Can an airplane takeoff from a treadmill?

Yeah, I think I was wrong. The trick is to not think about the "flying;" that's a red herring. Just focus on the center of the jets wheels, the axle. Now, with the engine off, what is happening? They're spinning along with the treadmill. Now, turn on the engines; what happens? Slowly, the center of the wheels move forward in response to the thrust. Once you buy this, you see the rest of the acceleration necessary to fly will occur.
 
the plane gets lift the way it always does, by moving forward through the air. again, you're thinking of it like a car or person, who uses the part of them touching the ground (our feet, the car's wheels) to create forward motion to counteract the treadmill moving and to stay in one place. with a plane on a treadmill, the engines push it forward relative to the air no matter what the treadmill is doing. the only difference between a plane on a runway and on a treadmill is that the wheels spin twice as fast (assuming the treadmill is going the same speed as the plane) b/c the treadmill's motion is also causing them to rotate. but the treadmill doesn't keep the plane from moving forward and thus creating lift. the wheels are just their to rotate and reduce friction, they don't create any movement.
 
Short and simple answer: Yes, but the plane's wheels would just be spinning faster, that's all.

My guess is that if the treadmill is motorized or not, regardless of how fast it is moving, would not present much "resistance" to the jet once the pilot hit the throttle. The aircraft is propulsed by the thrust, not by some motor in the wheels. So, while the wheels would indeed be spinning at a faster rate than they would be on a stationary surface, the plane's thrust is pushing against air mass just like it does normally. The treadmill could be going 2000 mph and as long as the bearings in the wheels could handle the speed, the plane would still move forward almost as if the ground were stationary. That had better be a long treadmill, though.

Think of it this way. If you are wearing rollerblades on a moving treadmill and you are holding onto the handrails of the treadmill. It is not really any harder at all to pull yourself forward toward the front of the treadmill than it would be if the treadmill were not moving. There is not much resistance. The plane would be doing the essentially the same thing, but pushing against the air mass behind it instead.

Pose the question the other way around: If the treadmill had no motor and was just a free-spinning treadmill, would the jet taking off cause the treadmill to turn? Very, very little.
 
ok, i think i see where the disconnect is here. the power for forward thrust is not applied by the wheels on the ground. so, assume that there is no friction in the wheel rotation. an aircraft is at point x on a stationary treadmill of whatever length. as the treadmill begins to move, in either direction, the wheels rotate but the plane remains stationary at point x, like a car in neutral. thrust is then applied by the engines. the plane begins to move forward without regard to the fact that the wheels are already spinning fast enough to counteract the treamill's movement, because the forward thrust is not applied through the ground, but through the air around the engines.

the way i initially read the question, i was thinking of a plane with engines full throttle but actually motionless as it rolls along on a treadmill.

now that i get it, i feel no need to be smug about it.

as for the kite analogy, try this. intstead of a kite, get on a treadmill with a bottle rocket. get going and light that sumbitch. it will go ijust as well with you running against a treadmill as it would with you standing on the ground. you are like the plane's wheels, negating the affect of the treadmill.
 
it seems the only debate is in clarifying the question. if anything thinks that planes use their wheels for propulsion or the speed of the wheels is somehow related to lift, then i don't even know what to say to that.
 
I also have an aero undergrad degree. Just remember for a plane to maintain level, unaccelerated flight

Lift has to equal weight (L=W) and thrust has to equal drag (T=D)

L is proportional to velocity squared and velocity is generated by the thrust of the engines that are fighting drag

On the treadmill, if the engines produced enough thrust to overcome the velocity of the treadmill then the plane would takeoff. Otherwise, it would just remain stationary.
 
Egads this thread is crazy.

Of course the plane will take off.

The only way to reasonably approach this is of course to assume frictionless wheels. Or else we get into far too complicated calculations.

So the statement that the engines have to provide enough thrust to overcome the speed of the treadmill becomes absurd. 1 pound of thrust would be enough to overcome the speed of the treadmill. An airplane's wheels are not connected to its driving mechanism. The wheels are there to roll. Think about it this way: If you slowly lowered an airplane onto a treadmill, assuming frictionless wheels, with zero velocity in the horizontal direction, the airplane would remain motionless after being lowered onto the treadmill. What exactly would cause the plane to move backward?

Let's make an example out of it. Let's say that our airplane requires 200mph of air speed to take off. Now let's take some different treadmill speeds (all assume 0mph wind):

1.) Motionless treadmill: The plane's engines thrust it forward to a speed of 200mph. Because of the frictionless assumption, the treadmill doesn't move. The speed relative to the ground of the airplane is 200mph. The speed relative to the ground, therefore, of the center of the plane's wheels is 200mph (same w.r.t. the treadmill, which is motionless). The speed relative to the ground of the top of the plane's wheels is 400mph (same w.r.t. the treadmill). The speed relative to the ground of the bottom of the plane's wheels is 0mph (same w.r.t. the treadmill).

2.) Treadmill moving backward at 200mph (the tricky one): The plane's engine's thrust the plane forward at 200mph relative to the ground. Therefore the plane is moving 400mph w.r.t. the treadmill. The center of the plane's wheels are moving 200mph relative to the ground (400mph w.r.t. the treadmill). The top of the plane's wheels are moving 600mph relative to the ground (800mph w.r.t. the treadmill). The bottom of the plane's wheels are moving 200mph backward relative to the ground (0 mph w.r.t. the treadmill).

