Re: [Flightgear-devel] Latest stupid helicopter trick
Erik Hofman [EMAIL PROTECTED] wrote: If you got the latest CVS code it shoudl just work. Got it - I took the YF-23 for a reconnaissance flight What will the sailboat do if it reaches the shoreline ? Will it turn around ? 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] Latest stupid helicopter trick
Martin Spott wrote: Erik Hofman [EMAIL PROTECTED] wrote: If you got the latest CVS code it shoudl just work. Got it - I took the YF-23 for a reconnaissance flight What will the sailboat do if it reaches the shoreline ? Will it turn around ? Not at this moment, no. That would require intervention from a Nasal script (which isn't implemented yet). Erik ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Latest stupid helicopter trick
Erik Hofman wrote: Not at this moment, no. That would require intervention from a Nasal script (which isn't implemented yet). Actually, if you guys used property ties to wrap your internal variables, you could drive it with Nasal right now. You can either tie a pointer to the actual data, or hook callbacks to the get/set() methods. The stuff in JSBSim/FGPropertyManager does very similar things; you can look there for examples. Writing a full-on set of Nasal extension functions is pretty involved. See the props.Node implementation. For really fancy stuff or core classes where you can't avoid the complexity, it's acceptable. For something like this, I think the property system is the appropriate glue. Andy ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Latest stupid helicopter trick
Andy Ross wrote: Erik Hofman wrote: Not at this moment, no. That would require intervention from a Nasal script (which isn't implemented yet). Actually, if you guys used property ties to wrap your internal variables, you could drive it with Nasal right now. You can either tie a pointer to the actual data, or hook callbacks to the get/set() methods. The stuff in JSBSim/FGPropertyManager does very similar things; you can look there for examples. Writing a full-on set of Nasal extension functions is pretty involved. See the props.Node implementation. For really fancy stuff or core classes where you can't avoid the complexity, it's acceptable. For something like this, I think the property system is the appropriate glue. Even for (say) a dozen of simultaneously active dynamic models? I'm not sure, but it would be a good thing to look into. Erik ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Latest stupid helicopter trick
Erik Hofman wrote: Even for (say) a dozen of simultaneously active dynamic models? I'm not sure, but it would be a good thing to look into. Even for hundreds. The overhead for a property tie is pretty close to zero. You pay the cost only when the property is accessed -- to your internal C++ code, it's still just a variable. The only way to get into performance difficulties is if you are setting the values repeatedly (every frame, for instance) from a script. Nasal isn't terribly slow, but spinning in an interpreter like that is just a bad idea. :) There's a similar issue with the current bo105.nas script -- it hooks a timer at 20Hz to do a rear door animation. For just one of these, it's obviously not a problem. For dozens or hundreds of animated objects, this is likely to be suboptimal. For situations like this, I'm working on (actually almost done -- just need to find time to test) a SGInterpolator subsystem which can be used from either Nasal or C++. The idea is that you pass it a property node, and a list of target value/delta time pairs. It then smoothly interpolates the property value each frame, with no input needed from user code. This is basically as efficient (one 10-line function call per frame per interpolant) as you can get without ditching the property system entirely. And it enables a lot of stuff that used to be difficult: I know Lee has hooked the YASim gear up/down property to drive animations, but this is limited. Having an interpolator that you can drive from a script means that you can do stuff like variable-speed gear retraction (one wheel first, etc...), light pulsing (off for a long time, interpolate to bright over .25sec, then off again...), etc... All of it with no dependency on frame rate. :) Andy ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Latest stupid helicopter trick
Andy Ross wrote: Erik Hofman wrote: Even for (say) a dozen of simultaneously active dynamic models? I'm not sure, but it would be a good thing to look into. Even for hundreds. The overhead for a property tie is pretty close to zero. You pay the cost only when the property is accessed -- to your internal C++ code, it's still just a variable. The only way to get into performance difficulties is if you are setting the values repeatedly (every frame, for instance) from a script. Nasal isn't terribly slow, but spinning in an interpreter like that is just a bad idea. :) Thinking about it a bit further. When populating the world with hundreds or thousands of scenery bound dynamic objects (just like it could be done with the static scenery at the moment) this doesn't sound like a good solution. I think a Nasal object (like the properties bindings) would bet a better solution without overloading the property tree with too much information. Erik ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Latest stupid helicopter trick
Martin Spott wrote: Erik Hofman [EMAIL PROTECTED] wrote: Here is another challenge. Put it on the deck of a moving sailboat: http://www.a1.nl/~ehofman/fgfs/gallery/sailboat.jpg I must admit that I didn't manage to spot the sailboat. From the perspective it looks like the boat is cruising in the SF bay, marginally east of KSFO (concluded from the hill behind the plane and the bridge in the background). But as I already said: I dind't find the boat. Did I miss any trick ? If you got the latest CVS code it shoudl just work. To get a better detectable moving ship you could replace sailboat.ac with container_carrier.ac in the ai section of FlightGear/data/preferences.xml Erik ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Latest stupid helicopter trick
Maik Justus wrote: Thie is in the fdm (adv. in the bo105.xml file) (with the real angles for the bo) - adv. + resp. Maik ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Latest stupid helicopter trick
