Airplane on a treadmill!

[HumblePie]

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

Discussed to death years ago.

Pretty much. The thrust of the jet engine isn't pushing off the wheels. It is pushing on the air behind the plane which will move the plane forward regardless of the wheels and whatever those are doing. The wheels on a nice flat ground where they can properly turn means the speed of the plane moving forward will allow enough airflow under the wings to take off. All the treadmill part of the equation does is make the thrust forward of the plane not so fast and smooth. Eventually the thrust of the engines is going to push the plane forward.

This isn't the same result if the plane wasn't a jet engine plane though.

The answer is simpler if you think of this in terms of a friction-less piece of ground contact or even in space. A ship in space that isn't moving then has an engine provide thrust in a given direction. The ship will move in the opposite direction of the thrust of the propellant despite the lack of any surface by which the have the ship act upon.

 

[WelshBloke]

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.

How fast the treadmill is going is irrelevant. The drag from the treadmill is not the limiting factor to the planes speed.

At worst its going to burn out the bearings on the wheels but the plane is still going to take off.


Edit: Awwww, What the fuck am I doing in this thread again? I'm getting a drink. Fuck you guys.

 

[Bubbleawsome]

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

Oof, maybe it is. :$

This thread is bad and you should feel bad.

I should but I don't! :wub:

isn't this a debate from a decade ago?

Did the OP just join the internet?

Also, with how many explanations there are of the correct answer by this point, how are so many people still getting this wrong?

conclusion: OP is just trolling

I saw it first a couple years back (2008 maybe?) and decided to bring it up again. It was a bit of a troll but see? Now I've corrected my ways, I see the plane will take off.

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

That's less probable

I bet the treadmill takes off.

Obviously the right answer here.



Glad I could help you all get your jimmies rustled.

 

[Jeff7]

Solution: Use an F-35.
Done.

Yes, but is 0.999999999999(infinity) really 1?

Only at cruising altitude, after the plane has taken off. The time dilation effect that results from the higher relative speed is just enough to make them equal.

 

[MongGrel]

The first time I ever did see this I misunderstood the way it was set up myself.

It will gain airspeed due to thrust and forward momentum, the wheels will just spin faster during takeoff.

Unless something is applying drag to the plane to restrict it from moving forward, it will just move forward and achieve airspeed.

Does require a long treadmill.

 

[Humpy]

I like that smiley.

 

[Bubbleawsome]

I like that smiley.

Yeah, I wish we had it over here. He's from OCN, but if you want a massive smiley list go here. Warning, some are mildly NSFW

 

[Jeff7]

How fast the treadmill is going is irrelevant. The drag from the treadmill is not the limiting factor to the planes speed.

At worst its going to burn out the bearings on the wheels but the plane is still going to take off.


Edit: Awwww, What the fuck am I doing in this thread again? I'm getting a drink. Fuck you guys.

Ah, but what if the bearings then seize up?

I don't know which will fail first: The tires or the bearings.
I'm thinking the tires will have a problem first and add extra drag.

On the other hand, those engines are pretty damn powerful.


I think of it like this:
- The engines move the plane forward at 1mph.
- The belt moves fast enough to generate bearing and rolling friction to counteract this, and slow the plane back to 0mph. To do that, the belt must be moving a lot faster than 1mph.
- The engines now try to move the plane to 1mph again.
- The belt increases in speed once again to produce suitable bearing and rolling friction to counteract the increased engine force.

Pretty soon, that belt is going to be moving very quickly. (What's the exhaust velocity of a 747 engine?:hmm
The tires probably can't tolerate that kind of speed.


