What makes wings lift

Lift is generated by every part of the airplane, but most of the lift on a normal airliner is generated by the wings. Lift is a mechanical aerodynamic force produced by the motion of the airplane through the air.

Because lift is a force, it is a vector quantity , having both a magnitude and a direction associated with it. Lift acts through the center of pressure of the object and is directed perpendicular to the flow direction.

There are several factors which affect the magnitude of lift. There are many explanations for the generation of lift found in encyclopedias, in basic physics textbooks, and on Web sites. Unfortunately, many of the explanations are misleading and incorrect.

Theories on the generation of lift have become a source of great controversy and a topic for heated arguments. To help you understand lift and its origins, a series of pages will describe the various theories and how some of the popular theories fail. Lift occurs when a moving flow of gas is turned by a solid object. The flow is turned in one direction, and the lift is generated in the opposite direction, according to Newton's Third Law of action and reaction.

It used to be claimed that the air travelling over the top of the wing took the same time to reach the back of the wing as the air travelling along the bottom. This has been shown to be incorrect, but it has been shown that the speed of the air over the top is faster than the speed of the air under the bottom.

The shape of the aerofoil is different for different aircraft. It is designed to give the best trade-off between lift and drag for each aircraft. On many aeroplanes, the bottom of the wing will curve downwards slightly instead of being flat. On other aircraft, such as gliders, it will curve upwards. On a stunt plane, which is just as likely to fly upside down as it is to fly the right way up, the curve on the bottom of the wing will be the same as it is on the top.

Discover more about the principles of flight. This website discusses how aeroplane wings really work and describes the common explanation based on Bernoulli and the physics explanation using Newton. This simulation from NASA shows how both angle and wing shape affect lift.

Use content from the Hyperphysics website to explore the Bernoulli Equation further. Add to collection. Nature of Science Science ideas and concepts are constantly being challenged. Activity ideas Continue the learning with your students with one or more of these activities Aerofoils and paper planes — learn how to make an aerofoil and to make and fly paper planes. Making a glider — handcraft a glider from balsa wood and in the process learn about aerofoil wing shape, glider parts and terminology.

Then experiment with flight using variables of wind and nose weight. Kites — learn about some kite history and how kites fly before making and flying a kite. Birds and planes — explore the importance of wing shape and size and how this determines the flight capabilities of birds and planes.

Balloons and air density — air density affects flight. This activity enables students to visualise differences in air density. Colder air is denser, which contributes to engine performance and air lift in planes and lift in hot air balloons. Useful links This website discusses how aeroplane wings really work and describes the common explanation based on Bernoulli and the physics explanation using Newton.

Give this plane a velocity axis roll of degrees, you get a plane with -ve angle of attack, and hence a negative lift. But a plane cannot sustain flight with negative lift, so what the upside down flying planes need to do is to increase the -ve angle of attack to positive, by pulling the nose up that would be pushing the nose towards the sky in an upside down plane.

A plane flies by several mechanisms. The first is the Bernoulli effect caused by wing camber that generates a pressure differential pushing the wing upwards as it moves forwards through the air. Note that birds have cambered wings. However, it is possible to have a plane with completely flat wings and no camber at all, so it is a mistake to think this is the only source of lift as some of the answers above have done.

The angle at the wing root is also important. If you stick your hand at an angle out of car window, you will feel it forced upwards. This same effect is accomplished in an aircraft by angling the wings slightly upward relative to the plane of the fuselage. Finally, you should be aware that the reason a plane stays aloft has nothing to do with lift, but with the surface area it presents to the ground.

The primary force holding a plane up is air resistance which is a function of this surface area. The force of this air resistance is much greater than the force generated by the previous two effects.

A square fuselage will present more surface area to the ground, thus having greater efficiency in staying aloft. For this reason, nearly all early aircraft had square fuselages. However, a round fuselage will be more efficient moving forwards than a square one, so in a plane built for speed, round is better. An aircraft with a round fuselage goes faster, but is less fuel efficient than one with a square fuselage. The same argument holds true for wing area. The larger the wing, the more air resistance.

For this reason, gliders have relatively large wings compared to powered aircraft. The drawback of a large wing is the same as that of a square fuselage: the plane goes slower. So, to recap, there are three factors that keep an aircraft aloft: vertical air resistance due to downward facing surface area, the angle of the wings at the wing root, and the Bernoulli effect associated with the camber in the wings.

Sign up to join this community. The best answers are voted up and rise to the top. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Learn more. How do wings generate lift? Ask Question. Asked 6 years, 4 months ago. Active 1 year, 4 months ago. Viewed 38k times. Improve this question. Jay Carr Jay Carr Show 13 more comments.

Active Oldest Votes. Pressure means that air particles oscillate all the time and bounce into other air particles. The more bouncing, the more force they exert on their surroundings. Viscosity means that air molecules, because of this oscillation, tend to assume the speed and direction of their neighbors. Flow over the upper side of the wing Now to the airflow: When a wing approaches at subsonic speed, the low pressure area over its upper surface will suck in air ahead of it.