Maik Justus [EMAIL PROTECTED] said: This makes the apparent torque effect lighter, but the aircraft will still tend to crab at low speeds. Is this feature incorporated into the fdm calculation for torque effect? Sorry, I didnt find crab in my dictionary. But what is not simulated is the effect of the downwash onto the stabs, which have great effect on the flying behaviour. The term crab as defined in the webster dictionary is: the angular difference between an aircraft's course and the heading necessary to make that course in the presence of a crosswind. The way I used it refers to the action crab which is flying on that angle (with the nose pointing in a slightly different direction than the one you are traveling). In the case of helicopters it is not only the crosswind effect, but also the anti-torque thrust, correct? And the vertical stab is not of the original size and the horizontal stab is missing as well as the fuselage. Oh... I hadn't thought about that. How are you maintaining stability on that axis? You mentioned last week that you had ground effect done. Is it worth submitting a patch for that? I am interested to see how it affects take off and landing. Currently it takes almost full collective to break the skids off the ground for take off, and it is almost impossible to get a gentle landing. Of course the landing is probably just my lack of skill, but I suspect the ground effect would do something to assist. Thanks, Jim ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Latest stupid helicopter trick
Hi Jim Jim Wilson said: The term crab as defined in the webster dictionary is: the angular difference between an aircraft's course and the heading necessary to make that course in the presence of a crosswind. The way I used it refers to the action crab which is flying on that angle (with the nose pointing in a slightly different direction than the one you are traveling). In the case of helicopters it is not only the crosswind effect, but also the anti-torque thrust, correct? I think you are correct. And the vertical stab is not of the original size and the horizontal stab is missing as well as the fuselage. Oh... I hadn't thought about that. How are you maintaining stability on that axis? Very simply: ther is nothing which gives instability on that axis. You mentioned last week that you had ground effect done. Is it worth submitting a patch for that? I am interested to see how it affects take off and landing. Currently it takes almost full collective to break the skids off the ground for take off, and it is almost impossible to get a gentle landing. Of course the landing is probably just my lack of skill, but I suspect the ground effect would do something to assist. I am sorry, but up to now I didn't find the time to test this. I wrote this on my portable in a train, where I had no joystick to test it. Thanks, Jim Maik ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Latest stupid helicopter trick
[EMAIL PROTECTED] [EMAIL PROTECTED] said: On Monday 24 November 2003 19:42, David Megginson wrote: Here's another fun landing: http://www.megginson.com/flightsim/water-tower.jpg Here's another one: http://www.8ung.at/mars/images/heli-touchdown.jpg Oh, all right... http://www.spiderbark.com/fgfs/h2otower.png http://www.spiderbark.com/fgfs/penthouseview.png Best, Jim ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Latest stupid helicopter trick
Jim Wilson wrote: [EMAIL PROTECTED] [EMAIL PROTECTED] said: On Monday 24 November 2003 19:42, David Megginson wrote: Here's another fun landing: http://www.megginson.com/flightsim/water-tower.jpg Here's another one: http://www.8ung.at/mars/images/heli-touchdown.jpg Oh, all right... http://www.spiderbark.com/fgfs/h2otower.png http://www.spiderbark.com/fgfs/penthouseview.png Here is another challenge. Put it on the deck of a moving sailboat: http://www.a1.nl/~ehofman/fgfs/gallery/sailboat.jpg Good luck! Erik :-D ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Latest stupid helicopter trick
On Sunday 30 November 2003 19:45, Jim Wilson wrote: http://www.spiderbark.com/fgfs/penthouseview.png Very nice landing. ;) Best Regards, Oliver C. ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Latest stupid helicopter trick
On Sunday 30 November 2003 19:45, Jim Wilson wrote: Oh, all right... http://www.spiderbark.com/fgfs/h2otower.png http://www.spiderbark.com/fgfs/penthouseview.png Best, Jim Now try this: :) http://www.8ung.at/mars/images/heli-skyscraper1.jpg http://www.8ung.at/mars/images/heli-skyscraper2.jpg Best Regards, Oliver C. ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Latest stupid helicopter trick
[EMAIL PROTECTED] [EMAIL PROTECTED] said: On Sunday 30 November 2003 19:45, Jim Wilson wrote: http://www.spiderbark.com/fgfs/penthouseview.png Very nice landing. ;) Thanks. It was a crash the first try. First I got into a lot of circling around trying to figure where to land and how to approach it. This resulted in quite a few near misses with the buildings. Then once I decided the approach, I came down too fast and went around to the east (big mistake) where there were a bunch of buildings and flew right in to one. I'm almost there as far as getting it...hovering in slowly is a lot like balancing a pole or stick vertically in the palm of your hand (or maybe even more like spinning a plate on a stick which I've never tried). It involves a constant flow of miniscule adjustments... probably hundreds per minute. Best, Jim ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Latest stupid helicopter trick
Erik Hofman [EMAIL PROTECTED] said: Here is another challenge. Put it on the deck of a moving sailboat: http://www.a1.nl/~ehofman/fgfs/gallery/sailboat.jpg Years ago when I lived very close to Bar Harbor (now about an hour away) there was a premier of a Mel Gibson movie. This is an extremely rare occurrence by the way, and not suprisingly, the movie was nothing spectacular. What was spectacular in my opion was Elton John's Yacht (power) that was moored down at the town pier. It arrived in town a couple of days before the premier. The day of the premier not one but two small helicopters flew in and landed on top of the boat. I didn't see the boat earlier, just heard about it, but I assume the boat came in with the helos and they went up to Bangor International to pickup up the host and guests the day of the event. I happened to see the birds flying over the harbor from a distance, went down to investigate and found them strapped onto pads way up top of the boat (very small pads in fact). Hehe...so I guess that isn't so far fetched. Might a be a little tight on that sailboat though. How well does that cub hover? :-) Best, Jim ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Latest stupid helicopter trick