- Tires fly apart or burst or flatten. Now the friction is higher.
- The belt slows down fair amount due to the increased friction.
- Tires finish abrading away, now it's wheel-hub-on-belt.
- Assumed metal-on-metal, so friction drops, and the belt speed must now increase to product sufficient friction force to counteract the engines.
- Wheel hubs melt, eventually leaving the landing gear supports grinding on the belt.
- Pilot considers reducing thrust and aborting, but he's committed now and doesn't want to look stupid.
- Supports grind away.
- Body of aircraft grinds on belt, engines still at full power.
- Advise flight crew to postpone beverage service.
- Body ablates away until the engines themselves begin to sustain damage.
- Thrust decreases as engines catastrophically fail.
- Belt slows down.
- What's left of the airplane does not take off.

Can't believe it took 11 posts for someone to say what needed to be said.

OT is slow and we can't make parody threads. We're bored.

 

[gorcorps]

https://www.washingtonpost.com/news...rslide-doughnuts-on-snow-then-take-off-again/

related

 

[John Connor]

This crap was posted all over the Internet and was finally debunked by Myth Busters.

 

[sdifox]

This crap was posted all over the Internet and was finally debunked by Myth Busters.

To be clear, they didn't debunk anything, just showed the idiots that the plane takes off.

 

[randay]

Ah, but what if the bearings then seize up?

I don't know which will fail first: The tires or the bearings.
I'm thinking the tires will have a problem first and add extra drag.

On the other hand, those engines are pretty damn powerful.


I think of it like this:
- The engines move the plane forward at 1mph.
- The belt moves fast enough to generate bearing and rolling friction to counteract this, and slow the plane back to 0mph. To do that, the belt must be moving a lot faster than 1mph.
- The engines now try to move the plane to 1mph again.
- The belt increases in speed once again to produce suitable bearing and rolling friction to counteract the increased engine force.

Pretty soon, that belt is going to be moving very quickly. (What's the exhaust velocity of a 747 engine?:hmm
The tires probably can't tolerate that kind of speed.


- Tires fly apart or burst or flatten. Now the friction is higher.
- The belt slows down fair amount due to the increased friction.
- Tires finish abrading away, now it's wheel-hub-on-belt.
- Assumed metal-on-metal, so friction drops, and the belt speed must now increase to product sufficient friction force to counteract the engines.
- Wheel hubs melt, eventually leaving the landing gear supports grinding on the belt.
- Pilot considers reducing thrust and aborting, but he's committed now and doesn't want to look stupid.
- Supports grind away.
- Body of aircraft grinds on belt, engines still at full power.
- Advise flight crew to postpone beverage service.
- Body ablates away until the engines themselves begin to sustain damage.
- Thrust decreases as engines catastrophically fail.
- Belt slows down.
- What's left of the airplane does not take off.





OT is slow and we can't make parody threads. We're bored.

even with this highly impossible scenario designed to somehow make everything fit so that some treadmill can stop an airplane, you are wrong.

the treadmill will break long before the airplanes tires do. the belt would likely blow apart due to centrifugal forces. there would then be nothing holding the tires back(or the plane) and the plane takes off.

 

[Jeff7]

even with this highly impossible scenario designed to somehow make everything fit so that some treadmill can stop an airplane, you are wrong.

the treadmill will break long before the airplanes tires do. the belt would likely blow apart due to centrifugal forces. there would then be nothing holding the tires back(or the plane) and the plane takes off.

I established earlier that the belt is made of an improbablium alloy that should be able to withstand the insane forces required. But because of its inherent nature, its probable properties are difficult to know.


Centrifugal force on the treadmill need not be an issue either. You just need sufficiently large auto-tensioning rollers at the ends to ensure that the forces don't exceed its yield strength.
It's not practical at all, and would likely cost.....oh, maybe $1.5T and 30 years to research, build, and operate. Sounds like a good public works project. North Korea can do the small version with a scale-model 747. USA will go big to properly address this important issue.

For good measure, we'll paint one wing blue and black, and the other white and gold, with a callsign of 0.999... for the plane.






(I know the plane takes off. It's not easy to make a plausible scenario where it doesn't. The topic's been done to death, and I felt like typing something stupid. Mission accomplished.)

 

[SSSnail]

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

Holy fuck you just took it to a whole new level of stupid.

