How Wings ACTUALLY Create Lift!

This video looks at how wings produce lift to allow an aircraft to fly. Wings, also called Aerofoils or Airfoils produce lift by turning the air as it passes over the surfaces of the wing. Common incorrect explanations which are given include the Equal Transit or Longer Path theory based on the Bernoulli Principle.

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DISCLAIMER: While this video is intended for educational purposes, I must stress that I am not a professional pilot or instructor and I am not certified in any way with regards to aviation or education. Every subject I talk about is based on my personal study and understanding. Therefore the information I give may be incorrect or inaccurate and should NOT be used as a reference for real world flying.

[tourfish]

Who says the separated air must meet at the trailing edge at the same time? Bernoulli didn't say that! Definitely Bernoulli's principle is true, but everyone is using this principle based on a wrong premise.

[eduardpertinez]

None of the explanations I Had heard made any sense to me until now. Great job done 5 years ago!!!

[karbondikade]

I just made an airplane using this and it worked! Thanks bra

[NAWR]

The only way in which the wing surface can feel forces is either through tangential or normal forces, with tangential forces being viscous shear forces, and normal forces being pressure. The air cannot impart force on the wing surface accept through these means. What this means is that a pressure difference IS the reason a wing generates lift. Experimentation shows clearly that an airfoil shape creates differences in pressure all along the surface and when you integrate the pressure over the whole curve of the airfoil shape, the net force has some component in the normal direction to the freestream, and some component parallel to the freestream, with the normal component being what we call lift. The net result of causing this pressure difference is a turning of the flow, since the only way the flow can be turned is through the pressure gradients within it. So, from a mathematical standpoint, you are correct, the flow is turned by an amount exactly required to generate the amount of lift that is generated, but to say that lift is not actually caused by a pressure difference is incorrect, because again, the only way the wing surface can feel force is through the pressure and viscous forces acting on it directly (viscous forces barely contribute to lift, but rather contribute mostly to drag). The turning of the flow is just another result of the pressure differences within the flow field. The reason, then, that the Equal Transit Time theory is wrong, is not because it explains that pressure differences cause lift, but instead because of HOW it explains the pressure difference is created in the first place, which is admittedly much more complicated than can be explained without some very complicated math and physical principles. Equal Transit theory is not based on Bernoulli's Principle, it just uses Bernoulli's Principle to explain the result in change of pressure from the false premise it starts with. Don't equate the Equal Transit time fallacy with Bernoulli's Principle because there are plenty of valid uses of Bernoulli's equation.

[prandtlmayer]

This explanation is outdated and proved to be wrong and incomplete already. I suggest the book from Doug McLean

[gustube]

Please check your references, the air DOES NOT join at the SAME TIME at the trailing edge of the wing, “same time” is simply a totally WRONG statement.

[aaronwilliamson]

Can you please make a video on how gyros work, particularly the way an aircraft's gyroscopic instrument works. Thanks

[ACP]

The equal transit theory is false. Lift creation is very complex but it’s mainly caused by the pressure differential between the top and bottom of the wing and the downward deflection at the trailing edge. So it’s a combination of Bernoulli’s principle and the third law of motion.

[Polypropellor]

Good video for the shortness of it. You are correct- exactly! Basically, the various "theories" of why wings work to create lift all say the same thing, but in different ways. The idea of alerting the airflow to create lift, is best explained with your explanation. Air has mass- quite a lot of mass, actually. Anytime you move mass, there is an equal and opposite force created. In order to get any aircraft off the ground, you must move (at velocity) a mass (or weight) of air equal to the mass (or weight) of the aircraft in the opposite direction in which you want the aircraft to move. Any given volume of air (a "slug") has specific weight. You can calculate what amount of force is being generated by centripetal force of moving that weight. So, basically, the wing lifts for the same reason a weight being slung around a center point get's "heavier"- the faster the weight is slung, the "heavier" it gets. the redirection of the air slugs by the wings angle of attack, eventually is going fast enough to literally force the wing upward against the weight holding it down. this is why even a flat, angular board held at an angle to the direction of flow will cause lift- the rectangular wing will fly (though with higher drag) without the curvature (I've proven this to the vast chagrin of "Bernoulli" adherents with RC airplane models. The advantage of a curved or "Bernoulli" wing is a reduction in drag AND and enhancement of more easily redirecting the airflow in a different and downward direction, thus causing more efficient lift. The fundamentalist Bernoulli people have a hard time explaining why properly curved wings can fly (still generate lift) when flying upside down...and don't even get them going on the symmetrical (curved the same on both sides of the wing surface) fly better, with less drag and more lift at higher speed than the traditional "Bernoulli" models - that is the "flat bottom" wings.

