What I found interesting is that once you reach a certain thrust the conveyor speed becomes irrelevant. You can make it as fast as you want and the plane would remain stationary, if you add any more thrust and the plane will move foward.
Woo Hoo! I own page two.

[This message has been edited by avengador1 (edited 12-23-2007).]

Anybody got a excercise treadmill, a piece of string, a spring scale, and a vehicle with wheels that would fit on the treadmill? Put the wheeled vehicle on the treadmill. Tie the string to the front of it.Tie the other end of the string to the spring scale, and then fix the scale to an anchor point.Start the treadmill, and note the reading on the scale. gradually make increments to the speed of the treadmill, and note how much more 'drag' is registered on the scale.The move from inertia to motion will register momentarily on the scales as the change from inertia to movement, and then drop back to a steady reading. Speed the treadmill up, and the drag registered on the scale will remain almost constant. Or increase at a MUCH lower rate than the speed of the treadmill. Then read my previous post
Nick

Obviously, some members here failed physics and need to stick to ground transportation.


THE PLANE WILL FLY.

All those who say it will not, here is a chance for a free car. My pink against yours.
Put your Fiero where your lack of understanding in physics is.


Gene

quote Originally posted by Gokart Mozart: If the plane is effectively stationary, even if the engines are full throttle, the only wind flow over the wings are not enough to give it lift.

OK, we've identified where or what is the problem is here, you are assuming the plane is stationary and can't move forward. Why do you assume that? What is holding it back? The conveyor? If that's what you believe is holding the plane back then have have an incorrect assumption. If the plane was wheel driven like an automobile then, you would be totally correct, the conveyor could essentially keep the car or plane stationary relative to it's surroundings minus the conveyor which would be passing under the wheels. But, in that the Plane does not rely on its wheels to move forward as in powered movement, the wheels or how fast they turn has virtually no effect other than holding the plane up off the ground. Thrust developed by the engine whether that be from a prop, a jet or a rocket motor will propell the plane forward until it reaches an effective airspeed as it relates to that aircraft to develop enough lift to fly.

Ever blow up a ballon and then let the air out of it? The air that is released from the balloon is the thrust it's using to fly around the room. You could hold that balloon over the conveyor but when you let go, it's going to go flying off one direction or another, regardless of what the conveyor is doing.

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Ron

It's the Soldier, not the reporter
Who has given us the freedom of the press.
It's the Soldier, not the poet,
Who has given us the freedom of speech.
It's the Soldier, not the politicians
That ensures our right to Life, Liberty and the Pursuit of Happiness.
It's the Soldier who salutes the flag,
Who serves beneath the flag,
And whose coffin is draped by the flag.

A bi-plane tore loose from its tie downs at the local airport. It managed a half roll and ended
upside down on top of the hanger. No conveyor needed here!!

If forces in the forward direction exceed forces in backward direction, you'll get motion.
Simple, no?
Neither one has unlimited power. If the power (resulting speed) of the conveyor
is greater than the thrust of the engine, no forward movement, no net airflow, no flight, yes?.

If plane can exceed conveyors speed ability then you'll get motion. MAYBE enough airflow
for flight.
Anyone know how much prop wash contributes to lift on a plane? just wondered.

AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAGHHHHHH!!

<----

[This message has been edited by Xanth (edited 12-23-2007).]

quote Originally posted by TennT: Neither one has unlimited power. If the power (resulting speed) of the conveyor is greater than the thrust of the engine, no forward movement, no net airflow, no flight, yes?.NO!! If plane can exceed conveyors DRAG ON THE WHEELS OF THE PLANE not (speed ability) then you'll get motion. DEFINITELY enough airflow for flight.