 

[Humpy]

I established earlier that the belt is made of an improbablium alloy that should be able to withstand the insane forces required. But because of its inherent nature, its probable properties are difficult to know.


Centrifugal force on the treadmill need not be an issue either. You just need sufficiently large auto-tensioning rollers at the ends to ensure that the forces don't exceed its yield strength.
It's not practical at all, and would likely cost.....oh, maybe $1.5T and 30 years to research, build, and operate. Sounds like a good public works project. North Korea can do the small version with a scale-model 747. USA will go big to properly address this important issue.

For good measure, we'll paint one wing blue and black, and the other white and gold, with a callsign of 0.999... for the plane.






(I know the plane takes off. It's not easy to make a plausible scenario where it doesn't. The topic's been done to death, and I felt like typing something stupid. Mission accomplished.)

Because we know damn well how to do it best, 'Murica has already built a 180 mph treadmill for NASCAR inside a 180 mph wind tunnel.

Scale that bad-boy up, plop a 747 on it, and this thread can RIP in peace.

 

[Phanuel]

Won't make much difference. As the XKCD link way earlier pointed out. The speed the treadmill needs to reach approaches infinity as soon as the plane moves.

Nothing will stop the plane from taking off short of being bolted to the ground via a mount that has a sheer force greater than the engine force. Or having a landing gear failure resulting in the plane crashing into the ground and then being flung backwards/disintegrated by the infinite mph treadmill sanding it down.

 

[sdifox]

F15-K has a weight to thrust ratio of 1.29
Stand it on its tail and you can takeoff.

 

[jagec]

Won't make much difference. As the XKCD link way earlier pointed out. The speed the treadmill needs to reach approaches infinity as soon as the plane moves.

That's not true. The wheels have mass, and the bearings have friction. Both of those can couple treadmill speed to airplane speed, leading to a takeoff failure, IF you make non-realistic assumptions.

In any real-world scenario, the plane takes off, or the wheels get destroyed and the outcome depends on engine power vs. wheel-stub resistance.

In a physics-assumption scenario (massless wheels, frictionless bearings) the plane takes off. No couple between treadmill and plane.

In a mixed scenario (perfect treadmill, indestructible wheels+bearings, BUT wheels have mass and/or friction), there is a couple between airplane speed and treadmill speed, and so we can prevent takeoff.

In a wheel-friction-limited environment, the wheels just have to spin fast enough for friction forces to equal engine thrust. This is very hard to achieve in the real world (wheels have to dissipate an equal amount of heat to the thrust being generated by engines, and treadmill speed has to be equally crazy), but in the non-real world of this problem, it stops the plane. Without relativistic treadmill speeds.

In a frictionless, indestructible (but mass-containing) wheel environment, the wheel WEIGHT is the key, and the thrust of the engines goes into an increase in wheel inertia. The treadmill ends up spinning at a surprisingly substantial fraction of the speed of light, but eventually you run out of fuel and the plane still hasn't taken off.

If you have a perfect treadmill, frictionless and indestructible wheels, AND infinite fuel, the problem goes fully relativistic and we simply don't have the physics to predict the outcome.

 

[Phanuel]

Uh, what?

No?

As soon as the plane moves, which it while, because overcoming stationary wheel mass/inertia is a joke, the treadmill must accelerate to try and negate the plane's inevitable forward movement.

Since the treadmill will be unable to stop the forward movement, barring a catastrophic wheel failure, it will accelerate to infinity because no speed it reaches will matter until such a failure occurs as the plane continues to accelerate relative to the air around it and the ground (treadmill) beneath it.

Why would the plane give a shit how fast a functioning wheel is traveling as the wheel has no job other than to provide a non-fixed connection with the ground unless used for braking forces?

 

[jagec]

Uh, what?

No?

As soon as the plane moves, which it while, because overcoming stationary wheel mass/inertia is a joke, the treadmill must accelerate to try and negate the plane's inevitable forward movement.

