Will an airplane on a treadmill be able to takeoff?

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MistaX

MistaX

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MistaX1
A plane is standing on a runway that can move (like a giant conveyor
belt). This conveyor has a control system that tracks the plane's
speed and tunes the speed of the conveyor to be exactly the same (but
in the opposite direction).

Will the plane be able to take off?



(This is not my own question, It's been all over the interweb, I'm just curious what GTP can come up with)
 
It's also been on GTP already.

The answer is a resounding no. Unless the wings of the plane have air passing over them the plane will not take-off. Ever.
 
I asked a few people and they said it hadn't been here yet.

Argh.
 
Like he said its a defo no. the wings need to have a certain amount of air crashing over at speed for lift to be generated, if you plane is on a massive dyno, the engines will be working hard but the wings will not. And that is why you cannot fly on a big treadmill.
 
Well it seems pretty obvious to me that the plane would never take off also. What would be the reason anyone would think different???
 
Because the wheels are free turning and it's quite possible that enough thrust would be produced to lift the wheels off the treadmill, and thus it WOULD take off.
 
Slick Rick
Well it seems pretty obvious to me that the plane would never take off also. What would be the reason anyone would think different???
Click to expand...

Perhaps people are confused as to how aerodynamics work?

It seems pretty obvious to me, but...
 
This has actually prompted me to post a thread on a physics question put forward by my physics lecturer.
 
MistaX
Because the wheels are free turning and it's quite possible that enough thrust would be produced to lift the wheels off the treadmill, and thus it WOULD take off.
Click to expand...

The wheels do not create anywhere near enough lift to allow a plane to take off, also the are not moving only rotating, therefore in no wind they are creating very little lift indeed, wings are the reason a plane flies, without wings not enough lift would be generated.
 
Why wouldn't it be possible?
If the plane's engine has enough pulling strength, it doesn't matter how fast the runway is moving in the opposite way, as long as the wheels of the plane don't cause to much traction. It's the engine that causes the plane to move, not the tires.
 
But it's the tyres that allow it to gain the desier airspeed. Even a prop' driven plane wouldn't be able to take off as it would need to accelerate first before the air being pushed over and under the wings would induce enough lift.

MistaX
Due to that being 2 years ago, I think it's fair to keep this thread.
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Why? Physics hasn't changed that much in the last 2 years ;)

[EDIT 2]
Perfect analogy for a car foum.

Does a car on a dyno (with without a wind tunnel in work, and with neglible air flow from cooling fans) create downforce? No. Thank you.
 
A car needs his tires for forward movement, a plane doesn't.

If the engine sucks in enough air, the plane will start moving forward and the tires, because of the belt, will start to move backwards at twice the speed of the forward movement.
(the belt moves at the same speed of the plane, not the tires)

If the plane has enough forward speed it will gain lift and it'll take off
 
DustDriver
A car needs his tires for forward movement, a plane doesn't.
Click to expand...
When a plane is trying to take off, it requires tyres, skids floats, something to move in relation to the earth in order for it to accelerate and reach the correct velocity.

Planes don't just reach take off speed, that's why runways are so long.

[EDIT] Extended quote.
If the engine sucks in enough air, the plane will start moving forward and the tires, because of the belt, will start to move backwards at twice the speed of the forward movement.
(the belt moves at the same speed of the plane, not the tires)
Click to expand...
Last time I checked, the tyres were part of the plane. If they weren't needed, they wouldn't be there. I'm sure in 100 years of aviation someone would have realised that ;)
 
Hang on! A workmate of mine asked me the exact same question a few weeks ago, and we quickly came to the conclusion that the plane will take off whatsoever. The explanation actually is pretty simple:

Let's make the same experiment with a car, asking if the car will ever move in relation to the ground if it runs on a conveyor belt that matches the speed of the car in the opposite direction. The answer is no, simply because the belt will always match the speed of the tires, which propel the car. So if the car goes 100mph on the belt, and the belt obviously does 100mph in the opposite direction, the resulting speed for the stationary observer is 0mph.

