A plane on a runway, how smart is r3vlimited?

[LINUS]

Without doing any research, I'll shoot from the hip.

Plane no fly = treadmill setup. landing gear rotation has absolutely nothing to do with lift. air around the wings isn't moving so lift wouldn't be generated.

Plane fly = treadmill was actually a wind tunnel. then you would have air moving at unequal speeds on each side of the wing, producing lift.

[erik325i]

The treadmill isn't accelerating and decelerating everytime you tug on the string is it - unlike the question stated. Nice try Mike.

That doesn't matter.
Even if the treadmill were to increase speed when you tugged on the string, the car wouyld still be pulled forward. The wheels are free spinning (just like the wheels on a plane)

-Erik

[Rigmaster]

Well, then the question is mis-stated or the setup is misinterpreted.

It's a moot point really- because I think everyone would agree that:

1- if the plane is allowed to move forward- it will take off provided it moves fast enough to attain the amount of lift needed to take off.

2- if the plane is not allowed to move forward, it will not take off.


It all boils down to your individual interpretation of the original set up.



Bret

[Dave]

I have yet to go to an airport that had a conveyor belt for anything other than moving bags around . . .

Unless you count those moving walkways.

[Erick]

Without doing any research, I'll shoot from the hip.

Plane no fly = treadmill setup. landing gear rotation has absolutely nothing to do with lift. air around the wings isn't moving so lift wouldn't be generated.

Plane fly = treadmill was actually a wind tunnel. then you would have air moving at unequal speeds on each side of the wing, producing lift.

Yes, exactly my thoughts. I dont buy the explanation that trent posted. Without some sort of headwind, there is no way lift could be generated.

[Mastrcruse]

The plane will fly. I have said this because I want someone to argue with how in the hell I got that it will fly.
It will fly because of......................................

[Mastrcruse]

Cause Rob Said So!

[erik325i]

Well, then the question is mis-stated or the setup is misinterpreted.

It's a moot point really- because I think everyone would agree that:

1- if the plane is allowed to move forward- it will take off provided it moves fast enough to attain the amount of lift needed to take off.

2- if the plane is not allowed to move forward, it will not take off.


It all boils down to your individual interpretation of the original set up.



Bret

Well, of course it may not be obvious to everyone, but that is the point of the thread. The question is not mis-stated. You just need to think about it...

If it were a car on the conveyor belt, it would stay stationary because it uses it's wheels to drive forward. With the conveyor belt moving backward, it can't move.

In the case of the airplane, the plane uses jet engines to propell itself, so the speed of the conveyor belt is irrelevant. The example Borat stated with the toy car attached to a string on a treadmill is perfect. Even if the treadmill goes the same speed as you are pulling the string, the car will still move forward.

-Erik

[rwh11385]

Sorry, but you are wrong. The conveyor belt is not keeping the plane stationary.
The wheels on a plane are simply there to roll. No power is going though the wheels. All the conveyor belt is doing is spinning the wheels really fast. It has no effect on the speed of the plane.

Imaging a toy car sitting on a dinner table. If you yank on the table cloth, the wheels will spin, but the car will remain on the table. That is exactly the same as the airplane on the conveyor belt.

Even if you turn the conveyor belt to 1000mph, the plane will still be able to take off. You may need to replace the wheel bearings because of the rediculous speed the wheels are spinning, but the plane is still being thrust forward by the jet engines.

-Erik

Bingo. wheels spin twice as fast but the plane is moving forward and takes off.

[808BMW]

I'd call in a bomb threat and ground that bitch, no math, converyor belts, headwinds, or anything involved.

[Erick]

Bingo. wheels spin twice as fast but the plane is moving forward and takes off.

How in the hell? The question says the belt works backwards with the airplane meaning the airplane remains stationary. The wheels spin, but the plane itself.... stays stationary to anyone watching from the outside.

The stationary plane cannot generate it's needed lift... or any lift at all for that matter.

Until someone shows me evidence, I will not be convinced otherwise.

- Erick
PS: If it really WOULD take off... why dont compact planes use these "rollers"? Somehow aircraft carriers still rather bet on the flat grounds.

[joshh]

The thrust of the engines have to make the wheels go forward don't they. The weight of the plane sits on the wheels correct? ......so if the wheels are already spinning as fast as the engines can propel the aircraft forward, the plane will not take off.
The treadmill simulates the power of the engines forcing the plane mass forward.

[SykoBMW]

I don't care, call MythBusters already.

[erik325i]

How in the hell? The question says the belt works backwards with the airplane meaning the airplane remains stationary. The wheels spin, but the plane itself.... stays stationary to anyone watching from the outside.

Erick, you are thinking about it like it were a car.
Just because the belt is spinning backward does not mean the plane is staying stationary. The thrust from the jet engines has nothing to do with the ground.

PS: If it really WOULD take off... why dont compact planes use these "rollers"? Somehow aircraft carriers still rather bet on the flat grounds.

Putting a plane on a huge conveyor belt would not be of any benefit. The plane would still need the exact same amount of runway to take off, whether or not the ground is moving...

-Erik

[LINUS]

Well, of course it may not be obvious to everyone, but that is the point of the thread. The question is not mis-stated. You just need to think about it...

If it were a car on the conveyor belt, it would stay stationary because it uses it's wheels to drive forward. With the conveyor belt moving backward, it can't move.

In the case of the airplane, the plane uses jet engines to propell itself, so the speed of the conveyor belt is irrelevant. The example Borat stated with the toy car attached to a string on a treadmill is perfect. Even if the treadmill goes the same speed as you are pulling the string, the car will still move forward.

-Erik

Maybe my interpetation of the setup is distorted but the core basic theory I base my "No fly" answer on is this:

The two forces at work here are the conveyer belt in one direction, and the jets in exactly the opposite direction to match speed.

You can fire those jets as fast as you want, but there is no air movement around the wings. No air movement = no lift.

Conversely, if you put the same plane in a wind tunnel and generated wind in sufficient volume and directly at the plane, you could generate lift without even firing the jet engine. You could tether the plane to limit movement from the stationary point to keep the plane in the wind current, and it would hover in that spot as lift was being generated - and you wouldn't need the turbine.