Will it Fly?

[aurik]

If you have a perfect wheel, no amount of speed is going to stop the plane from moving forward.

eot.

[Lockecole7]

If you have a perfect wheel, no amount of speed is going to stop the plane from moving forward.

eot.

Explain this in further detail? If anything I'd see a perfect wheel (one that can move at an infinite speed without breaking, and keep up with the increased speed of a jet's propulsion on the plane itself) as the one thing that would instead support a plane from not moving on a perfect treadmill. (one that can keep up with an equal counterforce) Unless that's what you're saying and I'm reading it wrong.

Do you mean "No amount of speed is going to make the plane move forward"? (because both wheels and the counterbalance treadmill are capable of equating each other's force.)

[Yeargdribble]

I used to be in the no-fly group, but realized my error long before the Mythbusters episode.

Yes, hypothetically if a treadmill could hold a plane in some static equilibrium, it wouldn't take off because there would be no air moving across the wings to create lift. So the question becomes, "Could any treadmill actually hold a plane in a static state?"

The answer is no. Even if the treadmill were going 10x the speed of the opposing thrust of the engines, it would make no difference. The wheels are free-spinning and produce negligible friction. Because of this, they do not function at all like a car. There is no speed matching. The wheels work on the ground and the engines create thrust in the air. The wheels are a moot point because of their lack of friction.


People are arguing about this like crazy on the Discovery MB Board. Basically it is because they (like myself once upon a time) do not actually understand the question.

[Thevaultdweller]

http://img509.imageshack.us/img509/1...nsworthsa7.jpg

The plane doesn't move at all. The world moves around it.

[Avinor]

If you have a perfect wheel, no amount of speed is going to stop the plane from moving forward.

eot.

Explain this in further detail? If anything I'd see a perfect wheel (one that can move at an infinite speed without breaking, and keep up with the increased speed of a jet's propulsion on the plane itself) as the one thing that would instead support a plane from not moving on a perfect treadmill. (one that can keep up with an equal counterforce) Unless that's what you're saying and I'm reading it wrong.

Do you mean "No amount of speed is going to make the plane move forward"? (because both wheels and the counterbalance treadmill are capable of equating each other's force.)

If 'perfect' implies 0 friction, then the runway couldn't assert any lateral force on the plane through the wheels, it could only spin them. I doubt the nature of the wheels will be the deciding factor ultimately, as long as we assume the wheels are strong enough to withstand unreasonable amounts of stress. Assuming the runway itself has friction (which it must, or else the problem is over instantly) then the movement of the runway will also drag the air in the same direction, against the plane. This will provide a counter force to the thrust of the jet engines (as long as the plane is not frcitionless and has drag), but it will also be giving the plane the one thing it needs to get off the ground - air moving over its wings.

One problem, however, is because the runway's movement is whats causing the air to move, there is a velocity gradient in the air speed, dropping off exponentially as you get further from the ground. So that will hurt the ability of the wings to make lift, since air will be moving faster the closer you get to the ground, underneath the wing (which is the opposite of what you want for lift). At this point I suppose it boils down to technicalities - how much does the plane weigh, how much lift do the wings provide (assuming they can still provide 'lift'), how close are the wings to the ground, how much drag the plane has and how much thrust the engines can provide. But if the engines can produce enough thrust to force the treadmill to throw enough wind at the plane so the wings can provide lift, eventually the plane would take off even if its not moving at all relative to a stationary observer.

[Jotaru]

^

Incorrect train of thought.

[Lockecole7]

I used to be in the no-fly group, but realized my error long before the Mythbusters episode.

Yes, hypothetically if a treadmill could hold a plane in some static equilibrium, it wouldn't take off because there would be no air moving across the wings to create lift. So the question becomes, "Could any treadmill actually hold a plane in a static state?"

Unless I'm confused, wasn't the whole point of the original OP's scenario that the treadmill COULD keep and match the planes velocity, and keep it stationary? Just like you assume on a treadmill that regardless of how fast you run, as long as you adjust the speed that it will keep you stationary?

People use the "push argument" that if someone ran up behind you and pushed you, you'd obviously fall forward because of the outside force while on a treadmill. Only thing wrong with this comparison is, that it assumes your legs won't compensate for the extra force being applied. Wheels on a plane do that (well perfect wheels do, imperfect wheels obviously could fail at any point for obvious reasons due to ridiculous speeds). Say you were on that same treadmill, someone pushed you, and your legs automatically compensated for the increased speed and force you added, and also the treadmill increased its speed to compensate. You would STILL stay in the same place, barring any balance issues haha.

The answer is no. Even if the treadmill were going 10x the speed of the opposing thrust of the engines, it would make no difference. The wheels are free-spinning and produce negligible friction. Because of this, they do not function at all like a car. There is no speed matching. The wheels work on the ground and the engines create thrust in the air. The wheels are a moot point because of their lack of friction.

Lack of friction? How so? Do you even know why a plane lifts off of the ground? Because of the air forcing itself around the wings. This plane would not be moving, therefore regardless of its speed, all of the force and friction would be forced onto the wheels, still keeping it on the ground, and still keeping it on the treadmill. Am I wrong in this line of thinking?

[Rigor]

I visit foh forums too :D

[Slapper]

What if...

http://img297.imageshack.us/img297/5...eadmillyc8.jpg

[Lockecole7]

What if...

http://img297.imageshack.us/img297/5...eadmillyc8.jpg

The plane, can also be... a hat!

[aurik]

If you have a perfect wheel, no amount of speed is going to stop the plane from moving forward.

eot.

Explain this in further detail? If anything I'd see a perfect wheel (one that can move at an infinite speed without breaking, and keep up with the increased speed of a jet's propulsion on the plane itself) as the one thing that would instead support a plane from not moving on a perfect treadmill. (one that can keep up with an equal counterforce) Unless that's what you're saying and I'm reading it wrong.