Now let's get to the plane. The plane is propelled by its engines, "screwing" themselves through the air. The wheels are there simply for the plane not to lay on the ground, resulting in a fairly low rolling resistance. Now, as the tires are not the devices that push the plane forward, rather than the engines, the thing pays little attention to what its tires do. The only result the conveyor belt will produce is that the tires will go twice as fast as the plane.
So when the pilot turns up the engines, they will start pushing the plane forward through the air, and the fact that the belt underneath matches the speed in the opposite direction has no negative effect on that. So if the plane does 100mph at takeoff, the only result is that its tires will do 200mph (100 by the plane and 100 by the belt). Still, this does not prevent the plane from taking off.
 
And that's exactly what i said :) (or was trying to say)

The conveyor runway just needs to be longer than a normal one, since the wheels moving backwards will cause friction and air resistance.
But the plane will still eventually take off.
 
What about an airplane on a treadmill inside a wind tunnel?

Would it be able to take off then?
 
Okay lets create another analogy. :rolleyes:

You place a free wheeling cart on a treadmill. A light shines from it onto a light sensor. If that light moves forward of the sensor the speed of the treadmill will increase, in the opposite direction. A GPS locator is placed on the cart, this will measure the velocity of the cart in relation to the earths surface, and in effect, through the air that surround sit.

As you push the car from the back it moves forward on the treadmill but the sensor senses this and increases the rate of the treadmill. The harder you push the cart the higher the speed of the treadmill. Compare this pushing force to the thrust of an engine.

The GPS locator shows no movement of the cart over the earths surface. If the cart does not move, the air does not flow past it. If there were wings there would be no lift.

The conveyor does not change velocity in proportion to the wheels, but to the force of the thrust.

[edit]Now let's get to the plane. The plane is propelled by its engines, "screwing" themselves through the air. [/quote]
Untill the plane reaches terminal velocity, the engines are more like pushing air backwards.

The wheels are there simply for the plane not to lay on the ground, resulting in a fairly low rolling resistance. Now, as the tires are not the devices that push the plane forward, rather than the engines, the thing pays little attention to what its tires do.
Click to expand...
No. the tyres allow the plane to accerlerate with mimimum resistance. The plane will not reach take off velocity instantly. Again, that is why runways are so long.

The only result the conveyor belt will produce is that the tires will go twice as fast as the plane.
So when the pilot turns up the engines, they will start pushing the plane forward through the air, and the fact that the belt underneath matches the speed in the opposite direction has no negative effect on that. So if the plane does 100mph at takeoff, the only result is that its tires will do 200mph (100 by the plane and 100 by the belt). Still, this does not prevent the plane from taking off.
Click to expand...
No, the tyres will rotate in the equal and opposite speed as the conveyor belt. The speed of incident between the tyres and conveyor will be exactly double that of the speed of one of them individually. However, when you add the speed of rotation of the conveyor belt to the speed of the wheels the resultant is ZERO. You seem to think the tyres are a seperate being to the plane. They are not. If the wheels have no resultant over the ground it is on, the plane will remain still, the wheels will rotate.
 
lol, just looked the question up on the internet and 1 of the comments on a site was this:
Exactly what I was thinking. I wasnt even thinking about the wheels... just the fact the plane isn't really moving, therefore no lift force provided to make the plane actually go... up!

An example would be like sitting on those gym bikes with no wheels. You can peddle as fast as you want, but you wont feel the fresh breeze of that speed. No breeze, no wind... no lift!
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He is right about the gym bike, but a gym bike isn't a plane.
If you put a propeller on the front of the bike and find a way to make it turn when you're peddle, you will get that breeze.
It's not enough to make the gym bike move, but if you put tires under it, so that it can roll freely, it will if you peddle fast enough.
Now, if you put it on a treadmill, to gain the same forward movement, you will have to peddle faster, but eventually you will drive off the the treadmill.
It's best to put an engine on there, instead of peddling yourself, but you get the picture.
 
