how do airplanes fly?

“Airplane wings are curved on the top which make air move faster over the top of the wing. The air moves faster over the top of a wing. It moves slower underneath the wing. The slow air pushes up from below while the faster air pushes down from the top. This forces the wing to lift up into the air.”

More: http://inventors.about.com/library/inventors/blairplanedynamics.htm

Actually, I’ve been hearing a lot of science stories lately that say that explanation (Bernoulli’s Principle) is a gross oversimplification and does not in fact explain how planes stay up. It seems that no can really explain why planes stay in the sky.

@syz, links to said science stories?

planes stay in the sky because of magic fairies?

Bernoulli explains why planes fly, lift created by the pressure difference has been measured…why the doubt?

Bernoulli’s Principle (described by djbyron) is important in creating lift, but so is Newton’s Third Law (“Every action has an equal and opposite reaction”) – if the plane wing is angled in such a way as to push the air DOWN, then that, in turn, pushes the wing UP. This angle is called the “angle of attack.” The greater the angle of attack, the more lift is created, but if the angle of attack becomes too great, this creates turbulence and causes the aircraft to “stall.”

Lift is the force that counters the force of gravity, and thrust is the force that counters friction. Thrust in an airplane is created by the engines.

www.airlinepilotforums.com/showthread.php?p=314511

**cracks knuckles**

I’d like to comment on a few explanations as well as sum up how lift is produced by an airplane wing.

The Bernoulli Equation does explain why there is a pressure difference between the upper surface and lower surface of a wing: however, it is not the the best explanation of what actually happens.

It is actually fairly simple to explain how airplanes fly and there is no one who knows anything about physics who would say that lift cannot be explained.

Bernoulli’s Equation does not explain lift well because it makes explaining the lift on a symmetric airfoil much more difficult. The best way to explain is similar to how @christybird has explained it but I will go into a little more detail.

Newton’s 3rd Law states that for every force there is an equal force opposing it. A wing is designed to turn the air and create something called circulation. Circulation is a way of describing the action that a wing has on the air that passes by it. In a wing that has camber (curvature of the upper and lower surfaces) the camber causes the air to flow parallel to the surface of the wing. As the air reaches the trailing edge of the wing it is travelling in a different direction than when it started. If a wing has positive camber (meaning the it is convex on the top and concave, or flat, on the bottom) the air will be turned by the shape of the wing because the flow has to leave the trailing edge of the wing parallel to the surface. The new direction of the air is caused by a force of the wing on the air. The redirection of the air has an equal and opposite force on the wing which is called lift.

As also mentioned you can change the angle of attack of a wing. The angle of attack is the angle that the wing makes with the incoming airflow. A symmetrical wing (one that does not have any curvature) at an angle of attack does much the same thing as a cambered wing. It also makes the flow on both sides of the wing go in a different direction. The incoming airflow will hit the wing at an angle and then flow smoothly over the upper and lower surfaces. This smooth flow over the surfaces is what allows both cambered and symmetrical wings to create circulation and thus lift.

@christybird Has some good thoughts but has misunderstood a few things about stall. Stall is when the flow over the wing has become separated.. Separation happens when the angle of attack is too great for the airflow to stay “attached” (or moving smoothly over the surface). A flow becomes detached because of something called an adverse pressure gradient. Basically there is a high pressure on a part of the wing behind the leading edge the makes it hard for the flow to continue flowing smoothly over the wing so it becomes detached from the surface.

This is an example of attached smooth flow over an airfoil

This is an example of detached flow over an airfoil