Aircraft create lift (upwards force) because they push down on the air and so change its momentum (combination of mass and velocity). If they pushed up on the air they’d create a downforce - physics doesn’t care about the direction…

Newton’s second law says force is equal to rate of change of momentum so when I change the momentum of a bit of air I get a force. (In fact this force isn’t just lift it’s also a bit of drag but that’s not important right now…)

There is, however _also_ a change of pressure over the wing - these two effects aren’t separate they’re two sides of the same coin; pressure is just force distributed over an area. Newton’s third law which says that (to paraphrase) “if I push on this air it pushes back on me with equal strength in the opposite direction”. So if an aircraft pushes down on the air, the air must push up on it, hence lift. Pressures are the way that these forces are transferred to the structure of the aircraft.

There’s no magic, physics doesn’t somehow ignore aircraft.

The air _does_ flow faster over the top of a wing because of two reasons, incidence (angle to the airflow) and the shape of the wing. This is why an aircraft goes nose-up to increase lift and why it can use flaps and other control surfaces, they change the shape of the wing. This increase in speed is a result of and part of lift generation.

Bernoulli’s principle is in operation on all aircraft but it’s an approximation that assumes that air is incompressible. This is nearly true for low-speed aircraft (light planes etc.) but becomes increasingly inaccurate as speeds rise. At the speeds of modern airliners it’s useless as a way to predict anything. Bernoulli’s principle isn’t a ‘natural law’ it’s a tool for prediction of effects.

Helicopters work the same way - and they can also fly upside down but usually don’t.

Originally it was thought the Bernoulli principle was what gave airplanes lift until the problem of the upside down airplane was considered. Then the investigation into new wing shapes also distanced Bernoulli’s as the primary source of lift.

More on the angle of attack from NASA at http://www.grc.nasa.gov/WWW/K-.....cline.html

Early in the days of aviation the Bernoulli principle seemed to be what was holding planes up but when exotic aircaft types with different wing shape were investigated it was found that something else was providing lift.

Read about it at NASA’s web page.

http://www.grc.nasa.gov/WWW/K-.....cline.html

NASA also maintains a webopage that specifically addresses the rotating cylinder concept http://www.grc.nasa.gov/WWW/K-12/airplane/cyl.html

This is known as the Bernoulli’s principle and it is not why planes fly. If’n it were the case airplanes could not fly upside down.

The Magnus effect is one of many various quirks in aerodynamics that is just not scalable. Yeah a bumble bee can fly but you are not going to see a man sized bumble bee type flying machine.

http://en.wikipedia.org/wiki/M.....ng_Machine

> Many flying machines incorporate this idea by generating lift with a
> rotating cylinder at the front of a wing that allows flight at lower
> horizontal speeds. [1] (Flettner rotor plane)
>
> A remote controlled prototype was featured on the DIY network show,
> “Radio-Control Hobbies” that used the Magnus effect as the primary lift
> and thrust mechanism. It consisted of a fan-like rotator generating the
> Magnus effect which allowed it to lift off after traveling only a few feet
> forward.
>
> A series of prototypes were built of a design called FanWing. Wind-tunnel
> tests were conducted in 1998 by Pat Peebles at the University of Rome.
>
> A patent was filed by Fred Ferguson in the 1980’s for an airship which
> used the Magnus effect as its primary lift and propulsion.
>
> The Rotor and UFO kites use the Magnus effect for lift.