Would a plane take off on a tredmill?

[accordaffair]

It didn't take me very long to understand this, without the reply's.

The thrust of the engines pushes the plane forward, not the wheels.

A treadmill can only counteract something that is propelled by its wheels...think about it.

How does a rocket work? How do missiles work?

It doesn't take long to realize that the treadmill will have little effect. The engines will push against the air, not against the ground.

[J-specCb4]

You might want to go back to physics class.

The wheelsMOVE INDEPENDENTLY OF THE AIRPLANE!!!!!!!!!!!!

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in·de·pen·dent
Function: adjective
1 : not dependent on others (as parents) for livelihood; especially : not a dependent <declared she was independent on her financial aid form>
2 a : not affiliated with another usually larger unit <an independent adjuster> b : not contingent on something else <an independent promise> —in·de·pen·dence noun —in·de·pen·dent·ly adverb
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They can roll backwards at 7,000 miles an hour and the airplane still has the ability to move forward because the wheels are negating nothing.

This is how it would work in real life. I am going to try and find a video camera and a treadmill and I will demonstrate this "impossibility" in real life.

1) The plane is stationary,the treadmill is stationary, the wheels are stationary

2) The pilot applies power, the plane begins rolling forward. The treadmill begins moving backward at the same rate (the question was very specific about stating that the treadmill matched the speed of the plane). The wheels begin turning at twice the rate the other two are moving because they have to match the difference in speed between the two objects.

3) The plane continues to accelerate. We are now at 20 knots (1 knot = 1.15 MPH). The treadmill is moving backwards at 20 knots. The wheels must move at 40MPH to keep up because they have to account for both speeds. Because the wheel roll independently of the airplane, this doesn't matter. It is no different than if the airplane was moving 40 knots over a stationary runway.

4) The plane continues to accelerate, because the thrust of the jet is still reacting against the atmosphere propelling the aircraft forward. We are now at 100 knots. The treadmill is moving backwards at 100 knots, and the wheels are now turning at 200 knots. Again this makes no difference because it is the same as if the airplane was moving over a stationary runway at 200 knots. All the wheels know is that they are rolling.

5) The thrust is still thrusting, and the plane is still accelerating because the acceleration is dependent on the thrust of the engines and not the rolling of the wheels. We have now accelerated to 150 knots and it is time for lift off. The treadmill is rolling backwards at 150 knots, and the wheels are now rolling at 300 knots! This is exactly the same as if the airplane was rolling over a stationary runway at 300 knots. The jets are still pushing and since the airplane's movement is dependent upon the thrust of the jet, the aircraft is still moving forward.

6) Rotate! The nose of the aircraft begins to lift off, as the nose gear clears the ground, the nose wheels starts to decellerate. Why? Because it is no longer rolling across the runway. BUT WAIT THERE'S MORE! The airplane is still moving at 150 knots, the treadmill is still rolling at 150 knots in the opposite direction, and the main wheels are still rolling at 300 knots because they are still in contact with the treadmill.

7) The nose continues to rise and finally the angle of attack is large enough to create sufficient lift to takeoff. The plane begins to rise, the main wheels come free of the treadmill, and the airplane continues to fly.

Most people think of simple force addition. It used to confuse me too. The problem and the thing that confuses people is that the wheels have absolutely nothing to do with the movement of the airplane.

Their operation is completely independent of what the airplane does.They don't have any effect on the operation of the airplane, which means that any force you apply to them will also have absolutely no effect on the operation of the airplane. Since our treadmill is applying force to the wheels and only the wheels, it affects NOTHING.

Even if the treadmill were setup to match the speed of the wheels, it still affects NOTHING, because the wheels still have no effect on what the airplane is doing. They can't stop it, they can't change it, they are just being pulled along for the ride.

If you were to tie the airplane to a tree and then turn the tread mill on, and the airplane stays where it is because of the rope, have you altered the movement of the airplane? No you have not. The treadmill will go backwards, and the wheels will roll, but the airplane will stay still because of the rope.

The exact same concept works in this example. The thrust and only the thrust is what dictates the movement of the airplane.

Everything else is superfluous. It has nothing to do with anything.

As long as there is thrust pushing the plane forward, IT WILL ACCELERATE, because thrust is what accelerates it.

Period.

Once it begins to accelerate it begins to generate lift, because lift is dependent on airflow over the wing and nothing else.

Period.

You can have an airplane full of sandbags or nuns, and as long as that wing is moving through the air, lift WILL be generated. As long as those engines are producing thrust, it WILL accelerate.

As long as it is accelerating AND producing lift it WILL fly.

The wheels have nothing to do with anything. Even if they are moving at 1,000 miles per hour.

Sorry that is just the way it is.

