By suction. The top of a wing creates suction as it moves through the air. You will never encounter the word “SUCTION” related to wings or to lift but suction is what happens when a wing moves through the air. The bottom of the wing pushes up while the top sucks up and the suction is much greater hence more important than the push.

A wing is sucked up!

It is sucked upwards. It is SUCTION that lifts a plane.

Why isn’t “LIFT” explained as “SUCTION”?

Lift is what a moving wing does. SUCTION is the cause of the LIFT. Suction causes Lift!

SUCTION is LOW PRESSURE AIR. If you could kiss and aircraft wing and suck inwards you would be doing exactely what the wing is doing as it moves through the air. You cannot see suction. Even if you watch a wing in a wind tunnel you will not be able to see the suction.

Suction is invisible. It’s there but you can’t see it just like you cannot see the air all around you at this very moment. It’s hard to visualize what the wing is doing because you cannot see the suction. The wing is being sucked up. That’s why the Wright Brothers had such a hard time trying to get an aircraft to fly. They had no way to know the wing had to be sucked up for the aircraft to fly.

A wing is a giant sucker.

Here’s the rather naïve explanation of “LIFT” from Wikipedia: Notice that it fails to identify the suction that causes the lift!

“A fluid flowing around an object exerts a force on it. Lift is the component of this force that is perpendicular to the oncoming flow direction.[1] It contrasts with the drag force, which is the component of the force parallel to the flow direction. Lift conventionally acts in an upward direction in order to counter the force of gravity, but it can act in any direction at right angles to the flow.

If the surrounding fluid is air, the force is called an aerodynamic force. In water or any other liquid, it is called a hydrodynamic force.

Dynamic lift is distinguished from other kinds of lift in fluids. Aerostatic lift or buoyancy, in which an internal fluid is lighter than the surrounding fluid, does not require movement and is used by balloons, blimps, dirigibles, boats, and submarines. Planing lift, in which only the lower portion of the body is immersed in a liquid flow, is used by motorboats, surfboards, windsurfers, sailboats, and water-skis.”

***************************************

See? No SUCTION! No Suction, No Lift yet is fails to mention Suction. This little article by me may change that. It may introduce the non-engineers who don’t really grasp “LIFT” to the idea of actually measuring the suction. It can be done. It’s rather complicated because it’s not just one amount of suction at one place on a wing. the amount of suction varies from front to back and from side to side over every nanometer of the top of the wing. The suction goes from a negative value which is pressure to a positive value which is negative pressure which is suction. It’s impossible to imagine exactly how the wing is producing lift unless you visualize the suction. Once you get the idea of the suction it’s possible to visualize a variable force field that is the negative pressure which is the suction that is happening that is lifting up the aircraft. If you lean the aircraft left or right the suction will be the same but in a very different direction relative to the earth and its the amount of suction that’s perpendicular to the earth that’s important.  Tilt the aircraft and the suction is still there but it’s no longer operating perpendicular to the earth. Tilt is enough and the aircraft will have zero perpendicular suction, zero lift so it has to compensate somehow to stay in the air. The pilot can do that very easily by maneuvering the aircraft to get lift a different way. When an aircraft is flying with the wing straight up and down the lift comes from the propeller and the rudder.  It’s a bit more complicated than that so don’t go out and try it. In fact, flying is a pretty complex activity so don’t ever try it without sufficient information and skill. In other words, go get an instructor but a word of caution. DOn’t talk about suction. It might confuse the instructor because they aren’t instructed in suction. 🙂

Views: 4