[EMAIL PROTECTED] [EMAIL PROTECTED] said: On Sunday 30 November 2003 19:45, Jim Wilson wrote: Oh, all right... http://www.spiderbark.com/fgfs/h2otower.png http://www.spiderbark.com/fgfs/penthouseview.png Best, Jim Now try this: :) http://www.8ung.at/mars/images/heli-skyscraper1.jpg http://www.8ung.at/mars/images/heli-skyscraper2.jpg Can't beat that. You aren't using the magic carpet fdm for that are you? ;-) Best, Jim ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Latest stupid helicopter trick
Jim Wilson wrote: Thanks. It was a crash the first try. First I got into a lot of circling around trying to figure where to land and how to approach it. This resulted in quite a few near misses with the buildings. As someone with no helicopter experience, I'll guess that you want to approach directly into the wind if you can -- that way you don't have to worry about sideways drift. When you get close to a hover, it's very easy to tell which direction the wind's coming from. All the best, David ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Latest stupid helicopter trick
On Sunday 30 November 2003 20:50, Jim Wilson wrote: [EMAIL PROTECTED] [EMAIL PROTECTED] said: On Sunday 30 November 2003 19:45, Jim Wilson wrote: http://www.spiderbark.com/fgfs/penthouseview.png Very nice landing. ;) Thanks. It was a crash the first try. First I got into a lot of circling around trying to figure where to land and how to approach it. This resulted in quite a few near misses with the buildings. Then once I decided the approach, I came down too fast and went around to the east (big mistake) where there were a bunch of buildings and flew right in to one. I'm almost there as far as getting it...hovering in slowly is a lot like balancing a pole or stick vertically in the palm of your hand (or maybe even more like spinning a plate on a stick which I've never tried). It involves a constant flow of miniscule adjustments... probably hundreds per minute. I agree, i just tried two minutes ago to land with the helicopter between the two pillars of this skyscraper you can see on this screenshot: http://www.8ung.at/mars/images/pillars.jpg But i allways crashed. :( The helicopter gets quite unstable when trying to fly with less than 20 mph. Best Regards, Oliver C. ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Latest stupid helicopter trick
[EMAIL PROTECTED] wrote: On Sunday 30 November 2003 20:50, Jim Wilson wrote: "[EMAIL PROTECTED]" [EMAIL PROTECTED] said: On Sunday 30 November 2003 19:45, Jim Wilson wrote: http://www.spiderbark.com/fgfs/penthouseview.png Very nice landing. ;) Thanks. It was a crash the first try. First I got into a lot of circling around trying to figure where to land and how to approach it. This resulted in quite a few near misses with the buildings. Then once I decided the approach, I came down too fast and went around to the east (big mistake) where there were a bunch of buildings and flew right in to one. I'm almost there as far as getting it...hovering in slowly is a lot like balancing a pole or stick vertically in the palm of your hand (or maybe even more like spinning a plate on a stick which I've never tried). It involves a constant flow of miniscule adjustments... probably hundreds per minute. I agree, i just tried two minutes ago to land with the helicopter between the two pillars of this skyscraper you can see on this screenshot: http://www.8ung.at/mars/images/pillars.jpg But i allways crashed. :( The helicopter gets quite unstable when trying to fly with less than 20 mph. How does FlightGear calculates hitboxes for objects anyway? - Matevz ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Latest stupid helicopter trick
[EMAIL PROTECTED] [EMAIL PROTECTED] said: I agree, i just tried two minutes ago to land with the helicopter between the two pillars of this skyscraper you can see on this screenshot: http://www.8ung.at/mars/images/pillars.jpg But i allways crashed. :( The helicopter gets quite unstable when trying to fly with less than 20 mph. http://www.spiderbark.com/fgfs/hitchhiker.png Best, Jim ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Latest stupid helicopter trick
On Monday 24 November 2003 19:42, David Megginson wrote: Here's another fun landing: http://www.megginson.com/flightsim/water-tower.jpg Here's another one: http://www.8ung.at/mars/images/heli-touchdown.jpg Best Regards, Oliver C. ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Latest stupid helicopter trick
On Thu, 27 Nov 2003 16:26:45 +0100, Maik Justus [EMAIL PROTECTED] wrote: Hi, the Westland Lynx has nearly the same rotor than the bo (they both were developed in the same project at boelkow). Maik Maybe originally but current versions use the BERP (British Experimental Rotor Program) blade. http://www.enae.umd.edu/AGRC/Aero/berp.html http://halfdome.arc.nasa.gov/publications/abstracts/abs6.html http://home.online.no/~dagrs/lynxmk.htm The team you saw displaying were the Blue Eagles http://www.deltaweb.co.uk/eagles/bluehome.htm The Sharks flew only Gazelles Rotorheads: http://www.b-domke.de/AviationImages/Rotorhead.html Rick -- Help the Waterway Recovery Group to help restore the Uks canal network Make a donation to the 'Right Tool' Appeal http://www.wrg.org.uk/cgi-bin/fmaker.pl?appeal.htm ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Latest stupid helicopter trick
