[1.3.1] Ferram Aerospace Research: v0.15.9.1 "Liepmann" 4/2/18

[Red Iron Crown]

The F-14 used spoilers for roll control when its wings were swept, too.

Not aware of a plane that uses CoM shifting for control (other than trim), but hang gliders are controlled this way.

[DaMichel]

from xkcd

Here is pic of how it works http://hyperphysics.phy-astr.gsu.edu/hbase/fluids/airfoil.html

And yes, AoA is the angle between the wing center line and the incoming air flow. The lift force increases with increasing AoA. Why? Newtons 3rd law i suppose. Unless the flow is separated, air will "stick" to the wing surface and thus be deflected in some way. The lift force is the reaction force on the plane.

[Gryphon]

Interestingly enough, the image you linked is the first result that Google returns for the terms biplane, inverted, and -stamp (because of that famous, valuable stamp with an inverted biplane). However, here is, I think, a better image because it's from the side, and it shows the ground in reference to the aircraft:

Oracle Biplane Cutting Streamer by j97531, on Flickr

You'll note a little tilt inherent in the photo, but also a noticeable separation from the line of smoke versus how the aircraft is pointed.

I only intend for people to think on these things. Ferram, you needn't concern yourself with charge physics for the sake of the game. It's a bigger overhaul than anyone is willing to take on. But since the game still represents the best, most accurate physics of ANY game (especially thanks to you, sir), it seems only right that we continue down that course. It's a perfect opportunity to do so. Just exploration, here.

I'm pretty sure Ferram knows more about aerodynamics than either you or I. With that said, he's open to being corrected, but he wants solid science to justify doing so. Provide him with

data, theories or models to back it up

and he'll be a happy camper.

[Bakase]

I wouldn't call spoilers and slats control surfaces. Both can be used to control a plane (I know that Messerschmitt designed a plane in the 1920s (or very early '30s) with flaps on the entire wing, and spoilers/slats (forgot which, will be able to check in a couple of days) as ailerons).

And then there are twistable wings (one stick to twist left wing, one to twist right wing - basicly changing the AoI).

So a plane without control surfaces could be build if we only call something a control surface if it is a "classical" control surface.

The most Kerbal solution is ofcourse to shift your CoM to control your plane, but I doubt that that was ever used.

Nonetheless, these all serve to control AoA.

- - - Updated - - -

The up-vector is an up-vector relative to gravity. How would gravity know the plane had flipped? What is the mysterious mediating particle interaction which would tell the Earth (or Kerbol) that the plane had flipped? If the back edge of the wing is somehow producing thrust up relative to the craft, due to AoA or curvature of the wing body, this would be inverted in an inverted flight. It would be thrusting down relative to the craft, which would be up relative to gravity, and planes would not be able to generate lift while flying inverted, by definition.

Uh, yeah, no it's not and I have no idea what gives you that impression. There is no 'up' vector. There is a LIFT VECTOR dependent on AoA (in a symmetric aerofoil). Angle of attack is NOT A FIXED PROPERTY OF THE WING. It's a product of how the aircraft is flown -- the angle between the airstream and the wing surface.

You're the only one in this thread who thinks there's a 'mediating interaction' telling the earth that the plane's flipped.

No, most old planes could NOT adjust their AoA and had no mechanisms at all in their wings to do so. There is nothing magical about it, but there is everything magical about the standard answers here. We need to do better than that. We need real answers, not dodges.

Uh... yes they could. Even the Wright brothers' aircraft had control surfaces for turning the plane and hence adjusting the AoA. A plane that can't adjust AoA CANNOT TURN (and doesn't exist).

But we notice it in flight parameters. Again, old biplanes didn't have adjustable AoAs, but they both flew and flew inverted just fine. That's the problem with the AoA answer, right there. Still no up-vector.

Well, they did. Find me a biplane without control surfaces.

I only intend for people to think on these things. Ferram, you needn't concern yourself with charge physics for the sake of the game. It's a bigger overhaul than anyone is willing to take on. But since the game still represents the best, most accurate physics of ANY game (especially thanks to you, sir), it seems only right that we continue down that course. It's a perfect opportunity to do so. Just exploration, here.

