Something to think about

[Guest]

Those trees will remain stationary relative to the aircraft which remains stationary relative to the ground which moves relative to the moving surface of the treadmill.Unless you assume an imperfect treadmill of course.

[Christopher Low 5,331]

The airflow would be ZERO, therefore no take off.Chris Low.

[Guest enave]

>The airflow would be ZERO, therefore no take off.>>>Chris Low.>The airplane would move relative to the ground, because there is nothing to stop it from moving. Therefore there would be airflow, and it would take off.

[Christopher Low 5,331]

It would be moving along the treadmill at an ever increasing speed, but it wouldn't move relative to the Earth itself (and more importantly, the Earth's ATMOSPHERE). This would result in ZERO airflow, and therefore no take off.Chris Low.

[kerosene31 349]

>It would be moving along the treadmill at an ever increasing>speed, but it wouldn't move relative to the Earth itself (and>more importantly, the Earth's ATMOSPHERE). This would result>in ZERO airflow, and therefore no take off.>>>Chris Low.>Yes, it would move. That is the common mistake. A car on a treadmill would not move, because the wheels put force directly on the moving track. A jet/prop engine puts all its force into the air. A runner doesn't move on a treadmill, because the tread moves at the same speed as his/her feet. The airplane wheels spin freely, and the thrust into the air pushes forward, regardless of the treadmill. The airplane does move forward on the treadmill. It does not stay in one spot. The treadmill cannot hold the plane stationary, even if it matches the speed. It took me forever to see it too.

[Guest victorwest]

Are we all seeing forward motion of the aircraft in the same way? The "non movers" like myself see Thrust produces movement of plane = corresponding movement of treadmill in an equal but opposite amount in the other direction.Victor

[Christopher Low 5,331]

Craig,Yes, I have been exploring the internet for other discussions regarding this, and it seems that the aircraft would indeed accelerate down the runway as if the treadmill wasn't there. To be honest, I would love to see it demonstrated......just to settle the mind :-)However, what are the chances that the airliner would take off before all of its tyres exploded ? I am well aware that this is irrelevant to the true meaning of the original question, but it is worth asking all the same ;-)Chris Low.

[Guest]

>>Yes, it would move. That is the common mistake. >wrong, the common mistake is that it would move.>A jet/prop engine puts all its force into the air. >Which gets counteracted by the moving treadmill.>A runner doesn't move on a treadmill, because the tread moves>at the same speed as his/her feet. >Correct. Same way something else wouldn't move either.>The airplane does move forward on the treadmill. It does not>stay in one spot. >>The treadmill cannot hold the plane stationary, even if it>matches the speed. >It can, but it would probably need to be a powered treadmill, which is the most common kind of equipment to keep people stationary.An unpowered treadmill can't probably provide enough of a force to stop the aircraft from achieving the thrust needed to overcome friction (unless the surface of the treadmill has very high friction and can move freely at any speed maybe).Consider the treadmill to be a surface with unusually high friction and that's the logical outcome.

[Guest]

>Craig,>>Yes, I have been exploring the internet for other discussions>regarding this, and it seems that the aircraft would indeed>accelerate down the runway as if the treadmill wasn't there.>To be honest, I would love to see it demonstrated......just to>settle the mind :-)>It wouldn't.At the very least it would need longer to achieve takeoff velocity, at best it would never leave its initial position.

[kerosene31 349]

All the wheels need to do is spin twice as fast as the normal takeoff speed. Friction will enter into it, but I'm not sure how much. The way I "got" it was the guy on rollerskates example.

[Guest oyvindhansen]

>Consider the treadmill to be a surface with unusually high>friction and that's the logical outcome.>But the friction of the threadmill surface is of course of little consequence. The only thing that matters is the rolling resistance of the wheels, determined by the deformation of the tire and the friction in the wheel bearings. It is small. You cannot transfer any force to the aircraft body without friction.Don't know why I even bother to write this anymore...-

[Guest victorwest]

But ultimately, if the aircraft is to move, it has to be moving forward at a faster rate then the treadmill is moving back. I do not see this to be in the spirit of the statement "..this treadmill could match the forward speed of your aircraft exactly, but running in the opposite direction". Victor

[Guest Charlie]

Oyvindhansen, "Short circuit of though" is not a polite term in my book. It may well be less offensive than the term you wanted to use, but that doesn

[mgh 89]

"Wrong, the common mistake is that it would move."Sorry, that is wrong"Which gets counteracted by the moving treadmill."How? Please explain the mechanism that generates a force equal and opposite to the thrust at the wheels of the aircraft"Correct. Same way something else wouldn't move either."Incorrect. Again please explain the source of the force that stops an aircraft rolling"Consider the treadmill to be a surface with unusually high friction and that's the logical outcome."Why introduce unusually high friction? The original problem referred to an aircraft with wheels that can rotate, like any other aircraft. Why not consider the aircraft bolted down to the treadmill? - it's just as irrelevant to the subject.

[Guest Charlie]

Yep, that's the nitty-gritty of this debate, Victor. In order for there to be a clear answer, "forward speed" must be precisely defined as to what it is relative to. If it it relative to the treadmill, there is no takeoff.