Plane vs. Conveyor belt.......old but interesting

[Torqueless]

So I'm sure a lot of people have heard the question...

A plane is standing on a runway that can move (some sort of band conveyor). The plane moves in one direction, while the conveyer moves in the opposite direction. Can the plane take off?

I wanted to see what the 1addict community thinks.

[Oregon]

Depends on the speed of the plane and conveyor and assuming the referred-to directions are opposite. Should the conditions amount to zero air-speed for the aircraft, the aircraft stays on the ground.

[Torqueless]

you can assume the conveyor move's at the same speed as the plane in the opposite direction if you want.

[plexiglass]

Plane will take off. The wheels are not the driving force of the plane. The thrust from the props/jet move the plane.

[1ster]

Originally Posted by plexiglass

Plane will take off. The wheels are not the driving force of the plane. The thrust from the props/jet move the plane.

But there's no speed differential between the wings and the surrounding air, which remain stationary relative to one another, so how does it get any lift?

[plexiglass]

The wheels are not driving the plane forward. The thrust from the props/jet are. If it helps to imagine take the wheels off the plane and put ski's on instead.

Here's another question. The top of tank tracks are moving at 20mph. How fast are the tracks moving on the bottom?

[JohnL135I]

no, plane will not take off.... there's no air to create lift over the aircraft. Now, is there a severe headwind, in excess of 150mph

[plexiglass]

The plane will take off......unless the I don't see that Torquless means that the planes engines are not running...

[JohnL135I]

Originally Posted by plexiglass

The plane will take off......unless the I don't see that Torquless means that the planes engines are not running...

If the plane's engines, either jet or props.. they provide thrust to move the jet.. As the jet increases speed, airflow over the wings provides the lift.

Now, if the conveyer belt below the jet is matching the increase in speed... then no lift will be created. The aircraft is not moving.

Its like running on a treadmill, does not matter how fast you run, your not moving forward through the air.

[JohnL135I]

Also, think of a jet airplane when it does an engine run. MAX power on the jet engines, however brakes are set. Plane is not moving....hence no lift.

Same thing if its on a conveyer belt. Yes, wheels will be spinning, jet engines at max thrust, but still no lift.

[plexiglass]

The



Plane


will


take


off



and NO AND THEN.....

[JohnL135I]

How?

[USC2000]

The plane will not take off. There is no air flowing across the wings to create lift.

[Torqueless]

Damn, plexiglass figured it out on the first page... oh well good job

he's exactly right, the power isn't transmitted through the wheels like on a car, the entire plane is thrust foward by the engine regardless of how fast the conveyor moves in the opposite direction. The plane will take off. But you might lose your tires with all the heat generated by the wheels spinning so fast so landing could be a problem.

[JohnL135I]

Originally Posted by Torqueless

Damn, plexiglass figured it out on the first page... oh well good job

he's exactly right, the power isn't transmitted through the wheels like on a car, the entire plane is thrust foward by the engine regardless of how fast the conveyor moves in the opposite direction. The plane will take off. But you might lose your tires with all the heat generated by the wheels spinning so fast so landing could be a problem.

How is the plane moving forward if the wheels are spinning on the conveyor belt, thus not allwong it to actually TRAVEL forward?

[ichiban]

deathnote!

[Oregon]

Originally Posted by plexiglass

Plane will take off. The wheels are not the driving force of the plane. The thrust from the props/jet move the plane.

Duh! Damn box...

[JohnL135I]

figured it now......duh!

[Sherifftruman]

Why are people assuming that because the runway is moving that all the air above it also moves? This is simply not true. Sure, the air molecules touching the runway will move and the next area of molecules will be moved a little less by the first and so on, but the further away it gets the slower the air will be (and within inches or maybe a foot, the movement will be effectively zero) and the plane will definitely take off.

[Madjack]

The amount of air that the props is moving would not provide enough lift for a plane to generate lift. If the props could do this, there would be no reason to have wings any larger than the props. Also, think about where the thrust of a jet engine goes....behind the wings. So, this is not generating any wind to the plane, but yet it still flys.

The only way this plane is getting off the ground is if there is more air moving under the wings than over, thus providing the necessary lift.

If you look at the plane from the side, there is no movement since the conveyor belt is negating any of the effects of the props/engines. Since there is no forward movement, there is not enough air moving over the wings to generate the necessary lift for flight.

This plane is staying on the ground and wasting gas.

[Templedogg]

NO Motion no lift. Period. Regardless of trust if the plane is stationary (like on a treadmill) it will not have any forward motion, therefore NO lift.

Good site for explaining this. http://www.grc.nasa.gov/WWW/K-12/airplane/lift1.html

[mergen]

Well, assuming you need, say, 100 knots airspeed to get airborne, if your wheel bearings and tires can endure an apparent 200 knots, you should be able to get off the ground. During takeoff roll, the plane will proceed through the air at 100 knots and the runway will proceed in the opposite direction at 100 knots. It may take more time and a longer field to achieve this condition since there will be more wheel friction to overcome. If your tires or wheels give out before that, you may have a big problem. The only way the plane would sit still on the field would be if the increase in bearing and wheel friction were huge enough to offset the forward thrust. Not likely until they started to fail.