Probably best to start with understanding the physics you're trying to criticise.

[kcs123]

There is no issue. The static anlysis and stability derivs work through the same exact code, and so will move the control surfaces to the same exact AoA. There is no wrong behavior there.

If they use same function and gave different result, perhaps input data for those function call is somehow different ?

Anyway, just checked again to be absoulutly sure that no other mods influence this.

ModularFlightIntegrator

ModuleManager 2.6.5

FAR dev build f7d0a135b9

Same reproducing steps as stated before:

- Create craft with cockpit and some parts that makes hull.

- Put some canrads in front and adjust -100% of AoA authority to them.

- Rotate whole craft, so it pitching by 10-15 degree in SPH.

- Sweep AoA in Static Analysis - canrads rotate in one direction along with airflow.

- Next, calculate Data+Stability derivates - canrads rotate in oposite direction.

Here is some screenshots that describe mentioned:

Javascript is disabled. View full album

Anyway, it is just probably visual glitch in SPH, in flight control surfaces behave as expected. Not a big deal, but I noticed it and reported.

If both, Sweep AoA and stability derivates uses same part of code for this and they give different behaviour it must be something different in input data for that part of code. Maybe that is same reason why we have to recalculate stability derivates few times in a row until we get exectly same derivate "green" numbers ?

[ferram4]

I've always been amazed that aerodynamics somehow brings out the greatest crackpots; I think it has something to do with the number of incompetent teachers that pushed the "equal-time across each side" theory of lift because they were too lazy/stupid to try and explain the way it actually works.

In any case, Jared, since you intend people to think on things, I suggest you do the following:

1. Read up on Thin Airfoil Theory and the derivation of it. That describes the mechanisms of how lift is generated over an airfoil, and thick airfoils work by the same mechanism (though not as simplified).
   
2. Take a look at the literature on airfoils. May I suggest the paper that defined and measured the performance of the NACA 4-digit series of airfoils? You should note the data (particularly lift coefficient, Cl) beginning on page 7 of the report (page 9 of the pdf) that includes changes in the lift of a symmetrical airfoil with AoA and that the lift force switches direction and becomes negative once the AoA becomes negative for those sections. You will also note for cambered sections that the primary change is simply a shift of the Cl curve, and that it still increases with AoA until stall.
   
3. Actually understand the terms that you're using. Lift is perpendicular to the airflow, always. AoA is always measured from a reference orientation on the vehicle to the airflow direction, always. Stop trying to confuse people by using terms wrong.
   

Aerodynamicists have known how airfoils create lift since the 20s. We know what's going on, the only thing to think on is whether a particular model reflects reality better or not. And yell at the teachers for failing at their one job so badly.

@kcs123: There is still no issue, regardless of how much you insist. The deflection angle is the result of the last AoA set point calculated, which will be different for the Stab deriv analysis (which finds a steady point with lift completely cancelling gravity) and the AoA sweep (which will end at the lowest AoA chosen).

Edited June 16, 2015 by ferram4
While lift is life in flight, life coefficient isn't a thing

[Kitspace]

Why is there so much debate about which model of describing lift is better and why?

The aerodynamic science understands wings good enough to design them.

Why is there a problem with it at all and what is the official scientific version then?

[tetryds]

Why is there so much debate about which model of describing lift is better and why?

The aerodynamic science understands wings good enough to design them.

Why is there a problem with it at all and what is the official scientific version then?

There is no problem with anything, just lots of internet misconceptions.

[Ryds]

Hello,

I have a bit of an issue with ailerons and elevators. I've set each one to have the correct input, ailerons with only roll percentage and elevators with only pitch percentage but both sets move when a separate roll or pitch input is given.

E.g when i put the stick to straight left roll the pitch elevators also move (in the opposite direction). It happens with stock control surfaces and procedural. I'm not sure if its a bug or not or whether I need to change something else in the SPH. I've included a pic of the aileron settings - apart from the pitch/roll distinction the inside elevators have the same settings.

Any help gratefully received,

Thanks!

