quote Originally posted by Wolfhound: If you put racing slicks on an airplane will it take off faster? And why?

Slower due to increased tire drag.

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BTW, I didn't read any further than this reply above ^^^. Am I correct in inferring that the conveyor belt will automatically *counteract* any forward motion before it really gets going at all? If so then if there's no limit to the belt's speed, it will always be able to overcome the engine thrust.

Explanation: Theoretically, if we assume that there is no maximum speed for the belt, the plane would not fly. Tires and wheel bearings aren't 100% frictionless, so the belt moving will tend to very slightly pull the plane back if the belt moves. Like pulling a piece of paper from underneath ball bearings or marbles... if you go slow enough, you'll never overcome the friction and the balls will move backward on the paper without rolling. The faster you move it, the sooner you'll overcome the force of the friction and they'll start rolling, but they WILL still cmove back slightly. Unless your tires and bearings are 100% friction free, there will be an effect. Because the original question said the belt "tracks" the speed of the plane, I'm assuming the engine thrust starts at 0 and keeps increasing until its max, and also that the acceleration of the belt is theoretically infinite while the acceleration of the engines is finite. As the plane tries to move forward, let's say the conveyer belt speeds up enough to counteract 100% of the potential forward motion. Even if the belt needs to move at 100 bazillion mph to do so, it can theoretically prevent the plane from moving forward. The plane reaches 100% of its thrust potential and the conveyer can stop accelerating. If the engines had no limit to their thrust, the belt would just have to keep accelerating. Any thought of the belt causing enough wind to move the plane is probably unlikely because it would be too turbulent.

Realistically, it would probably fly if the engines/props were going, depending upon the max conveyer speed vs. the thrust of the engines. There is and probably never will be any kind of conveyer belt that can move backward fast enough to completely counteract acceleration due to the engines' thrust. In the real world, even if you could have a belt accelerate like that, it would utterly destroy the tires, etc because of the friction at that iNsAnE tire speed. Then it definitely wouldn't fly.

I'm always right so if you disagree you're obviously wrong. End of discussion, end of thread. I will not be following any replies to this thread

[This message has been edited by FieroGT42 (edited 01-02-2006).]

Someone put a stop to this!!!!!

quote Originally posted by FieroGT42: I will not be following any replies to this thread

You obviously didn't bother to read any of the earlier responses in this thread either.

It's all been hashed out ad nauseam. The plane WILL fly. And this is coming from someone who strongly believed (and argued) it would NOT fly, until I re-read the original posted scenario with a clear head and realized my error.

Funny, Patrick and I were of the same conclusion originally, that the plane would not fly. We have since changed our minds.I chose to make an experiment myself!! This should explain it all beyond any doubt!!
Imagine a model aircraft, sitting on a long conveyor belt.It is at the rear of the belt.Tie a piece of string to the front of the plane, and tie the other end to a fixed point, beyond the front of the belt.This piece of string can be thought of as the propeller/jet of the plane, which is set to counteract the opposite speed of the conveyor belt. The belt is started, and the string maintains the plane in situ, as would the engine/propeller.Just the wheels would turn as they run over the belt.
Now replace the string with a piece of rubber band, under tension.This then represents the engine at full power.The plane will have to be held in place, against the pulling force of the elastic. With the conveyor belt static, or not moving, release the plane and it will shoot forward and take off Start the conveyor, run it at full speed, holding the tail of the plane so it stays in place on the belt. The wheels will be running forward, at the same speed as the surface of the belt is running backwards.Open up the engine, or in this case release the tail, and the motive force of the elastic, or in real life the engine/propeller that it is simulating, will pull the plane forward at a speed that will enable it to cause lift over the wings, and take off.One must regard the mounting point of the string/elastic as being the force against which the planes engine/propeller works in real life...the surrounding air.
Now I have helped spread the reality, I retire for ever from this thread!!!
Hahaha
Nick

[This message has been edited by fierofetish (edited 01-02-2006).]

quote Originally posted by blackrams: I'm guessing you were current and qualified in a wheel driven A/C. Can't say I've ever been current on one of that type so I'll have to agree with you on that particular type of A/C. All of the thrust propelled A/C I've ever flown didn't give a hoot about how fast the wheels were spinning. Happy Fieroing

The original quote states that the plane is standing on the belted runway and therefore not in the air. if it is to fly then it will have to go twice the speed of the conveyor in the opposite direction to create the 50mph to fly as previously stated. As people have said before, wheels to do not make a planes fly it is the relative wind and there is no relative wind when the plane is spinning its wheels and the plane itself is stationary.

