why is this thread still alive?

This one is for Kramer ( i am using the treadmill example)

IT IS EXACTLY LIKE A GUY ON A TREAD MILL....EXCEPT THAT THE GUY IS ON A SKATE BOARD AND IS PROPELLING HIMSELF WITH HIS ARMS AND HANDS ON THE RAILS....END OF STORY

Here is the relationship breakdowns ....
skateboard=wheels and undercarrage of the plane
guy = plane
arms and hands= engines
rails on the tread mill= air

[This message has been edited by the right one (edited 12/4/2006 3:43p).]

i think some people are refusing to let the plane take off

quote:

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why is this thread still alive?

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Because watching people who are wrong adamantly defending their position is funny.

[This message has been edited by Bighamp03 (edited 12/4/2006 3:42p).]

Bighamp03.........I'll help you help me to understand, how is that??/ ok, I think it's save to assume (because it is fact) that planes rise off the ground because of the lift from the wings. Lift from the wings comes from the different air speeds moving across the wing (ie, no airspeed across the wing, no lift). please tell me where this airspeed comes from?? a plane moves forward due to the thrust making the wheels turn forward, correct?? if the wheels move forward just as fast as the conveyor moves back, then the plans just stays in the same spot, correct, even though the wheels are moving.

bottom line is the plane can't fly if the plane isn't moving forward, the plane isn't moving foward if the conveyor is keeping it still from a permanent frame of reference.

quote:

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IT IS EXACTLY LIKE A GUY ON A TREAD MILL....EXCEPT THAT THE GUY IS ON A SKATE BOARD AND IS PROPELLING HIMSELF WITH HIS ARMS AND HANDS ON THE RAILS....END OF STORY

Here is the relationship breakdowns ....
skateboard=wheels and undercarrage of the plane
guy = plane
arms and hands= engines
rails on the tread mill= air

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And, no matter how fast the belt is spinning, eleventy gagillion MPH, the guy can still pull himself forward. Plane flies.

quote:

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The belt is irrelevant.

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The belt is irrelevant if you assume that the movement of the conveyor belt is caused by the wheels of the plane in a conventional power transfer mode (think gears/friction). It is NOT irrelevant if you consider the conveyor belt as having an external power source with the ability to counteract the forward motion of the plane.

This is the crux of the controversy and why everyone can think they are right and everyone else is an idiot.

For this to work we must have a magic conveyor belt. This is impossible. The situation is impossible. We all agree that IF the plane does not move forward, it does not take off. The question is whether or not the plane moves forward. If it does, then what is the rotational velocity of the wheels compared to the conveyor belt? These must be different if the wheels are ever to leave the belt. If the wheels never leave the belt, how can the plane takeoff?

Nawlins....address please. Sending some people over to get your ring and possibly your diploma

[This message has been edited by CopeIt (edited 12/4/2006 3:48p).]

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BINGO Nothing else needs said

to BigHamp03

[This message has been edited by Old Faithful (edited 12/4/2006 3:50p).]

But if the rails are moving, he can't.

The purpose of the conveyour belt is to counteract the thrust of the engines.

I'm done. I can understand why you'd think differently, but I believe you are wrong. Like I said, I'll take the word of the pilot.

The pilot needs his ring taken also......Kramer, if you have one I will be needing it too.

Come and take it!

first of all, COPELT, great arguement there


second of all, Dad-O-Lot, I agree with you. if the plane does not move forward, it cannot take off. if the plane moves forward, it has to do so with enough speed to produce lift, whatever speed that is, I don't know, but that's not the concern. it was my understanding that the conveyor belt kept the plane from moving forward. I believe that was the point of the questions.

how can it take off without moving?

Lets just do a little experiment. Anyone want to donate a plane and a bunch of money for me to build a giant conveyor belt?

A plane does not have to move forward to fly.

I've seen (with my own two eyes) a J-3 Cub fly into a strong enough headwind to go backward. Airspeed 48 mph, Groundspeed -5.

the plane is a harrier. Jokes on all of you.

Nawlins, I have already made my arguments...feel free to go back and find them...I am just on this thread to let yall know you are wrong at this point. No need to re-explain.

actually, I re-read the original question, and agree it will fly. But only because of the exact wording...

quote:

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A plane is standing on a movable runway(something like a conveyor) As the plane moves, the conveyor moves but in the opposite direction. The conveyor has a system that tracks the speed of the plane and matches it exactly in the opposite direction.

