Airplane on a treadmill!

[Ichinisan]

I understand. Mythbusters' call it 'BUST' is definitely faulty, or at least premature. The original preposition was that the plane was supposed to remain stationary as the treadmill kept the forward motion in check.

NO. The original FAILURE IN UNDERSTANDING is that the treadmill keeps the plane stationary.

It does not. It cannot.

 

[LTC8K6]

I'm still not convinced how the plane will take off. I've read bunch of stuff that it would because the velocity of the wheel doesn't matter.

But I can't picture it.

So the plane is literally sitting still, just the wheel spinning. Then once the plane start to lift off, is it going up vertically or at an angle? If at an angle, is it suddenly bursting into speed into the air? I don't see that happening physically.

Help me understand here. I had to do a motion with my hand being a plane and how it would nose up while being still. I don't get how it can take off.



Link? I highly doubt whatever miniaturized test they did proves that a real 700,000 pound 747 taking off on an equally large theoretical treadmill.

https://www.youtube.com/watch?v=0KsdMuhYJPw

What the hell, the plane wasn't stationary.

What, in your mind, is keeping the plane stationary if it's on a treadmill?

Let's put you on a treadmill while wearing roller skates. Put your arms out like you are an airplane. I'm going to play the part of your airplane engine by pushing you forwards. Can the running treadmill stop me from pushing you forwards?
Can the running treadmill keep you stationary?

No, it can't. I can push you forwards on the running treadmill just as if you were on your driveway.

For all practical purposes, the treadmill is the same as the runway to an airplane with free spinning wheels. There is no difference.

The minor amount of bearing and tire friction is mathematically there, but practically it can be dismissed.

 

[Tweak155]

The only time the treadmill can match the speed of the wheels is when the plane's engines are off or in other words no thrust is being applied to the plane. The only feasible scenario without external forces that I can think of that creates this is if the plane is not moving, and neither is the treadmill.

If something held the plane in place while the treadmill spun the wheels, this is also possible to match the speed. Otherwise, if engines are applying thrust to the airplane, that treadmill can never match the speed of the wheels. The wheels will always be moving faster.

 

[Humpy]

This one is about an airplane (a 747) on a (perfect) treadmill. The treadmill matches the speed of the airplane exactly. The key here is in the wording. It only matches the speed, so based on your interpretation of speed, you'll have different answers.

The only way to win is not to play as few of the details required to solve the problem are presented.

I've filled in the blanks in such a way that, based on my calculations, the plane doesn't take off but still arrives at its destination yesterday.

 

[ultimatebob]

It takes off, the speed of the treadmill makes no difference.

Discussed to death years ago.

Yeah, the plane isn't driven by the wheels. It's being pushed by massive jet engines! It doesn't matter how fast the treadmill goes, the plane takes off anyway.

Mythbusters already did this a long time ago.

 

[sdifox]

This might just be the pwnage of the year thread all over again :biggrin:

 

[dainthomas]

These kinds of threads should be an insta-ban for the OP.

 

[BlitzPuppet]

This thread is bad and you should feel bad.

 

[Thebobo]

Mythbusters did it....

Spoiler

plane takes off

http://m.youtube.com/watch?v=YORCk1BN7QY

Yea and whats funny is the pilot doing that thought it would not take off. Proving pilots can be idiots as well.

 

[edro]

Can a water plane take off pointing up river?!?!? OMG!

 

[gorcorps]

The plane is not sitting still just because the treadmill matches its speed. The treadmill cannot make a plane sit still. If the treadmill matches the plane's speed, the plane is still moving forward at normal speed...but the tires are spinning at twice their normal speed. Relative to the ground, the plane moves just as far/fast as it normally would.

We're doing this again. FUCK.

Don't fall for it. There's so many different explanations out there that Zeze can look it up himself if he's really not understanding it.

 

[Humpy]

Can a water plane take off pointing up river?!?!? OMG!

That's totally different. Maybe.

Waterfalls, sandbars, logs, icebergs, and how can a plane be made of water? Or, like a water balloon, is a water plane just filled with water?

I'm freaking out.

 

[TwiceOver]

I bet the treadmill takes off.

 

[GagHalfrunt]

The only way to win is not to play as few of the details required to solve the problem are presented.

I've filled in the blanks in such a way that, based on my calculations, the plane doesn't take off but still arrives at its destination yesterday.