It is merely the re-direction of mass that causes airplane wings to create lift- that's the whole bottom line. All the other aspects of a wings design are for reducing drag while enhancing that re-direction of mass.

Excellent video. Excellent explanation of why wings create lift.

[iforced]

3:38 unless I'm mistaken a wing in stall still produces lift, it's just that it's overcome by drag so not very practical, and uncontrollable due to no flow over control surfaces.

[MitchellEssenmacher]

While it is true that the flow tends to remain attached to the surface of the airfoil, it is not because of the Coanda effect. This effect specifically applies to jet flow, which an airfoil would not experience. The equal transit time theory is wrong as you stated, but the relative pressure fields between the top and bottom surfaces of the wing would play a role in generating lift. Pressure and velocity changes are coupled when looking at a flow like you displayed, meaning they change continuously with each other. This is a big misconception when it comes to explaining lift.

[CommKommando]

I don’t get why most descriptions focus on the low pressure above the wing, instead of the high pressure beneath the wing. The high pressure is what creates the lift after all.

[AlienRelics]

A basic symmetrical airfoil shape is a flat sheet wing with a shape added around it to allow thickness for spars, and to improve aerodynamics at different angles of attack.

A flat bottom airfoil is really a cambered sheet wing with an airfoil added around it. So if you look at the centerline of that flat bottom airfoil, you can see that when the flat bottom is parallel with the direction of travel, the wing itself really has a slight positive angle of attack.

Hence lift at what seems like a neutral angle of attack, but which is really slightly positive.

[q.e.d.]

The Bernoulli/Newton dispute is a false dichotomy. They are simply different ways of describing the same phenomonem. Newtonian mechanics is arguably the more fundamental explanation, but the proximal cause of the lift (the only thing the wing feels) is the pressure differential that is a resultant of that Newtonian action/reaction. And that pressure drop is known as the Bernoulli effect, although Newton himself had observed the effect in tennis balls and concluded correctly (of course, ) that it was due to action/reaction with the passing air.
So, probably go with Newton since he was a couple of centuries earlier than Bernoulli.

[nielsdaemen]

1:56 Correct, The wing is indeed turning the airflow downward.
But there is also a pressure difference between the top and bottom of the wing!
The lift force is literally equal to the average pressure difference between. The bottom and top of the wing times the surface area of the wing!

And it is in fact the pressure gradient formed arround the wing that turns the airflow downward!

Please correct your mistake!

[tommyv]

Damn it, I'm gonna have to watch this a couple more times..I got distracted by the animations on the wing

[PrateekJain-pijc]

Beautifully explained. I wish this video series was around when I first found this game about ten yrs ago

[MI_]

The only video about lift that actually makes sense

[spencerrichardson]

As an aerospace engineer, this is a useful explanation for the average person to understand what creates lift, but we can’t totally disregard the fact that there is a pressure difference. I disagree with you when you say that a pressure difference is not what creates lift. In fact, there are many times where we can actually compute the lift force (or lift coefficient) on an airfoil WITH the pressure distribution and using calculus to integrate the difference in pressure acting on the top and bottom. At the end end of the day, there are two natural sources that cause for all aerodynamic forces and they are none other than the pressure distribution and the viscous shear stress. I’m not saying you’re wrong for thinking this (although I am saying you’re wrong for saying the pressure theory is wrong), but I think they go hand in hand. You can’t have one without the other. To say one idea is more correct than the other would be ignorance. I appreciate the video though and it helped me deepen my understanding a bit because I had never heard it explained this way. Thanks! 👍🏼

[michal.gawron]

To delay a stall you can also use vortex generators on top surface of wing. Vortices tend to "stick" to the wing better than regular air, so the separation occurs at higher AoA.