Maryjane - as you stated if I do hold the plane in place then technically I am providing "thrust" to keep it from zooming off the back of the treadmill, but the thrust is only enough to counter the rolling belt and there is no relative wind, therefore the plane will not takeoff.

Hmmm..I see you chose to ignore my example..don't blame you!! You can't argue against it !!
Nick
Edit: oh pooo!! I said I was finished posting!! Hahaha!! Compulsive stuff..

[This message has been edited by fierofetish (edited 01-02-2006).]

quote Originally posted by stalen88GT: The original quote states that the plane is standing on the belted runway and therefore not in the air. if it is to fly then it will have to go twice the speed of the conveyor in the opposite direction to create the 50mph to fly as previously stated. As people have said before, wheels to do not make a planes fly it is the relative wind and there is no relative wind when the plane is spinning its wheels and the plane itself is stationary. Maryjane - as you stated if I do hold the plane in place then technically I am providing "thrust" to keep it from zooming off the back of the treadmill, but the thrust is only enough to counter the rolling belt and there is no relative wind, therefore the plane will not takeoff.

No, the plane only has to move fast enough to counter the tiny bit of friction in it's wheel bearings.
Actually, it takes a very minimal effort to hold it in place, even if the conveyor is moving very fast. I tried it with a non powered toy, on a variable speed conveyor, with the conveyor set at max travel speed. If you will think about it, or put a non powered wheeled vehicle of any kind on a treadmill, you will instantly see the error in your mental visualization. The plane will move fwd just as they always do, except the wheels are now spinning a little faster. Remember, the belt only matches the speed the plane is actually moving in the real world. The real world being defined as something like this:
The conveyor is running left to right in front of the airport contol tower. The plane is positioned exactly in front of the tower. As soon as the plane begins moving to the left of the tower, the conveyor matches that movement in the other direction, which only means the wheels are spinning faster. The plane is steadily moving to the left--AWAY from the tower.

Since there is air in the space around the plane, as it moves to the left and away from the tower(and it will), it also is moving thru air.
As the thrust is increased, so does the conveyor's speed, resulting in an equal increase of the plane's wheel rpm, but nothing more.

Think about it. Or use one of the examples others have posted above. You will see.

Take a long peice of paper, such as a roll of shelf liner. Set a marker, such as a book, off the side of the paper. That book is simulating the tower (The real world, which is full of air) . Set the plane right in front of the book, on the shelf liner. Have someone pull the shelf liner in one direction, while you pull a toy car in the other direction. You will find, that no matter how fast your helper pulls the paper, you (the propellor or J79) will be able to move the toy in the other direction. And, you won't have to exert but a tiny bit of pull, especially when compared to the speed your helper is moving the rolled out paper.

Keep in mind, that the conveyor does NOT move any faster than the plane's travel thru the real world. It does not increase to whatever speed might be required to keep it stationary on the conveyor, tho that is really irrelevant. The conveyor in fact CANNOT run fast enough to prevent the plane from moving.

[This message has been edited by maryjane (edited 01-02-2006).]

quote Originally posted by stalen88GT: The original quote states that the plane is standing on the belted runway and therefore not in the air. if it is to fly then it will have to go twice the speed of the conveyor in the opposite direction to create the 50mph to fly as previously stated. As people have said before, wheels to do not make a planes fly it is the relative wind and there is no relative wind when the plane is spinning its wheels and the plane itself is stationary. Maryjane - as you stated if I do hold the plane in place then technically I am providing "thrust" to keep it from zooming off the back of the treadmill, but the thrust is only enough to counter the rolling belt and there is no relative wind, therefore the plane will not takeoff.

