Plane on a treadmill

[The Ston]

A plane is standing on a runway that can move (like a giant conveyor
belt). This conveyor has a control system that tracks the plane's
speed and tunes the speed of the conveyor to be exactly the same (but in the opposite direction).

Will the plane be able to take off?

 

[Dean]

Of course!  A plane's power is not applied to the ground through the wheels, but to the air behind it.

[The Ston]

I'm still thinking about this.

At first I thought not, then I thought that it would be able to, with the wheel speed being twice the forward speed of the airplane BUT the wheel speed has to equal the ground (i.e. treadmill speed) if you consider that the wheels don't slip...er...

*brain a'splode*

I think I need a beer now!  

[pauly75]

But if the plane is stationary, there would be no air moving over the wings to create the lift required to get it airborn.

[The Ston]

Ineed, that's the crux of the matter.  

Even if the treadmill is driven (backwards) at a speed which matches/tries to match the forward speed of the plane, can the plane acheive forward motion, thereby generating air speed over its wings->lift->takeoff ?

[miguel]

But if the plane is stationary, there would be no air moving over the wings to create the lift required to get it airborn.

bingo!  

the only reason a plane needs to move forward at a high rate of speed during takoff is so that air moves over (and more importantly, under) the wings.

the speed of the ground under the plane's wheels is inconsequential (sp?).

[djrussell]

there's actually an option that is available on airplanes that allows it to take off in a tailwind of something like 20-40mph. you'd think it could do that anyway cause a tailwind should push it. it actually decreases the amount of rearward (ha, AFT) airflow over the wings. a plain definitely will not take off if it doesn't have enough airflow over the wings.
now, if you really want to be nerdy about it.... there will be some air that "grabs" the treadmill belt and gets pulled along with it. this is called a boundary level. depending on the roughness of the belt (it'd have to be a LOT), the boundary layer might get thick enough to reach the wings and the plane might take off. as soon as it does take off though, it will exit said boundary layer into still air and crash to the ground.
okay, nerdy quota reached for the day. whew....  

[darkrose]

But if the plane is stationary, there would be no air moving over the wings to create the lift required to get it airborn.

bingo!  

the only reason a plane needs to move forward at a high rate of speed during takoff is so that air moves over (and more importantly, under) the wings.

the speed of the ground under the plane's wheels is inconsequential (sp?).

Wow, this came up on another forum too.  Many, many arguments about this.  I agree with the above statements.  I say we call Mythbusters and put them to the test!  

[miguel]

But if the plane is stationary, there would be no air moving over the wings to create the lift required to get it airborn.

bingo!  

the only reason a plane needs to move forward at a high rate of speed during takoff is so that air moves over (and more importantly, under) the wings.

the speed of the ground under the plane's wheels is inconsequential (sp?).

Wow, this came up on another forum too.  Many, many arguments about this.  I agree with the above statements.  I say we call Mythbusters and put them to the test!  

that's not a bad idea...i love that show!  (and not only because of sexxy Kari Byron...and let's not forget Scottie - a good looking woman with tatts that can weld!)

[Dean]

Mmmmm, Kari.    Her smile knocks me out!

But back on topic...as I said, the treadmill thingy matters not.  The plane's wheels aren't driven!

Analogy:  YOU are on a treadmill, running along.  I come along a give you a healthy shove on the back What will happen?  You'll fly forward!  

So will the plane.

[darkrose]

Okay, but nobody is "shoving" the plane.  It's stationary with no air flow beneath the wings, which is needed for lift.  What if it was sitting in a huge wind tunnel instead of on a conveyer belt?  When the wind speed was great enough to create the correct amount of negative pressure under the wings, then the plane would lift off the ground.

Uh oh, I'm getting pulled into this one....must....resist....urge to......squash.....illogical statements.....

[Dean]

Okay, but nobody is "shoving" the plane.

Yes, the engines are.  Think about the difference between how a car moves forward and how a plane moves forward.  A car is moved forward by the motor turning the wheels, which push the car forward.  The car requires contact with the ground to move forward.  A car can't move forward on a giant treadmill, because the treadmill is canceling out the force that the wheels are imparting to the ground

For a plane, the air is the 'ground.'  The engines don't turn the wheels, they push against the air.  So, to use your example, you would need a windtunnel with enough airflow to balance the amount of thrust from the engines to get the plane airborne yet remain stationary.  In this case, you are only moving the ground, so no force is cancelled out and the plane takes off as normal.

[djrussell]

i think the assumption from the beginning is that the engines are running and 'shoving' the plane. any speed possibly gained from the engines would be accounted for in the speed of the treadmill. no matter how you look at it, no air over the wings, no take off.

[waverider]

If you changed the wheeled plane to a float plane (i.e., on skiffs, no wheels), would anyone's answer change??

[miguel]

If you changed the wheeled plane to a float plane (i.e., on skiffs, no wheels), would anyone's answer change??

nope.  still not enough airflow at the wings.  it's not a matter of the plane's speed across the surface it's resting on...it's a matter of the plane's speed as it moves through the atmosphere.