Javascript is disabled. View full album

Edited June 16, 2015 by Ryds
Trying to post image album correctly

[Bakase]

Hello,

I have a bit of an issue with ailerons and elevators. I've set each one to have the correct input, ailerons with only roll percentage and elevators with only pitch percentage but both sets move when a separate roll or pitch input is given.

E.g when i put the stick to straight left roll the pitch elevators also move (in the opposite direction). It happens with stock control surfaces and procedural. I'm not sure if its a bug or not or whether I need to change something else in the SPH. I've included a pic of the aileron settings - apart from the pitch/roll distinction the inside elevators have the same settings.

Any help gratefully received,

Thanks!

I think you forgot your image!

Does this happen using WASD input, or is it just the stick?

[Crzyrndm]

You want the sliders in the middle of the bars for no deflection, all the way to the left is (as indicated) reversed direction (-100% deflection).

EDIT

[Ryds]

Haha! Brilliant, seems obvious now

About to try it out and will report back.

Bakase, I tried to post an embedded imgur album for the first time and had a few difficulties.

[kcs123]

@kcs123: There is still no issue, regardless of how much you insist. The deflection angle is the result of the last AoA set point calculated, which will be different for the Stab deriv analysis (which finds a steady point with lift completely cancelling gravity) and the AoA sweep (which will end at the lowest AoA chosen).

Ah, that explains weird behaviour. I didn't know that AoA sweep ends with lowest chosen angle and that is last visual representation of it on craft in SPH. Good to know about it, missed that info elsewhere.

Sorry that I have bothered you with this, but it was confusing behaviour in SPH that was misinterpreted as bug.

[Ryds]

I'm up!

I've been playing KSP with FAR for a number of years now but only this week have I tried building a plane. I skipped building small little planes and went straight to spaceplanes. It would be an understatement to say that I've had a pretty frustrating few days trying to wrestle this beast into orbit, all because I was putting -100% and not 0% on the control surfaces, jeez!

My sense of achievement meter has just hit "First Landing and Return From The Mun" levels but I think I'll hold off on landing the plane until tomorrow (I've never landing anything on the runway).

Thanks for pointing out the negative deflection percentages Crzyrndm!

[JaredTheDragon]

I've always been amazed that aerodynamics somehow brings out the greatest crackpots; I think it has something to do with the number of incompetent teachers that pushed the "equal-time across each side" theory of lift because they were too lazy/stupid to try and explain the way it actually works.

In any case, Jared, since you intend people to think on things, I suggest you do the following:

1. Read up on Thin Airfoil Theory and the derivation of it. That describes the mechanisms of how lift is generated over an airfoil, and thick airfoils work by the same mechanism (though not as simplified).
   
2. Take a look at the literature on airfoils. May I suggest the paper that defined and measured the performance of the NACA 4-digit series of airfoils? You should note the data (particularly lift coefficient, Cl) beginning on page 7 of the report (page 9 of the pdf) that includes changes in the lift of a symmetrical airfoil with AoA and that the lift force switches direction and becomes negative once the AoA becomes negative for those sections. You will also note for cambered sections that the primary change is simply a shift of the Cl curve, and that it still increases with AoA until stall.
   
3. Actually understand the terms that you're using. Lift is perpendicular to the airflow, always. AoA is always measured from a reference orientation on the vehicle to the airflow direction, always. Stop trying to confuse people by using terms wrong.
   

Aerodynamicists have known how airfoils create lift since the 20s. We know what's going on, the only thing to think on is whether a particular model reflects reality better or not. And yell at the teachers for failing at their one job so badly.

Describing that the wing causes lift is not the same as explaining how the wingcauses lift. You give lift to AoA and camber, which is certainly the standard answer. Regurgitating textbooks is fine, and I agree with you that most instructors likely failed to explain this properly, for the same reasons you've listed above. Often it's given to the control surfaces, but those control the plane after the lift is generated, of course. If control surfaces created the lift, we wouldn't need wings, merely attachment structures, and control surfaces could fly on their own.

