A photograph of Boeing Bobby discovered on the WWW

[Evan]

I too cringe that you continue to say “we don’t know how lift is generated”.

Did I say that?

I'm saying two things:

- Many, many people (if not most people) who know a thing or two about aviation, some of whom are pilots, have a false understanding of how lift is generated.
- Hydrodynamics, aerodynamics and thus the nature of lift are observed phenomena, for which the mechanics are empirically observed and theoretically deduced to form a single universally-accepted theory.

On the first point:

This may come as a shock to many readers, because all sorts of standard references claim that the air is somehow required to pass above and below the wing in the same amount of time. I have seen this erroneous statement in elementary-school textbooks, advanced physics textbooks, encyclopedias, and well-regarded pilot training handbooks.

Or...

The lower stream is SLOWED because this board is plowing through it and PUSHING it down (and forward just a tad).
The upper stream is accelerated because a 'vacuum' PULLS it down and back and into the low pressure area that even goes behind the wing.

And...

There is a widely-held misconception that it is the velocity relative to the skin of the wing that produces lift. This causes no end of confusion.

Bernoulli’s principle is very easy to understand provided the principle is correctly stated. However, we must be careful, because seemingly-small changes in the wording can lead to completely wrong conclusions.

On the second point:

Kutta condition- It is a bit of a mystery why the air hates turning a corner at the trailing edge, and doesn’t mind so much turning a sharp corner at the leading edge — but that’s the way it is.

A full discussion of turbulence and/or separated flow is beyond the scope of this book; indeed, trying to really understand and control these phenomena is a topic of current research.

Etc. Yes, aerodynamic predictions are largely accure these days. Yes, I overstated it for effect, and you, of course, recreated it as a black-and-white statement, but, while aerodynamics are very well-understood by aeroengineers, I contend that their mathematical predictions are less reliable than those of other areas of science and engineering because of the phenomena involved. Some of the 'whys' are still open to debate.

And there even seems to be argument here:

Now, air is difficult to see, so let's play with water. Take that spoon and hold it hanging lightly from the tip of the handle, now put the round part under this stream of water from the tap. Slowly. SO what did you see? Correct! The shape of the spoon gets the water is deviated, pushed to one side, and the spoon is pushed to the other side.

You may have heard stories saying that the Coandǎ effect explains how a wing works. Alas, these are just fairy tales. They are worse than useless.

[Evan]

Well, I tried Lift = k * r *V^2 * AoA.

It can't be a technical equation.

I also tried "Wing pushes air down, air reacts pushing wing up".

The problem with this is that it is too simple. Too vague. Therefore, it is wide open to misintepretation.

A better 'simple' version would be: "The wing, interacting with the surrounding airstream, produces a lower pressure above the wing than below it, which causes the wing to lift upward."

But, that is still too simple and open to misinterpretation and erroneous understanding of the 'whys' involved.

But that didn't work.
Then I tried with #23, #33, #62 and others.

#23 was an explanation of wing shape, not lift itself (but very informative on that subject).
#62 was a list of misconceptions.
#33 was very helpful but too detailed and tooooo looong for most non-aeroengineers.

So, continuing to build on:

The wing produces circulation in proportion to its angle of attack (and its airspeed). This circulation means the air above the wing is moving faster. This in turn produces low pressure in accordance with Bernoulli’s principle. The low pressure pulls up on the wing and pulls down on the air in accordance with all of Newton’s laws. This causes the wing to lift upward.

1) Circulation cannot be explained simply, but the reason for it can be included (as a 'convenience').
2) We don't need to name-drop. We can omit Bernoulli and replace him with the general theorum.
3) Same goes for Newton.

So, let's try this:

As the wing begins to move forward, the interaction of the wing and the surrounding air produce an initial air disturbance called a vortex, and this vortex, in turn, produces an opposite 'bound' vortex, or 'circulation', which flows around the entire wing shape, moving from front to back across the top of the wing and back to front along the bottom of the wing. This force of this circulation causes the air travelling above the wing to move faster and the air travelling below the wing to slow down. Since a faster-moving parcel of air has a lower pressure than a slower-moving parcel of air, this creates an area of lower pressure above the wing which pulls up on the wing and pulls down on the air. This, along with some other contributing factors, causes the wing to lift upward. The amount of lift = airspeed × circulation × air density × wingspan.

Now, keep in mind that this is an explanation for a general audience intended to replace the equally brief erroneous explanations that currently pervade everything from the internet to actual piloting manuals. This requires it to be brief and succinct. If anyone wants to know about the Kutta condition and Navier–Stokes equations and viscosity and the Magnus effect and Newton and Bernoulli and all the actual mechanisms and physics involved in detail, they can dive down that rabbit-hole to their heart's content.

Would you disagree with that general explanation?