Andy Ross [EMAIL PROTECTED] wrote: Martin Spott wrote: No, because the BO105 - contrary to the 'usual' Bell's for example - has a rigid rotor. Please have a look here: http://www.b-domke.de/AviationImages/Rotorhead.html#Eurocopter Well, that explains my confusion... I guess this just shows my helicopter ignorance. My belief had always been that such a configuration was impossible due to the bending moments along the blade, [...] Bending is far not such an issue with the rotor blade. Most of the probable bending forces are compensated by huge centrifugal forces. When you look at the rotor blades of a helicopter standing on the ground then you'll realize that these blades are absolutely unqualified to bear bending forces :-) http://www.b-domke.de/AviationImages/Halo/2052.html What is the rationale behind the decision to make them rigid on the BO105? The only advantage I can see is that you save a few axles and bearings, which are moving parts that can wear out. But you pay for it in extra stress cycles on the blade, [...] The first is correct, the latter is not (see above). Pilots love this helicopter because of his outstanding manouverability. It's even capable of doing serious aerobatic - up to inverted flying (AFAIR with a modified gear box lubrication), 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] Latest stupid helicopter trick
On 07:50 Thu 27 Nov , Martin Spott wrote: The first is correct, the latter is not (see above). Pilots love this helicopter because of his outstanding manouverability. It's even capable of doing serious aerobatic - up to inverted flying (AFAIR with a modified gear box lubrication), Check out the Westland Lynx. I've seen these at a couple of airshows this year and the pilots did manage quite a bit of inverted flight during their routines. These too have a rigid rotor head with elastomeric bearings and the blades are intentionally made more rigid to prevent tail strikes during high-G and sharp stop maneuvers. Impressive engineering in all modern helos I think you'll agree :-) All the best, Matt. ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Latest stupid helicopter trick
On Thu, 27 Nov 2003, Matthew Law wrote: Check out the Westland Lynx. I've seen these at a couple of airshows this year and the pilots did manage quite a bit of inverted flight during their routines. These too have a rigid rotor head with elastomeric bearings and the blades are intentionally made more rigid to prevent tail strikes during high-G and sharp stop maneuvers. Impressive engineering in all modern helos I think you'll agree :-) I remember seeing the army display team at RAF Waddington a couple of years ago - 4 gazelle 1 lynx all lined up in the hover, then the lynx pilot backflipped the aircraft out of the lineup. The first time you see it you really can't believe what you've just seen. -- Jon Stockill [EMAIL PROTECTED] ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Latest stupid helicopter trick
Hi, the Westland Lynx has nearly the same rotor than the bo (they both were developed in the same project at boelkow). Maik Matthew Law wrote: On 07:50 Thu 27 Nov , Martin Spott wrote: The first is correct, the latter is not (see above). Pilots love this helicopter because of his outstanding manouverability. It's even capable of doing serious aerobatic - up to inverted flying (AFAIR with a modified gear box lubrication), Check out the Westland Lynx. I've seen these at a couple of airshows this year and the pilots did manage quite a bit of inverted flight during their routines. These too have a rigid rotor head with elastomeric bearings and the blades are intentionally made more rigid to prevent tail strikes during high-G and sharp stop maneuvers. Impressive engineering in all modern helos I think you'll agree :-) All the best, Matt. ___ 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] Latest stupid helicopter trick
On 14:48 Thu 27 Nov , Jon Stockill wrote: I remember seeing the army display team at RAF Waddington a couple of years ago - 4 gazelle 1 lynx all lined up in the hover, then the lynx pilot backflipped the aircraft out of the lineup. The first time you see it you really can't believe what you've just seen. Yes, that was one of the airshows I saw this year. I think they were called the Sharks. IIRC at one point they had a Lynx barrel rolling (with a portion of inverted) around a line of other aircraft. They also did loops and other crazy stuff that helicopters clearly can now do. Very cool. Were it not for the ridiculous costs, I would've much rather learned to fly rotary wing than fixed. As one of my work mates puts it: 'Yeah, even when the engine stops they still fly, cos they're still ugly and the earth still repels them!' All the best, Matt. ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Latest stupid helicopter trick
Hi, one think/thing added: Maik Justus schrieb: Hi, I try to explain my confusion: Lets think the heli is in forward flying and the rotor is spinning counter clock wise (seen from top, like the bo 105). Relative to air the rotor blades at the left side are slower and on the right side are faster. So they produce more force at the right side and less on the left side. Because of the gyroscopic effect the result is 90° shifted, so the blade will be up in front and down in back (flapping). The heli will rise the nose if you don't correct the cyclic input. (Up to this point I think I understood it.) m is the mass of one pointlike blade r is the radius to this mass (which vary with flapping and teetering) r0 the radius without flapping and teetering w (omega) the rotational speed of the blade a flapping angle The angular momentum ( m r w) is conservated. If the blade flapps up, r will be changed (r=r0 cos a, if we assume the hinge in the rotor center), so w has to be increased (that is what we know as teetering). If we assume a positive cone angle of the rotor (and this is the normal case) than the rotorblade will be faster in front position than in back position. And will produce more force in front position than in back position. And with thy gyro we have a roll moment, but to the right and not to the left as our helicopter has in real. It is very easy to run into more confusion. Lets think of a rotor system like the Jet Ranger has. The rotor can flap free around the center, so the only force to the mast is the centripetal force. The centripetal force is m r w w. Without teetering this force is m r0 w w cos a. If the rotor is tilted to the front and has a positive cone angle the blade will produce higher centripetal force in front position than in back position. A effective force to the rotormast pointing forward results. The CG is lower than the rotor head, so this result in a forward roll moment. ok. But what is the result of the teetering? If m r w is constant, than w must be w0/(cos a) (remember: r=r0*cos a). And the centripetal force is then m r0 w0 w0/(cos a), which means, that a forward tiltet rotor will produce