Oh, yeah. Since we are throwing qualifications around, I have been around airplanes since I was young too, in fact several years before you were even born...and I fly them everyday, and I have an entire degree based on how they work, and I have read every single airplane book I could get my hands on from the age of 5 when I started learning to read ( I was actually looking at pictures at 4, but they didn't explain much). I have a closet full of books on airplanes if you ever want to come read them.

If those aren't enough for you, I can put you in touch with any number of friends that have a doctorate in any number of fields relating to this topic.

If you still think I am full of shit, go get a treadmill, and a rubber band airplane and try it out. It is a fun experiment. I know because I have seen it.

I want my Million Bucks!

yeah if the wheels move independently ithey wont slow the thrust from the engines or the speed of the plane for that matter.... therefore thrust=lift=takeoff

[owequitit]

yeah if the wheels move independently ithey wont slow the thrust from the engines or the speed of the plane for that matter.... therefore thrust=lift=takeoff

correct. The treadmill ultimately has no effect on the thrust of the engines.

Since it doesn't affect what moves the airplane, then it won't affect the acceleration.

[J-specCb4]

correct. The treadmill ultimately has no effect on the thrust of the engines.

Since it doesn't affect what moves the airplane, then it won't affect the acceleration.

true now the only thing that might effect it is if the wheels infact were spinning 7000 mph and the bearings burned up and locked the wheels.... ok enough of me being a smartass

[owequitit]

true now the only thing that might effect it is if the wheels infact were spinning 7000 mph and the bearings burned up and locked the wheels.... ok enough of me being a smartass

Hey just like I told Accord R33...who was gracious enough to quote it in his sig!

I would rather be a smartass than a dumbass.

[TypeG]

it's similar to having a bee on a string....it flies, but doesn't go anywhere. free entertainment. later.

[deevergote]

It amazes me how hard this is to grasp for some people...

The plane, unlike a car, doesn't rely on the wheels for movement. The treadmill is moving the wheels, not the plane. A small amount of thrust from the engines will move the plane forward as if it were sitting on stationary ground, regardless of the speed of the wheels.

[cp[mike]]

mr scottman is correct.

wheels are independant of the plane, they could be sideways, or gone, for all it matters. the treadmill only affects the wheels, but the jets/propeller WILL make the plane take off.

now the theoretical question is, what if there were a way to BLOW the air towards the plane as fast as the engines could pull it, what would happen. haha.

asking about putting a plane on a treadmill is a pointless question, as again, the wheels and motion of the plane rolling on the ground means nothing. its the engines pushing against the atmosphere and (cue music) the wind beneath its wingsssss.... that matters.

[Masamune]

Oh god, I can't stop laughing!

[skubydobdo]

wait just a minute.....WHAT if there were SNAKES ON A PLANE ON A TREADMILL?????

[The G-Man]

omg, I am owned. But still, arguing on the internet is pointless, and do not even know why I tried.

[accordaffair]

now the theoretical question is, what if there were a way to BLOW the air towards the plane as fast as the engines could pull it, what would happen. haha.

I did this once with a styrofoam plane, I hung its wings from supports and blew a fan on high in front of it, surprise, it had lift.

[owequitit]

now the theoretical question is, what if there were a way to BLOW the air towards the plane as fast as the engines could pull it, what would happen. haha.

I am sure you know the answer to that question, but for those who do not: The wings only care about airflow over them.

As stated in my previous example, if the takeoff speed is 150 knots, and we put the airplane on the ground in a hurricane straight into the wind of 150 knots, then YES the airplane would be able to take off and hover (assuming the correct throttle setting) without rolling an inch.

It is easier to do in light planes, as even a 20 or 30 knot headwind makes a large difference. As an example, a Cessna 172 rotates at 55 knots, so if the headwind is 30 knots, our actual ground speed will be 25 knots or barely 30 mph when the plane lifts off.

That is one of the main reasons an airplane will always take off into as much of a headwind as possible, because it reduces the amount of runway needed to get airborne.

On an aircraft carrier, they will always turn the boat and steam full speed into the wind (about 35knots) during launch and recovery operations. It increases the margin of safety on catapult launches.

[Ralphie]

Wow ok yea i never saw this thread and i got it right away and im not the brightest dude around.

As the plane moves foward the wheels will keep moving in reverse no matter how fast or slow the treadmil moves becasue the thrust coming out of those engines(which is powerfull enough to blow pickup trucks down the street btw) will push that plane right off the treadmil....and if the plane is being held stationary by some odd force or by chains or some shit then of course the fucking plane wont go anywhere, that is untill the chains break lol.

[stewie]

isnt there like a jet plane of some sort that can do vertical take offs, then once its high enuf it just goes full throttle and can instantly take off from a stationary position in the sky?