Plane on a treadmill

[Nuro]

Ok, so this argument has come up again.
If a plane is on a treadmill, would the plane be able to take off?

My argument is that of course it would take off: The force of the engine is pushing against the air, not the ground. The treadmill could be spinning 3 times as fast for all I care, the wheels of the plane would simply turn faster while the engines start creating thrust against the air, and the plane would gain velocity. The assumption is that the friction of the bearings in the wheels is almost irrelevant (e.g. the wheels are free moving).

Of course, a car is a different story since the power of the engine is used to turn wheels, which use the ground for traction. The point is that if the plane is on a treadmill, the air is not moving with the treadmill, and since the engines push against the air and not the ground, the plane would gain velocity, and eventually take off.

 

[xrapidx]

You need lift under the wings - and there will be no wind coming from the front to provide the lift.

Maybe if you attach the treadmill band to a fan that blows from the front as the plan moves on the treadmill - but then the plan might crash into the fan...

Also - will an emergency stop be attached to the plans wing, in-case it falls off the back?

 

[Ecco]

The wings are use to generate lift. The wings would only work if they are moving through the air.

 

[Nuro]

You need lift under the wings - and there will be no wind coming from the front to provide the lift.

Well yes, since the treadmill is spinning but the plane wheels are simply free wheeling, the plane would start moving forward when the thrust from the engines kick in. The wheel speed of the plane would not match actual speed, but that does not matter, since they are free moving. When the plane starts moving forward, we get air movement over the wings and eventually lift. The air is stationary, since air does not normally move with a treadmill. The key is that the air is staionary, and the engines are thrusting againt stationary air, so there is nothing to cancel out the thrust of the engine. Which means acceleration, and evetual take off.

 

[xrapidx]

But you won't be moving on a treadmill, so no moving wind under the wings? Or will the plane be going faster than the treadmill - which means you're going to need a pretty long treadmill to get the required wind for lift

 

[oober]

Well yes, since the treadmill is spinning but the plane wheels are simply free wheeling, the plane would start moving forward when the thrust from the engines kick in. The wheel speed of the plane would not match actual speed, but that does not matter, since they are free moving. When the plane starts moving forward, we get air movement over the wings and eventually lift. The air is stationary, since air does not normally move with a treadmill. The key is that the air is staionary, and the engines are thrusting againt stationary air, so there is nothing to cancel out the thrust of the engine. Which means acceleration, and evetual take off.

In short it won't take off.

 

[Ou grote]

There's youtube video about this, and a whole website.
www.youtube.com/watch?v=cDliz-YinyY

You're going to fsck the gym up btw.

 

[Keeper]

It would not take off. whether the wheels of the plane are turning or not, doesn't matter - wheels have nothing to do with flight.

if the wheels had anything to do with it, then you could theoretically create a Harrier Jet by simply connecting a treadmill to each wheel. I don't see that working unfortunately.

 

[waynegohl]

There's youtube video about this, and a whole website.
www.youtube.com/watch?v=cDliz-YinyY

You're going to fsck the gym up btw.

Virgin Airways on a treadmill at Virgin Active.

 

[Nuro]

Or will the plane be going faster than the treadmill - which means you're going to need a pretty long treadmill to get the required wind for lift

Exactly. We are taking about a long treadmill (or conveyor belt) here.

Reverse the situation, and it makes even more sence. If a plane is sitting on a stationary free moving treadmill, the treadmill will not start moving just beacuse the plane engines are running and creating acceleration. The engine power is not translated to the wheels, so there is nothing to "push" the treadmill belt.

 

[Nuro]

It would not take off. whether the wheels of the plane are turning or not, doesn't matter - wheels have nothing to do with flight.

Ok, so we agree there...
Then if the wheels had nothing to do with flight, but rather air moving over the wings, why would a treadmill matter? The harrier comparison does not hold, beacuse still the wheels are free moving, they having nothing to do with what the engines and wings are doing. The engines interact with the air, not the ground.

 

[Ou grote]

Put a treadmill on a plane and see if you can run on it.

 

[xrapidx]

Exactly. We are taking about a long treadmill (or conveyor belt) here.

Well - I'd assume if treadmill is going at x speed (say 100km/h) <---- that way and the plane needs y speed (say 300km/h) to take off going -----> that way .... It'd need x + y speed to take off, i.e. 400km/h.

 

[Nuro]

Well - I'd assume if treadmill is going at x speed <---- that way and the plane needs y speed to take off going -----> that way.... It'd need x + y speed to take off.

No. The plane's speed relative to the air is 0. It needs to move through the air at speed y to create lift. The wings dont care what the ground does (again, the wheels are free moving).

 

[oober]

No. The plane's speed relative to the air is 0. It needs to move through the air at speed y to create lift. The wings dont care what the ground does (again, the wheels are free moving).

If the net effect of the engine's forward force and the treadmill's backwards force is zero nothing will happen. It feels like we are all saying the same thing here. So the engines will have to overcome the treadmill's force and then the force required to generate lift before the plane will fly.

 

[xrapidx]

No. The plane's speed relative to the air is 0. It needs to move through the air at speed y to create lift. The wings dont care what the ground does (again, the wheels are free moving).

I'm not talking about ground speed- I'm talking about the speed necessary to create enough lift under the wings. If it was going the same speed as the treadmill (but in the opposite direction) the plane would be standing still - and there would be no wind under its wings.

 

[Nuro]

If the net effect of the engine's forward force and the treadmill's backwards force is zero nothing will happen. It feels like we are all saying the same thing here. So the engines will have to overcome the treadmill's force and then the force required to generate lift before the plane will fly.

If the wheels are free moving, why does the treadmills speed have ANY effect on the plane? The plane does not need to cancel out any force.

 

[Rosaudio]

In short, If the plane is not moving, It wont take off.

Plane on a treadmill = not moving anywhere

 

[Keeper]

Ok, so we agree there...
Then if the wheels had nothing to do with flight, but rather air moving over the wings, why would a treadmill matter? The harrier comparison does not hold, beacuse still the wheels are free moving, they having nothing to do with what the engines and wings are doing. The engines interact with the air, not the ground.

Well your 1st post says that it CAN take off like that, that's what is confusing me

if this was possible then all we need to do is attach treadmills to a plane's landing gear, and BAM - no runway needed for take-off

 

[xrapidx]

In short, If the plane is not moving, It wont take off.

Plane on a treadmill = not moving anywhere

So if the plane is going 400km/h forwards, and the treadmill 100km/h backwards, its not moving?