If lift is perpendicular to the airflow, we have the same problems with both ascent and descent. I argue that lift is perpendicular to the Earth (or K-body), in opposition to the gravity vector. Why? Because a plane with no AoA, flying straight forward, still feels lift. If AoA were generating the lift in the fluid-dynamics theory you're describing, then we should have no lift with no AoA, correct? Or do you think the control surface harness the lift? I'm asking genuinely here, despite the tone. We have an up-vector which is floating mass, due to a forward vector of course (take-off). Rockets don't feel lift this way; which is why we generate it for them with rockets. I have a great deal of experience with fluid dynamics and use them quite often in Maya, both for physics simulations and for my architectural work.

Notice how in almost all the standard diagrams, we have the airflow lifted before it reaches the wing.

But that's a blatant dodge, because the angle is supposed to cause the lift AFTER the airflow hits the wing. With me? The airflow has no reason to be moving up to hit that wing at all, in the second diagram on the left there especially.

We go to Maya, and I run a quick fluid sim with both a straight wing and an angled-up wing, for some confirmation:

Notice how we have no field-lines pushing up for some magical reason, before the wing? Also, notice how even in Maya those arrows are just field indicators? They're a post-hoc overview of the field lines. A tracing, basically, showing how the fluid is moving. Now notice that none of them are pushing up on the wing, much less the rest of the plane itself. We don't have any up-vectors at all until after the wing. How can those up-vectors push an entire craft upwards, when the craft isn't even there anymore to begin with, due to the forward-vector?

The fluid sims are working just fine, given fluid dynamics as it stands in an atmosphere with gravity and charge. I'm not questioning those models. But they don't answer my question.

I'm looking for the cause of the up-vector here, nothing more. Thank you for clearing up the terms especially in regards to AoA, and I am still studying quite heavily, but was chiefly curious if you or anyone here could explain it. There's really no need to be angry; I certainly am not. I am not a crank, crackpot, or any other ad hom, but a curious physics student trying to fill in holes, either in my understanding or in theories as I find them. Which is why I brought it up here, since most of you folks have a wealth of knowledge on these topics. As I stated, your mod is just fine without filling this hole in the theory, and works beautifully and I thank you very much for all your hard work! I'll read that paper again.

[andymc1]

Great mod. One thing is confusing me though. On re-entry as my pod hits the thicker part of the atmosphere below 30,000m it now continues to speed up, instead of slowing down. How come?

[Crzyrndm]

I'm looking for the cause of the up-vector here, nothing more.

So if the fluid is deflected downwards, what happens to the object that did the deflecting...

[ferram4]

@Jared:Why are you ignoring everyone saying that both AoA and camber contribute to lift? I'm not surprised that you didn't bother to look at the derivation for Thin Airfoil Theory, considering that it would have explained both the contribution of AoA and camber to lift, as well as explained how pressure disturbances can move forward from the trailing edge to create the upward deflection of the air just ahead of the wing. This stuff is documented, explained, and tested very well; you don't get to argue that the theory is wrong (which is what you are doing, don't try to deny it) when it has been verified so much without being a kook. If you are a physics student, you should be well equipped to work through the integrals and calculate the streamlines around an airfoil at an angle of attack, and you will see the upwash at the leading edge created by circulation around the wing; it's a very well documented effect, needs to be considered in the effects on the fuselage in airplane stability, believe it or not.

Seriously, go and look at the theory; thin airfoil theory, potential flow, and the singularity distribution method of generating solutions to linearized potential flow (focused primarily on vortex distributions) will have everything form nice and completely. Your thoughts would be correct, but you're forgetting that this is subsonic flow, where the downstream effects can shape the upstream flow, and that's what happens; the entire flow around the airfoil in subsonic flow is controlled by the flow at the trailing edge.

Now, here's two last questions: if you're right, and AoA and camber are not the cause of lift, what is the mystical aerodynamic-like force that only cares about the plane's orientation wrt the ground, without regard for any fluid dynamics? And why are you so insistent on arguing rather than actually looking at tested theories? This is like going and arguing ballistic trajectories with someone who hasn't started with kinematics.

@andymc1: Known issue, should be fixed in the dev build, hopefully an updated version soon-ish once I get some other things fixed.