Every fixed winged A/C I have ever been in/on started it's flight from a runway. Once the engine provided the thrust to move the plane we eventually flew. Whether or not the runway has the ability to move or not has no effect on whether or not the A/C can fly. Have you ever taken off from a ice covered runway? Ever flown a helicopter? Understand relative wind and it's effect on the aircraft? Ever make a down wind landing?
This is a fun question to play with, if you insist the plane won't fly, OK, your plane won't fly.

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Ron
Freedom isn't Free, it's always earned.
My imagination is the only limiting factor to my Fiero. Well, there is that money issue.

I havnt read through all the posts, but seriously c'mon the plane will obviously fly. Even if their was a wind coming at the plane that exactly matched the thrust of the prop it would still fly once it reached the wind speed required to lift the plane, although in that case it would stay in one spot and just lift off the ground like a helicoptor

are their still people who believe it wont fly?

Originally posted by stalen88GT:

quote As people have said before, wheels to do not make a planes fly it is the relative wind and there is no relative wind when the plane is spinning its wheels and the plane itself is stationary.

And this is where you are incorrect.
1. The the plane is not spinning it's wheels. The conveyor is spinning them--but only half of that rpm is attributed to the rearward movement of the conveyor belt. The other half, is attributed to the thrust which is created by the propellor.

2. Nor is it stationary. If the circumference of the tire is 50 inches, the plane will move forward 50 inches for every 2 rpms the tire spins. 1 rpm caused by the propellor's influence on the air--1 rpm from the conveyor belt's influence on the tire. It has also moved 50 inches thru air. The conveyor has zero effect on the air. It can only affect the wheel rpm and neither the surrounding air nor the plane care how fast the wheel rpm is.
The plane took off last year and has already delivered Christmas presents all over the world.

Think folks, Think.

[This message has been edited by maryjane (edited 01-02-2006).]

quote Originally posted by maryjane: Think folks, Think.

The main problem as I see it, is that many people misinterpret the original scenario as it was presented. They either miss something which was clearly posted or they imagine something which was never stated. I was one of those guilty people, but I eventually saw the light and converted my beliefs. Praise Jesus!!! Oops sorry, got carried away (by the plane).

quote A plane is standing on a runway that can move (some sort of band conveyer). The plane moves in one direction, while the conveyer moves in the opposite direction. This conveyer has a control system that tracks the plane speed and tunes the speed of the conveyer to be exactly the same (but in the opposite direction). The question is: Will the plane take off or not?

The plane will fly ! Ok people here is a differant way to look at this. A boat is trying to go upriver........ Oh never mind . So if we put a Harrier on the same belted runway would it be able to take off ?

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HARDCORE SBC CRONIE AND PROUD OF IT ! GOT TQ ?

quote Originally posted by FIEROPHREK: The plane will fly ! Ok people here is a differant way to look at this. A boat is trying to go upriver........ Oh never mind . So if we put a Harrier on the same belted runway would it be able to take off ?

NO!! because the harrier uses its wheels to fly, and if you get a flat while cruising at mach5000 you just gotta bail

[This message has been edited by EightBall (edited 01-02-2006).]

I can't believe that this thread is still alive! I gave the answer to this question already...

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For the latest Fiero apparel and accessories, please visit my online store Fiero Lives Online