You forgot to carry the 1.

 

[FeuerFrei]

So what if we remove the wheels? What then? :sneaky:

Yea and whats funny is the pilot doing that thought it would not take off. Proving pilots can be idiots as well.

And what's funnier is that the unexpected takeoff caught the pilot flatfooted and he accidentally flipped the plane.


oh wait ... that never happened

 

[OverVolt]

The wheels spin twice as fast.

Airspeed and groundspeed are different.

 

[WHAMPOM]

In the spirit of the current 48÷2(9+3) = thread we have going, let's get another debate going.

This one is about an airplane (a 747) on a (perfect) treadmill. The treadmill matches the speed of the airplane exactly. The key here is in the wording. It only matches the speed, so based on your interpretation of speed, you'll have different answers.

Many are seen here on xkcd. We're also ignoring all real-life tests because you can't have a perfect treadmill that can match a 747.

Many people (including me) seem to think the best way to interpret the issue is that the treadmill is always going fast enough to prevent the plane from moving relative to the ground, thus keeping it from acquiring enough lift to take off.

Some people think the treadmill will eventually move fast enough to cause air currents moving backwards to cause enough lift to make the plane take off.

The other theories I don't understand enough to post about, so let's debate!

Forget the threadmill, does a plane with its brakes locked and engines running at full power take off? Better yet, just aim that plane uphill(not much of a slope even, that is why airfields are level) it will never reach take off speed.

I am more practical in my resoning the plane never takes off because the plane's wheels get stuck in a valley between two rollers and can't make it over the bump.

 

[Fanatical Meat]

Forget the threadmill, does a plane with its brakes locked and engines running at full power take off? Better yet, just aim that plane uphill(not much of a slope even, that is why airfields are level) it will never reach take off speed.

I am more practical in my resoning the plane never takes off because the plane's wheels get stuck in a valley between two rollers and can't make it over the bump.

The way I understand it is its a momentum thing. The plan may not be moving to us but if we were on the conveyor belt it would be moving. So no a plan with its engine at full but being held in place by its breaks would not take off because its not moving.

 

[manlymatt83]

Prop plane... Assuming the treadmill is stable, you're applying right rudder to compensate for p-factor and torque.. you'd get some lift from the prop wash, which would probably (briefly) airborne the aircraft, causing it to move slightly forward, only to stall. There's no relative wind here (other than prop wash) so there's no lift.

Jet? No way. Not going anywhere.

/thread

 

[flexy]

Jet? No way. Not going anywhere.

/thread

And how is the treadmill supposed to STOP the plane from moving forward? The plane is not attached, the treadmill can move as it wants, it doesn't apply a force onto the aircraft which could "hold back" the aircraft (by pulling it back, negating air speed from thrusters/prop). All the treadmill does is making the wheels spin faster.

 

[sdifox]

Forget the threadmill, does a plane with its brakes locked and engines running at full power take off? Better yet, just aim that plane uphill(not much of a slope even, that is why airfields are level) it will never reach take off speed.

I am more practical in my resoning the plane never takes off because the plane's wheels get stuck in a valley between two rollers and can't make it over the bump.

Lulz. Plane on wheel chokes will overcome the chokes when you go full throttle, just not very fuel efficient. The problem in question is theoretical anyway. No one has the money to build a treadmill big enough or fast enough for a plane.

 

[LTC8K6]

I bet the treadmill takes off.

It might as well, given the trolling, and/or lack of common sense in this and the other threads on the subject.

 

[TwiceOver]

It might as well, given the trolling, and/or lack of common sense in this and the other threads on the subject.

Exactly.

 

[cubby1223]

NO. The original FAILURE IN UNDERSTANDING is that the treadmill keeps the plane stationary.

It does not. It cannot.

The failure, and it's all just ego-thumping, is the original parameters of the situation are that the treadmill is moving backwards at the same speed the plane is forward, thus the plane is not moving when viewed from a stationary spot on the ground. That is the defined situation.

The original parameters do not mention anything about throttle speed. Can a treadmill prevent a plane at full throttle from flying? No. Can a plane at a small fraction of full throttle, be stationary relative to the ground on a treadmill? Yes.

The latter satisfies the parameters of the original situation, the former does not.

 

[dainthomas]

Every time someone says the treadmill keeps the plane from taking off, baby Jesus cries.