Re: [Flightgear-devel] Clarification on YASIM input (actionpt)
On Saturday, June 18, 2011 08:00:41 PM Jon S. Berndt wrote: From: syd adams [mailto:adams@gmail.com] Does jsbsim ? I've just begun to look into it , so I don't really know jsbsim's capabilities. It's not automatic - not a natural effect calculated by JSBSim code itself. Like many things in JSBSim, the facilities are present to let the aircraft flight model developer add these kinds of things. The contributions from the tail, (such as moment due to elevator, lift due to elevator) are functions of alpha and qbar. Both alpha and qbar are affected by propwash, since propwash speeds up the airflow immediately behind it if it is producing thrust. When defining lift or moment contributions from the elevator, the alpha and qbar that are parts of that definition can be modified by a function that includes the effects of propwash. So, it's very configurable. You could even include the effects of beta (sideslip) so the effects are blended out if beta is too high. Here's an example from Hal's P-51D Mustang. This is from an old version, so it may have changed by now, but it illustrates the approach. In the aerodynamics section of the config file - but outside of any axis element - is this definition of qbar due to propwash: [Note: v is shorthand for value, and p is shorthand for property.] function name=aero/thrust-qbar_psf product v 0.5 /v p atmosphere/rho-slugs_ft3 /p pow sum p velocities/u-aero-fps /p product p propulsion/engine/prop-induced-velocity_fps /p v 2.0 /v /product /sum v 2.0 /v /pow /product /function Later, within the pitch axis definition, is this definition: function name=aero/coefficient/Cmde descriptionPitch_moment_due_to_elevator/description product propertyaero/thrust-qbar_psf/property propertymetrics/Sw-sqft/property propertymetrics/cbarw-ft/property propertyfcs/elevator-pos-rad/property table independentVarvelocities/mach/independentVar tableData 0.-0.8 2.-0.200 /tableData /table /product /function These were never in any of the code I worked with and were removed before I started working on the FDM. My current Cmde function looks like this: function name=aero/coefficient/Cmde descriptionPitch_moment_due_to_elevator/description product propertyaero/qbar-psf/property propertymetrics/Sw-sqft/property propertymetrics/cbarw-ft/property propertyfcs/elevator-pos-rad/property table independentVarvelocities/mach/independentVar tableData 0. -0.9 0.66 -0.6 0.74 -0.4 1. -0.05 /tableData /table /product /function This is using the qbar-psf which is not influenced by prop wash. The Cmde function Jon has above has a lookup table that goes from MACH 0 to MACH 2 in a linear fashion. This looks like something intended for a supersonic aircraft and is not what I would expect from a subsonic aircraft. The table I am using goes from MACH 0 to MACH 1 and has a strong inflection at MACH 0.74 which is unlike the one in Jons function since it is non-linear. There are other interesting things in the look up table. MACH 0.66 is were MACH drag becomes a factor for the P-51 series and MACH 0.74 is the speed at which compressibility effects start to set in. I have not changed this function and this is what I grabbed from the JSBSim code repository when I started working on the P-51D. So someone, perhaps Jon, worked on this at some point. It looks to me like this is basically correct for the P-51 since the MACH values used are right from the NACA reports. The above should cause a very mild tuck at speeds above MACH 0.66 and the tuck should get much stronger above MACH 0.74. This is sort of what happens to the real thing at these speeds but it also porpoises above MACH 0.74. I have a seperate compressibility function that adds more tuck and also causes the porpoise affect above MACH 0.74 by changing the pitch moment in a sinusoidal fashion with the frequency and strength increasing at higher MACH numbers. All of this is writen in pure JSBSim functions with no need for Nasal. The airframe will break up at about MACH 0.8 since the G forces from the porpoising will cause too much negitive G. I also agree with Jon that JSBsim is VERY powerful and if you understand how some force should act on the airframe you are modeling you should be able to write a function or a set of functions that will provide those forces for your model. But it can take a lot of effort to put these things together. One thing that we need is for modelers to start building up example JSBSim code for things that
Re: [Flightgear-devel] Clarification on YASIM input (actionpt)
