will it take off ?

Question

Imagine a plane is sat on the beginning of a massive conveyor belt/travelator type arrangement, as wide and as long as a runway, and intends to take off. The conveyer belt is designed to exactly match the speed of the wheels at any given time, moving in the opposite direction of rotation.
There is no wind.
Can the plane take off?

Answer 1

The speed of the wheels means nothing. They're just there to keep the bottom of the airplane from dragging on the ground.

A fixed wing airplane must have air moving over (and under) the wing's surface to produce lift.

In your scenario, there is no wind, but the thrust from the engines will impart forward motion to the aircraft to move the wings through the air and allow them to create lift. Your treadmill may add a bit of drag to the wheels as they roll backwards but the airplane should still move forward, and if the airplane can accelerate to reach lift-off speed, then it can take off and fly.

Answer 2

If you imagine the situation, you start with a stationary aeroplane at the base of this conveyor. Let's assume the wind is calm and the air around the plane is motionless. You power the engines up to full power and by Newton's 3rd law of motion this will result in the plane's acceleration relative to the stationary ground. However, if the conveyor always matches the speed of the wheels, the ground is no-longer stationary and as it is moving at the same speed in the opposite direction then the aircraft's speed relative to the air is now zero.
Here lies the problem. In order for a plane to fly, there needs to be a pressure difference between the top and bottom surfaces of the wing. This is achieved by moving air passing over the carefully designed shape of the wing - known as an aerofoil. To amplify the resulting force pushing the wing upwards, the pressure difference needs to be increased. This is done by increasing the speed of the air passing over the wing. To do this, you need to have the plane moving quickly relative to the air.
In your situation the aircraft would not move at all, so there would be not air flow over the wing, so no pressure difference would be created, so no force on the wing, so NO LIFT.
In answer to your question - no it would not fly.

Answer 3

Elementary my Dear Watson - It would not take off. Had you studied Brenouli's Theorum you would have kept in mind that the plane will never have a forward movement and will stay stationary at the place where it was - only the wheels will rotate. The wings of the planne are so designed that when they move forward they cut through the air which has to flow like a stream over the wings. The upper surface of the wing is humped and tapers off at the edge away from the front. The lower side of the wing is almost flat. As such the wind has to travel over a longer distance when it flows over that upper surface and so it travels faster than the stream of air under the wing which has to travel less in the same time on the underside. As is commonly known Less Velocity means higher pressure and vice versa. So as the plane cuts through the wind - the upper surface has low pressure and the lower surface has a higher pressure which produces what is commonly called lift in elementary aeronautics. So the plane experiences lift which causes it to rise and at a particular velocity the lift is so great that it lifts the plane off the ground. Then the thrust provided by the propellers of the jet (engines which operate on the basic third law of Issac Newton ) causes the plane to continue its forward motion and the plane rises and flies away.

Answer 4

The answer is definitley NO! Stupid is wrong. Regardless of how much thrust is applied, if the conveyor matches the rotation of the wheels the plane will not move. It would effectively be the same as leaving the brakes on. If the plane cant move forward, lift is not generated and thus will not fly.

Its exactly the same as a car on a rolling road. It could have its wheels doing 100mph but the car wont be going anywhere will it.

Answer 5

Doesn't a runway move in the direction opposite to wheel rotation then ( in respect to the planes movement)

As no drive from the engines is transmitted to the wheels, and provided the brakes are off, the aircraft will move forward powered by the thrust generated by the engine acting upon the air around it.

All you are doing by using this belt system is speeding the rotation of the wheels up during the takeoff sequence, through air speed will remain the same, and so will the lift generated.

The aircraft creates it own 'wind'.


*****************************************************************

P.S. just tried this to prove a point using a model aircraft on a belt sanding machine.

Had to hold the aircraft initially to overcome the drag of the wheel spindles, but the motor had more than enough power to achieve take off.


********************************************************************

Nuvver little point that everybody seems to have forgotten - the engines transmit their power to the air surrounding it ,NOT to the wheels - therefore airspeed will be related to the thrust generated against the surrounding air, less the small amount of drag from the free wheeling wheels.

Answer 6

Too many people here think airplanes work like cars. Jetdoc and others are correct. A plane doesn't care about the speed of its wheels, just the thrust of the engines. Once the engine thrust overcame what tiny effect the moving surface had on the wheels the plane would move forward and take off when it had enough airspeed. The belt sander experiment proved that.

Answer 7

No. The 'lift' under the wings is created by the wings travelling through the air. The air passing over the top of the wing has further to travel than the air passing under the wing and is therefore less dense, so the wing rises. This lift cannot be created if the wing is not travelling through the air. However the plane could take off if you use a huge fan to blow air past the wings at the right speed.

Answer 8

No. An aeroplane creates lift from air traveling over its wings. The aircraft has to go at high speed to take off because at this speed the air travelling in the opposite direction will create the required lift. If the plane is not moving through the air it will not lift off. However if you don't actually want the aircraft to move, you could (hypothetically) stick a turbofan in front of it, or at least its wings. So long as the air travels over the wings at the required speed, the aircraft would lift off from the ground.

Answer 9

My answer is Yes, despite the No's around here.

It doesn't matter whether the wing and the wind is moving, as long as there is adequate relative wind flow over the wing, there will be enough lift for the plane to rotate. But the thing is afterwards if no further thrust is produced by the plane, it will just all back onto the ground.

Answer 10

Not a chance. 0%. The aircraft will never leave the ground as it requires an airflow over and under the wing to produce lift. No airflow, no lift. The aircraft will be stationary in relation to the air. You would simply be running the engines, wasting fuel and tyre tread. In answer to those who say the aircraft would still move forward, Thrust (from the engines) would equal drag (from the conveyor belt) and so there would be no resultant force, ensuring that the aircraft would stay perfectly still.