Will an airplane on a treadmill be able to takeoff?
- Thread starter MistaX
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the Interceptor
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- theInterceptor77
That's the whole solution in one sentence.Danoff
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One other interesting problem.
Buttered toast has been scientifically proven to land buttered side down more than the dry side. Cats are known for always landing on their feet. If you stuck a piece of toast on the back of a cat with the buttered side up, would the cat spin in mid air?
Buttered toast has been scientifically proven to land buttered side down more than the dry side. Cats are known for always landing on their feet. If you stuck a piece of toast on the back of a cat with the buttered side up, would the cat spin in mid air?
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- (GTP_) dustdriver
if the cat is heavier than the butter on the toast, the cat will land first.
If the butter is heavier, it will land first.
If it's equal, the cat and the toast will land on their side 💡
If the butter is heavier, it will land first.
If it's equal, the cat and the toast will land on their side 💡
A plane needs to have air flowing over its wings to be able to fly. Any situation you can come up with that satisfies this requirement is sufficient. No need to talk about the belt, or the wheels, or anything else, just the one question of whether or not there is enough air flowing over the wings.
I guess all the confusion arises from people using the ground (or more confusingly, the moving treadmill belt) as a frame of reference, when in reality the "air" should be the frame of reference. That's why a plane that only requires 60mph of airflow over its wings could take off in a 60mph headwind and fly while remaining "stationary" above the ground. Conversely, that same plane could be travelling over the ground at a rate of 60mph yet still fall like a rock if it suddenly encountered a 60mph tailwind.
I guess all the confusion arises from people using the ground (or more confusingly, the moving treadmill belt) as a frame of reference, when in reality the "air" should be the frame of reference. That's why a plane that only requires 60mph of airflow over its wings could take off in a 60mph headwind and fly while remaining "stationary" above the ground. Conversely, that same plane could be travelling over the ground at a rate of 60mph yet still fall like a rock if it suddenly encountered a 60mph tailwind.
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Ive read through the thread and now I can see the plane taking off because when I first read the question I made a mistake and forgot the power pushing the plane forward isnt generated by the wheels, Their just there to keep the underside off the ground. The jet engines work off the ground and use the friction of the air to push itself forward. Cars use the friction of the tyres against the road to push itself forward.
The car analogy which I was thinking about earlier is useless for this question. I guess it would fit in if you asked: 'Can an airplane take off in a vacuum.'
The car analogy which I was thinking about earlier is useless for this question. I guess it would fit in if you asked: 'Can an airplane take off in a vacuum.'
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- bramturismo
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The propeller doesn't generate airflow over the wings, it generates thrust to pull the wings through the air.
Smallhorses
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This was discovered at UKGTP V, back in May of 2006. As yet we've not found an investor to finance research into the important field of anti-gravity!
The discovery of anti-gravity devices created by putting butter & marmalade on the back of a cat!*
* It works on this principle:- if you drop a cat it lands feet first. If you drop toast with butter or marmalade on, it lands butter or marmalade side down. Thus antigravity can be achieved by dropping a cat which has its back covered in butter or marmalade. In accordance with the above rules, the effects of trying to land on its feet will be negated by the effects of trying to land butter & marmalade side down, and hence the cat will float above the ground!
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- GTP_Venari
EDIT: Uh, looks like I missed awhole page of discussion. Brain the size of a (gt) planet...
Uh... the plane will take off.
Put it this way, the plane has to move in order for the wheels to rotate, which then puts the conveyor runway in motion. When the plane's airspeed reaches 1mph, the conveyor is moving backwards at 1mph, and thus their relative speed is 2mph (which is what the wheels see as a ground speed.)
The coefficient of friction of a wheel is very low, but even if you put skids under the plane instead of wheels, it would (probably) eventually take off. The longer time taken to take off is the result of increased freiction.
What is happening here is that you are (roughly) quadrupling the coeffcient of friction of the wheels resisting the plane's engine's thrust.
Why quadrupling? Because you're doubling the actual rotational speed of the wheels, you're increasing the amount of kinetic energy by the square of that amount. I say roughly because the wheel might not be rated to spin at that speed, and might sieze up through heat or something. Whatever, that plane's going up.