2011/6/19 Hal V. Engel hven...@gmail.com: On Saturday, June 18, 2011 08:00:41 PM Jon S. Berndt wrote: From: syd adams [mailto:adams@gmail.com] Does jsbsim ? I've just begun to look into it , so I don't really know jsbsim's capabilities. It's not automatic - not a natural effect calculated by JSBSim code itself. Like many things in JSBSim, the facilities are present to let the aircraft flight model developer add these kinds of things. The contributions from the tail, (such as moment due to elevator, lift due to elevator) are functions of alpha and qbar. Both alpha and qbar are affected by propwash, since propwash speeds up the airflow immediately behind it if it is producing thrust. When defining lift or moment contributions from the elevator, the alpha and qbar that are parts of that definition can be modified by a function that includes the effects of propwash. So, it's very configurable. You could even include the effects of beta (sideslip) so the effects are blended out if beta is too high. Here's an example from Hal's P-51D Mustang. This is from an old version, so it may have changed by now, but it illustrates the approach. In the aerodynamics section of the config file - but outside of any axis element - is this definition of qbar due to propwash: [Note: v is shorthand for value, and p is shorthand for property.] function name=aero/thrust-qbar_psf product v 0.5 /v p atmosphere/rho-slugs_ft3 /p pow sum p velocities/u-aero-fps /p product p propulsion/engine/prop-induced-velocity_fps /p v 2.0 /v /product /sum v 2.0 /v /pow /product /function Later, within the pitch axis definition, is this definition: function name=aero/coefficient/Cmde descriptionPitch_moment_due_to_elevator/description product propertyaero/thrust-qbar_psf/property propertymetrics/Sw-sqft/property propertymetrics/cbarw-ft/property propertyfcs/elevator-pos-rad/property table independentVarvelocities/mach/independentVar tableData 0. -0.8 2. -0.200 /tableData /table /product /function These were never in any of the code I worked with and were removed before I started working on the FDM. My current Cmde function looks like this: function name=aero/coefficient/Cmde descriptionPitch_moment_due_to_elevator/description product propertyaero/qbar-psf/property propertymetrics/Sw-sqft/property propertymetrics/cbarw-ft/property propertyfcs/elevator-pos-rad/property table independentVarvelocities/mach/independentVar tableData 0. -0.9 0.66 -0.6 0.74 -0.4 1. -0.05 /tableData /table /product /function This is using the qbar-psf which is not influenced by prop wash. The Cmde function Jon has above has a lookup table that goes from MACH 0 to MACH 2 in a linear fashion. This looks like something intended for a supersonic aircraft and is not what I would expect from a subsonic aircraft. The table I am using goes from MACH 0 to MACH 1 and has a strong inflection at MACH 0.74 which is unlike the one in Jons function since it is non-linear. There are other interesting things in the look up table. MACH 0.66 is were MACH drag becomes a factor for the P-51 series and MACH 0.74 is the speed at which compressibility effects start to set in. I have not changed this function and this is what I grabbed from the JSBSim code repository when I started working on the P-51D. So someone, perhaps Jon, worked on this at some point. It looks to me like this is basically correct for the P-51 since the MACH values used are right from the NACA reports. The above should cause a very mild tuck at speeds above MACH 0.66 and the tuck should get much stronger above MACH 0.74. This is sort of what happens to the real thing at these speeds but it also porpoises above MACH 0.74. I have a seperate compressibility function that adds more tuck and also causes the porpoise affect above MACH 0.74 by changing the pitch moment in a sinusoidal fashion with the frequency and strength increasing at higher MACH numbers. All of this is writen in pure JSBSim functions with no need for Nasal. The airframe will break up at about MACH 0.8 since the G forces from the porpoising will cause too much negitive G. I also agree with Jon that JSBsim is VERY powerful and if you understand how some force should act on the airframe you are modeling you should be able to write a function or a set of functions that will provide those forces for your model. But it can take a lot of effort to put these things together. One thing that we need is for modelers to start building up example JSBSim code for things that are not part of the default Aeromatic generated FDM so that others can leverage that work and apply it to their modeling efforts. Jon thanks for the above code. I will look into integrating this into the current P-51D. Also shouldn't the same sort of thing happen with the rudder? And
