yes it does. slightly.

For anyone who still doesn't get it:

1) Engines push on wings
2) Wings pull on fuselage
3) Fuselage IS PLANE AND MOVES
4) Wheels come along for the ride as they happily spin underneath

If you prefer to think about people pushing the plane along by its wings WHO AREN'T ON THE CONVEYOR BELT then feel free to do so, because it amounts to the same thing.

EDIT:

I suppose you could also imagine it as a sea plane taking off against the current. The prop provides the forward motion there too.

The conveyor belt takes off.

This is all useless without video.

This fog is getting thicker.



And Leon is getting laaaaarrrrrger.

The explanation is simple:

the problem makes it sound like the plane is stationary and therefore no air is flowing over the wings. This is deceptive, because the plane actually moves along the conveyor belt just like it would the runway.

People always mention the wheel friction could cause any problems there could be but honestly it's the conveyor belt friction and structural integrity that would cause problems. It'd be bloody hardier to build a conveyor belt capable of such speeds compared to building regular airplane wheels. So, it's more likely the conveyor belt would break down, and unless it simply jams suddenly, it could undulate sending a small aircraft flying in a way not quite intended. Not to mention if it ruptured it could totally crush the aircraft in pieces, preventing it from taking off forever.

I really doubt building huge conveyor belts functional at such high speeds is everyday business.

I think it's safe to assume in a hypothetical problem that nothing is going to break.

Let's assume the conveyor belt and the plane's wheels are frictionless (because either breaking doesn't give us the answer we're looking for).

You can either assume the plane is stationary relative to the ground (as the original question implies) or you can assume the plane is progressing along the conveyor belt.

Either way, it doesn't matter as the question is still "Will the plane reach it's minimum Air Speed on the conveyor?". If the plane is stationary relative to the ground, then no it won't.

If the plane is moving along the conveyor (for reasons known only to previous posters in this thread), it will need to overcome it's Stall Speed before it runs out of runway (conveyor).

But on the other hand, I think a small biplane or triplane might be able to take off from the conveyor (stationary or not) as there would be a vast amount of wing area compared to weight, and there would be some prop wash over most of this area (although this would be 'dirty' air, not laminar flow).

Craft that take off using pure thrust and ignore aerodynamics more often than not are "rockets", not aeroplanes.

First you say the friction should be ignored because it's not relevant to the question, yet then you proceed to say the conveyor runway might be too short... Isn't that some sort of a logical error? If we assume the conveyor belt can handle the friction (the airplane wheels certainly can; they should be rated for much more burden than a take-off requires to be safe), then it's stupid not to assume the conveyor belt would as well be as long as needed for a take-off.

Engines push wings.
Wings attached to plane.
Plane is pushed forward.
Conveyor belt is irrelevant.

Didn't bother to read most of the replies, but as mentioned, if the conveyor belt isnt going fast enough to keep the plane in one spot, it will take off. If the plane does not move forward on the conveyor belt, it will not take off. You can have all the thrust imaginable but with no movement comes no lift.

Sigh.

Of course there is no lift with no movement. But the conveyor belt does NOT PREVENT THE PLANE FROM MOVING.

Imagine holding a toy car on a supermarket conveyor belt. No matter how fast the conveyor belt is moving, you can still slide the car forward or backward at will.

MARTYN. ANGRY.

DETTY SMASH.

Then start over and read, because you just ignored like 50 explanations about why you're wrong.

You know, most planes have powerful enough jet engines that they'd probably be able to take off even with the brakes on and the wheels chucked.

I have to take that one back I'm afraid.

Had a quick look at:
http://www.airliners.net/discussions/tech_ops/read.main/136068/

The wheels/conveyor act as a frictionless system under the aircraft and the thrust is against the air, so yes it will take off.

Ofcourse it'll take off.

In my mind it's a harrier.

Well, I have to agree with everyone. The plane would take off. However, I think they might have problems with this on Mythbusters. And I suggest everyone watch it so we can end this thread with a definite answer.

There already IS a definite answer. This is not a philosophical question, or advanced quantum mechanics, it's basic physics.

Yes, but the only true law is Murphy's law;)

No, no. It's NII

Oh, and we need a physics101 smiley NOW.

I can imagine all sorts of problems with building a conveyor belt such as the one described in the problem. If it so happens that the mythbusters fail to make the plane take off, it's because their budget was too small or the time frame for shooting was too short.

I'm not clicking this thread anymore because I might start stabbing people.

I understand why and how the plane will take off. I understood even before I made my post. What I misunderstood was the question, exactly as Freelancer described. I thought this was another one of those stupid hypothetical physics questions where impossible things are assumed possible, such as the conveyor causing the plane to remain stationary.

Also, I'm willing to bet the Mythbusters screw it up. Their show has been pretty bad for the last season or two. I stopped watching it regularly.

This is :science:

Hold on, let's get the premise straight.

The plane is on a conveyor belt. The plane is going forward at x metres per second. The conveyor belt is going backwards at x metres per second. To an observer on the ground (or someone sitting in the plane), the plane remains stationary. Right? This is how I understood the problem..

That would only be true if the wheels exerted a force on the rest of the plane. The wheels on a plane's gear are not part of any drive system, they just spin freely. In fact, in a frictionless system, the wheels would spin and the plane would stay stationary. Until it turns on its engines, that is, and then it would move forward.

Imagine it this way. A plane is flying through the air with its landing gear down. Let's say there are three wheels on this plane's gear. All of a sudden, three flying gremlins fly up under the plane and start spinning the wheels backwards.

Is the plane going to fall to the ground?

No, to an observer it would look the same as if the plane was on a normal runway. The only difference is that the wheels are spinning more quickly on the plane that is on the conveyor.

I'll have to remember this the next time somebody doesn't understand.

In any case, I think it's pretty telling that nobody on the "plane doesn't take off" side is willing to put their money where their mouth is and take me up on my bet

Urgh. I wouldn't consider any conclusions made by Mythbusters to be definitive answers. The show might be good for a laugh, but it always comes down to "lets build something that vaguely represents what we should be trying to test."

:science:

You got my hopes up.

I agree, Jin, especially recently. The first two seasons were pretty solid, though. I think they did a good job on various firearm myths.

Simply, a plane is not like a car. If a car was on a conveyor belt going at a certain speed while the conveyor belt was going in the opposite direction at that speed, the car would appear stationary. This is because a car uses it's wheels to provide forward thrust in direct contact with the ground.
This is not the case with a plane. The wheels on a plane are only to reduce friction between the plane and the ground, the wheels provide absolutely no thrust. Completely forget about the wheels on a plane for this problem. The forward thrust is provided by the propellors/jet engines. Since the engines are pushing the air backward (thus pushing the plane forward) The plane will take off on a conveyor belt. It's because the plane is pushing against air for thrust, not the ground.

That's a pretty good analogy, although a very heavy current will push on the plane. Probably not enough to inhibit takeoff, though.

Anyone ever hand-launch an RC plane?

I'm loving your Gremlin analogy too Far better than mine

The plane flies because of the air speed over the wings.. adding a conveyor belt under neath the plane will not accelerate this process