Sharky.
What about an airplane on a treadmill inside a wind tunnel?

Would it be able to take off then?
Click to expand...
No, it wouldn't. I'm just not entirely sure if you're taking this problem as serious as it is. :odd:

Anyway, here's another shot that'll probably bring more light in the dark. Let's make an experiment with Exige Excel on a bike, driving on a treadmill that matches his speed.

The question is: will he ever move in relation to the surrounding floor?

The answer: no, because the treadmill will always match the speed he's doing. If he does 5mph, so will the treadmill, if he does 10, so will the treadmill, and so on.

So what if Exige Excel takes his feet off the pedals and utilises one of those bagpack propeller engines paragliders sometimes use?

The question: will he move on the treadmill now?

The answer: yes, he will. The treadmill will still match the speed the tires of the bike will be doing, but now, his propellant is the bagpack thing he wears. It utilises the surrounding air (which is stationary in our experiment) to move itself and the attached person fordward. For that, the only question is the speed of the surrounding air. So if the air moves at 0mph, and the propeller is good for 30mph, Excige Excel will move forwards at 30mph. At the same time, the bikes tires will do 60mph, but that won't stop him from moving.
 
Yes, the plane will be able to take off, as long as it has somewhere to go, and the conveyor belt is the length of a runway.
 
DustDriver
lol, just looked the question up on the internet and 1 of the comments on a site was this:


He is right about the gym bike, but a gym bike isn't a plane.
If you put a propeller on the front of the bike and find a way to make it turn when you're peddle, you will get that breeze.
It's not enough to make the gym bike move, but if you put tires under it, so that it can roll freely, it will if you peddle fast enough.
Now, if you put it on a treadmill, to gain the same forward movement, you will have to peddle faster, but eventually you will drive off the the treadmill.
It's best to put an engine on there, instead of peddling yourself, but you get the picture.
Click to expand...

No because as much force as you apply, the exact opposite force will be applied (we are assuming without lag so no acceleration happens therefore no steadily increased forward momentum) the wheels are just a medium for reducing friction, thanks to gravity the wheels will only move according to what force is applied in a direction, if an equal opposite force is produced then the acceleration equals zero.
 
the Interceptor
No, it wouldn't. I'm just not entirely sure if you're taking this problem as serious as it is. :odd:
Click to expand...
You guys are saying on a treadmill there's no air moving over the wings. Put it in a wind tunnel and you get instant air-flow, so the plane should take off.

Actually taking off safely in a wind tunnel is another matter :lol:
 
Sharky.
You guys are saying on a treadmill there's no air moving over the wings. Put it in a wind tunnel and you get instant air-flow, so the plane should take off.
Click to expand...
Okay well, that depends on which version you believe in. If you are with Exige Excel saying that the plane stays stationary in relation to the ground, a wind tunnel producing an airflow will enable the plane to take off. What I was thinking of a conveyor belt and a wind tunnel, both matching the opposite speed of the planes movements. Then, it wouldn't take off, but that way of understanding it includes that you believe my version of the story.

EDIT:
DustDriver
And about the car on a dyno.
What will happen if you put a car powered with a jet engine on a dyno. You can turn the wheels all you want, that car will still run off it.
Click to expand...
A great example! 👍
 
edit: @ ExigeExcel's last post on the previous page.
That is a completely different situation, and in that situation you're right.
If the friction and air resistance of the tires moving backwards is equal to the trust made by the propeller, the plane will not go forward.
But in the original question it sais "his conveyor has a control system that tracks the plane's
speed and tunes the speed of the conveyor to be exactly the same"
Nothing is said about trust, only about moving the conveyor at the same speed the plane is moving.


And about the car on a dyno.
What will happen if you put a car powered with a jet engine on a dyno. You can turn the wheels all you want, that car will still run off it.
 
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