Re: [Flightgear-devel] Clarification on YASIM input (actionpt)
2011/6/17 Emilian Huminiuc emili...@gmail.com: On Friday 17 June 2011 08:15:36 xsaint wrote: Thank you Emilian and Buck Ok i tested changing the location of the point to ahead of the engine and also behind the engine, near exhaust. Irrespective of the location, looking at the results at the Yasim solver, i do not see much impact. Surprisingly i do not see any change to Drag Coef or lift ratio. The only slight change seems to occur rightfully at Tail incidence and approach elevator... Is this how it is ment to be? Cheers You'll most likely see the differences in flight, in asymetric configurations. This is incorrect. The parameter 'actionpt' is involved in the evaluation of the moment generated by the thrust. Therefore it is not surprising that it does not impact the drag and lift calculations since they result from the forces equilibrium. Changing the thrust lever arm with respect to the CG will result in a different moment around y if your airplane is symmetric with respect to the x-z plane which is very likely. The moment around y is mainly resisted by the tail even in steady flight hence the slight changes in tail incidence and approach elevator that xsaint mentions. Bertrand. -- EditLive Enterprise is the world's most technically advanced content authoring tool. Experience the power of Track Changes, Inline Image Editing and ensure content is compliant with Accessibility Checking. http://p.sf.net/sfu/ephox-dev2dev ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] Clarification on YASIM input (actionpt)
2011/6/17 Gary Neely grne...@gmail.com: On Fri, Jun 17, 2011 at 12:17 AM, xsaint xsa...@gmail.com wrote: Hello Folks... Was wondering if any nice souls will assist clear this doubt on mine... In YASIM, what does actionpt really refers to? Is it the point the engines pull the air through? which the point will be ahead of the engines or is it the point at back the end of the engine where the exhaust takes place? OR Do we have different application for actionpt based on the aircraft we are modeling. For example, if it is a passenger jet, the actionpt is ahead of the engines and if it is a military jet, then the actionpt is behind the nozzle? Thank you all for the clarifications cheers I've always understood actionpt to be the location where thrust should be applied with respect to the airframe. For a propeller-driven engine, I use the approximate location of the main thrust bearing. For a jet, I reckon it depends on the type of jet and the degree of bypass. An older jet engine develops its thrust from the exhaust chamber region. Modern engines with high bypass ratios develop more of their thrust from the fan, so the action point would likely move forward closer to where the main thrust bearings of the fan are located within the engine. I'm not an engine expert by any means, but these are the assumptions I've used. Moving the point of action of a force along the line of action of the aforementioned force does not change the moment. Since the thrust line of action is almost parallel to the turbine/propeller/fan shaft, moving the point of action from the fan bearing to the exhaust region will only marginally change the resulting moment. So my advice FWIW is to not bother about that. Bertrand. -- EditLive Enterprise is the world's most technically advanced content authoring tool. Experience the power of Track Changes, Inline Image Editing and ensure content is compliant with Accessibility Checking. http://p.sf.net/sfu/ephox-dev2dev ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] Clarification on YASIM input (actionpt)
My more simple understanding was the actionpoint was the point where thrust was applied relative to the engine mass , like the documentation states. an actionpt subelement to place the action point of the thrust at a different position than the mass of the engine. Works for me. Cheers -- EditLive Enterprise is the world's most technically advanced content authoring tool. Experience the power of Track Changes, Inline Image Editing and ensure content is compliant with Accessibility Checking. http://p.sf.net/sfu/ephox-dev2dev ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] Clarification on YASIM input (actionpt)
2011/6/18 syd adams adams@gmail.com:
My more simple understanding was the actionpoint was the point where
thrust was applied relative to the engine mass , like the
documentation states.
an actionpt subelement
to place the action point of the thrust at a different
position than the mass of the engine.
