Thank you ... The wing is rammed through the air by the engines or as the plane falls during a descent due to gravity (and the engines...). A such it, due the wing's shape and the angle of attack (relative to the airplane's velocity vector not the ground) You obtain pressure differences above and below the wing. These are deliberately caused by the mechanical movement of the plane doing work on the air. Now a hand out the window does so as well, but a wing is carefully engineered to obtain the desired pressure differences without inducing too much drag. This pressure difference is designed then to have a lower pressure above the wing, hence causing a partial vacuum so partially the pressure under the wing will serve to hold it up. However, the wing is of course in motion and so the air further above the wind rushes down into the vacuum then off the tailing edge creating a downdraft. We can see evidence of this with observing streamlines in a wind tunnel. The air above turns more dramatically indicative of a lower pressure. It is the same logic that describes the flight of a curve ball. (There may be a Magnus 'Effect', but it is all due 'lift' in the direction caused by the spin on the ball and its speed) In its simplest interpretation, there is thus a partial vacuum force bringing all this air downward due to the pressure differential created by the wing action described above and so by Newton's Third Law, there has to be an equal an opposite force pushing the plane upward. The control of flight is such that by the proper control of the angle of attack, engine thrust and wing shape, you can achieve a balance between the cumulative force forcing the air down and that holding up the plane and any drag. This gives level flight. When climbing, we use additional engine power to further offset a bit of gravity (most of the plane is still supported by the lift) and at the same time create the most efficient lift to get the airplane to the desired altitude. The descent has reduced power, using largely gravity and then finer control so that the landing is at a safe vertical speed, and enough forward speed is maintained to just have a bit less lift than the weight of the plane. We also use flaps and leading edge slats closer to the ground to change the wing geometry to optimize the pressure differential at slower speeds, especially at landing where the slowest possible speed for a given aircraft weight and geometry is desired for safety. The theory described above is largely an American phenomenon. It got in the textbooks in the early 60's. In all other countries airplanes fly according to the laws of physics, only in the US does this Equal transit theory be upheld (and with some fervor in my experience). I even saw it getting prominence at the Air and Space Museum for goodness sake. Lift is NOT Bernoulli and it is not Equal Transit time etc. Really ... If you are a CFI or a physics teacher you should THINK for a minute. If this equal transit theory actually worked then there would be NO DOWNWASH from a helicopter! Sure, listen to your instructors, but THINK as well. Yes, we can trot out some impressive partial differential equations in university to describe this, but when I taught, I always covered airplanes and flight for my advanced high school physics students. Interested students can understand the above and explain it and love seeing images of various types of planes and why they worked and their role in history. Now, to extend this ... When a plane turns, it requires a very significant force due to the large mass and high speed of the airplane. This is not going to be accomplished by the small control surfaces. Instead the bank and rudder control change the lift vector of the wings to some thing off vertical, but in the direction of the desired turn. Suppose you bank a plane 25 deg. Then the force towards the turn is sin 25 = 0.416 or ~40% of the lift the wings are providing. However, at the same time the force holding up the airplane is cos 25 = 0.906 or ~91% of the required lift. So the pilot has to make a slight increase in angle of attack using the elevators to maintain altitude. So the wings are actually lifting the plane around a turn. Yes, I realize that 40+91 Not(=) to 100. However, that is the magic of elementary trigonometry and makes that aspect of flying so much easier! One of my students when confronted with this said ... 'but that's cheating' ... and so nature does. Finally, a good video on this topic. Thank you.
Saying that "nobody knows how lift is produced" is another common myth. We do know how it is produced, but we don't know(or have a consensus on) how to explain it without expecting everyone to take a 4 year college course on it.
@@tahoeflightacademy //"I said nobody knows exactly how lift is produced"// I know you said that, but that's wrong. osuWhite is correct that we know, it's just VERY hard to explain without getting down into the master/PhD level of physics.