[This message has been edited by fierofetish (edited 12-23-2007).]

quote Originally posted by blackrams: OK, we've identified where or what is the problem is here, you are assuming the plane is stationary and can't move forward. Why do you assume that? What is holding it back? The conveyor? If that's what you believe is holding the plane back then have have an incorrect assumption. If the plane was wheel driven like an automobile then, you would be totally correct, the conveyor could essentially keep the car or plane stationary relative to it's surroundings minus the conveyor which would be passing under the wheels. But, in that the Plane does not rely on its wheels to move forward as in powered movement, the wheels or how fast they turn has virtually no effect other than holding the plane up off the ground. Thrust developed by the engine whether that be from a prop, a jet or a rocket motor will propell the plane forward until it reaches an effective airspeed as it relates to that aircraft to develop enough lift to fly. Ever blow up a ballon and then let the air out of it? The air that is released from the balloon is the thrust it's using to fly around the room. You could hold that balloon over the conveyor but when you let go, it's going to go flying off one direction or another, regardless of what the conveyor is doing.

Exactly...

If the plane is affixed to a non-moving point regardless of the treadmill, it will not fly. No amount of thrust against the surrounding air will allow it to fly as there will not be enough airflow over the wings to allow it to create the lift necessary for sustained flight due to a lack of forward momentum. Now, put the same plane on a conveyor, with the plane fixed to a stationary point relative to it's surroundings, and you have the same dilemma. The conveyor will continue to move backwards, the wheels of the plane will move as if the plane itself was moving forward, but you have the same dilemma. The engines are pushing against air, and only moving the air from in front of the engine to in back of the engine. There is no air flow over the wings of the aircraft, thus, no lift.

Now, same plane, same conveyor, the plane is free to move forwards by any means it can. Conveyor starts rolling backwards, engine thrust comes up to keep the plane stationary relative to it's surroundings. You have thrust, you have conveyor movement, the plane is not fixed, but the plane will STILL not fly because the plane is not moving enough air over the wings to generate lift.
Bring the thrust up even more, and the plane will begin to move forward relative to it's surroundings. The conveyor speeds up, and the wheels on the aircraft spin faster. But the plane is pushing against the air around it, thrust is forcing the plane forward, since it is pushing against the air, and the plane now has air flow over the wings. The faster the plane moves relative to it's surroundings, the more air flow is generated over the wings thus creating the low pressure as the air moves quicker over the top of the wing, and thus generating lift.

The only way the plane would not be able to take off by generating thrust, not being affixed to a stationary point, and with the conveyor moving against the direction of the plane is when the wheel bearings burn up creating enough drag to cause the plane to lose momentum and crash. :P

[This message has been edited by Synthesis (edited 12-23-2007).]

I can't believe how many people think aircraft are powered through their landing gear.

In their world, a backwards moving conveyor can keep the plane from moving forward and taking off. But what gets me is how they would explain how a plane flies normally, from a regular airport? Once the wheels leave the ground - there's nothing there to power the aircraft! How can it stay in the air without the wheels pushing it forward?!?!?!

quote Originally posted by fierofetish:

Yep, as long as the force the plane exerts exceeds the conveyors, it's the same old
Force=massXaccelleration physics.
Positive force/mass=accelleration
AccellerationXtime=speed
Enough speed gets it up and off. Hmmm sounds like some OTHER college education I got

quote Originally posted by Formula88: I can't believe how many people think aircraft are powered through their landing gear.

I can't believe this is so hard and has continued for so long. Hell even pilots still think it won't fly.

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Though I am branded a devil in priests clothing I cast not the raiment I wear for I am not beholden to any flock with which any color has been given to me.

I give up.

------------------
Ron

It's the Soldier, not the reporter
Who has given us the freedom of the press.
It's the Soldier, not the poet,
Who has given us the freedom of speech.
It's the Soldier, not the politicians
That ensures our right to Life, Liberty and the Pursuit of Happiness.
It's the Soldier who salutes the flag,
Who serves beneath the flag,
And whose coffin is draped by the flag.