Sorry but your interpretation is incorrect. I have extracted below the
relevant code that shows that actionpt should be taken relative to the
aircraft global origin not relative to the engine position (it
actually overwrites the default position which is set at the engine
position).
src/FDM/YASim/FGFDM.cpp
413: } else if(eq(name, actionpt)) {
414: v[0] = attrf(a, x);
415: v[1] = attrf(a, y);
416: v[2] = attrf(a, z);
417: ((Thruster*)_currObj)-setPosition(v);
src/FDM/YASim/Thruster.cpp
20: void Thruster::getPosition(float* out)
21: {
22: int i;
23: for(i=0; i3; i++) out[i] = _pos[i];
24: }
25:
26: void Thruster::setPosition(float* pos)
27: {
28: int i;
29: for(i=0; i3; i++) _pos[i] = pos[i];
30: }
src/FDM/YASim/Model.cpp
382: for(i=0; i_thrusters.size(); i++) {
383: Thruster* t = (Thruster*)_thrusters.get(i);
384: float thrust[3], pos[3];
385: t-getThrust(thrust);
386: t-getPosition(pos);
387: _body.addForce(pos, thrust);
388: }
src/FDM/YASim/RigidBody.cpp
139: void RigidBody::addForce(float* pos, float* force)
140: {
141: addForce(force);
142:
143: // For a force F at position X, the torque about the c.g C is:
144: // torque = F cross (C - X)
145: float v[3], t[3];
146: Math::sub3(_cg, pos, v);
147: Math::cross3(force, v, t);
148: addTorque(t);
149: }
Bertrand.
--
EditLive Enterprise is the world's most technically advanced content
authoring tool. Experience the power of Track Changes, Inline Image
Editing and ensure content is compliant with Accessibility Checking.
http://p.sf.net/sfu/ephox-dev2dev
___
Flightgear-devel mailing list
Flightgear-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] Clarification on YASIM input (actionpt)
On Sat, Jun 18, 2011 at 10:38 AM, Bertrand Coconnier bcoco...@gmail.com wrote: 2011/6/17 Gary Neely grne...@gmail.com: I've always understood actionpt to be the location where thrust should be applied with respect to the airframe. For a propeller-driven engine, I use the approximate location of the main thrust bearing. For a jet, I reckon it depends on the type of jet and the degree of bypass. An older jet engine develops its thrust from the exhaust chamber region. Modern engines with high bypass ratios develop more of their thrust from the fan, so the action point would likely move forward closer to where the main thrust bearings of the fan are located within the engine. I'm not an engine expert by any means, but these are the assumptions I've used. Moving the point of action of a force along the line of action of the aforementioned force does not change the moment. Since the thrust line of action is almost parallel to the turbine/propeller/fan shaft, moving the point of action from the fan bearing to the exhaust region will only marginally change the resulting moment. So my advice FWIW is to not bother about that. Bertrand. I agree, with reservations. Some engines, for instance some turboprops, have thrust bearings significantly offset from the engine/prop mass. Perhaps that's trivial in most cases, but in my opinion if the designer has good information on where an actionpt would reside, it makes sense to use that information. Working toward fidelity is part of the fun of this stuff. -Gary -- EditLive Enterprise is the world's most technically advanced content authoring tool. Experience the power of Track Changes, Inline Image Editing and ensure content is compliant with Accessibility Checking. http://p.sf.net/sfu/ephox-dev2dev ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] Clarification on YASIM input (actionpt)
On the other hand, YASim does not take into the wing downwash or the propwash while computing the tail incidence (while they are first order contributors) so I would not use the word 'fidelity'. Does jsbsim ? I've just begun to look into it , so I don't really know jsbsim's capabilities. Cheers -- EditLive Enterprise is the world's most technically advanced content authoring tool. Experience the power of Track Changes, Inline Image Editing and ensure content is compliant with Accessibility Checking. http://p.sf.net/sfu/ephox-dev2dev ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] Clarification on YASIM input (actionpt)
