Plane on conveyor... Will it ever take off?
 

A plane is standing on a runway that can move (some sort of band conveyer like a treadmill). 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 opposite direction).

The question is:

Will the plane take off or not? Will it be able to run up and take off?

Oh Jesus not this again....the answer is no, because at the takeoff speed of 175mph the air moving under the wings aids the air produced by the jets.

Huh??

Yes, because the wheels do not drive the plane, the jet engines do so they will move the plane through the air (even if the wheels are on the ground).

However you will probably encounter some parasidic drag from the wheels rolling resistance, and possibly tire/wheel bearing/ undercarriage failure from teh extra heat and or forces from the wheels having to spin at twice their normal speed.

Will this ever die... please die...

Are you guys crazy? Airplanes fly because of lift, the engines create forward motion, forward motion cause air movement around wings which creates lift, no forward motion, no lift, no lift, no fly! Basic.

Wrong. It doesn't matter what the wheels do. The wheels could be spinning at 1000 mph and it doesn't matter. The thrust of the engine will push it forward. Now if you have a 10,000 foot conveyor, the plane will take off.

It is very basic indeed, just gotta think about what makes an airplane move... but you're still incorrect, lol


And yes, will this thread ever die !!!!:skep:

hahaha! You're right! Because the engines pull/push the plane though the air. The wheels will just turn. Ha all of you guys are right, I am a dumbass and don't deserve to live!!! man, I got stuck on forward motion but the wheels don't dictate that on a plane, duh!

Quoted

Hey it's true! That's probably why I'm where I'm at!!!:lol:

Its the combination of the thrust of the engine (jets moving air which goes over the wings) and the air velocity at 175mph (air moving over the wings) COMBINED that moves the plane. Yes if the engine jets were big enough, the plane would move w/o the air velocity of the moving plane. Its like how do you turn a bike fast. You do A PLUS B. Countersteer and lean. Can you still turn w/o leaning? Yes, but is takes much more force.

Exactly!

Don't feel bad.... This thread was posted on just about every forum on the net about a year or so ago, and you would absolutely not believe how many people just simply can't grasp such a simple concept, even after you explain it in full. So hey at least you got it right away!

But again the real question is if the rolling equipment will be able to withstand the conveyor belt at 350 mph? Because if it fails, that plane is gonna burn in a firey crash

The jets pull air over the wings in addition to the forward motion.

If by "moving" it means moving in relation to the Earth, not just in relation to the belt, then yes eventually it will take off. Doesn't fucking matter what the belt is doing --- All that matters is airspeed over the wings. Get enough of that, and it will lift off, even if the engines are dead.

Huh?? :skep:

I don't have the slightest clue what you're trying to say....

But the plane doesn't give a f**k about thrust, all it needs is air moving across the wings. If the plane is sitting still and there is a 175 mph headwind, it will lift up and take off. Engines don't move any air across the wings, all they do it push it forward

No, they don't

It still has forward motion. You could run the tread mill in reverse and still take off. You don't even need wheels on a plane.

http://www.johnnyjet.com/images/PicF...FloatPlane.JPG

James

The wheels don't matter at all ( unless they're cemented into place). What about planes with floats or planes with skis? :tremble:

I haven't used this gif in a year

http://img.photobucket.com/albums/v7...animated-1.gif

Jeff

Turbines pull air over the wings which aids in lift. How much I don't know. I agree the main thing the turbine does is create a low pressure in front of the plane which causes the rear air pressure to push the plane forward. But, the force of air backward acts on the wings the same way the moving plane air acts on the wings.

I'm sure if you reached the 175mph and stopped the engines the plane wouldn't lift. You would have to increase speed. But yes air moving across the wings is the only thing lifting the plane, but we are discussing where that air is coming from.

The part your missing is the belt would not be able to hold the plane in place because the plane moves through air no matter what the wheels are doing.

Yeah, maybe ur right. At 175mph is doesn't matter what is happening to the engines...the 175mph is what the engines are giving out regardless if something is pushing it, pulling it whatever.

Dude, seriously!?!?! Where do you come up with this stuff??