[Bakase]

Describing that the wing causes lift is not the same as explaining how the wingcauses lift. You give lift to AoA and camber, which is certainly the standard answer. Regurgitating textbooks is fine, and I agree with you that most instructors likely failed to explain this properly, for the same reasons you've listed above. Often it's given to the control surfaces, but those control the plane after the lift is generated, of course. If control surfaces created the lift, we wouldn't need wings, merely attachment structures, and control surfaces could fly on their own.

Nobody said control surfaces control lift. Control surfaces are for turning the plane.

If lift is perpendicular to the airflow, we have the same problems with both ascent and descent.

What problems? There are no problems here.

I argue that lift is perpendicular to the Earth (or K-body), in opposition to the gravity vector. Why? Because a plane with no AoA, flying straight forward, still feels lift. If AoA were generating the lift in the fluid-dynamics theory you're describing, then we should have no lift with no AoA, correct?

ONLY if we're talking about asymmetric or cambered aerofoils. Plenty of people have covered this. If you turn one of these aerofoils upside down, its lift vector points downwards.

Or do you think the control surface harness the lift? I'm asking genuinely here, despite the tone.

Doesn't make sense.

We have an up-vector which is floating mass, due to a forward vector of course (take-off).

What? Do you know what a vector is?

I have a great deal of experience with fluid dynamics and use them quite often in Maya, both for physics simulations and for my architectural work.

As you have so kindly demonstrated, experience is not equivalent to knowledge -- of which you have none, and I'm inclined to doubt the former too.

Notice how in almost all the standard diagrams, we have the airflow lifted before it reaches the wing.

https://www.grc.nasa.gov/www/K-12/airplane/Images/incline.gif

But that's a blatant dodge, because the angle is supposed to cause the lift AFTER the airflow hits the wing. With me? The airflow has no reason to be moving up to hit that wing at all, in the second diagram on the left there especially.

Yes, it does. That's just the effect of the wing propagating forwards (because the wing is not in a vacuum, effects can propagate in the form of pressure differences).

We go to Maya, and I run a quick fluid sim with both a straight wing and an angled-up wing, for some confirmation:

http://i.imgur.com/4BcSaOa.jpg

http://i.imgur.com/Soj9PNK.jpg

Notice how we have no field-lines pushing up for some magical reason, before the wing? Also, notice how even in Maya those arrows are just field indicators? They're a post-hoc overview of the field lines. A tracing, basically, showing how the fluid is moving. Now notice that none of them are pushing up on the wing, much less the rest of the plane itself. We don't have any up-vectors at all until after the wing. How can those up-vectors push an entire craft upwards, when the craft isn't even there anymore to begin with, due to the forward-vector?

A) I think the simulation doesn't seem terribly good, but I don't really know how to interpret this.

Your simulation won't display any effect on the craft, even if it predicts one there -- which it does. Notice that the net movement of the flow is DOWNWARDS? Ever heard of a little thing called Newton's third law? I do hope you're not a physics student, as anyone who lacks that understanding is surely going to fail.

I'm looking for the cause of the up-vector here, nothing more. Thank you for clearing up the terms especially in regards to AoA, and I am still studying quite heavily, but was chiefly curious if you or anyone here could explain it. There's really no need to be angry; I certainly am not. I am not a crank, crackpot, or any other ad hom, but a curious physics student trying to fill in holes, either in my understanding or in theories as I find them. Which is why I brought it up here, since most of you folks have a wealth of knowledge on these topics. As I stated, your mod is just fine without filling this hole in the theory, and works beautifully and I thank you very much for all your hard work! I'll read that paper again.

There really is no hole in the theory -- or at least not one you have hit upon. If lift always points upwards, do you think planes can fly on their sides? Why do we need wings?

I think you'll forgive me for saying that you do seem like a crank or a crackpot for trying to dispute established principles with no understanding of even the most basic physics.

[JaredTheDragon]

@Jared:Now, here's two last questions: if you're right, and AoA and camber are not the cause of lift, what is the mystical aerodynamic-like force that only cares about the plane's orientation wrt the ground, without regard for any fluid dynamics? And why are you so insistent on arguing rather than actually looking at tested theories? This is like going and arguing ballistic trajectories with someone who hasn't started with kinematics.