an effective force pointing backward, which is obviously nonsense. In this calculation I forgot to split the centripetal force into a component along the blade (the only direction a force can attac) (which is F *(cos a) ) and at the flapping hinge this force has to be splitted into a component along the mast (the lift) and one perpendicular to it (which makes a rotational moment). the one perpendicular has a (cos a) factor, the parallel one a (sin a) factor. This results: r0 w0 w0 (cos a) for the component perpendicular to the mast and r0 w0 w0 (sin a) parallel to the mast. So teetering has no effect to the forces (in first order). Somehow I lost one (cos a) term in my older calculations which rides me into confusion, but now it seems to be clear to me. But the translational roll moment has still the wrong sign... Does someon know, if the Bell 206 (or the r 22) has this roll moment and how large is it? My only idea to solve this: The teetering hinge at every real heli is not in the rotor center. It is out of center. Every teetering angle produces a force to the blade which wants to reduce the teetering angle, so the change of w will be smaller (the missing angular momentum goes to the rotor mast). But if you look in detail into this, you find, that this is a osscillator, which is nearly in resonance. One solution is to think of a big damping constant, but the teeter hinge at model helicopters needs no damping. Maybe the damping can be explained aerodynamically? I don't know. Or is there a big error in this calculations? Confused, Maik a little bit eased, Maik ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Latest stupid helicopter trick
Andy Ross [EMAIL PROTECTED] wrote: Maik Justus wrote: By the way: With this changes the heli is not anylonger parallel to ground (while hovering). It is tiltet to the left to compensate the tail rotor force. That sounds wrong to me. The *rotor* should be tilted, but the airframe is experiencing no net force and should be hanging straight down from the shaft. No, because the BO105 - contrary to the 'usual' Bell's for example - has a rigid rotor. Please have a look here: http://www.b-domke.de/AviationImages/Rotorhead.html#Eurocopter Or did I misunderstand your objection ? 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] Latest stupid helicopter trick
Martin Spott wrote: No, because the BO105 - contrary to the 'usual' Bell's for example - has a rigid rotor. Please have a look here: http://www.b-domke.de/AviationImages/Rotorhead.html#Eurocopter Well, that explains my confusion... I guess this just shows my helicopter ignorance. My belief had always been that such a configuration was impossible due to the bending moments along the blade, and that the articulated rotor was a necessary invention to make the idea of a helicopter work. Must have been propaganda. :) But the physics behind that meme is sound: there *are* very high bending moments on a rigid blade. To first approximation you're holding the whole aircraft up by the tips of the blades (the inner parts of the blade produce some lift, but not much; the outer portions are where all the force is felt). What is the rationale behind the decision to make them rigid on the BO105? The only advantage I can see is that you save a few axles and bearings, which are moving parts that can wear out. But you pay for it in extra stress cycles on the blade, so I can't see how this is a win. The articulation joints really aren't very complicated, especially compared with the cyclic control system which you have to have anyway... Andy ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Latest stupid helicopter trick
Hi Andy, Andy Ross wrote: What is the rationale behind the decision to make them rigid on the BO105? The only advantage I can see is that you save a few axles and bearings, which are moving parts that can wear out. But you pay for it in extra stress cycles on the blade, so I can't see how this is a win. The articulation joints really aren't very complicated, especially compared with the cyclic control system which you have to have anyway... Andy It's the flight behavior. This rotor system works in a range from -5 to +5 g (maybe more on the positive side) (i.e. the bell jet ranger rotor works only at positive g ) and has a extremely fast reaction on control input. You can do acrobatics with the bo105 and it is much easier to fly than many other helicopters. Maik ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Latest stupid helicopter trick
Hi David David Megginson wrote: Even as slow as 10 kt, the bo105 barely needs any input from the anti-torque pedals. How realistic is this? It certainly makes flying easy. All the best, David It is very unrealistic. But you can change this very easiely. Just remove the notorque=true tags in the bo105.xml file (or write notorque=false). You should also change the min- and maxcollective of the tail rotor to be unsymmetric (I don't have the original values, I can just guess, maybe -10..+20?) Maik ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Latest stupid helicopter trick
Hello Jim Jim Wilson wrote: One big gap right now is the lack of autorotation. The ground effect needs to be modeled to do that correctly, doesn't it? It's not only the ground effect. The main thing is the power consumption of the rotor, which is up to now very simplified. By the way: I had some time the last days to work on the model. I have changed the calculation of the translational lift and added the ground effect. I have to check this some time and will mail the changes soon. Also the rolling tendency in translational lift is missing. That is a very complicate thing. Allways if I think about I run into confusion. Best, Jim Maik ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Latest stupid helicopter trick
Maik Justus wrote: Also the rolling tendency in translational lift is missing. That is a very complicate thing. Allways if I think about I run into confusion. Is it just a gyroscopic effect? All the best, David ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Latest stupid helicopter trick
Maik Justus wrote: It is very unrealistic. But you can change this very easiely. Just remove the notorque=true tags in the bo105.xml file (or write notorque=false). You should also change the min- and maxcollective of the tail rotor to be unsymmetric (I don't have the original values, I can just guess, maybe -10..+20?) Yes, it is a bit more work flying with those changes. Do you mind if I check them in? All the best, David ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Latest stupid helicopter trick