The classic curved wing shape DOES make lift by the upper molecule needing to speed up relative to the under side...but agree that they don't exactly meet again at the trailing edge which is why those wings create turbulence behind them which also creates drag. A symmetrical airfoil works on the same theory as a rock skipping on a lake (as mentioned by phil below)....by planing which creates lift mostly by the impact of the molecules on the underside and much less due to any acceleration across the top surface. There IS acceleration across the top when a symmetrical wing is creating lift due to planing at some angle of attack, but it's more troublesome as this causes transonic shockwaves at high speeds. Wing theory IS about as complicated as you want to make it...but saying that the old Piper Cub style wing doesn't make lift at '0' angle of attack is wrong....so that lift happens because of the upper surface acceleration which is what has been taught for over a century.
@@tahoeflightacademy Who said it would? Not me! The conventional 'Piper Cub' type airfoil WILL make lift at '0'...while the symmetrical airfoil NEEDS angle of attack to create lift. I never said otherwise and it seems your reading comprehension could use some remedial attention.
@recoilrob324 I think you're missing the entire point of the video. It's not a discussion of how lift is generated, it's about the equal transit theory being false, of which the symmetrical airfoil is a prime example.
Air hits the bottom of the wing and the wing turns the air down by a certain angle, the wings angle of attack. Combine that with the mass of the air being deflected and you can calculate the lift generated. The faster the plane goes, the higher the mass of air being deflected and the greater the lift. This is well understood and not very conplicated. More details can be added, but in the end its mostly just mass and angle.
Flatten your hand a stick it out the window of a moving car. There's no bernouli effect, but you will feel lift. The lift is generated by newton's 3rd law in this case. Your hand is running into air molecules and accelerating them. At an angle, you get a combination of lift and drag. The bernouli effect just makes the lift more efficient by reducing the pressure above the wing
It's simple deflection. Same thing occurs of your hand hits water, or a rock. There is almost no phase of flight where lift is needed and there is a zero angle of attack.
Thank you ...
The wing is rammed through the air by the engines or as the plane falls during a descent due to gravity (and the engines...). A such it, due the wing's shape and the angle of attack (relative to the airplane's velocity vector not the ground) You obtain pressure differences above and below the wing. These are deliberately caused by the mechanical movement of the plane doing work on the air. Now a hand out the window does so as well, but a wing is carefully engineered to obtain the desired pressure differences without inducing too much drag. This pressure difference is designed then to have a lower pressure above the wing, hence causing a partial vacuum so partially the pressure under the wing will serve to hold it up. However, the wing is of course in motion and so the air further above the wind rushes down into the vacuum then off the tailing edge creating a downdraft. We can see evidence of this with observing streamlines in a wind tunnel. The air above turns more dramatically indicative of a lower pressure. It is the same logic that describes the flight of a curve ball. (There may be a Magnus 'Effect', but it is all due 'lift' in the direction caused by the spin on the ball and its speed)
In its simplest interpretation, there is thus a partial vacuum force bringing all this air downward due to the pressure differential created by the wing action described above and so by Newton's Third Law, there has to be an equal an opposite force pushing the plane upward. The control of flight is such that by the proper control of the angle of attack, engine thrust and wing shape, you can achieve a balance between the cumulative force forcing the air down and that holding up the plane and any drag. This gives level flight. When climbing, we use additional engine power to further offset a bit of gravity (most of the plane is still supported by the lift) and at the same time create the most efficient lift to get the airplane to the desired altitude. The descent has reduced power, using largely gravity and then finer control so that the landing is at a safe vertical speed, and enough forward speed is maintained to just have a bit less lift than the weight of the plane. We also use flaps and leading edge slats closer to the ground to change the wing geometry to optimize the pressure differential at slower speeds, especially at landing where the slowest possible speed for a given aircraft weight and geometry is desired for safety.
The theory described above is largely an American phenomenon. It got in the textbooks in the early 60's. In all other countries airplanes fly according to the laws of physics, only in the US does this Equal transit theory be upheld (and with some fervor in my experience). I even saw it getting prominence at the Air and Space Museum for goodness sake. Lift is NOT Bernoulli and it is not Equal Transit time etc. Really ...