Flow over the lower side of the wing A packet of air which ends up below the wing will experience less uplift and acceleration, and in the convex part of highly cambered airfoils it will experience a compression. Lift can be explained in several, equivalent ways Following the picture of a pressure field outlined above, lift is the difference of pressure between upper and lower surface of the wing. Lift is a matter of definition Lift and induced drag are both part of the pressures acting on the wing.

Improve this answer. For anyone else reading this, btw, make sure you look at DanHumes answer as well, it goes over some of the common myths about how lift is generated. It's also very useful. This youtube. And I read somewhere that air over lower side of the wing is slow down and then sped up, is this true? Or the air is just "less accelerated: than over the wing upper surface? On thin airfoils at high angle of attack, flow over the lower side is slowed down and pressure is higher than ambient.

In most cases the pressure and speed are close to ambient. On thick airfoils at low angle of attack your last sentence is correct: Air will be less accelerated on the lower side. At the end of its run, the air will assume ambient speed and pressure again, so it will speed up or slow down depending on the state it had before. Add a comment. Lift from Pressure-Area When a fluid moves over an object or vice-versa , the pressure is different at different points. Lift from Flow Turning Both surfaces of the wing turn the flow of air.

Wrong Theory 1: Equal transit time As I said, to invoke the Bernoulli effect, you have to explain why the air on the upper surface is moving faster. Wrong Theory 2: Skipping stone This page discusses when people realise the air "bounces off" the bottom surface of the wing, but neglect the top surface. Wrong Theory 3: Venturi Some people imagine the top surface of the wing as a half of a Venturi nozzle a nozzle which speeds up fluid flow by constricting it.

Bernoulli and Newton This last page just sums up that the wrong theories start with well-known physics Newton's laws or the Bernoulli effect , but then try to oversimplify everything to make them fit the situation, so they end up with explanations which make wrong predictions. Dan Hulme Dan Hulme One should remember that flow turning is the effect of the lift Which was created by pressure difference , rather than the cause of lift.

They are both properties of the fluid flow. However for explanation purposes, the direction in this answer is correct, mainly because the opposite direction is not possible ; you can derive lift from Kutta-Joukowski theorem, but you can't derive Kutta-Joukowski theorem from lift. It does not explain it.

Show 9 more comments. Newton's 3rd Law On the Newton's 3rd law side the net aerodynamic force is caused by a redirection of the relative wind downwards known as "downwash". Final Comments One more aerodynamic phenomenon that I will relate to this explanation is a "stall". Useful sources: allstar. Murey Tasroc Murey Tasroc 1, 11 11 silver badges 16 16 bronze badges. Paul Smith Paul Smith 4 4 silver badges 7 7 bronze badges.

It does not say anything about why wings , in particular, generate it. Any shape can generate lift if the circumstances are right, the shapes of wings just happen to be better at pushing more air down then up then, for example, a brick.

Exactly the same physics apply to an aerofoil through water such as those used in the Americas Cup racing. Speed has nothing to do with it.

The material moved forward pushes back drag and the material pushed down pushes up lift. Show 2 more comments. This effect could be reduced by using a cambered plate instead of a flat plate, reducing vortex on the upper surface: But the issue remains that as soon as the cambered plate is tilted further, it creates a lot of drag, in the same way as the straight flat plate.

Koyovis Koyovis Making the airfoil thicker increases drag, but widens the angle of attack range in which it works well. It is a great read, I agree :. I guess I should say a relative vacuum. BillOer's link explains why. If it were that way, paper planes, kites, and some kinds of gliders wouldn't fly.

The test results: --Short steep curve pointing downwards in the front, long less steep curve in the back pointing upwards. Community Bot 1. Ralf Vandebergh Ralf Vandebergh 11 2 2 bronze badges.

Your wing indeed looks like slow, high lifters found at Airfoil Tools on the net. I have also found that thin under cambered wings make for delightfully slow walking speed balsa gliders.

You may find thinner wings are better for wind penetration less drag. Comparisons of eagle and albatross wings can give good insights on wing design.

The thick wing high lift profile was disigned for particular tests on flow turning to see a strengthened effect in short flight. As you said, thinner is better for less drag. I also have a curved flat plate version of this wing with flexible curve. Here you see it in action. The video actually shows the auto pitch correction: vimeo. Nor is air a "fluid", it is a compressible gas.

Flow turning indeed is related to low pressure on top of the wing. The great Coanda realized the deflected air flow creates a local low that the wing up and the airstream down tries to fill.

A simple sink top aspirator creates a strong vacuum. Lift force is also created by airstream striking an angled surface bottom of wing. There is more than one source of lift. It may be the lift over the top of the airfoil, as covering the bottom of the wing seems to make my gliders go faster and farther. I believe this to be most draggy and inefficient, but can make for very slow flying speeds!

Show 4 more comments. The curved surface here is similar to the wing. The mentioning of gravity only makes matters difficult, as people can think gravity is involved in the creation of lift. A better image would have the ball travelling on a straight line, and colliding with the curved surface. This avoids the need for gravity, and makes the analogy with an airfoil better. Furthermore, if there is no curvature, the pressure also decreases, which doesn't show from your explanation.

The asymmetry causes different velocities on the top and bottom portion of the airfoil because of the following reason: When a fluid reaches the Leading Edge of the airfoil, some part of the fluid is displaced upwards, while some of it is displaced downwards.