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If the conveyor "tracks the speed of the plane and matches it exactly in the opposite direction" then I say that means the conveyor is moving at 150 mph (say, south) while the plane is moving 150 mph the other way (north).

So, the wheels are only turning at the rpms equivalent to 300 mph on a stationary runway. They wouldn't explode at that speed (I wouldn't think).

If the original wording had said "tracks the speed of the plane and COUNTERS it exactly in the opposite direction" then I would say the runway was infinitely powerful and fast, and would move as quickly as it needed to to generate enough force by friction through the wheels in order to counter "exactly" the thrust of the engines, so that the plane remained stationary to the ground.

In the first case, it flies, in the second, it clearly doesn't. It's all in your reading of the question and the assumptions you make based on your understanding of it. Re-reading it changed my mind.

kramer is right, lift is produced by airspeed, no airspeed, no lift. airspeed comes from moving through the air. this is done by speed from the thrust. no thrust = no airspeed = no lift.

Goose is also right, a plane does not need to be moving forward, it needs airspeed. if wind along produced enough airspeed, it can fly, but that was not part of the question, even though he is 100% correct.

CopeIt is wrong. yet again, he cannot difute what we are saying except for "you are an idiot, you are wrong."

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

goose, but there is no air movement.

read the link above your last post and you'll see that there is.

someone please put it in dumbass terms for me

I know of no airplanes where the engines turn the wheels. The wheels roll freely along the ground.

The thrust, whether from jet or prop, will move the aircraft forward. Any difference due to a conveyor belt turning underneath will be due to overturning friction in the wheel bearings and will be pretty much undetectable.

Ok, my final post about this, and it sums it all up......

TX AG 88 is correct in what he said, it's all about how you read the question. everything I said is correct. you need airspeed to make a plane fly. if the plane isn't moving forward and there is no airpseed, it will not fly. given that, you could read the question as saying that the conveyor matches the speed of the plane, meaning the plane is moving forward at 100 mph, the conveyor moves backwards at 100 mph, the wheels actually are spinning like if it were moving 200mph on a stationary runway. if you look at it like this, yes, the plane is moving fowrard, which will give it the airspeed needed for lift.

it all depends on how you read the question. again, everything I said was correct, and copeit did nothing to prove me.

it is not a problem of velocity it is a force problem....

the only force the conveyor belt puts on the plane is rolling frictional force

the plane "pushes against the air" for force...not the ground

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The movement of the plane is caused by the intake of air through the turbines creating exhaust, NOT through the transfer of friction to the wheels.

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No.

The thrust is due to the jet exhaust, not the jet intake.

On a propeller driven aircraft, the propellers act as screws pulling the aircraft forward. Some people erroneously think the lift comes from the propellers pushing past the wings at high scpped.

The matchbox car on paper visualization is excellent.

And as the first non-Video poster to say that it takes off, let me laugh at you poor kids.

By the way, let me say that pilots aren't trained to think like engineers who design airplanes and the operational systems that run them.

Kramer: the "rails" aren't moving, unless the conveyor belt finds a way to move the air above it. The rains/treadmill solution is perfectly feasible.

Thrust causes the plane to move forward. Due to the weight of the plane, there is a high amount of friction between the wheels and the ground. Because the friction of the bearings of the wheels are less than the friction between the wheels and the ground, the wheels turn. The wheels turn because the plane moves, not the other way around. That said, if the wheels are on a conveyor belt that is made to move synchronously with the wheels of the plane, then the thrust of the plane effectively causes the conveyor belt to move. Assuming there is no slippage between the wheels of the plane and the conveyor belt, then the plane is never allowed to break the friction between the plane's wheels and the surface of the ground (the conveyor belt). Because the plane is not allowed to overcome that friction, the plane remains stationary but the conveyor belt and the wheels are spinning like crazy.

If you assume that there is slippage between the wheels and the conveyor belt, then you are a realist/engineer, the plane moves and as such will eventually take off. If you assume there is no slippage between the wheels and the belt, then you are a dreamer/physicist and the plane remains stationary in this imaginary situation.

Nawlins and others:

The only way I can explain it is the treadmill/rollerblades/rope example. No matter how fast the treadmill is spinning, you can still pull yourself forward with the rope or handrails.

Pulling rope = propeller pushing against air. Plane moves and flies, no matter what the conveyor is doing.

Folks,

How in the Sam Hill is the conveyor belt going to prevent forward motion?

I agree with MKF, trusting a pilot as the authority on answering this question is like arguing about how a diesel motor works because a bus driver said so.