I can't believe that no one has posted this authoritative reference before:

quote Originally posted by Monty Python: [opening music] [wind] [clop clop clop] KING ARTHUR: Whoa there! [clop clop clop] SOLDIER #1: Halt! Who goes there? ARTHUR: It is I, Arthur, son of Uther Pendragon, from the castle of Camelot. King of the Britons, defeater of the Saxons, Sovereign of all England! SOLDIER #1: Pull the other one! ARTHUR: I am,... and this is my trusty servant Patsy. We have ridden the length and breadth of the land in search of knights who will join me in my court at Camelot. I must speak with your lord and master. SOLDIER #1: What? Ridden on a horse? ARTHUR: Yes! SOLDIER #1: You're using coconuts! ARTHUR: What? SOLDIER #1: You've got two empty halves of coconut and you're bangin' 'em together. ARTHUR: So? We have ridden since the snows of winter covered this land, through the kingdom of Mercia, through-- SOLDIER #1: Where'd you get the coconuts? ARTHUR: We found them. SOLDIER #1: Found them? In Mercia? The coconut's tropical! ARTHUR: What do you mean? SOLDIER #1: Well, this is a temperate zone. ARTHUR: The swallow may fly south with the sun or the house martin or the plover may seek warmer climes in winter, yet these are not strangers to our land? SOLDIER #1: Are you suggesting coconuts migrate? ARTHUR: Not at all. They could be carried. SOLDIER #1: What? A swallow carrying a coconut? ARTHUR: It could grip it by the husk! SOLDIER #1: It's not a question of where he grips it! It's a simple question of weight ratios! A five ounce bird could not carry a one pound coconut. ARTHUR: Well, it doesn't matter. Will you go and tell your master that Arthur from the Court of Camelot is here? SOLDIER #1: Listen. In order to maintain air-speed velocity, a swallow needs to beat its wings forty-three times every second, right? ARTHUR: Please! SOLDIER #1: Am I right? ARTHUR: I'm not interested! SOLDIER #2: It could be carried by an African swallow! SOLDIER #1: Oh, yeah, an African swallow maybe, but not a European swallow. That's my point. SOLDIER #2: Oh, yeah, I agree with that. ARTHUR: Will you ask your master if he wants to join my court at Camelot?! SOLDIER #1: But then of course, uh, African swallows are non-migratory. SOLDIER #2: Oh, yeah. SOLDIER #1: So, they couldn't bring a coconut back anyway. [clop clop clop] SOLDIER #2: Wait a minute! Supposing two swallows carried it together? SOLDIER #1: No, they'd have to have it on a line. SOLDIER #2: Well, simple! They'd just use a strand of creeper! SOLDIER #1: What, held under the dorsal guiding feathers? SOLDIER #2: Well, why not?

Now do you all understand? The airplane will fly!

[This message has been edited by Marvin McInnis (edited 04-05-2006).]

For the situation in which the conveyor belt is set to offset the thrust of the engine:

Alright I will state this one more time. THE PLANE WILL NOT FLY!

the wheels create friction, which holds the plane back. So if the conveyor belt moves fast enough to create enough friction it can counteract the thrust of the engine. Period. IT IS POSSIBLE TO CREATE ENOUGH FRICTION THROUGH THE WHEELS TO COUNTERACT THE THRUST!

I swear to god almighty that I am correct. want me to start bringing in referrals? I am a pilot, my instructor agrees with me, as well as an Aeronautical Engineer.

Hell I flew today. So you people who believe it will fly, tell me why when I was doing my ground roll I was at 55kts at takeoff, but instantly when I left the ground my airspeed increased to 60kts. explain that to me please. How does that work?

For the answer for the actual question asked:

The plane will fly. If the belt is set to match the speed of the plane in the opposite direction, it will not create enough drag to counteract the thrust, therefore it will be able to take off.

[This message has been edited by MDFierolvr (edited 04-05-2006).]

RESURRECTION!!!

quote Originally posted by Marvin McInnis: Now do you all understand?

Perfectly. Now what is the airspeed velocity of an unladen swallow?

I disagree with some forum members whom I respect greatly. But nevertheless...

...my vote is...

the plane will not fly.

[This message has been edited by Cheever3000 (edited 04-05-2006).]

quote Hell I flew today. So you people who believe it will fly, tell me why when I was doing my ground roll I was at 55kts at takeoff, but instantly when I left the ground my airspeed increased to 60kts. explain that to me please. How does that work?