I still must be missing something. The way its stated as I understand it, is the instant the plane starts to move forward, the treadmill counters by spinning the opposite way to keep it stationary. Stationary means it will not fly. The way I see it is the wheels spinning has nothing to do with anything...it could be on skids, floats or skis. If the plane is moving forward FASTER than the treadmill, yes then it will get lift and fly when it gets to V1 speed....but then it wouldnt be going at the same speed to counter the movement. I guess we will have to wait and see.

quote Originally posted by rogergarrison: I still must be missing something. The way its stated as I understand it, is the instant the plane starts to move forward, the treadmill counters by spinning the opposite way to keep it stationary. Stationary means it will not fly. The way I see it is the wheels spinning has nothing to do with anything...it could be on skids, floats or skis. If the plane is moving forward FASTER than the treadmill, yes then it will get lift and fly when it gets to V1 speed....but then it wouldnt be going at the same speed to counter the movement. I guess we will have to wait and see.

The treadmill cannot counter the speed of the aircraft as it moves forward. Since the aircraft is only sitting on the treadmill, and the wheels on the aircraft freewheel, the treadmill can spin at 2,000 MPH and the plane can still take off as long as it's engine thrust can overcome the rolling resistance of the wheels and wheel bearings on the conveyor.

There is no possible way for the treadmill to keep the plane stationary since the wheels are rolling freely, and the engine is thrusting against the air.

quote Originally posted by Formula88: I can't believe how many people think aircraft are powered through their landing gear. In their world, a backwards moving conveyor can keep the plane from moving forward and taking off. But what gets me is how they would explain how a plane flies normally, from a regular airport? Once the wheels leave the ground - there's nothing there to power the aircraft! How can it stay in the air without the wheels pushing it forward?!?!?!

Totally agree, the prop or jet pushes or pulls it thru the air fast enough to provide lift. The wheels simply hold it up off the ground. Again the way I read it, the conveyor is speeded up as it even starts to move forward so that it never moves forward ???? If it does move forward, the idea of the conveyor speeding up is out the window. If it only goes up to a set speed, then the plane will overcome it and move forward at some point, then fly.

" The treadmill cannot counter the speed of the aircraft as it moves forward. "

but the whole concept, again as I read it, says the treadmill DOES counter the forward motion. The wheels are not driving it, but they do turn relative to any forward motion the plane would be making. If i had a speedometer attached to the landing gear, it would show speed increasing as the plane propells itself down the runway. Airspeed = the planes movement forward relative to surrounding air, groundspeed (speedometer) indicates how fast the wheels are spinning by knowing how far it moves for each rotation= speed relative to the stationary ground.

[This message has been edited by rogergarrison (edited 12-23-2007).]

quote Originally posted by rogergarrison: I still must be missing something. The way its stated as I understand it, is the instant the plane starts to move forward, the treadmill counters by spinning the opposite way to keep it stationary. Stationary means it will not fly. The way I see it is the wheels spinning has nothing to do with anything...it could be on skids, floats or skis. If the plane is moving forward FASTER than the treadmill, yes then it will get lift and fly when it gets to V1 speed....but then it wouldnt be going at the same speed to counter the movement. I guess we will have to wait and see.

quote Originally posted by rogergarrison: 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?

Where does the question state the aircraft remains stationary? Roger, you're thinking like a ground pounder. I'm not making fun or flaming here. What's going to keep the plane stationary? Is it tied down? So what if the conveyor runs the opposite direction of the forward motion of the plane, the conveyor will just make the wheels spin faster.

------------------
Ron

It's the Soldier, not the reporter
Who has given us the freedom of the press.
It's the Soldier, not the poet,
Who has given us the freedom of speech.
It's the Soldier, not the politicians
That ensures our right to Life, Liberty and the Pursuit of Happiness.
It's the Soldier who salutes the flag,
Who serves beneath the flag,
And whose coffin is draped by the flag.

I guess I have a mind block where the original premis is stated. Ill have to wait and watch.