As said, if the plane requires 100mph airspeed to take off, all you've got is a bit longer time to get there, the plane is translating through the air at 100mph, the conveyor is moving backwards at 100mph, and the wheels think their doing 200mph.
Uh... the plane will take off.
Put it this way, the plane has to move in order for the wheels to rotate, which then puts the conveyor runway in motion. When the plane's airspeed reaches 1mph, the conveyor is moving backwards at 1mph, and thus their relative speed is 2mph (which is what the wheels see as a ground speed.)
The coefficient of friction of a wheel is very low, but even if you put skids under the plane instead of wheels, it would (probably) eventually take off. The longer time taken to take off is the result of increased freiction.
What is happening here is that you are (roughly) quadrupling the coeffcient of friction of the wheels resisting the plane's engine's thrust.
Why quadrupling? Because you're doubling the actual rotational speed of the wheels, you're increasing the amount of kinetic energy by the square of that amount. I say roughly because the wheel might not be rated to spin at that speed, and might sieze up through heat or something. Whatever, that plane's going up.
As said, if the plane requires 100mph airspeed to take off, all you've got is a bit longer time to get there, the plane is translating through the air at 100mph, the conveyor is moving backwards at 100mph, and the wheels think their doing 200mph.
- 41,075
The way I see it, if you put a plane on a treadmill that moved similar to a dynometer (it spins if the wheel turns on its own power), the treadmill wouldn't move. If you put the plain on a treadmill that did move, the plane would stay in place in theory (but would more likely fall backwards).
If both the treadmill and the plane were powered, the treadmill pushing back wouldn't negate the plane pushing forward, because the plane doesn't use the wheels to move. The plane would still go forward, but the wheels would just be spinning faster than normal. Depending how efficient the wheels are would determine how much of an effect the treadmill would have, but it would never be enough to push the aircraft back if the engine was on.
As Venari said, a treadmill moving 100MPH against a plane moving 100MPH would just make the wheels spin faster and would make it so the plane would take a little longer to take off. So it would take off, but it would require (marginally) more space than a conventional runway. For a treadmill to negate a planes speed it would have to be going much faster (exponentially so) than the plane was to make friction of the wheels high enough to prevent forward motion of the plane.
If both the treadmill and the plane were powered, the treadmill pushing back wouldn't negate the plane pushing forward, because the plane doesn't use the wheels to move. The plane would still go forward, but the wheels would just be spinning faster than normal. Depending how efficient the wheels are would determine how much of an effect the treadmill would have, but it would never be enough to push the aircraft back if the engine was on.
As Venari said, a treadmill moving 100MPH against a plane moving 100MPH would just make the wheels spin faster and would make it so the plane would take a little longer to take off. So it would take off, but it would require (marginally) more space than a conventional runway. For a treadmill to negate a planes speed it would have to be going much faster (exponentially so) than the plane was to make friction of the wheels high enough to prevent forward motion of the plane.
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- DerAlta
Actually, the lot of you missed this Thread.
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And they'll keep missing it. This is one of those damnable questions I wish were dead and buried. In fact, it is one of those threads I'd put right up there with the "9-11 Loose Change Conspiracy" and "Fake Moon Landings".
Which is why airplanes always take off into the wind (as Famine says in the 2005 thread)... and, interestingly enough, the treadmill phenomenon used to cause a lot of crashes... Pilots banking into a wind used to misjudge their airspeed by using the ground as a reference, often with horrible results.
Which is why airplanes always take off into the wind (as Famine says in the 2005 thread)... and, interestingly enough, the treadmill phenomenon used to cause a lot of crashes... Pilots banking into a wind used to misjudge their airspeed by using the ground as a reference, often with horrible results.
GilesGuthrie
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... he says, then doesn't close the thread!!!
I hate this question! It keeps coming up (not least at an Aviation Forum I administer), and all the wrong'uns are so passionate in the reasoning for their wrongness, and most all the right'uns singularly fail to explain themselves in a cogent manner. However, Danoff nailed it in the previous thread, so I'm taking an executive decision on this one, notwithstanding Mista X's interesting assertion that the fundamentals of at least one of Physics; Aircraft Design; Treadmill Design have significantly and surreptitiously changed within the last two years, without so much as a 'by your leave'.
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