[3WE]

That didn't work either.
So I stopped trying,

Evanie made one valuable point: That there’s much, varied, and somewhat questionable information out there on how wings work- CONVERSELY - given the predominance of fuel injection we don’t hear much about that carburetor part called the Venturi.

[vaztr]

So, my 2c,

Wings on yachts. In the 'old days' a cloth sail was used, now some boats use a solid 'wing' larger than a A380 wing.

While the Newtonian - action/reaction is true with the wind from behind for a boat, the quickest speed a boat can reach is when the wind is from 45* from the front - some Newtonian and some pressure differential 'lift' that allows the boat to travel FASTER THAN THE WIND TRAVELLING

[LH-B744]

Well, I tried Lift = k * r *V^2 * AoA.
I also tried "Wing pushes air down, air reacts pushing wing up".

But that didn't work.
Then I tried with #23, #33, #62 and others.

That didn't work either.
So I stopped trying,

We should open a contest with 'the shortest forum entry'. The Academy Award for the longest, or for the most forum entries is for you (not quite true..).
For the most forum entries, that seems to be a discipline where still another 'senior' based on DUS has a slight advantage (tennis). Probably I should warn him
('Gabe reaches 7000 within the next 30 minutes. Be aware.') .

D/arn, I tried to avoid Politics as much as I can, but could you imagine a Regime that only communicates via the jetphotos forum? And after all, only failures? 'I took a 747 to Hanoi, and the result will be nothing.'
That's idiocy. If Hanoi were part of the LH winter schedule, there is always a result. We need time, we need fuel, you don't get something like that for nothin.

Probably I should stop here, with the result, ask Holt (or me) if you honestly like to hear something about international diplomacy!

PS: That one was not really for meant you Gabe. Only part of my internal thoughts for the early sunday.. 41.. Does it get better with 42, less sorrows?

[LH-B744]

You can call me a Pseudo-Italian, or not-a-half-Genovese, but there is one thing which we all understand.

The connection with O'Hare airport. The newest thing is, Alitalia only goes ORD seasonal?! And Fiumicino refused money and knowlegde from a source which
definitely better treats the LIMC (Milano Malpensa), LIMJ (Genova) and LIRQ (Firenze) airports,
better than AZ ever tried?!

Lord forgive me, it's Carnival Sunday. Experienced aviation enthusiasts are Boeing enthusiasts, or what would you say, Rick Santelli.

The news, Alitalia only goes ORD seasonal. Ok.. I know that his a/c type does not need any further recommendation but..

Take 'the replacement flight', LH #430 (a/c type B748_), code share with UA, AC, AI, and Thai Airways (TG).

PS: Sorry, but there should be 1 Italian moment each week. And be it 1956 in Chicago. Btw, a little bit too much NBC friendly is better than a little bit too less criticism for the Regime. Holt again is such a brilliant example, first of all the Regime thought that he's a flawless Democrat, because Holt almost destroyed what appeared after Obama, in a first interview.
Criticism for the Regime does not only take place amongst Democrats. I really love Holt (who is an officially listed Republican member) for that interview!

[Gabriel]

Well, I tried Lift = k * r *V^2 * AoA.
I also tried "Wing pushes air down, air reacts pushing wing up".

But that didn't work.
Then I tried with #23, #33, #62 and others.









That didn't work either.
So I stopped trying,

[LH-B744]

The best part is that LHBs post just above reminds me that, on post #1 of this thread, I said, “Don’t over think this”.

Now I know why Gabe is my friend. He's able to write longer forum entries than me. Let's combine his #23 here and his #33 and his #62, together that must be more than I've ever written here on this platform since more than 10 years.

The problem really is time. Let's say that Gabe's entries at least are always 10 or 41 (!) times longer than the average jp forum entry which you or me write. Further let's assume that if I really try to control myself, as in the recent A380 topic, you need 15 seconds to read one of my entries.

That would mean, for an average Gabe entry, we need 41x15 = 615 seconds, or a little bit more than 10 minutes, only to read it, without the answer.

That's the truth, isn't it. I'm too old today to lie!

PS: Another problem is, that Gabe's entries (most of the time) contain good stuff. Not for nothing I call him a flight instructor. So, most of the time, it's even worth the 10 minutes.

[3WE]

Holy left winglet!

The best part is that LHBs post just above reminds me that, on post #1 of this thread, I said, “Don’t over think this”.

[LH-B744]

It's inappropriate to put personal stuff like this up- but his face is obscured, BUT his aircraft is not.- hopefully the mods won't mind.

Is this suitable for uploading to the photo database?

PS- Do not over think this, the intent is light humour.

Click to see full size.
[ATTACH=CONFIG]21966[/ATTACH]

Oh, don't you try to be funny, on his 51st birthday... please.

[ATLcrew]

Holy left winglet!

[Evan]

I don't remember what this part said, how how he got to that conclusion (because the guy doens't just say something like that without a previous explanation).