Since the treadmill will be unable to stop the forward movement, barring a catastrophic wheel failure, it will accelerate to infinity because no speed it reaches will matter until such a failure occurs as the plane continues to accelerate relative to the air around it and the ground (treadmill) beneath it.

Speed doesn't matter, but acceleration does. A continuously accelerating wheel becomes a flywheel and stores the energy input by the force of the engines as inertia. Friction continuously bleeds away this energy.

Infinity is a concept that is only achieved by those who oversimplify the initial problem.

 

[Jeff7]

Speed doesn't matter, but acceleration does. A continuously accelerating wheel becomes a flywheel and stores the energy input by the force of the engines as inertia. Friction continuously bleeds away this energy.

Infinity is a concept that is only achieved by those who oversimplify the initial problem.

Yeah, good old rotational inertia and rolling resistance.

 

[rudder]

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

Discussed to death years ago.

https://m.youtube.com/watch?v=Sr5YRuGYmKo

Imagine if the car was an airplane. In order for an airplane to lift off the ground it must produce lift. The amount of lift produced is based on wing area, coefficient of lift, and velocity of air over the wing, so if the car in the video had wings, there would not be enough airflow over the wings to creat enough lift to overcome the weight of the aircraft.

Assuming a perfect treadmill. Otherwise you would need an aircraft like a Maule.

http://www.controller.com/listingsd...AULE-M7-420AC/2000-MAULE-M7-420AC/1389113.htm

Those planes are light, have huge engines, bug Hersey bar wings and can lift into the air with a very short roll down a runway. A jet aircraft would never take off.

 

[Zorba]

You still have to deal with exploding wheels though

Tires on commercial aircraft have speed ratings well in excess of their takeoff speed. One plane I work on typically takes off around 130 knots and has tires rated at 235 knots.

This was a stupid debate from like 2005. The plane takes off. They way I always liked to explain it is think if you were in an office chair on a treadmill, could you pull yourself forward in the chair while the treadmill ran backwards? Obviously the answer is yes, therefore the plane will take off. No thrust is transferred through the tires on an aircraft, unlike a car.

 

[Zorba]

I understand it's the propeller taking in air and expelling it behind for thrust and how that enables flight. I also understand it has nothing to do with the wheels. I also understand wheels just spin around freely to whatever momentum the propeller & air provide.

But the mythbuster episode was faulty or inconclusive at best to the original proposal of the question.

The belt did NOT match the wheel's speed. It moved FORWARD (prior to takeoff) because the belt couldn't match it.

Let's suppose the plane's wheels were gear-shaped with teeth, and they were locked to the opposing teeth holes in the conveyor belt. Therefore we know 100% that plane couldn't move forward PRIOR to takeoff. If the plane nosed up and took off while remaining STATIONARY (which mythbuster truly failed at), then I'll believe it. Because THAT WAS THE PROPOSAL.

No I'm not trolling. I'd like to learn here and I think I presented valid points. Or at least, the Mythbusters failed at it.

The belt moving at the same speed mean that if the plane is moving forward at 10mph the belt is moving backwards at 10 mph. If the plane wasn't moving, the belt wouldn't be move. I.e. matching. Or equal and opposite.

Read the rest of the thread, holy shit people use a dictionary. "The conveyor belt is designed to exactly match the speed of the wheels, moving in the opposite direction." That means V(treadmill) = -1*V(wheels). Make the basic assumption by "speed of the wheels" they mean linear speed, not rotational, since if they actually meant rotational the equation would only be valid with a treadmill speed of zero. No where does it ever say it would hold the plane stationary, it says it would match in the opposite direction. Here is the definition of match: "be equal to (something) in quality or strength." If the treadmill ever went faster than the aircraft, it would NOT match and you'd violate the basic premise of the question.

I really hope people are just trolling.

 

[MongGrel]

Thrust applies to the frame of an aircraft, not the wheels.

Short of the bearings on the landing gear locking up due to the speed of the treadmill increasing X2 on the wheels, it will continue to move forward and gain take off speed.