From: syd adams [mailto:adams@gmail.com] Does jsbsim ? I've just begun to look into it , so I don't really know jsbsim's capabilities. It's not automatic - not a natural effect calculated by JSBSim code itself. Like many things in JSBSim, the facilities are present to let the aircraft flight model developer add these kinds of things. The contributions from the tail, (such as moment due to elevator, lift due to elevator) are functions of alpha and qbar. Both alpha and qbar are affected by propwash, since propwash speeds up the airflow immediately behind it if it is producing thrust. When defining lift or moment contributions from the elevator, the alpha and qbar that are parts of that definition can be modified by a function that includes the effects of propwash. So, it's very configurable. You could even include the effects of beta (sideslip) so the effects are blended out if beta is too high. Here's an example from Hal's P-51D Mustang. This is from an old version, so it may have changed by now, but it illustrates the approach. In the aerodynamics section of the config file - but outside of any axis element - is this definition of qbar due to propwash: [Note: v is shorthand for value, and p is shorthand for property.] function name=aero/thrust-qbar_psf product v 0.5 /v p atmosphere/rho-slugs_ft3 /p pow sum p velocities/u-aero-fps /p product p propulsion/engine/prop-induced-velocity_fps /p v 2.0 /v /product /sum v 2.0 /v /pow /product /function Later, within the pitch axis definition, is this definition: function name=aero/coefficient/Cmde descriptionPitch_moment_due_to_elevator/description product propertyaero/thrust-qbar_psf/property propertymetrics/Sw-sqft/property propertymetrics/cbarw-ft/property propertyfcs/elevator-pos-rad/property table independentVarvelocities/mach/independentVar tableData 0.-0.8 2.-0.200 /tableData /table /product /function [Note that while this function definition is named aero/coefficient/Cmde it is not really a coefficient, but an actual moment in units of foot pounds. The coefficient part of the name is a holdout from years past.] In the second code snippet you can see the aero/thrust-qbar_psf property used. I hope this helps a bit. Jon attachment: winmail.dat-- EditLive Enterprise is the world's most technically advanced content authoring tool. Experience the power of Track Changes, Inline Image Editing and ensure content is compliant with Accessibility Checking. http://p.sf.net/sfu/ephox-dev2dev___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] Clarification on YASIM input (actionpt)
On Fri, 17 Jun 2011 07:51:41 +0300, Emilian wrote in message 201106170751.41691.emili...@gmail.com: For a prop, it should be the blade/hub linkage, and thus commonly found ahead of the engine center of mass. ..it moves towards the down-going prop blade as aircraft AOA gets higher and higher. -- ..med vennlig hilsen = with Kind Regards from Arnt Karlsen ...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. -- EditLive Enterprise is the world's most technically advanced content authoring tool. Experience the power of Track Changes, Inline Image Editing and ensure content is compliant with Accessibility Checking. http://p.sf.net/sfu/ephox-dev2dev ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] Clarification on YASIM input (actionpt)
On Fri, Jun 17, 2011 at 12:17 AM, xsaint xsa...@gmail.com wrote: Hello Folks... Was wondering if any nice souls will assist clear this doubt on mine... In YASIM, what does actionpt really refers to? Is it the point the engines pull the air through? which the point will be ahead of the engines or is it the point at back the end of the engine where the exhaust takes place? OR Do we have different application for actionpt based on the aircraft we are modeling. For example, if it is a passenger jet, the actionpt is ahead of the engines and if it is a military jet, then the actionpt is behind the nozzle? Thank you all for the clarifications cheers I've always understood actionpt to be the location where thrust should be applied with respect to the airframe. For a propeller-driven engine, I use the approximate location of the main thrust bearing. For a jet, I reckon it depends on the type of jet and the degree of bypass. An older jet engine develops its thrust from the exhaust chamber region. Modern engines with high bypass ratios develop more of their thrust from the fan, so the action point would likely move forward closer to where the main thrust bearings of the fan are located within the engine. I'm not an engine expert by any means, but these are the assumptions I've used. -Gary aka Buckaroo -- EditLive Enterprise is the world's most technically advanced content authoring tool. Experience the power of Track Changes, Inline Image Editing and ensure content is compliant with Accessibility Checking. http://p.sf.net/sfu/ephox-dev2dev ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] Clarification on YASIM input (actionpt)