[This message has been edited by rogergarrison (edited 12-23-2007).]

quote Originally posted by rogergarrison: " The treadmill cannot counter the speed of the aircraft as it moves forward. " but the whole concept, again as I read it, says the treadmill DOES counter the forward motion. The wheels are not driving it, but they do turn relative to any forward motion the plane would be making. If i had a speedometer attached to the landing gear, it would show speed increasing as the plane propells itself down the runway. Airspeed = the planes movement forward relative to surrounding air, groundspeed (speedometer) indicates how fast the wheels are spinning by knowing how far it moves for each rotation= speed relative to the stationary ground.

Ok. HOW does the treadmill counter the forward motion? If the plane is physically free to move forward and not tied or tethered in any way, then how is it possible for the treadmill to counter the forward motion?

The wheels would spin faster than normal. That is the only thing that would happen. There IS a rolling resistance, but the rolling resistance will not increase proportional to the forward motion of the aircraft or the speed of the conveyor. The only thing that could slow the plane down would be an application of the wheel brakes, or a wheel bearing failure.

quote Originally posted by rogergarrison: Ok as this reads, as they attempt to move the plane forward, the belt moves in the opposite direction keeping the plane in the same position relative to the surrounding air/ objects. Correct ?

Incorrect. The plane will take off. The assumption that the conveyer can keep the plane from moving is inaccurate. This would be logical if a car was being used instead of a plane since the car gains forward momentum from it's drive wheels. A plane uses thrust to gain momentum. No conveyer in the world can stop the forward thrust of a plane's engines.

quote Originally posted by rogergarrison: I still must be missing something. The way its stated as I understand it, is the instant the plane starts to move forward, the treadmill counters by spinning the opposite way to keep it stationary.

Yes, you are missing something. You're assuming that the treadmill can keep the airplane stationary.

The rolling resistance of the tires, and frictional drag of the wheel bearings, is a fraction of the thrust. Putting the airplane on a treadmill will increase that drag. But it still will only be a fraction of the forward thrust. Therefore, the net force will still be in the forward direction. The three videos we've seen so far attest to that.

While it is theoretically possible to spin the wheels fast enough to generate enough drag to cancel out the forward thrust, the wheel speed required would probably melt the wheel bearings and/or shred the tires.

My guess is no. The speed of an airplane has little to do with the ground underneath. It has more to do that the wind has to move past the wings above the "stall speed" to generate lift.

A better myth would be to see if one could get an airplane to fly by putting it in front of a a huge fan that blows wind at the wings.

quote Originally posted by Austrian Import: My guess is no. A better myth would be to see if one could get an airplane to fly by putting it in front of a a huge fan that blows wind at the wings.

Your "guess" would be incorrect.

That would be a kite and though not quite the defination of "controlled flight", it is flying. Wind will develop lift.

------------------
Ron

It's the Soldier, not the reporter
Who has given us the freedom of the press.
It's the Soldier, not the poet,
Who has given us the freedom of speech.
It's the Soldier, not the politicians
That ensures our right to Life, Liberty and the Pursuit of Happiness.
It's the Soldier who salutes the flag,
Who serves beneath the flag,
And whose coffin is draped by the flag.

If you have a car on a bike roller , the car will sit still because the wheels will spin the rollers. A plane will sit because as the thrust starts to move the plane, the rollers will start to spin to compensate the forward motion. The plane won't take off.

I've seen planes jump chalks due to high winds and thrust. We used to tell newbies on the flightline the APU was a 454 that powered the plane on the ground.

The plane will move forward off the rollers and proceed to take off.

Edit: Unless it gets stuck in the rollers, in which case something will break.

[This message has been edited by Xanth (edited 12-23-2007).]

quote Originally posted by rogergarrison: but the whole concept, again as I read it, says the treadmill DOES counter the forward motion.

THAT is the error right there. The question doesn't say anything about the treadmill countering the forward motion. Here's the original question:

"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)."