Because your engine was developing excess thrust and that caused you to be in an acceleration mode.Had you reduced power to where you were no longer accelerating your airspeed would have remained the same but you would have lifted off in ground effect. Had you left the same power setting and tried to climb you would have had insufficient power to maintain a climb once you left ground effect and would have plummeted back to earth. (OK, just kidding on the last part, you would have SETTLED back either to the ground/runway or back into ground effect. There's also an excellent chance that you were not doing 55 knots at takeoff. You had an indicated airspeed of 55 knots, but most likely you were ROLLING less than that (unless you were silly enough to takeoff with the wind or it was dead calm).

Of course you are right, you did have a small burst of acceleration when you lost the friction of the wheels on the ground (and most likely as a newbie you were dragging the brakes ).

Your last statement is correct. As the question is originally posed, the aircraft wil fly. I've been flying for almost 25 years, commercial, single/multi engine land, instrument, AGI.

John Stricker

quote Originally posted by MDFierolvr: For the situation in which the conveyor belt is set to offset the thrust of the engine: Alright I will state this one more time. THE PLANE WILL NOT FLY! the wheels create friction, which holds the plane back. So if the conveyor belt moves fast enough to create enough friction it can counteract the thrust of the engine. Period. IT IS POSSIBLE TO CREATE ENOUGH FRICTION THROUGH THE WHEELS TO COUNTERACT THE THRUST! I swear to god almighty that I am correct. want me to start bringing in referrals? I am a pilot, my instructor agrees with me, as well as an Aeronautical Engineer. Hell I flew today. So you people who believe it will fly, tell me why when I was doing my ground roll I was at 55kts at takeoff, but instantly when I left the ground my airspeed increased to 60kts. explain that to me please. How does that work? For the answer for the actual question asked: The plane will fly. If the belt is set to match the speed of the plane in the opposite direction, it will not create enough drag to counteract the thrust, therefore it will be able to take off.

I'm halfway scared to do this because it looks like the majority of the people think the plane will fly based off the fact that the wheels have nothing to do with the takeoff and that even if the wheels were spinning 200kts along with the conveyer belt that the engine would have enough thrust to pull the plane into the air.

The simple fact is the engine does pull the plane, on wheels mind you, down the runway until the force of air under the wings allows the plane to begin to ascend. Even at 100% throttle how would the engines be able to pull the plane, on wheels, down the runway if the conveyer belt keeps the same speed as the wheels?

I'm not saying the wheels drive the plane into the air. I don't even want to hear those reponses. The wheels are loose and have no force in moving the plane except for the fact that they allow the plane to roll on a still surface or surface moving slower than the rate that the engine is pulling the plane. Remember, the belt has a sensor that keeps it moving the same speed as the plane would be moving. Think of the wheels and the belt of the runway being interlocked like gears, no place for error.

The real life fact is that no one would be able to build a conveyer belt that would be able to keep up with the plane's wheels and eventually the thrust would move the plane's wheels faster than the belt can move and it would take off.

However, given the fact that the question states that the belt WILL keep up with the speed that the plane is attempting to move. Think of it this way, the belt moving so fast would show a groundspeed of 200kts but since the wheels cannot move faster than the belt, the relative air speed would be 0. Dur.

quote The plane will fly. If the belt is set to match the speed of the plane in the opposite direction, it will not create enough drag to counteract the thrust, therefore it will be able to take off.

Thrust means nothing if the thrust is what is pulling the planes wheels to move faster.

More thrust = more pull = pulls the plane's wheels faster = makes the conveyer spin faster in the opposite direction = a stationary object= no wind to force the plane's fuselage upwards = a plane at 100% thrust going nowhere

The plane will fly.

There is no difference than a plane with pontoons that takes off from the water.

The speed/friction of the wheels will not hold it down.

A plane pushes against the AIR to move forward, not the ground (or the water).

The whole reason a plane rolls on wheels OR skims across the water is because it HAS to until it gets enough airspeed to act upon the wings and control surfaces. Until that happens, it ain't gonna fly.

quote Originally posted by ryan.hess: RESURRECTION!!!