As you can see, the wheels are simply rotating twice as quickly to make up for the treadmill. The treadmill has no mechanism by which to prevent the plane from moving forward. Therefore it has nothing to do with whether or not the plane takes off. The only thing affected by the treadmill is the wheels' rotational velocity.

The problem for you aerospace guys is that this is a mechanical problem.
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The plane does not need the ground to take off. The plane's wheels (tires) do not use friction with the ground to propel the plane forward.

One more way to look at it. The way you guys have approached the problem would mean that seaplanes would not be able to take off. Do seaplanes push against the water horizontally to propel forward? Of course not.
 
Huckleberry, your examples are confusing. I

f you put a plane on a motionless treadmill, then if you apply thrust the plane will take off. If you get on a motionless treadmill and run, you will run off of it.

If you have a 200mph treadmill and apply enough thrust (assuming frictionless wheels) then the plane will begin to move forward relative to the treadmill. The same way it would infliight with the wheels retracted. Also, the same way you would if you had frictionless roller skates and were pulliing on a rope tied to the wall in front of you. You would move forward. If no thrust is applied then the plane would remain stationary and the wheels would turn.
 
Doesn't matter. The plane will still take off.

Your assumption makes the treadmill act like the ground. Obviously planes take off from the ground.

It makes no difference what an airplane is on as long as it's in air. (Well, obviously assuming that there aren't any obstacles preventing the thrust from being turned into forward motion)
 
I agree. With thrust, the plane would take off. Without thrust it will not. I thought I said that in my original post.
 
I think people are misunderstanding the purpose of the original question. Of course the plain will take off if you apply enough thrust to counteract and overcome the drag created by the treadmill. But in that instance, you aren't talking about anything different from taking off of a stationary runway. The purpose of putting the plane on a treadmill is to keep the plane stationary. The suggestion that the question intends to imply anything other than the proposition that a plane could take off while stationary, completely misunderstands what is being asked. A person could outrun a treadmill and fall off the front end of it, but that defeats the purpose, as does this construction on this question.

The answer to the question asked is "no."
 
Wrong.

What do you mean by "drag created by the treadmill"?

Please describe your treadmill that keeps the plane from taking off. What exactly is it doing to prevent the plane from taking off? There is no treadmill that can be designed to keep the plane stationary. Essentially you have left the bounds of the laws of this universe in order to make the answer no.

Unless the OP really meant can an airplane take off from a treadmill while the engines are off just because the wheels are rolling. And that question is so absurd that it can't possibly be what was really meant.
 
the real question isnt whether or not the plane would take off or not but whether or not you would win a fight with a cheetah if you were locked in your bedroom with it...
 
The way I originally heard this question was that the plane was stationary relative to the ground with the engines providing enough thrust to counteract the friction from the wheels turning on the treadmill.

In reply to:
Click to expand...
 
This thread went past 5 posts? This subject has been discussed on multiple message boards?!? Holy **** the education system in America is horrible these days.

I'm assuming you won't find an answer on Google because no one wants to waste an hour of time creating a web page about why a plane can't take off from a ******* treadmill. Just do some research on how planes actually work, and then you'll have your answer.
 
I don't know how u could think the question would mean anything but the treadmill would be moving in an equal opposite direction so that the plane is stationary. Otherwise what the hell is the point of putting it on a treadmill. Isnt that the whole purpose of a treadmill? When u run on it u stay in a stationary position??

And no it can't take off from a treadmill, u need lift . Holla.
 
yes, if u put a bike axel on a treadmill and held it, it would remain stationary. Because u are applying force to it to keep it stationary. If u let it go it would fly off the back.

Do u think if u just sat on a bike on a treadmill u would stay in place without having to pedal?
 
I'm not an aerospace engineer, but this seems like a simple question (cue Holiday Inn Express jokes) Planes are designed to take off at a certain speed (factoring in altitude, temperature etc...). If it takes every bit of power that a plane can generate to take off on normal ground, than you wouldn't want to attempt to take off on a moving treadmill. If, however, the jet's engines can generate enough additional thrust to overcome the forces exerted on the plane by the treadmill (and there are forces...you cant assume frictionless contact between the wheels and axle) the plane should achieve the necessary speed relative to the air and generate the lift necessary for takeoff.

My attempt at an explanation: Try this quick hands on experiment. Take a small battery (or a pencil, pen etc) and place it on a piece of paper on its side. Move the paper back slowly and observe the battery move back with the paper. Jerk it back quickly and observe that the battery stays relatively in place with respect to the ground. This is where forgetting my college physics might get me in trouble, but I'm guessing that at some speed the friction between the surface area of the battery and the air becomes a larger force than the friction between the battery and the paper. So beyond a certain point, the speed at which you jerk the paper back will cease to matter. I think a parallel can be drawn with the airplane. If an airplane is parked on a treadmill, and the treadmill moves very slowly backwards, the plane will move backwards relative to the ground. This is due to the friction between the wheels and the ground and the wheels and the axle. But if the treadmill is sped up to 1000 miles per hour, the plane will not shoot back at a rate of 1000 miles per hour, because the force required to overcome the massive friction between the surface area of the plane and the air overwhelms the force that can be exerted on the plane by the treadmill through the wheel/axle point of contact.

So figure out the max force that can be exerted against the plane and just make sure you have enough "overhead" with the jets engines and the plane should take off.
 
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