No One Can Explain Why Planes Stay in the Air

I was always skeptical of the answers I was given in school. Some of them just made no sense. Turns out they were bluffing. They did not know how planes generate lift.

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Interesting quote from that article:

After all, the natural processes of evolution, working mindlessly, at random and without any understanding of physics, solved the mechanical problem of aerodynamic lift for soaring birds eons ago. Why should it be so hard for scientists to explain what keeps birds, and airliners, up in the air?
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I can’t be the only one coming away from that article thinking that the explanations of lift provided in the article are 99% satisfactory, and are exactly how I’ve just intuitively thought about lift my entire adult life?

Sounds like there are a few minutiae to work out but otherwise it’s pretty much all sorted out? It’s implied that some of these solutions are being introduced by McLean, Drela, etc, extremely recently, or is this a case where these explanations have existed for a long time but only recently have we been able to really experimentally test and confirm them (and/or describe them mathematically)? It’s just inconceivable to me that most of this isn’t immediately obvious to anyone looking at an airfoil in a wind tunnel.

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In my schooling, there was high emphasis on Bernoulli’s principle, which is really obviously incomplete, if not downright wrong. As the article states, moreover, the “equal transit time” dictum is just nonsense, and that is how Bernoulli’s principle was justified.

Intuitively, I thought angle of attack was important, but my teachers just told me I was wrong. Of course, angle of attack isn’t the whole story either, but it wasn’t wrong.

Frankly, reading that article, there is a serious problem in how this question is covered in science textbooks and classes, unless there has been a major reform since I was in school. Wow.

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I’m a huge F1 fan, so I’ve delved a bit into the aerodynamics of race cars. I think F1 cars can provide a great platform for understanding lift, or downward lift in the case of race cars. What is a boundary layer, and why is attached air flow important? What does it mean when a rear or front wing stalls? Why does turbulence increase drag, and what is laminar flow? How do vortexes increase aerodynamic efficiency? How does a rear diffuser work? All of these questions in F1 car design have direct application to the reason why wings on an airplane produce lift.

The Bible discusses birds. It even discusses the Creation of Flying Birds. But nobody expects that the Bible is going to explain how Birds fly.

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I think back to being a kid with my hand out the car when window, doing the slow sine wave. You can feel lift and resistance change with the position of your hand. Not that this solves anything, but I always thought about when imaging how birds must feel when flying.

Or anyone who’s tried to stick their flat hand out of a car while driving on the highway. Move forward at high velocity, make a flat hand and stick it into the wind, feel lift raise your arm at correct angles.

Air pushes on surface of object, object responds in an intuitively predictable way. C’mon.

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Even beyond that though, just looking at the way the air flows over something like an airfoil it seems obvious to me that a weak vacuum/area of low pressure is created in the “shadow” of the leading edge, and this obviously has the effect of “sucking in” the air flowing over the top of the airfoil, accounting for both the increased speed and and the flow of air tangential to the surface even as it curves.

Of course it is the higher pressure on the bottom of the wing and the lower pressure on the top that gives lift. We do notice that aircraft do not fly in space where there is no air. Could it be that’s why we call them air craft? Notice that aircraft propellers and helicopter blades are also airfoils.

The article just shows the lack of a fluid dynamics model that exactly describes what causes every little parcel of the different pressures.

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When I used to watch NASCAR many years back, I remember the cars got so fast they were actually starting to lift off the track. They had to introduce a restrictor plate to limit the air intake in the engine and slow the cars down.

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I don’t think we did aerodynamics in school physics, but I do remember having an old aeromodelling magazine that said an aerofoil wing narrower than 3 inches is probably less effective than a flat surface.

I also remember finding out that a few of the other things I learned in physics were wrong because they were oversimplified, and I wondered why they were taught that way.

I concluded that I’d have learned more about science and the world by being told that something was either complex or controverted. I’d have been spurred on by knowing that there were apparently simple problems left to solve, and humbled by realising that science is a quest to pursue, not a set of truths to absorb.

But tell the kids it’s all cut and dried, and science looks more like a priesthood than a bunch of explorers. Good for image, but good for knowledge? I’m not so sure.

That’s especially true when we’ve been building planes for 120 years, and gliders for longer, and any kid can build a model one in his bedroom - and yet we’re still not sure how they work. That surely is better for the sense of wonder and inquiry than “it’s easy - just reproduce this diagram in the exam and you’ll get an ‘A’.”

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@jongarvey

I think it is credible to say that aerospace science doesn’t give equal time to all facets of what makes a plane fly. But I think it is a bit much to dwell on our ignorance.

There is ignorance … that’s why we have wind tunnels to test designs. But it’s not like there are that many forces applied to a wing.