Sorry ... I couldn't help myself!

quote Originally posted by ryan.hess: ... what is the airspeed velocity of an unladen swallow?

African or European?

[This message has been edited by Marvin McInnis (edited 04-05-2006).]

The plane will fly.
According to the problem, the conveyor belt will not move at all unless the plane is moving. Therefore, by the problem alone we are guaranteed that the plane will move forward.
Seriously, watch the video on page 2. The rate of movement doesn't change at all regardless of whether the paper towels underneath are moving or not.

quote Originally posted by MDFierolvr: For the situation in which the conveyor belt is set to offset the thrust of the engine: Alright I will state this one more time. THE PLANE WILL NOT FLY! I swear to god almighty that I am correct. want me to start bringing in referrals? I am a pilot, my instructor agrees with me, as well as an Aeronautical Engineer. Hell I flew today. So you people who believe it will fly, tell me why when I was doing my ground roll I was at 55kts at takeoff, but instantly when I left the ground my airspeed increased to 60kts. explain that to me please. How does that work?

Hey!
55 Kts?
Sounds like a Cessna 172. I like flying those airplanes.
Tell you what! Plug THIS airplane into the equation.
Since this is all very fanciful with a conveyor belt runway and all--lets see what a Grumman Bearcat (post WW II piston engine fighter) could do if you were determined.
This is a fact--
At the national air races in Cleveland in 1946 a Bearcat left the runway with a TO roll of only 115 feet!
Consider that it came equipped with 2,400 HP, and one fookin' HUGE 4 blade prop..
Think things like wheel bearing and tire friction are gonna have much effect on an airplane like that?
A little bit snappier than a Cessna 172N-- at 805 ft TO roll according to my POH.
It only takes ONE airplane of all the airplanes ever built to succesfully perform the conveyor belt takeoff to make the answer-- YES.
BTW--
I think the original question was simply a theoretical brain exercise. And not to be taken too seriously.

good to have input from another pilot. Me, I am working on my commercial right now. And at least we agree on something. The way the question is posed, the plane will fly.

What I am saying in the other scenerio is that theoretically the belt can move fast enough to create enough drag on the wheels that it counteracts the thrust of the engine. In real life it is impossible, because that belt would be going some rediculous speed. my guess is well over 1500mph. But theoretically it is possible for the plane to not take off at full thrust.

We agree on a lot more than you think.

Our car is still one ahead of you on car domain, though, in the '85 Fieros.

John Stricker

quote Originally posted by MDFierolvr: good to have input from another pilot. Me, I am working on my commercial right now. And at least we agree on something. The way the question is posed, the plane will fly. What I am saying in the other scenerio is that theoretically the belt can move fast enough to create enough drag on the wheels that it counteracts the thrust of the engine. In real life it is impossible, because that belt would be going some rediculous speed. my guess is well over 1500mph. But theoretically it is possible for the plane to not take off at full thrust.

quote Originally posted by MDFierolvr: good to have input from another pilot. Me, I am working on my commercial right now. And at least we agree on something. The way the question is posed, the plane will fly. What I am saying in the other scenerio is that theoretically the belt can move fast enough to create enough drag on the wheels that it counteracts the thrust of the engine. In real life it is impossible, because that belt would be going some rediculous speed. my guess is well over 1500mph. But theoretically it is possible for the plane to not take off at full thrust.

OMG!
If the belt can go that fast then so can the wheels..

This thread is so old!! Die thread die.

The plane will fly.

Read the problem.
The conveyor will not even move unless the plane itself is, in fact, moving forward.
If the plane were not moving forward, the conveyer would not be moving at all.
So there is no situation where the plane would be standing still and the conveyor would be moving - the sensor control prevents it.
The problem states, in clear english, that conveyor will not move unless the plane is moving forward.
If the conveyor is moving 1500mph backwards, we are guaranteed that the plane is moving 1500mph forwards.
I think we can all agree that it takes much less than that for a plane to take off.
Simply put, if we have a plane that takes off at 100mph then it must be moving foward against the air for the conveyor to be moving backwards 100mph.
That is a grand total of 200mph difference in speed between the plane and the surface of the conveyor, and wheels have no problem rotating at 200mph.

