The airplane will fly

if the tredmill was going at the same speed to the plane in the opposite direction then only the wheels would be in motion, not the plane itself. for a plain to take off there needs to be air passing the wing. the design of the wing splits the air. the air passing over the wing passes slower than the air passing under the wing. it is this design of the wing that enables the plain to 'take off'. as the plane itself would not be in motion; then there would be no air passing the wing, therefore it would have no lift to take off. unless it was really really windie.

Therefore you have a big fan in front of the plane creating a stream of air strong enough to pass the wings to create an uplift force.

Am I kidding? Yes, of course.

The airplane will take off, but the wheels won't.

Originally posted by AThousandYoung
The airplane will take off, but the wheels won't.

explain plese

A propellor powered plane would send air over the wings.

Not much though.

By the way, real wings work by deflecting air downwards like a helicopter blade. The theory of air traveling at different speeds over the top and bottom of the wing is wrong. Their is no reason why the air sent over the top of the wing must meet with the same air at the back of the wing. Real wings slope downwards at the back and their is some negative pressure created above the wing as the air follows this downward slope, but most of the lift comes from the air under the wing being deflected downward.

Originally posted by asplandmatt
A propellor powered plane would send air over the wings.

Not much though.

By the way, real wings work by deflecting air downwards like a helicopter blade. The theory of air traveling at different speeds over the top and bottom of the wing is wrong. Their is no reason why the air sent over the top of the wing must meet with the same air at the back ...[text shortened]... downward slope, but most of the lift comes from the air under the wing being deflected downward.

Aye! 😞

Originally posted by asplandmatt
A propellor powered plane would send air over the wings.

Not much though.

By the way, real wings work by deflecting air downwards like a helicopter blade. The theory of air traveling at different speeds over the top and bottom of the wing is wrong. Their is no reason why the air sent over the top of the wing must meet with the same air at the back ...[text shortened]... downward slope, but most of the lift comes from the air under the wing being deflected downward.

correct, you just forgot that the air pressure is lower on top, and higher on bottom. Also the prop creates forward thrust.

Originally posted by drumset04
explain plese

Yes.

Originally posted by asplandmatt
A propellor powered plane would send air over the wings.

Not much though.

By the way, real wings work by deflecting air downwards like a helicopter blade. The theory of air traveling at different speeds over the top and bottom of the wing is wrong. Their is no reason why the air sent over the top of the wing must meet with the same air at the back ...[text shortened]... downward slope, but most of the lift comes from the air under the wing being deflected downward.

Did you just make this up? There is REASON why air on the top meets the air on the bottom, Because there is a vacuum, therefore creating faster air, and less pressure. That is why an airplane can stay aloft with zero Angle of Attack. Im getting a degree in Aviation science, and in class I seen simulators that show this, sometimes classes have contests to see who can design a wing with the most lift with no angle of attack. They test this in a wind tunnel.

At zero angle of attack the air still gets deflected downwards as it flows over the top surface of the wing. As I said, their *is* some negative pressure above the wing. If the air *must* meet up again at the back of the wing there would be zero drag. If negative pressure above the wing was the major factor in lifting a plane, all wings would be at zero attack angle (to reduce wind resistance and drag).
In the real world most planes can't fly fast enough to rely on negative pressure alone, so their wings are not at zero attack angle.

Originally posted by asplandmatt
A propellor powered plane would send air over the wings.
By the way, real wings work by deflecting air downwards like a helicopter blade.

Umm.. That's kindof obvious, is it not? That air must go downward for the plane to go up?

And that's not how most airplane airfoils generate most of their lift. A helicopter does this by modifying the pitch of the blades. Most airplanes have relatively level wings and generate lift due to the pressure differences generated above and below the wing. The greater upward pressure below the wing pushes the airplane upward.

BTW, you CAN have an airplane that has completely fixed, completely flat (thickness of the wing is constant at any point) wings. Of course the leading edge of the wing would have to be pitched upwards like a helicopter.....

Originally posted by Sickboy
Umm.. That's kindof obvious, is it not? That air must go downward for the plane to go up?

And that's not how most airplane airfoils generate most of their lift. A helicopter does this by modifying the pitch of the blades. Most airplanes have relatively level wings and generate lift due to the pressure differences generated above and below the wing. T ...[text shortened]... Of course the leading edge of the wing would have to be pitched upwards like a helicopter.....

No. it isn't obvious. 🙂
Imagine a plane with aiirfoils without control surfaces. Can it fly inverted?
The answer is yes.
Could someone tell why this happens? 😛

Originally posted by CrazyLilTing
No. it isn't obvious. 🙂
Imagine a plane with aiirfoils without control surfaces. Can it fly inverted?
The answer is yes.
Could someone tell why this happens? 😛

Of course, by changing it's angle of attack.

That's not why it's obvious. It obvious because to counteract gravity you have to push air downward somehow... Equal and opposite reactions, ya know?

Originally posted by Sickboy
Of course, by changing it's angle of attack.

That's not why it's obvious. It obvious because to counteract gravity you have to push air downward somehow... Equal and opposite reactions, ya know?

May be, but what about the drag?
In theory, the lift should be negative, so, as you've said, you must to increase the angle of attack to compensate.

In conlusion: this means that an airplane in inverted flight should be flying with his nose pointing upward (to increase the angle of attack) and reduce the thrust (to reduce the increased drag).
What is worst, the pilot should must being constantly correcting thrust, and the angle of attack to keep the plane velocity constant.
That no happen. Why?

- J

(BTW, when I said "obvious" I was referring to the post I quoted),

NB: This all happens as consequence of my initial hypothesis 🙂
This is a tricky one, lol.