I'd be very curious to see a wing without an upper surface, ghat could be used to test this. Maybe it's full of magnetic monopoles?

So how about symmetrical wings?


That is a very poor question that does not really test a student's understanding of the theory of lift.

Many 1970s era ultralights or hang-gliders.

I've flown one or two, and can verify that they do fly - just not usually very well.

Search online for "Chotia Weedhopper" for a good example.

G

I did that experiment as a kid in ~1950 building models. Covering the top surface only, it flew more or less normally, cover the bottom surface only and it would not lift anything like as good. Level glide compared to 30deg dive.

Lots of aerofoils used at the dawn of flight were 'concave' - the Wright flyer, Bleriot, Nieuport and, to a lesser degree, later ones too, such as the Fokker Dr 1 (Triplane) and Sopwith Camel.

However, even if you just had a single 'sheet' curved aerofoil, it would still have a top and a bottom.

Magnetic monopoles made from an Unobtanium/Eludium wishalloy might fit the bill :)

The whole concept of 'which part of the wing makes the lift' is bunkum. You could make a 'lifting surface' out of a rotating cylinder...

;^)

B.

This is more a question of a curved aerofoil compared to a flat one, as most aerofoils have a flatter underside than top. Even concave ones.
I don't think it's bunkum. Try stripping the fabric off the top of one side and the bottom of the other and see which way the thing will roll, even with a concave underside.
A rotating cylinder yes, non rotating, like most wings, no. Different principle, slightly.

It's the dumbing down I object to. It is annoying to see questions which try to make the whole subject 'easy' with pat answers when reality is that it is actually a complicated subject.

The closest thing to a right answer would be 'it depends on AoA and actual aerofoil shape'.

Here's another one which you never see but which would maybe be far more interesting to discuss:
Which part of the aerofoil section creates most drag?

:^)

B.

As usual, EASA questions only go halfway, or less. To understand how lift works, we must understand how static pressure works.

The weight of the air inside a column that is 1 foot square at sea level is 2116.16 lbs (on a standard day). This pressure surrounds the aircraft from above and below and all around. That is, the aircraft is being squeezed from all directions at a static pressure of around 2000 lbs per square foot. If you can reduce the pressure above its aerofoils by more than the weight of the aircraft, it will fly, which is what we do mechanically, by moving forward to concentrate the airflow over the top of the wing and bring its streamlines closer together, because we cannot affect static pressure directly.

Instead, we mess with the dynamic pressure over the upper surface of the wings, especially in the first quarter, which makes the changes we need. This is often discussed with reference to Bernoulli’s Theorem, whose involvement is b*llocks anyway for this discussion (except for altering the pressures), partly because it assumes a closed system, and no friction but, mainly, the theorem only applies if no energy is imparted to the system - a propeller is an actuator!

The aircraft is not sucked up into the air, as forces generally do not pull. Atmospheric pressure from underneath pushes the aircraft up. There is enough upwards pressure on a 10 foot square ceiling to support a 737. No air movement would be necessary were it not for the need to reduce the pressure on the upper surface.

Of course, we also start with the flat plate to deflect air downwards, with some shaping to help with the turbulence and to create the lower pressure, and a down force also comes from wingtip vortices (NASA).

An inverted aeroplane will still fly under the above conditions, of course, but with a much higher angle of attack.

Hopefully, that's a less gross simplification, Genghis! :)

I started reading the on line book above referred to, page 181 with pressure below wing exceeding pressure on top wing shows agreement with the last poster' text !
[I can't post the JPeg directly]

mike hallam

Sorry, I should have maybe used some appropriate emoticon. My point is that any wing has an upper surface, even if it's just the top of the lower surface (hence the remark about monopoles). So the question is completely meaningless. It seems to be a barely-disguisued variation on whether it's the pressure difference or the downwash that generates lift. Answer: since it's physically impossible to generate one without also generating the other (using an aerofoil), the question doesn't make any sense.

Of course if you take a normal wing and simply strip the top covering, it will make an extremely BAD aerofoil, and will not generate lift very efficiently. But it will still have a (rather bumpy) top surface. But as others have said, a single sheet of material, correctly shaped and braced, makes a reasonable aerofoil.