If you are a CFI or a physics teacher you should THINK for a minute. If this equal transit theory actually worked then there would be NO DOWNWASH from a helicopter! Sure, listen to your instructors, but THINK as well. Yes, we can trot out some impressive partial differential equations in university to describe this, but when I taught, I always covered airplanes and flight for my advanced high school physics students. Interested students can understand the above and explain it and love seeing images of various types of planes and why they worked and their role in history.
Now, to extend this ... When a plane turns, it requires a very significant force due to the large mass and high speed of the airplane. This is not going to be accomplished by the small control surfaces. Instead the bank and rudder control change the lift vector of the wings to some thing off vertical, but in the direction of the desired turn. Suppose you bank a plane 25 deg. Then the force towards the turn is sin 25 = 0.416 or ~40% of the lift the wings are providing. However, at the same time the force holding up the airplane is cos 25 = 0.906 or ~91% of the required lift. So the pilot has to make a slight increase in angle of attack using the elevators to maintain altitude. So the wings are actually lifting the plane around a turn. Yes, I realize that 40+91 Not(=) to 100. However, that is the magic of elementary trigonometry and makes that aspect of flying so much easier! One of my students when confronted with this said ... 'but that's cheating' ... and so nature does.
Finally, a good video on this topic. Thank you.
Saying that "nobody knows how lift is produced" is another common myth. We do know how it is produced, but we don't know(or have a consensus on) how to explain it without expecting everyone to take a 4 year college course on it.
I said nobody knows exactly how lift is produced. Yes, there are theories that we believe to be correct, but it's super complex.
@@tahoeflightacademy //"I said nobody knows exactly how lift is produced"//
I know you said that, but that's wrong. osuWhite is correct that we know, it's just VERY hard to explain without getting down into the master/PhD level of physics.
"turning air accelerates" I'd like to see some science on this one.
Check out the NASA link in the description!
The classic curved wing shape DOES make lift by the upper molecule needing to speed up relative to the under side...but agree that they don't exactly meet again at the trailing edge which is why those wings create turbulence behind them which also creates drag.
A symmetrical airfoil works on the same theory as a rock skipping on a lake (as mentioned by phil below)....by planing which creates lift mostly by the impact of the molecules on the underside and much less due to any acceleration across the top surface. There IS acceleration across the top when a symmetrical wing is creating lift due to planing at some angle of attack, but it's more troublesome as this causes transonic shockwaves at high speeds.
Wing theory IS about as complicated as you want to make it...but saying that the old Piper Cub style wing doesn't make lift at '0' angle of attack is wrong....so that lift happens because of the upper surface acceleration which is what has been taught for over a century.
A symmetrical airfoil will not produce lift at a zero angle of attack. I encourage you to check out the NASA site linked in the description.
@@tahoeflightacademy Who said it would? Not me! The conventional 'Piper Cub' type airfoil WILL make lift at '0'...while the symmetrical airfoil NEEDS angle of attack to create lift. I never said otherwise and it seems your reading comprehension could use some remedial attention.
@recoilrob324 I think you're missing the entire point of the video. It's not a discussion of how lift is generated, it's about the equal transit theory being false, of which the symmetrical airfoil is a prime example.
Air hits the bottom of the wing and the wing turns the air down by a certain angle, the wings angle of attack. Combine that with the mass of the air being deflected and you can calculate the lift generated. The faster the plane goes, the higher the mass of air being deflected and the greater the lift. This is well understood and not very conplicated. More details can be added, but in the end its mostly just mass and angle.
A Bombadier Challenger flies, thus proving an object with poor design can fly with enough power applied..
Flatten your hand a stick it out the window of a moving car. There's no bernouli effect, but you will feel lift. The lift is generated by newton's 3rd law in this case. Your hand is running into air molecules and accelerating them. At an angle, you get a combination of lift and drag. The bernouli effect just makes the lift more efficient by reducing the pressure above the wing
It's simple deflection. Same thing occurs of your hand hits water, or a rock. There is almost no phase of flight where lift is needed and there is a zero angle of attack.
Bernoulli effect is in play any time lift is being generated. It's a combination of that and Newton's 3rd law.