David Megginson wrote: Maik Justus wrote: Also the rolling tendency in translational lift is missing. That is a very complicate thing. Allways if I think about I run into confusion. Is it just a gyroscopic effect? If I'm not misunderstanding the terminology, this is the rolling moment due to airspeed along the plane of the rotor. One side is moving faster than the other, and produces more force. But like everything with the rotor, it does involve gyro effects. Outside of plain aerodynamic forces, none of the forces or moments on a helicopter act on the rigid body of the airframe. They all cause the rotors to tilt or flap (or even bend, if you really are into modelling this stuff), which *then* causes (and feels) a force/moment on the body. And since the rotor is spinning, it produces all sorts of non-intuitive behavior like the 90° precession phase shift (try to roll it left, it tilts forward, etc...). It's ugly. :) Andy ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Latest stupid helicopter trick
Andy Ross wrote: And since the rotor is spinning, it produces all sorts of non-intuitive behavior like the 90° precession phase shift (try to roll it left, it tilts forward, etc...). It's ugly. :) This one happens with single-engine airplanes as well. If you yank the nose up suddenly, you get a yaw to the left; if you push the nose down suddenly, you get a yaw to the right. I can imagine, though, that the effect is much more dramatic with that big gyro spinning up top. All the best, David ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Latest stupid helicopter trick
David Megginson wrote: This one happens with single-engine airplanes as well. If you yank the nose up suddenly, you get a yaw to the left; if you push the nose down suddenly, you get a yaw to the right. I can imagine, though, that the effect is much more dramatic with that big gyro spinning up top. Right, but there you can model the aircraft as a rigid body with some extra torque applied by a single rotational inertia. You just sum them all together and things work out; this effect works fine in YASim, for example. But with a rotor, you don't have a rigid body to work with as a base. You're constantly playing mind games with the rotational dynamics, because your intuitions about summing forces just don't work. Andy ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Latest stupid helicopter trick
Maik Justus [EMAIL PROTECTED] said: Hello Jim Jim Wilson wrote: One big gap right now is the lack of autorotation. The ground effect needs to be modeled to do that correctly, doesn't it? It's not only the ground effect. The main thing is the power consumption of the rotor, which is up to now very simplified. By the way: I had some time the last days to work on the model. I have changed the calculation of the translational lift and added the ground effect. I have to check this some time and will mail the changes soon. Cool! Let us know when you have patch for thatplease :-) Also the rolling tendency in translational lift is missing. That is a very complicate thing. Allways if I think about I run into confusion. What are the complications? I'm wondering if a simplistic estimation could be found since it'd only really apply to a fast moving helo which would be going forward (not sideways or backwards). Is there a translational wing you could split left and right (asi-rotor/asi+rotor) and apply as a weighted value to the body? Don't know Best, Jim ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Latest stupid helicopter trick
Hi David, David Megginson wrote: Yes, it is a bit more work flying with those changes. Do you mind if I check them in? All the best, David For me it's ok, but remember, that you than need pedals (or another analog controller for this axis) to fly helo. By the way: With this changes the heli is not anylonger parallel to ground (while hovering). It is tiltet to the left to compensate the tail rotor force. Maik ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Latest stupid helicopter trick
Maik Justus wrote: By the way: With this changes the heli is not anylonger parallel to ground (while hovering). It is tiltet to the left to compensate the tail rotor force. That sounds wrong to me. The *rotor* should be tilted, but the airframe is experiencing no net force and should be hanging straight down from the shaft. I might believe, because the side force from the tail acts a little lower than the opposing force from the rotor, that the airframe would experience a small torque away from exactly vertical. But I'd be surprised if this was a large effect -- certainly real helicopters don't appear to be leaning while hovering. :) Maybe I've misunderstood? Andy ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Latest stupid helicopter trick
Maik Justus wrote: Yes, it is a bit more work flying with those changes. Do you mind if I check them in? For me it's ok, but remember, that you than need pedals (or another analog controller for this axis) to fly helo. The mouse does fine as an analog controller for the rudder -- I use it often for the taildraggers, when I don't feel like hooking up a joystick. I just tried flying the bo105 (with torque) using the mouse, and while it was a bit fussier, I could still handle it OK. By the way: With this changes the heli is not anylonger parallel to ground (while hovering). It is tiltet to the left to compensate the tail rotor force. Interesting point -- thanks. All the best, David ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Latest stupid helicopter trick
