li... > https://lists.sourceforge.net/lists/listinfo/flightgear-devel > > > |
From: Maik J. <mj...@gm...> - 2006-06-25 21:49:56
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Hello Melchior, thank you very much. It helps me much to find the correct input for the tail rotor. Is it possible to switch it to a air-speed-drift-indicator? Maik Melchior FRANZ schrieb: > * Maik Justus -- Friday 23 June 2006 23:42: > >> @Melchior: is it possible to add an instrument, which shows the lateral >> movement of the helicopter or the direction of the translation? >> > > Done. There's a GSDI (Ground Speed Drift Indicator) on the right side, > under the VSI. The implementation is rather simple, and loosely modeled > after a photo. Unfortunately, it is almost impossible to get photos. > Seems to be top-secret stuff ... > I had another implementation first with direction needle, but thought > the current one was better. (?) > > m. > > Using Tomcat but need to do more? Need to support web services, security? > Get stuff done quickly with pre-integrated technology to make your job easier > Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo > http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642 > _______________________________________________ > Flightgear-devel mailing list > Fli...@li... > https://lists.sourceforge.net/lists/listinfo/flightgear-devel > > > |
From: Maik J. <mj...@gm...> - 2006-06-27 21:58:07
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Hi Joacim, Joacim Persson schrieb: > AFAIK, the yasim fdm-engine does not simulate rotor blades with twist. > Chinook blades are twisted as much as 12°. ("for stability reasons") > I'm working now on simulating the rotor on several points along the rotor blades (with twist). Maik |
From: Joacim P. <no...@tu...> - 2006-06-28 00:37:02
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On Tue, 27 Jun 2006, Maik Justus wrote: > I'm working now on simulating the rotor on several points along the > rotor blades (with twist). I suspect that twist to vary with load. It's the tips that has a 12=B0 hi= gher incidence (sic!) than the root, when the rotor is stopped that is. I gues= s that's a pre-tensioning of the blade; that the lift moment on the blade (= it has some naca profile if I remember it right) will twist it back to a mor= e straight shape under load or perhaps even twist it the other way. I have begun to develop some doubts if this reductionistic approach is th= e way to go for simulating an aircraft that under normal operation is flown with an electronic flight control system which does it best at making the aircraft behave like a much smoother thing to fly than it is with the FCS broken. What we want to simulate in the end is certain movements of the aircraft following a certain input, not necessarily all the gory details = in between that the pilot (normally) never have to worry about. But then again -- where's the fun in simplicity? ;) |