# Will a plane take off on a conveyor belt?

Discussion in 'Physics & Math' started by w00t, Jun 12, 2007.

1. ### w00ti'm with stupidRegistered Senior Member

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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?

3. ### AbsaneRocket SurgeonValued Senior Member

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Yes. I cannot count how many times this question has been brought up.

Edit: oh, you added the part about the conveyor belt matching wheel speed. In that case, no.

5. ### mikenosticStop pretending you're smart!Registered Senior Member

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Uhh, no. The plane needs airspeed. The wings need wind flowing above and below them in order to generate lift.* Now if you put it in a giant wind tunnel and had it blow the wind out at the same knots as the airspeed that the plane needs to rotate (off the runway) then yes, it would lift off the ground.

*You never had any type of aviation or aerodynamics classes did you?

7. ### mikenosticStop pretending you're smart!Registered Senior Member

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I took it as the OP meaning that the plane is stationary. But if he means the plane was moving, then yes. The catapult on an aircraft carrier is the same principle.

8. ### w00ti'm with stupidRegistered Senior Member

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My answer would be no, the plane will not take off due to the absence of lift. Just needed some smart people to confirm it.

9. ### AbsaneRocket SurgeonValued Senior Member

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See my edit.

But usually I hear the question like this:

http://txfx.net/2005/12/08/airplane-on-a-conveyor-belt/

The answer to this question is YES.

But I just read here that giving the OP's orginal assumptions, then it too can lift: http://www.straightdope.com/columns/060303.html

10. ### AbsaneRocket SurgeonValued Senior Member

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When I read that last page that I provided... it really depends on what you assume is also true of the question being asked. Depending on your own assumptions, the answer is yes or no. I answered "no" at first because I assumed a perfect system in which the conveyor exactly matches the force generated by the plane at every moment.

11. ### w00ti'm with stupidRegistered Senior Member

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I agree with you. But this perfect system cannot be attained by experimental purposes, only in theory.

12. ### D HSome other guyValued Senior Member

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This stupid topic keeps reappearing, dressed in slightly different clothes. A plane, unlike a car, does not propel itself by applying torque to the wheels. Of course it takes off.

The goal is obviously is to make the plane always stationary with respect to the ground. The above does not accomplish said end. The conveyor will simply move faster and faster as the plane gains ground speed.

Suppose the conveyor were coated with ice and the plane had friction-free skates instead of wheels. What would happen? The speed of the conveyor is irrelevant. An ideal wheel operates similarly to the skate on ice.

13. ### AbsaneRocket SurgeonValued Senior Member

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Well even in real life, we can build a conveyor that will equally match the plane's forward force so that it won't take off. One can do this by first making the treadmill just a little too fast (so the plane is going backward) will accelerating. Then we adjust the speed ever so slightly until there is a perfect match. Then the plane never takes off.

D H, I guess I am considering that the wheels are not 100% freespining and that any friction on the ground will, in some way, affect the plane.

14. ### w00ti'm with stupidRegistered Senior Member

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Suppose said conveyor does manage to make the plane always stationary with respect to the ground. What then?

15. ### leopoldValued Senior Member

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oh shit.
another "airplane on a conveyorbelt" thread.

the answer for the umpteenth time is YES the airplane will take off.

16. ### AbsaneRocket SurgeonValued Senior Member

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Maybe you mean a plane with no wheels and the plane on the ground has a coefficient of friction equal to 0.1. Then I would say it's very possible for the plane to remain stationary.

I was assuming that there was sufficient friction between the wheels and the plane. But with the conveyor going the "same speed" as the plane, I guess this isn't possible. Now it is possible if you make the conveyor go much faster than the plane.

17. ### temurman of no wordsRegistered Senior Member

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Wheels of an airplane is not active, the airplane gets its speed by pushing the air. So it does not matter what is happening with its wheels and conveyer, as long as the airplane is standing and there is not much friction, airplane will take off.

18. ### OliHeute der Enteteich...Registered Senior Member

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It gets lift by moving through the air.
If there is no airflow over the wing (usually caused by forward motion) then there is no pressure differential to cause lift.

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20. ### 15ofthe1935 year old virginRegistered Senior Member

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You didn't specify if it was an African or European conveyor belt.

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:roflmao:

22. ### leopoldValued Senior Member

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the first post is a little confusing.
it was stated that the belt moves backwards at the same speed the wheels move forward.

now, if the are plane doesn't take off the the wheels do not move hence the belt remains stationary.

for those that say the plane doesn't take off what is it that is holding the plane stationary?

23. ### nietzschefanThread KillerValued Senior Member

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I guess it could be confusing.

Basically I read it as conveyor belt acts like a frictionless surface(just moves as fast as the wheels turn no matter what speed).

With no wind(some a/c CAN take off if given enough wind), would would need a harrier jet or similar type. VTOL