On Friday 17 June 2011 07:17:45 xsaint wrote: Hello Folks... Was wondering if any nice souls will assist clear this doubt on mine... In YASIM, what does actionpt really refers to? Is it the point the engines pull the air through? which the point will be ahead of the engines or is it the point at back the end of the engine where the exhaust takes place? OR Do we have different application for actionpt based on the aircraft we are modeling. For example, if it is a passenger jet, the actionpt is ahead of the engines and if it is a military jet, then the actionpt is behind the nozzle? Thank you all for the clarifications cheers It should be the point of force application, which for a jet engine is the exhaust nozzle end, commonly found aft of the engine center of mass. For a prop, it should be the blade/hub linkage, and thus commonly found ahead of the engine center of mass. HTH Emilian -- EditLive Enterprise is the world's most technically advanced content authoring tool. Experience the power of Track Changes, Inline Image Editing and ensure content is compliant with Accessibility Checking. http://p.sf.net/sfu/ephox-dev2dev ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] Clarification on YASIM input (actionpt)
Thank you Emilian and Buck Ok i tested changing the location of the point to ahead of the engine and also behind the engine, near exhaust. Irrespective of the location, looking at the results at the Yasim solver, i do not see much impact. Surprisingly i do not see any change to Drag Coef or lift ratio. The only slight change seems to occur rightfully at Tail incidence and approach elevator... Is this how it is ment to be? Cheers On Friday 17,June,2011 12:51 PM, Emilian Huminiuc wrote: On Friday 17 June 2011 07:17:45 xsaint wrote: Hello Folks... Was wondering if any nice souls will assist clear this doubt on mine... In YASIM, what does actionpt really refers to? Is it the point the engines pull the air through? which the point will be ahead of the engines or is it the point at back the end of the engine where the exhaust takes place? OR Do we have different application for actionpt based on the aircraft we are modeling. For example, if it is a passenger jet, the actionpt is ahead of the engines and if it is a military jet, then the actionpt is behind the nozzle? Thank you all for the clarifications cheers It should be the point of force application, which for a jet engine is the exhaust nozzle end, commonly found aft of the engine center of mass. For a prop, it should be the blade/hub linkage, and thus commonly found ahead of the engine center of mass. HTH Emilian -- EditLive Enterprise is the world's most technically advanced content authoring tool. Experience the power of Track Changes, Inline Image Editing and ensure content is compliant with Accessibility Checking. http://p.sf.net/sfu/ephox-dev2dev ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel -- EditLive Enterprise is the world's most technically advanced content authoring tool. Experience the power of Track Changes, Inline Image Editing and ensure content is compliant with Accessibility Checking. http://p.sf.net/sfu/ephox-dev2dev ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
Re: [Flightgear-devel] Clarification on YASIM input (actionpt)
On Friday 17 June 2011 08:15:36 xsaint wrote: Thank you Emilian and Buck Ok i tested changing the location of the point to ahead of the engine and also behind the engine, near exhaust. Irrespective of the location, looking at the results at the Yasim solver, i do not see much impact. Surprisingly i do not see any change to Drag Coef or lift ratio. The only slight change seems to occur rightfully at Tail incidence and approach elevator... Is this how it is ment to be? Cheers You'll most likely see the differences in flight, in asymetric configurations. AFAIK the solver uses just the thrust value, and of course the engine weight for COG determination. -- EditLive Enterprise is the world's most technically advanced content authoring tool. Experience the power of Track Changes, Inline Image Editing and ensure content is compliant with Accessibility Checking. http://p.sf.net/sfu/ephox-dev2dev ___ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