No, the turbines do not move the air across the wings. Generally they're mounted UNDER the wings, and the outlet is BEHIND the wings. Some are even mounted in the back. Or how about a small plane with a single prop in front... how is that gonna move any are across the wings?? It's not even close

I don't know where you got this wacky idea that the engines are like a fan blowing air across the wings. THEY'RE NOT!! They have one purpose and one purpose only.... to move the plane forward. That is IT! Once the plane is moving forward, the surrounding air moving across the wings produces the lift

But since you want to argue.... by your logic, explain to me how this plane ever made it off the ground. Where's the turbines drawing the air across the wings?? Hmmmmm....

http://www.richard-seaman.com/Aircra...erburner_1.jpg


Seriously bro.... not trying to sound like a dick here or anything, but you might want to educate yourself a little bit on the subject matter before getting into an argument.... just sayin ;)

Read my post above snappy. And I never said the turbines are needed to lift a plane, I was simply saying that the air the turbines draw across the wings aid to the lift. 1% maybe:lol

If you strapped the plane down from the top and put it on a scale, spun up the turbines at full pop, would the plane weigh any less? If so, then there is some lift acting on the wings. Speaking of commerical jets with the turbines under the wings.

That's a sweet pic

Add you'd still have that. The wheels do not power the plane. The engines would get it up to speed regardless of what the wheels were doing.

Not as sweet as this one! heheheh

http://www.aviationexplorer.com/Comm...fterburner.jpg

Agree...the wheels would just spin at the ground speed plus the conveyor speed. Never argued against it. They can be neglected.

At least I'm smart enough to know when I'm stupid....:wink:

An Airplane does not need "propulsion to fly.
It needs airflow over the wing surfaces.

If you want aircraft to fly, you do not need ground speed...you need airspeed.

Simple way to show this is to stick a paper airplane in front of a fan.

Propulsion's purpose is to maintain airspeed (to over come aerodynamic drag) necessary to ensure lift.
In the case of a glider, gravity is used to achieve proper airspeed (once disconnected from the tow aircraft and aerodynamics take over.

A helicopter use the same principle with rotor hub altering the angle of attack during each rotation as the rotors experience vary airspeed.

You can get into more detail of aerodynamic (vortex crap, drag)


The key to creating lift is the negative pressure on top of the wing with some positive pressure under neath


Official NASA yapping

Dude ur not stupid...I mean ur no aeronautical engineer, but ur not stupid. :lol

<--Aero Engineer & Pilot here. :)

This is the correct and only answer.

All wheels on aircraft free spin. There is no direct link to the engine since there is no transmission.

They actually did it on Mythbusters and the plane flew.

But what if the plane was on the moon? Could it still take off if the freezer was full?

Would a snake on a conveyor belt take off?

What about a plane with a conveyor belt full of snakes in freezers on the moon?

Would the snakes still be cold, or would it just be a bunch of warm snakes wondering why the Government put them in a plane with freezers at a Top Secret moon replica facility, with a giant conveyor belt?

The answer is:

Fidel Castro.

It has to be.

JC

Tie a string to a toy car on a treadmill that's going 200mph in reverse, do you have to pull 200mph on the string to move it? Or will the slightest nudge cause it to move forward?

BRB


:leaving:

Snakes?

:lol:

JC

OK, a standard 110VAC treadmill won't go 200 mph. :tt:

When you rewire it for 440VAC, it lets all the magic smoke out of the wires and it doesn't work at all :willy:

Put it in freezer next time!

N00b.

JC

http://www.youtube.com/watch?v=0KsdMuhYJPw

http://www.youtube.com/watch?v=0ul_5DtMLhc

It's been about 4-5 years now....and it looks like it just won't go away....

If the belt and was moving at the exact same speed as the plane, how was the plane able to move forward? If I run at 10 mph on a treadmil that is going 10mph, I don't move forward, I stay stationary... If I speed up my pace to 11 mph while the treadmil is still at the orig 10 mph, I move forward on the belt, if I slow my pace to 9 mph, I fall off the back...

Read back a bit.
The movement of the plane has nothing to do with anything touching the conveyor. The thrust from the jet engines will push it forward while the wheels spin free.
We're sort of pre-wired to think only in terms of movement based on pushing against the ground... that's not how planes operate.

