Debate: Will this plane take off?

[Vashthestampede]

A plane (747 passenger jet) is sitting on a runway that can move (some sort of band conveyor). The plane moves in one direction, while the conveyor moves in the opposite direction. This conveyor has a control system that tracks the planes speed and tunes the speed of the conveyor to be exactly the same (but in the opposite direction).

The question is:

Will the plane (747 passenger jet) take off or not?

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I am pretty sure I know the answer with certainty after reading about 30pages of arguing about it on other forums so I'm gonna stay out of this, but what do you guys think will happen?

[squirrel]

No the plane will not take off. Air must be flowing over the wing to create the pressure difference between the top of the wing and bottom of the wing that makes flight possible. With the plane stationary, becasue the treadmill matches the speed of the plane, air is not flowing over the wing. So no take off.

[RandyA]

yeah what ^he said ;D

[Vashthestampede]

There is an aspect to this you guys are missing.

[wartang]

i would also have to say no for a nother reson a 747 needs to move forward it cant hover so when you put it on the rotory disk spining in the opisit direction of the drection of travel it stays stationary no forward movement no flight

[Gen]

Yes, it would be possible for the plane to take off.

The thrust of the engines would propel the plane forward. The conveyer belt is moving in the opposite direction, but since the propulsion of the plane has very little to do with the contact of the wheels to the ground, the plane would still move forward. So, the plane could acheive enough "air speed" to create lift and take off. Its "ground speed" would be greater since the belt is moving in the opposite direction.

[Ety]

Yes it would take off. It doesn't matter what the wheels are doing as long as the engines are pushing it until it can take off.

[Jackson]

I should have read some posts first. At first I thought, no way, it's just going to sit still but once you realize that the forward motion is not coming from the wheels but the jet engines, then it is possible.

[Nowhere]

Interesting question. I must think on this before posting a final answer.

[ferkjace]

I think it would take off...But it hurts my head.

Wouldn't that just make the wheels spin faster...not actually keep the plane still?

Yeah...That's my answer, for good or ill. The conveyer couldn't keep the plane in the same place: the force that moves the plane comes from the air pushing back on the jets, not from the ground pushing back on the wheels.

[Kreeper X]

Keep in mind that even with the Jets running, the treadmill is running in the oposite direction. So what's going to happen is that the jet engins are going to suck air in and thrust it out the exhaust, but since the plane isn't moving, there is no air flowing over or under the wing at all. The Jet engines only provide the forward movement to the plane that causes the wing to interact with the air and generate the lift. So the Jets are pretty much meaningless here.

Now on the other hand, the moving treadmill IS going to generate a flow of air below the wing since it is moving at a rapid speed, so as the plane isn't moving, the air above the wing is going to be moving slower than the air below the wing by default which COULD generate lift.

The main problem is again that ift is generated by the inteaction of the wing and the air rushing around it.

So my answer is going to be no. The lift that MIGHT be generated by the treadmill moving in the oposite direction of a jumbo-jet at full throttle wouldn't be enough to get the plane off the ground, though it may generate motion that the wings might experience some lift. It won't allow the plane to take off.

[Kozz]

My dad is an aircraft mechanic on corporate jets and he says no.

[RandyA]

if you run on a tread mill you dont feel as much, if any wind as you would if you were running down the street. granted the conveyor belt for the plane would be moving at a much faster speed. so it would create some wind but i doubt enough to create enough lift to launch the plane . unless you had the conveyor belt spinning at an incredible speed. the jets act much like your feet. they propel you forward. on a treadmill you are not actually moving forward. so i still say no

[Jackson]

I'm going to ask my physics teacher. But think of it this way, put someone on a skateboard on a treadmill. Then, standing off the treadmill, push him forward. You'll be able to do it, the wheels will just be moving faster. That's like a jet engine. The thrust does not rely on the ground, just on the air around it and Newton's "for every action there is an oppsite and equal reaction."

[RandyA]

but eventually you'll run out of treadmill. if you push the skateboard, then the skateboard is going faster then the treadmill.

originally posted by Vashthestampede

This conveyor has a control system that tracks the planes speed and tunes the speed of the conveyor to be exactly the same (but in the opposite direction).