This was in the context of steady, level flight.

For the airfoil in figure 3.6, under cruise conditions, there is almost no high pressure on the bottom of the wing; indeed there is mostly suction there.5 The only reason the wing can support the weight of the airplane is that there is more suction on the top of the wing. (There is a tiny amount of positive pressure on the rear portion of the bottom surface, but the fact remains that suction above the wing does more than 100% of the job of lifting the airplane.)

Of course it doesn't violate my Newtonian explanation.

I'm not saying it does. I'm saying it seems to. I'm not questioning your grasp of aerodynamics, I'm questioning your (and apparently every other aeroengineer's) grasp of explaining things in a consise, succinct manner (a summary that can be widely understood, especially by pilots and the people who train them) without introducing confusion. This is, itself, an art (if not a science).

Here's where I want to start:

The wing produces circulation in proportion to its angle of attack (and its airspeed). This circulation means the air above the wing is moving faster. This in turn produces low pressure in accordance with Bernoulli’s principle. The low pressure pulls up on the wing and pulls down on the air in accordance with all of Newton’s laws. This causes the wing to lift upward.

Not a bad start.

Now, there are things here that I call "conveniences". Think of them like plot conveniences. You are asked to accept them without understanding them. Annoyingly curious five-year-olds don't do that, and they shouldn't have to (up to a point where things become too technical for them, which is beyond, I think, where we need to go with this).

To begin with, 'The wing produces circulation' is, at this stage, a 'convenience'. It needs further explanation...

So, when I find time, I'm back to reading your link...

[Gabriel]

But a quick scan revealed this:

the fact remains that suction above the wing does more than 100% of the job of lifting the airplane.

I don't remember what this part said, how how he got to that conclusion (because the guy doens't just say something like that without a previous explanation).
But I am always willing to bet that it will be in line to what I explained in #51: You can have reduction of pressure both above and below the wing at the same time, just that it will be even lower above. So the lower side of the wing pushes down and the upper side pushes up harder. Hence, If you integrate the pressure over the upper area, you will get more than the lift=weight because you need to overcome the pull not only the weight but also the pull on the lower side.

Ok, aside from the fact that we cannot exceed "100% of the job of lifting the airplane", this also seems to contradict your Newtonian explanation:

Wing pushes air down, so air pushes wing up, is 100% accurate and accounts for 100% of the lift.

Of course it doesn't violate my Newtonian explanation. I am standing on rollers and y shove a bowling ball back at 10 MPH and, simultaneously, I shove another identical ball forward at 5 MPH. If I make a fore on the balls the balls make a force on me in the opposite direction, that force distributed over the contact area between the balls and my hand are pressures. Because I shoved back stronger than forward, the ball I shoved back will have done on me a greater forward force than the back force made by the one I shoved forward. The end result is that I end up moving forward on the rollers. But the ball I shoved forward made a force back on me, so the ball I shoved back had to make a forward force on me that is more than 100% of the force that is necessary to explain my final state of forward motion.

Is there any wonder I'm confused?

To be honest, no. Not at this point. But I agree that plain text with no voice, no slides, no gesture, no drawings and no real time interaction is hard to follow.

I am confident that if we were face to face with paper and markers on the table, in less than 2 hours you would not be confused anymore. How far away from El Paso are you?

Maybe I won't be after reading through this. But for the third time, this is only about arriving at a clear, concise explanation that can be understood by people without a deep understanding of physics.

I looks to me that, for some reason (and I can be part of the reason), you are making it more complicated than it really is.

[3WE]

Ok, aside from the fact that we cannot exceed "100% of the job of lifting the airplane", this also seems to contradict your Newtonian explanation:



Is there any wonder I'm confused?

We are constantly amazed at your understanding or lack thereof...and your lack of listening.

As Gabe ALREADY stated- top and bottom effects are inseparable- and it’s mostly semantics.

Suction on top actually depends 100% on pressure from below. Technically, there is no such thing as
suction anyway.

Is “the world” confused- sure. But, please don’t ask questions and express confusion about what Gabieeee already explained thoroughly and possibly repeatedly.

If you are saying: “Here’s another fun one”, fine...

[Evan]

This is the best material FOR PILOTS that I have ever found.

https://www.av8n.com/how/

Ok, this looks helpful. I have to find the time to concentrate on it.

But a quick scan revealed this:

the fact remains that suction above the wing does more than 100% of the job of lifting the airplane.

Ok, aside from the fact that we cannot exceed "100% of the job of lifting the airplane", this also seems to contradict your Newtonian explanation:

Wing pushes air down, so air pushes wing up, is 100% accurate and accounts for 100% of the lift.

Is there any wonder I'm confused?

Maybe I won't be after reading through this. But for the third time, this is only about arriving at a clear, concise explanation that can be understood by people without a deep understanding of physics.