Hi Andy, Andy Ross schrieb: Maik Justus wrote: By the way: With this changes the heli is not anylonger parallel to ground (while hovering). It is tiltet to the left to compensate the tail rotor force. That sounds wrong to me. The *rotor* should be tilted, but the airframe is experiencing no net force and should be hanging straight down from the shaft. I might believe, because the side force from the tail acts a little lower than the opposing force from the rotor, that the airframe would experience a small torque away from exactly vertical. But I'd be surprised if this was a large effect -- Yes, this effect is larger if the tail rotor is lower mounted (i.e. Jet Ranger). But as far as I know this effect is stil large for a tail rotor above cg. At the bo the tail rotor is nearly at the same height as the rotor centre. But the forces of the (bo 105) rotor act not in the center of the rotor, but at the position of the (virtual) flapping hinges, which are far outside the center. If you sum they, you find, that they produce a much higher moment to the mast which result in a tilted heli. certainly real helicopters don't appear to be leaning while hovering. :) But you never have looked for this phenomena? Look at a calm day to a hoovering helo and you can see it! Maybe I've misunderstood? Andy Maik ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Latest stupid helicopter trick
Hi, I try to explain my confusion: Lets think the heli is in forward flying and the rotor is spinning counter clock wise (seen from top, like the bo 105). Relative to air the rotor blades at the left side are slower and on the right side are faster. So they produce more force at the right side and less on the left side. Because of the gyroscopic effect the result is 90° shifted, so the blade will be up in front and down in back (flapping). The heli will rise the nose if you don't correct the cyclic input. (Up to this point I think I understood it.) m is the mass of one pointlike blade r is the radius to this mass (which vary with flapping and teetering) r0 the radius without flapping and teetering w (omega) the rotational speed of the blade a flapping angle The angular momentum ( m r w) is conservated. If the blade flapps up, r will be changed (r=r0 cos a, if we assume the hinge in the rotor center), so w has to be increased (that is what we know as teetering). If we assume a positive cone angle of the rotor (and this is the normal case) than the rotorblade will be faster in front position than in back position. And will produce more force in front position than in back position. And with thy gyro we have a roll moment, but to the right and not to the left as our helicopter has in real. It is very easy to run into more confusion. Lets think of a rotor system like the Jet Ranger has. The rotor can flap free around the center, so the only force to the mast is the centripetal force. The centripetal force is m r w w. Without teetering this force is m r0 w w cos a. If the rotor is tilted to the front and has a positive cone angle the blade will produce higher centripetal force in front position than in back position. A effective force to the rotormast pointing forward results. The CG is lower than the rotor head, so this result in a forward roll moment. ok. But what is the result of the teetering? If m r w is constant, than w must be w0/(cos a) (remember: r=r0*cos a). And the centripetal force is then m r0 w0 w0/(cos a), which means, that a forward tiltet rotor will produce an effective force pointing backward, which is obviously nonsense. My only idea to solve this: The teetering hinge at every real heli is not in the rotor center. It is out of center. Every teetering angle produces a force to the blade which wants to reduce the teetering angle, so the change of w will be smaller (the missing angular momentum goes to the rotor mast). But if you look in detail into this, you find, that this is a osscillator, which is nearly in resonance. One solution is to think of a big damping constant, but the teeter hinge at model helicopters needs no damping. Maybe the damping can be explained aerodynamically? I don't know. Or is there a big error in this calculations? Confused, Maik Andy Ross wrote: David Megginson wrote: Maik Justus wrote: Also the rolling tendency in translational lift is missing. That is a very complicate thing. Allways if I think about I run into confusion. Is it just a gyroscopic effect? If I'm not misunderstanding the terminology, this is the rolling moment due to airspeed along the plane of the rotor. One side is moving faster than the other, and produces more force. But like everything with the rotor, it does involve gyro effects. Outside of plain aerodynamic forces, none of the forces or moments on a helicopter act on the rigid body of the airframe. They all cause the rotors to tilt or flap (or even bend, if you really are into modelling this stuff), which *then* causes (and feels) a force/moment on the body. And since the rotor is spinning, it produces all sorts of non-intuitive behavior like the 90° precession phase shift (try to roll it left, it tilts forward, etc...). It's ugly. :) Andy ___ 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
[Flightgear-devel] Latest stupid helicopter trick
Here's another fun landing: http://www.megginson.com/flightsim/water-tower.jpg The hard part, for me, is watching the ground close to the helicopter when I'm close to the hover. In real life, when I'm flaring for a landing, I'm usually focussing on the far end of the runway, perhaps a mile or more away; in a helicopter, you seem to have to focus about 2 ft ahead or so. I'm controlling the (simulated) bo105 helicopter much better by picking an airspeed (say, 10 kt when maneuvering for a landing) and holding it as closely as possible with the cyclic. Once the airspeed is steady, I can use the horizon to hold it rather than having to watch the hud. I then use the collective as my up-and-down control (very small movements). Even as slow as 10 kt, the bo105 barely needs any input from the anti-torque pedals. How realistic is this? It certainly makes flying easy. All the best, David ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Latest stupid helicopter trick
