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#1
Discuss here and keep our demotivational picture thread going strong!


I say it wont as the whole idea of a plane taking off is that it picks up lots of speed and then takes off.

Discuss.
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#2
It's the air going through the turbines/under the wings that eventually lifts it, which wouldn't happen on a treadmill.

i could be very wrong though...
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#3
they did this in Mythbusters, i can't remember what the verdict was.
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#4
Lift is gained from the wind passing over the wings of the craft. Therefore, a plane on a treadmill would not take off.

Simple Physics FTW!
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#5
Yes it will. I don't remember exactly how, but mythbusters tested it on a small scale and with a real plane. You can probobly find the video online somewhere.
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#6
Of course it won't take off. As it rests in position, air particles won't collide with the spoilers on the wings at high speed, thus not resulting in an upwards force lifting the plane.

What is the point of this again?
#8
i don't think the treadmill would have much effect, i mean it's not like the planes wheels are providing the forward motion, so the plane would just go forward anyway as if it were just on a regular runway
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#9
Quote by metacarpi
Lift is gained from the wind passing over the wings of the craft. Therefore, a plane on a treadmill would not take off.

Simple Physics FTW!


the propeller moves air no?

guess depends on how fast it can get it moving in relation to staying still (i.e. the plane is not already travelling at 70km/h)


I want to seem them try it with a solid fuel rocket booster on a plane
Last edited by seljer at Aug 7, 2008,
#10
Quote by tobysaurus
It's the air going through the turbines/under the wings that eventually lifts it, which wouldn't happen on a treadmill.

i could be very wrong though...

You are very right though.
#11
Quote by Minderbinder
Yes it will. I don't remember exactly how, but mythbusters tested it on a small scale and with a real plane. You can probobly find the video online somewhere.


Yea, I remember that.
They used some long thing, some kind of carpet, that they pulled in the opposite direction of the plane.
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#12
Quote by seljer
the propeller moves air no?


But the air molecules moving around the wings is what provides the lift, not the propellers.
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#13
Quote by tobysaurus
It's the air going through the turbines/under the wings that eventually lifts it, which wouldn't happen on a treadmill.

i could be very wrong though...


Nope, you're right.

The things you need to achieve flight are lift and thrust (preferably forward thrust).

So, an aeroplane simply running on a treadmill or some similar kind of conveyer belt will not take off - it's only the wheels that are turning, and that doesn't affect the speed of the wind going past the wings. Basically, you must have air going both underneath and over the top of a wing for it to generate lift.
#14
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#15
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Nope, you're right.

The things you need to achieve flight are lift and thrust (preferably forward thrust).

So, an aeroplane simply running on a treadmill or some similar kind of conveyer belt will not take off - it's only the wheels that are turning, and that doesn't affect the speed of the wind going past the wings. Basically, you must have air going both underneath and over the top of a wing for it to generate lift.


airplanes don't have motors turning their wheels
#16
Quote by seljer
airplanes don't have motors turning their wheels


No, but the propellers provide forward motion, moving the wheels.

The treadmill would counter this, meaning there is no overall thrust, meaning no flight.
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I'm losing my grip, 'cos I'm losing my fingers.
#17
The plane would already have to be moving.
If the plane would not already be moving, it would fall off the treadmill.
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#18
A plane on a treadmill WOULD take off, regardless if there was a treadmill or not.

Because - think about it - what is the treadmill actually doing? If the plane is staying still, then the engines are still relative to the ground. The engines will still push the plane forward, gaining ground speed, and it will take off - all that would be different is the wheels would be going twice as fast. The engines still push the plane forward along the "real" ground, regardless of the treadmill or not.
#19
Right, this can mean 2 things.

The airplanes wheel brakes could be on, meaning it will be standing still on a giant treadmill wich is moving it though the air, giving it lift from the air hitting the wings etc. This way it will take off.

If the airplanes wheel brakes are off then the treadmill will move and the airplane would stay still, meaning the wheels will move and there will be no air hitting the wings etc to give it lift.

So the answer is, yes and no, depending how you look at it.
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#20
It makes it easier to take off.
The wheels don't provide thrust remember, the propeller does.
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#21
I'm pretty sure it wouldn't lift off unless the engines were directed down in some way. Pushing air behind you wont pick you up unless you have the upward pressure of the wind on the wings.
Have you ever gotten lift from farting while standing? I never have.
If the engines were pointing slightly downward on the other hand, there would be lift, because the air passing through the turbines/propellers would be exerting force on the ground. Newton's laws say that that would provide an upward force on the plane; possibly lifting it enough.

*edit* This is of course, assuming that the treadmill is keeping the plane in a "stationary" position on the ground.
Huh?

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Last edited by Eagerod at Aug 7, 2008,
#23
Besides, I've watched that mythbusters thing, and it's total bs. The point was supposed to be the aircraft staying IN POSITION while it "virtually" has take-off speed. At mythbusters the plane (not the small miniature one, nor the bigger plane) was actually resting in position.
#25
Quote by Eagerod
I'm pretty sure it wouldn't lift off unless the engines were directed down in some way. Pushing air behind you wont pick you up unless you have the upward pressure of the wind on the wings.
Have you ever gotten lift from farting while standing? I never have.
If the engines were pointing slightly downward on the other hand, there would be lift, because the air passing through the turbines/propellers would be exerting force on the ground. Newton's laws say that that would provide an upward force on the plane; possibly lifting it enough.