Notice is says NOTHING about countering the movement of the plane. Only that the conveyor's speed is exactly the same as the plane's speed, but in the opposite direction.

You've made the assumption that means the plane won't move, which is wrong.

quote Originally posted by rogergarrison: I still must be missing something. The way its stated as I understand it, is the instant the plane starts to move forward, the treadmill counters by spinning the opposite way to keep it stationary. Stationary means it will not fly. The way I see it is the wheels spinning has nothing to do with anything...it could be on skids, floats or skis. If the plane is moving forward FASTER than the treadmill, yes then it will get lift and fly when it gets to V1 speed....but then it wouldnt be going at the same speed to counter the movement. I guess we will have to wait and see.

But the plane is not pulling against the ground. The prop pulls against the air and that will pull it forward, no matter how quick the treadmill goes. The wheels are free spinning so even if the treadmill is doing 60mph the plane will still accelerate to whatever speed the engine and prop pull it to.

quote Originally posted by Patrick: Oh good gawd, this is hopeless...

What he said. And Roger is a *pilot*!

Ya bear and I flew F4s too. Im reading this hypothetical problem too literally I guess. Im seeing that they are saying that the treadmill CAN run fast enough to counter or match the forward thrust thereby keeping it stationary relative to the air. Let me try a little description of the way Im seeing it. we have a plane that can take off on a standard runway with no wind at 40mph. Now that plane could take off on its own with a 40mph headwind just setting there if not tied down. If its put on a carrier going say 30 mph forward, the plane only has to gain 10 mph to take off right. Now put the plane on the same carrier that is steaming backward at 40 mph as the plane is trying to take off going the other way (now with a 40mph tailwind).The plane with the same ground roll speed as before now is remaining stationary relative to the surrounding air...right..as its moving down the deck. It wont fly, but simply would fall off the end of the deck when it got there wouldnt it.

quote Originally posted by rogergarrison: but the whole concept, again as I read it, says the treadmill DOES counter the forward motion. Im seeing that they are saying that the treadmill CAN run fast enough to counter or match the forward thrust thereby keeping it stationary relative to the air.

Nowhere, absolutely nowhere, does the scenario as stated proclaim that the forward motion is "countered" (or prevented or eliminated). Nowhere in the scenario has it been stated that the plane remains stationary. YOU are the one imagining and stating these things, and you are simply wrong, wrong, wrong...

Roger, how many times do we need to point this out to you??????

Smarten up or we're going to be forced to revoke your Hooters membership and take away your cameras.

[This message has been edited by Patrick (edited 12-24-2007).]

OK, lol. Ill wait till Jan 30.

Maybe this will clear things up a bit for those that still think the plane will not fly.

Picture your Fiero with it's front wheels in a rollerbank (like when you get your brakes tested). The rollerbank on the front wheels has a control system that tracks the car's forward motion and tunes the speed of the forward rollers to cause the front wheels to spin in the opposite direction of the rear wheels at the exact same speed.

You slowly apply throttle.

Will the Fiero move forward?

quote Originally posted by Cliff Pennock: Maybe this will clear things up a bit for those that still think the plane will not fly...

Oh yeah, that example really helps!

I agree that the plane will fly, but after reading your example Cliff, I'm now afraid to drive my Fiero.

control system that tracks the plane speed and tunes the speed of the conveyer to be exactly the same (but in the opposite direction)

Forget the three rollers. That was just an example of a stationary device that keeps you stationary despite the power you use.

Forget how the bike is powered. Put a JATO on your back if you want. If you push the bike by hand, the control system will notice the speed increase and re-adjust the speed. Forward motion will not happen. It's not as if the ground is stationary, it's moving in reverse. You cannot get forward motion. If the plane is moving 3 mph, the conveyer is moving -3mph.

[This message has been edited by Gokart Mozart (edited 12-24-2007).]

Gokart, meet Roger.