Do you mean "No amount of speed is going to make the plane move forward"? (because both wheels and the counterbalance treadmill are capable of equating each other's force.)

Assuming a perfect wheel, the treadmill's motion has no impact on whether or not the plane will move forward or backward, because it exerts no horizontal force on the plane. Thus, if the plane's jet engines are creating horizontal thrust, it is impossible for the treadmill to counteract this force, regardless of whether the treadmill is moving at 1 meter per second or 100 meters per second.

[archibaldcrane]

This question is retarded, it completely depends on how much friction is between the wheels and the ground. If 0 (total hypothetical) then the treadmill has no effect no matter how fast it goes - the plane's engines could be off and the plane wouldn't move anywhere regardless of treadmill speed.

It's just a question of whether the plane's engines can overcome the friction between the wheels and the ground (which push it backwards) enough to achieve a fast enough speed to achieve adequate lift to take off. This would, of course, depend on the plane, the tires, the surface of the treadmill, etc. etc. etc.

Not enough details, cannot be answered as is.

[Lockecole7]

Well fuck me, apparently my understanding of exactly how physics works on a plane and where exactly a plane is being pushed from was a little flawed after discussing it with a friend.

http://www.youtube.com/watch?v=4owlyCOzDiE

This essentially shows that the plane, due to the "jet engines" force causing it to move forward due to pressure on the air around it, not the friction between the treadmill and the wheels. So essentially once the plane hits the speed necessary to "fly" it will move forward without relation to the ground below it, because the force of the plane and the mass of the plane will technically already be "flying" even while on the ground, because it will be traveling through the air, and using the force of the air around it to make it move forward, not the ground below it.

[Jotaru]

Not enough details, cannot be answered as is.

Yes it can, the wheel's frictional force is so remotely small compared to the force applied by the engines...

If it weren't, the airplane wouldn't be able to overcome the friction of the wheels with the runway NOT moving. The only difference is the wheels will be moving 2x as fast.

[Ishido]

So the answer is: It will take off from a treadmill that is as long as the runway a plane would normally require to take off.

I didn't really expect that, though admittedly I never put a ton of thought into it.

[archibaldcrane]

Not enough details, cannot be answered as is.

Yes it can, the wheel's frictional force is so remotely small compared to the force applied by the engines...

If it weren't, the airplane wouldn't be able to overcome the friction of the wheels with the runway NOT moving. The only difference is the wheels will be moving 2x as fast.

It's a minor distinction, but a plane that could barely reach takeoff speeds before being on the treadmill may not be able to with the additional, albeit very minor, additional frictional force.

It's not a plane I would want to fly on, but it's a possible situation that would render it false in real life. Usually it'll takeoff fine.

[Priran]

a system in place to constantly monitor the exact speed of the airplane on it. As the plane powers up the jet engines and moves forward, the treadmill moves rearward, in the opposite direction the plane is moving, at the same speed.

All I've seen so far are planes taking off from treadmills maintaining a constant speed. My understanding of the question was that the treadmill negated forward movement of the plane, and that the problem was whether or not the thrust from the engines of the plane would be enough to make it take off.


That being said I haven't seen this MythBusters thing, did it air yesterday?

[Lockecole7]

a system in place to constantly monitor the exact speed of the airplane on it. As the plane powers up the jet engines and moves forward, the treadmill moves rearward, in the opposite direction the plane is moving, at the same speed.

All I've seen so far are planes taking off from treadmills maintaining a constant speed. My understanding of the question was that the treadmill negated forward movement of the plane, and that the problem was whether or not the thrust from the engines of the plane would be enough to make it take off.


That being said I haven't seen this MythBusters thing, did it air yesterday?

Did you even watch the video I linked? In that video regardless of the speed of the treadmill (it varied from 2.5-10mph) the same torque on the plane was needed to keep it stationary. Essentially the truth is that no treadmill, regardless of the speed would work, in essence a conveyor belt type ground would act EXACTLY as a normal solid ground once a plane hit a certain speed. Go and watch it again.

[Priran]

a system in place to constantly monitor the exact speed of the airplane on it. As the plane powers up the jet engines and moves forward, the treadmill moves rearward, in the opposite direction the plane is moving, at the same speed.

All I've seen so far are planes taking off from treadmills maintaining a constant speed. My understanding of the question was that the treadmill negated forward movement of the plane, and that the problem was whether or not the thrust from the engines of the plane would be enough to make it take off.


That being said I haven't seen this MythBusters thing, did it air yesterday?

Did you even watch the video I linked? In that video regardless of the speed of the treadmill (it varied from 2.5-10mph) the same torque on the plane was needed to keep it stationary. Essentially the truth is that no treadmill, regardless of the speed would work, in essence a conveyor belt type ground would act EXACTLY as a normal solid ground once a plane hit a certain speed. Go and watch it again.

The idea that a plastic and foam toy plane, partially suspended by wires, is an accurate model of a real plane is a bit lulzy. That, and the guy doing it is completely unable to keep the plane still, let alone at a constant speed.

Also, did you even read the thing I wrote? The question, as I understood it, boiled down to whether or not a plane could take off on thrust alone. The treadmill just seems to be a device to illustrate that the plane is not moving horizontally, and the idea that the treadmill is able to cancel its movement can be taken at face value. Like, the train of thought here was "Could a plane take off if it wasn't able to move forward? - Why isn't it able to move forward? - Uh, it's on a gigantic treadmill", not "Dude would a plane take off if you put it on a treadmill?".

[Plow]

How are there 4 freaking pages about this?


PLANES AREN'T POWERED THROUGH THE WHEELS PEOPLE.