I've seen all the tested theories, Ferram. They don't address my question, nor do you. This isn't a pissing match, it's a simple matter of kinematics directly, so there's no need to straw man me when I'm addressing the kinematics and everyone else is dodging them. If it was a simple question, you'd have a simple answer. I've read and studied all manner of fluid dynamics and worked the integrals, and incorporated them in my models, but cannot produce the up-vector. "The theory" is not cohesive; it's fragmented as you've shown. One answer here is AoA, another is Cl there, and on like that. Dropping in some "singularity distribution method of generating solutions to potential flow" isn't physics, it's a dodge. Vortex distributions don't lift hundreds of pounds, much less thousands - those up-vectors are again ad-hoc, and don't push up with any distinctive force. The flow at the trailing edge cannot effect the flow at the leading edge, much less the surface area in between, because all of that surface area is no longer there to be effected due to the forward motion vector of the entire plane. Those events happen AFTER the lift. The air doesn't magically travel over the top of the wing at one speed, then massively accelerate around and underneath to catch back up with the already-accelerating plane (engine thrust) in FRONT of the wing to then push it up. At supersonic speeds, this occurs with some actual impact, but not at takeoff speeds. Takeoff requires the lift to already be occurring.

I'm not attacking you, so just relax. I'm attacking MY model, which is based mathematically on the standard fare. Your mod brought these questions to the forefront for me, so I asked them. Not a drop of offense intended, so please save your rancor for an actual enemy. And again, great work on this mod and the game wouldn't be nearly as accurate without it!

- - - Updated - - -

Bakase, yes, I'll forgive you for your countless logical fallacies because you actually addressed my question, finally.

If lift always points upwards, do you think planes can fly on their sides?

The plane is still being lifted up, as a body, or it would fall. We still have that forward vector, you see, which is tied to the up-vector. Not as much up as it is the more parallel the wings are to the ground, but it cannot be AoA pushing the plane up when the AoA isn't even aligned with the up-vector at all. Th up-vector I'm talking about is relative to the planetary body in this example: planes DO fly sideways, correct? And upside-down. I can illustrate this concept for you if need be, but that should be pretty straightforward.

Again, no need for the rancor. If you folks aren't interested in this discussion, simply say so. Attempting insult and raging on isn't necessary at all. I'm just asking questions, not calling you guys dummies. Ego need not apply.

[woot]

I'm reminded of the climate change denial crowd. How many extremely smart people have spent their whole careers thinking about aerodynamics, building on the knowledge of those that came before? Do you suppose, Jared, that you've discovered some fatal flaw in the science that invalidates all of that? Is it not possible that you simply lack the knowledge to understand how badly you misunderstand the topic? Unless you can thoroughly explain the established theory, you have no basis to disagree with it.

Edit: In other words:

Edited June 17, 2015 by woot

[JaredTheDragon]

I'm reminded of the climate change denial crowd. How many extremely smart people have spent their whole careers thinking about aerodynamics, building on the knowledge of those that came before? Do you suppose, Jared, that you've discovered some fatal flaw in the science that invalidates all of that? Is it not possible that you simply lack the knowledge to understand how badly you misunderstand the topic? Unless you can thoroughly explain the established theory, you have no basis to disagree with it.

Edit: In other words:

http://www.smbc-comics.com/comics/20111228.gif

Heard it all before, Woot. Your ad-hom is as original as your answer, here: no se existe. Attack my arguments, please. I don't see how I could have been more open and friendly about this. If nobody is interested in my question, fine by me. Nobody outside could answer it; I was hoping insiders could.

Again, at no point have I tried to make this a pissing match, so the arguments from authority are even more worthless than they would normally be. We KNOW that planes fly and generate lift and maneuver in certain ways, and at no point have I disputed that. I was born an Air Force brat in Korea and spent most of my life studying the F-16 specifically, especially in Ft. Worth where I got to fly in them, and have no doubts whatsoever that it flies like a dream.

[andymc1]

^ Tomato is a fruit isn't it?

@andymc1: Known issue, should be fixed in the dev build, hopefully an updated version soon-ish once I get some other things fixed.