Engines arnt pointed down, ther pointed straight. All they do is propel air through them making movement and air passing under wings. The wings do the lift.
Some people may call me tasteless, but i personally think Rickenbackers are the ugliest basses to ever land on this earth.
#26
1. If we're assuming there's no friction caused by the wheels on the treadmill, then Newton's Third Law (for every action, there's an equal but opposite reaction) says the plane should move forward in response to the thrust of the jets.

2. Planes generate lift by movement of air over the wings; since the jets are providing forward movement, the plane should eventually reach lift-off speed.
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#27
Quote by brokenbassboy
Engines arnt pointed down, ther pointed straight. All they do is propel air through them making movement and air passing under wings. The wings do the lift.


Which is why I'm saying that the only way they would provide lift is if they were pointed down, and since they aren't, there should be no lift applied to the plane from any direction because the air around the plane is stationary. I'm pretty sure it's the air around the plane that gives it lift, and the air being pushed by the engines gives it the propulsion.
Huh?

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#28
It will take of, since it's the propeller that drives the plane forward, and the wheels just "hang on", thus resulting in the plane going forward at normal speed, independent of the treadmill.
#29
Quote by Eagerod
Which is why I'm saying that the only way they would provide lift is if they were pointed down, and since they aren't, there should be no lift applied to the plane from any direction because the air around the plane is stationary. I'm pretty sure it's the air around the plane that gives it lift, and the air being pushed by the engines gives it the propulsion.



The air going past the plane provides the lift, darling, not the air moved by the engine. The engine merely gets the plane moving.
#31
For everybody who says no, here it is happening:

http://www.youtube.com/watch?v=0ul_5DtMLhc

They did it with a toy plane, and a guy in an actual pane. So we can stop arguing now.

Quote by webbtje
http://www.youtube.com/watch?v=0ul_5DtMLhc

Should point out that since the plane is actually still moving, that test is inaccurate.


Oops, you were way ahead of me. But of course the plane was moving, it was on a conveyor belt. Conveyor belts move things. That's what this whole discussion is about.
Last edited by Survivalism at Aug 7, 2008,
#33
Quote by bananaguitar
It will take of, since it's the propeller that drives the plane forward, and the wheels just "hang on", thus resulting in the plane going forward at normal speed, independent of the treadmill.


EXACTLY!!!

You put it way better than I did
#34
HEY! SCIENTISTS!

A full size plane will not take off on a treadmill.

Here's why:

Engines provide thrust, not lift.
Wings provide lift.
The wheels provide the ability to move.

So, the engines go really fast, they make the plane go forwards on it's wheels, and because it's moving forwards, air is now passing over/under the wings, creating lift!

And LIFT, as we all know, is what makes the plane go UP... If the plane were on a treadmill, there would be no air passing over the wings. Therefore there would be no LIFT!

In simple enough english for you? It might work on a small scale but not on a life size model.

Also, this theory only applies to xTOL aircraft, not VTOL. (xTOL: Take off and landing. Replace the 'x' with an 'S' to stand for 'short' in the case of aircraft that do not need a large amount of space to take off with. VTOL: Vertical take off and landing. Read - JUMP JETS.)
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Last edited by Jcore44 at Aug 7, 2008,
#35
Air flows over wing. Aerofoil is shaped (moreso when flaps/elevators are down) so that there is a difference in airspeed between the top and bottom of the wing. For airplanes, usually the foil will be shaped so that the air flows faster on top of the foil and slower underneath. The faster the air flow the lower the air pressure and vice versa (Bernoulli's principle).

Simply speaking high pressure air wants to go to low pressure air. Slower air travelling below the wing wants to get to the same pressure as the faster travelling air on top of the wing creating lift.

It's basically the opposite effect of a spoiler on a car.


edit: in relation to OP. Yes it's possible depending on windspeed and weight of the plane/model.
Last edited by goony at Aug 7, 2008,
#36
Quote by solid_moose


2. Planes generate lift by movement of air over the wings; since the jets are providing forward movement, the plane should eventually reach lift-off speed.


My point exactly.
Some people may call me tasteless, but i personally think Rickenbackers are the ugliest basses to ever land on this earth.
#37
Quote by webbtje
The air going past the plane provides the lift, darling, not the air moved by the engine. The engine merely gets the plane moving.


Which is what I said, just using different words.
Huh?

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#38
Quote by Eagerod
Which is what I said, just using different words.


OK, I need to read through posts more carefully next time

Quote by Survivalism
For everybody who says no, here it is happening:

http://www.youtube.com/watch?v=0ul_5DtMLhc

They did it with a toy plane, and a guy in an actual pane. So we can stop arguing now.


Oops, you were way ahead of me. But of course the plane was moving, it was on a conveyor belt. Conveyor belts move things. That's what this whole discussion is about.


Uh uh. The idea of the conveyer is to equal the speed which the propeller drives the plane at, so the wheels turn but the plane stays static. Here, the plane moved because the tarp didn't go fast enough.
#39
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#40
As I just said:
Quote by bananaguitar
It will take off, since it's the propeller that drives the plane forward, and the wheels just "hang on", thus resulting in the plane going forward at normal speed, independent of the treadmill.

END OF THREAD

Last edited by bananaguitar at Aug 7, 2008,
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