[This message has been edited by fierogt88 (edited 04-05-2006).]

Well this plane certainly won't fly .

I cannot believe there are actual certified pilots posting in this thread that say the plane will not fly

The plane in question WILL fly, hello it uses it's propellor to produce thrust not it's flippin wheels people JEEEEEZ !

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HARDCORE SBC CRONIE AND PROUD OF IT ! GOT TQ ?

From an aircraft mechanic.... Me

Hands down the dumbest thread EVER!

88Ironduke

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Pilots with out maintainers are just pedestrians with a cool jacket and sunglasses.
I.Y.A.M.Y.A.S.

quote If the conveyor is moving 1500mph backwards, we are guaranteed that the plane is moving 1500mph forwards.

Eh? If you run 5mph on a treadmill and the treadmill is turning 5mph...you move forward?

A propeller, even a jet engine isnt going to pull the plane straight off the ground.

In fact, the question doesnt say whether the sensors are equipped to the plane's airspeed sensors or the speed of the wheels. Either way, if the plane moves the treadmill moves. To say otherwise defeats the purpose of the problem saying the treadmill moves as fast as the plane.

quote Originally posted by fierofierofiero: Eh? If you run 5mph on a treadmill and the treadmill is turning 5mph...you move forward?

If you run on a treadmill, what's providing your forward thrust? Your feet pushing againts the treadmill, right?

What's providing thrust on an airplane? Propeller or jet pushing against AIR - NOT the treadmill.

[This message has been edited by Formula88 (edited 04-06-2006).]

Ok guys, here is another engineers opinion. I was with the no-fly crowd until just a moment ago. Think about this problem in forces and coordinate systems. The plane must move in the x-direction in order for it to have air speed enough to create lift and fly. The thrust delivered from the plane acts in the postive x direction. BUT the conveyor belt does not act on the plane at all, assuming that the wheels/bearings are frictionless, even though the belt is moving in the negative x direction. The conveyor belt's speed is irrelevant. Bottom line: the conveyor belt has no way of transfering its force to the plane other than through friction which can be over come by the engine. This problem is about FORCES and NOT velocities.

Someone used the comparison of a car on a dyno. If the opposing no-fly argument were true you would not need to tether the car on a dyno. It would simply stay stationary on its own.

The original scenario:

quote Originally posted by naskie18: A plane is standing on a runway that can move (some sort of band conveyer). The plane moves in one direction, while the conveyer moves in the opposite direction. This conveyer has a control system that tracks the plane speed and tunes the speed of the conveyer to be exactly the same (but in the opposite direction). The question is: Will the plane take off or not?

I initially thought the plane would not fly. I was wrong. From page 7 of this same thread:

quote Originally posted by Patrick: “... munch, munch, munch...” That’s the sound of me eating crow. The plane will fly. With the light of a new day I looked upon this thread again and immediately saw my error. Somehow I had convinced myself that the magical conveyor belt had been set up to cancel the forward speed of the plane by going in the opposite direction at ANY speed that was deemed necessary. I was envisioning the belt zipping along at incredible speeds, thus my concern with shredded tires and melted wheel bearings. This is incorrect. The scenario clearly states that the conveyor belt would go the SAME speed as the plane in the opposite direction. Oops, that’s quite different. I was wrong, wrong wrong.

quote Originally posted by Patrick: As the plane starts to move forward, the belt moves at the same speed in the opposite direction. This does NOT prevent the plane from moving forward, it just makes the wheels spin twice as fast. Yes, there is more friction, but not enough to slow the plane’s progress to any significant degree. As the plane picks up forward momentum, the belt also picks up momentum in the opposite direction. Again, the actual air/ground speed of the plane is not adversely affected by the conveyor belt, the plane continues to accelerate forward, and the wheels continue to spin twice as fast as the forward speed of the plane. This simply continues until the plane reaches lift off speed and flies off into the sunset.