Right ok. Well that sucks. I've only been playing a couple of days but I can't go back to stock now knowing that the air resistance model sucks but this is unplayable for me cos I play with mortal kerbals and no reverting. I guess I'll just put this game on hold then until this is sorted.

How can I find out when there's an update and what's included?

Thanks.

[blowfish]

The question you have to ask is in which direction does the wing deflect the air flow? The force on the wing will be in the opposite direction.

And downstream conditions can affect upstream conditions in subsonic flow.

[Bakase]

I've seen all the tested theories, Ferram. They don't address my question, nor do you. This isn't a pissing match, it's a simple matter of kinematics directly, so there's no need to straw man me when I'm addressing the kinematics and everyone else is dodging them. If it was a simple question, you'd have a simple answer. I've read and studied all manner of fluid dynamics and worked the integrals, and incorporated them in my models, but cannot produce the up-vector. "The theory" is not cohesive; it's fragmented as you've shown. One answer here is AoA, another is Cl there, and on like that. Dropping in some "singularity distribution method of generating solutions to potential flow" isn't physics, it's a dodge. Vortex distributions don't lift hundreds of pounds, much less thousands - those up-vectors are again ad-hoc, and don't push up with any distinctive force. The flow at the trailing edge cannot effect the flow at the leading edge, much less the surface area in between, because all of that surface area is no longer there to be effected due to the forward motion vector of the entire plane. Those events happen AFTER the lift. The air doesn't magically travel over the top of the wing at one speed, then massively accelerate around and underneath to catch back up with the already-accelerating plane (engine thrust) in FRONT of the wing to then push it up. At supersonic speeds, this occurs with some actual impact, but not at takeoff speeds. Takeoff requires the lift to already be occurring.

I'm not attacking you, so just relax. I'm attacking MY model, which is based mathematically on the standard fare. Your mod brought these questions to the forefront for me, so I asked them. Not a drop of offense intended, so please save your rancor for an actual enemy. And again, great work on this mod and the game wouldn't be nearly as accurate without it!

- - - Updated - - -

Bakase, yes, I'll forgive you for your countless logical fallacies because you actually addressed my question, finally.

The plane is still being lifted up, as a body, or it would fall. We still have that forward vector, you see, which is tied to the up-vector. Not as much up as it is the more parallel the wings are to the ground, but it cannot be AoA pushing the plane up when the AoA isn't even aligned with the up-vector at all. Th up-vector I'm talking about is relative to the planetary body in this example: planes DO fly sideways, correct? And upside-down. I can illustrate this concept for you if need be, but that should be pretty straightforward.

Again, no need for the rancor. If you folks aren't interested in this discussion, simply say so. Attempting insult and raging on isn't necessary at all. I'm just asking questions, not calling you guys dummies. Ego need not apply.

If you genuinely had a point, I'm sure I'd love to listen to you. Do point out my logical fallacies, of course.

Planes don't fly sideways. They do fall.

You keep confusing people's arguments based on symmetric and cambered aerofoils.

For the sake of establishing basic principles, keep to a symmetric aerofoil argument. A symmetric aerofoil operates the same both upside down and normally. This is the wing structure used on planes that do fly upside down, such as the one you posted a picture of. And let's skip all the complicated fluid dynamics, which will just confuse things for someone who doesn't understand physics, or the mathematics behind it. Don't try to pretend you've worked any of that through! Every point you made in the paragraph you replied to Ferram shows you haven't. Don't lie. It doesn't help your case as someone who wants to understand the physics.

We're able to skip out the fluid dynamics (well, the calculations) because there's only one effect we're interested in, and we don't need a quantitative description. If you want that, you're going to need more of an education than I can give you.

At zero angle of attack, our symmetric aerofoil generates no lift. We'll assume the plane is travelling forwards at a constant speed, for now. As you tilt your plane upwards (using control surfaces), your angle of attack changes -- the wing surface is now pitched upwards. Airflow travelling under the wing is deflected downwards. According to newton's third law, if the plane is exerting a downwards force on the airflow, an equal and opposite upwards force is exerted on the plane. This is what we call lift.

Happy?

If you're going to argue and say that a plane with a symmetric aerofoil can fly upside down with no AoA, you'd damn well better provide a source.