Ahhh... I didn't even think about the movable wheels not having any affect on the thrust. If the wheels were locked, and the thust was on, yes... the plane would be standing still...

That says it right there. Planes don't make sense. :lol:

that plane flys by sheer awesomeness alone.

Ok. You want to know what happens? I'll tell you what happens.

If you try to fly a plane off of a treadmill, it fucking explodes. The plane explodes, the treadmill explodes, the people in the plane explode. EVERYTHING FUCKING EXPLODES!!! First they all explode into smithereens, then the smithereens explode too, until finally, the sub-smithereen particles explode, and then catch on fire (obviously, very, very small fires).

Then the tiny little fires explode.

That's what happens.

JC

There's one other factor [er, two].

Because the plane (due to its being essentially temporarily "immobilized" on a treadmill) is not really moving against the ambient air (well, no more air than the thrusters will provide in airflow); the plane is essentially taking off with a matching tailwind, as the ambient air is not aided in differential movement across the plane by any takeoff-speed-provided airflow.

I agree that beyond this factor (and the minor issue of increased wheel speed, and a corresponding increase in bearing losses) the wheels play essentially no part in this.

The plane will still fly, because its true interaction (primary exchange of thrust) is via the air, not the ground via the tires, as they free-spin (as you pointed out).

I thought that was the point of the riddle, that the conveyor cannot immobilize the plane since the plane propels itself using air, not the wheels. So if the thrusters are set for 240mph and the treadmill is set for 240mph in the other direction, the plane still moves at 240mph but the wheels spin freely against the conveyor at 480mph. Or no?

Yes

The problem with this whole thing is that it's impossible for the magical treadmill to match the wheel speed of the plane. Unless some laws of physics are seriously tweaked, the plane will always move forward, and that means the wheels will always spin faster than the belt on the treadmill. If you made something in the real world that tried to constantly match the speed of the belt to the wheels, the belt would quickly keep going faster until something blew up (a la AMJ). The plane would continue on, blissfully unawares.

LOL, damn those smilies...

That wouldn't be impossible. If someone had pockets deep enough that could be built. But they done this on tread mills with remote control planes so its not to hard to believe.

And a float plane can take off on water. I think the floats would cause more drag then the wheels/wheel bearings being over worked and it has no problem taking off.

If you stand on a tread mill with roller skates on you are like a plane before the engines are turned off. Don't try to skate, just stand there because the plane doesn't get forward movement from its wheels. They are just like casters on your office chair. The wheels allow the object they are attached to to move freely across the ground when they pushed.

You push your office chair with your feet to move it. The plane uses and engine that will pull/push it self through the air, Once it is moving fast enough through the are for the wings to work it takes off. The speed of the ground under the wheels has no affect.

The ground is a moving platform on a aircraft carrier.

James

I asked this to a buddy whom is a retired AF Maj. Here is his answer:

Despite what Mythbusters says, this is not possible. If the treadmill is traveling at the same speed as the plane, there is no airflow over the wings. Without airflow, there is no lift.

Now, with that said, here is how they get around the issue. By using a propeller to generate the thrust needed to “move” the airplane at the same speed as the treadmill, the propeller is pushing air over the wings, causing some lift. In very light aircraft, you might even create enough lift to get the aircraft airborne, but you have changed the original equation. If you use a jet engine which bypasses the wings, the answer is a little clearer. Better yet, use a glider that matches the speed of the treadmill by having a support that keeps the glider from moving backwards. Unless you can get the treadmill going fast enough to generate airflow over the wings, it’s not gonna happen!

If you stick to the physics involved in the original setup, it is not possible. Mythbusters “disproved” the myth, but in both cases (model and full size) the aircraft was moving forward when it got airborne.

No. Just because he is in the air force does not mean he controls the laws of physics.

The plane will absolutely positively move forward and take off. The only purpose the wheels serve us to keep the belly of the plane from rubbing on the ground.

The turbine or prop will produce forward motion through the air. The wheels will just spin uselessly as wheels do not move a plane.