David Megginson [EMAIL PROTECTED] said: Here's another fun landing: http://www.megginson.com/flightsim/water-tower.jpg The hard part, for me, is watching the ground close to the helicopter when I'm close to the hover. In real life, when I'm flaring for a landing, I'm usually focussing on the far end of the runway, perhaps a mile or more away; in a helicopter, you seem to have to focus about 2 ft ahead or so. I'm controlling the (simulated) bo105 helicopter much better by picking an airspeed (say, 10 kt when maneuvering for a landing) and holding it as closely as possible with the cyclic. Once the airspeed is steady, I can use the horizon to hold it rather than having to watch the hud. I then use the collective as my up-and-down control (very small movements). Even as slow as 10 kt, the bo105 barely needs any input from the anti-torque pedals. How realistic is this? It certainly makes flying easy. Not very realistic I don't think. It seems like there should be constant input at given collective esp. at low speeds. But as I mentioned earlier the rudder control on my setup is a bit touchy so this probably makes it flyable for me. What I'm wondering is if the anti-torque on a real helo requires constant pressure like a rudder, or if it stays where you put it. The tail seems to do what it should as far as pushing toward the direction opposite of movement and wind direction. The torque on the airframe should be about the same for a given collective setting with the only difference in anti-torque required being this tendency. That might change in translation, but I would think the wind forces would overwhelm any main rotor torque effect once translational lift was achieved anyway. Another effect that might need to be modeled is the tendency for the anti-torque to push the aircraft off course. Best, Jim ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Latest stupid helicopter trick
David Megginson wrote: I'm controlling the (simulated) bo105 helicopter much better by picking an airspeed (say, 10 kt when maneuvering for a landing) and holding it as closely as possible with the cyclic. Out of curiosity, how do pilots do this in real helicopters? I wouldn't think a traditional ASI would work very well at 10 kts... Even as slow as 10 kt, the bo105 barely needs any input from the anti-torque pedals. How realistic is this? It certainly makes flying easy. Here's a candidate solution for that problem (I didn't test it). It's not that the aero force is too high, it's that the moment of inertia of the helicopter is too low. I see the following in the YASim definition: airplane mass=2813 ... ballast x=-3.0 y=-.0 z=1 mass=1820/ So 2/3 of the craft's weight is modeled as a point mass at a location that, one presumes, is right under the rotor. Point masses don't oppose torques very well. :) Really, what's needed here is a shell configuration, where several point masses are placed on the edge of the fuselage where the weight is concentrated. YASim's built-in fuselage and wing declarations models the airframe as strings of point masses. This works OK for long-aspect things like (heh) wings and fuselages. It's not going to produce good results for a spheroidal helicopter fuselage. It wouldn't be too hard to write an ellipsoid declaration for low-aspect fuselages, I guess. But a quick hack would be to split out that ballast point into, say, a square of masses of the right size and centered on the c.g. (the c.g. is really easy to find on a helicopter, BTW: by design, it has to lie very close to axis of the rotor). Andy ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Latest stupid helicopter trick
Andy Ross wrote: Out of curiosity, how do pilots do this in real helicopters? I wouldn't think a traditional ASI would work very well at 10 kts... You could probably build one that did -- after all, the aenemometers that weather stations use can register down to less than 5 kt. Still, I'm guessing that a real helicopter pilot just watches the ground, since that's what matters in the slow-speed regime. Really, what's needed here is a shell configuration, where several point masses are placed on the edge of the fuselage where the weight is concentrated. YASim's built-in fuselage and wing declarations models the airframe as strings of point masses. This works OK for long-aspect things like (heh) wings and fuselages. It's not going to produce good results for a spheroidal helicopter fuselage. It looks like the YASim helicopter is pretty popular, so any work you could contribute would be much appreciated. One big gap right now is the lack of autorotation. All the best, David ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Latest stupid helicopter trick
Out of curiosity, how do pilots do this in real helicopters? I wouldn't think a traditional ASI would work very well at 10 kts... You could probably build one that did -- after all, the aenemometers that weather stations use can register down to less than 5 kt. Still, I'm guessing that a real helicopter pilot just watches the ground, since that's what matters in the slow-speed regime. In real life you don't need to watch the ground any more than you need to watch the road surface to know you're crawling along at 5-10mph in a traffic jam. You're just aware of it through your normal sense of speed. This is something that is sorely lacking in a sim unless something is done to enhance the situational awareness. Lack of high res detail in the ground textures, lack of real 3D perception and lack of motion cues make judgement of speed, height, attitude (and changes in all of these) much more difficult in a sim than real life. Mally --- Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com). Version: 6.0.543 / Virus Database: 337 - Release Date: 22/11/03 ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] Latest stupid helicopter trick
David Megginson [EMAIL PROTECTED] said: Andy Ross wrote: Out of curiosity, how do pilots do this in real helicopters? I wouldn't think a traditional ASI would work very well at 10 kts... You could probably build one that did -- after all, the aenemometers that weather stations use can register down to less than 5 kt. Still, I'm guessing that a real helicopter pilot just watches the ground, since that's what matters in the slow-speed regime. Really, what's needed here is a shell configuration, where several point masses are placed on the edge of the fuselage where the weight is concentrated. YASim's built-in fuselage and wing declarations models the airframe as strings of point masses. This works OK for long-aspect things like (heh) wings and fuselages. It's not going to produce good results for a spheroidal helicopter fuselage. It looks like the YASim helicopter is pretty popular, so any work you could contribute would be much appreciated. One big gap right now is the lack of autorotation. The ground effect needs to be modeled to do that correctly, doesn't it? Also the rolling tendency in translational lift is missing. Best, Jim ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