Once enough forward momentum is reached by this plane moving forward (not stationary) then lift will be created and the plane will take off.


In fact, if the plane originally could take off on 100 feet of runway, it would only need 100 feet of conveyor.

Sorry lucky.


There is your disconnect.

The question isn't whether it could take off from a standstill on a conveyor, its whether or not the thrust of the prop or turbine would move it forward enough on the conveyor to reach take off speed.

Well there goes my whole belief system. :td:

Yeah, if the Air Force doesn't control the laws of physics, who does? :tremble:

JC

Well up until a few minutes ago I never wondered about these things! Not I'm in a dead panic!:panic:

No? Really? Damn... I need to do more research then... I also thought that wind is made by trees swaying back and forth in the atomsphere...


When a fighter jet lines up at the end of the runway, it typically runs its engines up to full speed before releasing brakes. The speed of the wheels on the jet is equal to the speed of the runway below it (0 mph). The air coming out of the back of the engine is over 1000 mph, much faster than the aircraft needs to get airborne. If the myth is right, the aircraft should lift off!

And here is the argument you typically hear:
But wait, the brakes are set!!! That is why it doesn’t work!
So the second the pilot lets go of the brakes, the jet gets airborne?
No, it gets airborne when the speed through the air (not over the ground) reaches the point to cause enough lift over the wings to overcome gravity (the weight of the jet.)

The compressibility of air and temperature differences result in vast differences in one if you try to hold the other constant.

In theory yes but because the wheels are a friction point it would take slightly longer to get to Vr(Rotate speed). Your V1, V2, and Vr would all be the same speed as normal takeoff, it would just take a little longer to get there dependent on how much faster the conveyor was running than the take off speed.

So you agree? :idk:

Rider, I know what you're saying.

But, I honestly think the friction increase woudld be so small that the bearings of the wheels would still be well within their operating range.

I agree that if you add thrust, yes the plane will take off, so long as the pressure around the wings is great enough to sustain lift... but if you do not add thrust, no the plane will not move.

Yes it will, it will move in the direction the conveyor is moving. :lol:

:lol

Gentlemen: Since the plane is on a treadmill, it is not being forced through the air, creating an artificial headwind. The only thrust to create speed differential with the surrounding air is the plane's thrust.

If the plane is of a design as to have enough thrust to get airborne essentially with no headwind (at least none induced by moving the plane forward, which the treadmill assures cannot happen), and by its own thrust alone, then it will take off.

The freewheel on the tires is exactly doubled, as has already been said. I believe the frictional losses, if within the spec of the wheels, is probably relatively inconsequential.

Thats the thing. The glider has no thrust. If the tread mill is doing 300 mph and the gliders wheels are turning at 300 mph because of the tread mill moving then you have no lift. But a glider glides and as someone said uses gravity to pull it through the air which allows the wings to create lift.

Now take a regular plane and do the same thing. Leave the engines off and its like the glider. With the tread mill moving at 300 mph and the wheels turning at 300 mph we have a plane sitting still. BUT...if the tread mill is moving 300 mph and the PLANE itself is moving 300 mph it will fly.

The plane gets trust from engines that move air NOT a transmission connected to wheels.


Try this one. The bottom of a small plane is about 3 feet off the ground or so, right? Lets take a crazy pilot and have them fly over the runway at 3 feet off the ground (in a small plane that can retract its wheels) its over the same height off the ground as the plane on its wheels. If it does this at 150 mph, the ground will be moving under it at 150. The plane flies.

Now take this same crazy pilot and the same plane but have him fly the same way over a big ass tread mill the size of a runway. The ground (or treadmill belt) will be moving at 150 mph, the plane is going in the opposite direction at 150. Because of this it if you took the speed of the belt it should be like its going 300 mph. But the plane will still fly over it. It would have no affect on the plane.

If the plane did this over a tread mill with the belt going in the SAME direction of the plane you could have someone hang from the plane and step off the plane and they would be standing beside the plane moving (well the 150 mph wind should not the guy on his ass but if he could stand in the wind he would be standing by the plane.

The treadmill doesn't stop the air from moving. When the PLANE is doing the speed its needs to create life it will take off. It doesn't care what speed the ground is moving at, it only matters what speed the plane is moving throught the air.

Thats the key there. Air speed.

James

The ground is irrelevant.

All that matters is air. thrust is used to overcome drag.

Everything else is swirlies...


fucking bitches

There is no spoon

Right so then how will a treadmill stop it from flying? It won't. The air going through the jet engine isn't moving over the wings. When they release the brakes it moves forward, gaining speed then when its moving fast enough through the air for the wings to create lift it will fly. Put it on skis and it will do it on snow. Put it on floats it will do it on the water. And the reason that works is because the wheels and ground don't matter.

James

The CIA.

Duh.


Sheesh.

That's where the confusion lies. A treadmill cannot immobilize a plane, it can only rotate it's wheels, which will do absolutely nothing to slow it down.

Of course not.

It exploded.

JC

Yeesh, I'm not as stupid as I thought I guess... Even the pilot on Mythbusters didn't think it would work. I'm sorry Lucky but I operated a Vulcan cannon and jumped out of airplanes for 10 years, that doesn't mean that I can explain how the system works or even how chutes work from a physics standpoint.

Nope, it really is impossible. The treadmill could never match the speed of the wheels, because there's nothing it could do to keep the plane from moving forward through the air. And that means the wheels always go faster than the belt.

And Avatard, uh. no. The treadmill doesn't do anything to the plane, except spin its free-wheeling wheels. It's just like taking off from a regular runway.

Damn, I swore I wouldn't get sucked into this after the last time it came up.

The belt doesn't need to go as fast as the wheels. It needs to go as fast as the plane as far as the myth goes. So it is possible to build this. And yes your right the wheel speed increase but the fact that fact still shows that it has no effect on the plane at all.

So it is possible to build this and prove this point. Anything short of a bearing failure would not stop the plane from flying so it will prove that wheel speed doesn't matter at all.

James

Well, you were supposed to, but I can't even have faith in that anymore.
I'll be damned if I'm leaving Scotch & cookies for you this Christmas Eve.


ps. Is this argument still going on? Really people... someone just needs to ask NASA for a computer sim because this is wasting far too many peoples' time and brain power.

We don't need a computer sim. Mythbusters did it full scale. How much better can you get then that?

James

Clearly that's not proving it to some people since they're still arguing that it won't work. :idk:
That's an argument here for you... if you can't be right arguing it your way, change the specifications of the experiment so that you sound right anyway. :lol:

We can run the Mythbusters test again. Use a prop plane. If they feel so confident that it won't move they can stand in front of it.

James

The list of people I'd toss in front of a moving prop-driven plane gets longer every day... don't tempt me.
We could do the same with a jet, but my dad has instilled in me too much respect for the gas turbine to want to see someone get sucked into it.

With the economy and fuel prices it would be irresponsible to use a jet engine. Plus with the prop plane we can have an Aston Powers roller moment.

http://www.youtube.com/watch?v=J6Ipd...rom=PL&index=9


James

The answer is no, planes take off based on lift (Bernoulli effect) which requires high pressure under the wings and low pressure above. The shape of the wings make this happen as air passes over them. If the plane is stationary and the tires are spinning and the engine is running it will just burn fuel and wear out the tires.

The plane moves forward. It doesn't stay stationary.

If the plane were stationary, the question might as well be, "Can planes take off when they're cemented to the ground in a hangar.".

LOL, I'm remembering a different version, I guess. I remember hearing that the treadmill exactly matches the plane's wheel speed, which is the part that's impossible (and usually f's people up).

If people need (yet another) analogy to make this make sense, pretend you're talking about your kid's Hot Wheels car on a treadmill with your hand holding it in place. Can you imagine anything that you could do to that treadmill to make it impossible for your hand to move that little car forward? No. The plane is the same, except it's the Hand of God moving the plane. :lol:

The treadmill could quadruple the wheel speed indefinitely until a rip in interdimensional fabric occured. The plane would still move forward relative to the ground and take off.

Until that singularity opened and the back end was sucked into the time rift where the passengers slated to die were removed to help save the human race in the future where pollution and genetic manipulation has made us incapable of reproducing.