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-   -   Plane on a Conveyor Belt (https://www.airlinepilotforums.com/hangar-talk/21670-plane-conveyor-belt.html)

TonyC 02-07-2017 08:57 AM


Originally Posted by FallingWithStyle (Post 2287169)

Ok it's 2017 and yes I saw the mythbusters episode.

What if each wheel of the plane was placed on a non electric treadmill?

That was my original thought when first ever hearing this question. If the plane doesn't get forward momentum how could it take off?

In the show it clearly moves along the conveyor belt allowing air to flow over the wings so of course it will take off.

I thought though that the conveyor belt would be fast enough to basically keep the wheels spinning in place. In that scenario it seems the plane could not take off.

Yes there are some really light planes whose thrust could maybe produce enough airflow to get it off the ground, but I'm talking about the 747 in the original question.

So, if a 747 has each wheel on a non electric treadmill, will it off?



Here's the original question:
A plane is standing on runway that can move (some sort of band conveyor). The plane moves in one direction, while the conveyor moves in the opposite direction. This conveyor has a control system that tracks the plane speed and tunes the speed of the conveyor to be exactly the same (but in opposite direction).

The question is:

Will the plane take off or not?
The original question includes the statement, "The plane moves ..." There is no assumption that the moving surface beneath the airplane keeps the airplane from moving forward relative to the ground, or relative to the air, which is the movement which will result in lift and therefore flight. In fact, there is a statement within the original question as posed to the opposite -- THE.PLANE.MOVES.

A moving surface beneath the wheels simply will not prevent the airplane from moving. All it will do is increase the speed of the turning wheels.


Your new question includes an assumption that some type of device under the wheels keeps the airplane from moving. Instead of moving forward, the airplane is held in place, and therefore will not fly.

But, no matter how fast the moving belt, and no matter how it is propelled, be it electric or non-electric, the moving surface beneath the wheels cannot keep the airplane from moving. It will only make the wheels turn faster, the same as taking off with a tailwind.

IF -- Huge IF -- IF there were some sort of device that would keep the wheels from moving relative to the ground and the surrounding air, you would be correct -- the airplane would be held in place, and therefore would not fly. That device would be called a tiedown.






.

tomgoodman 02-07-2017 11:35 AM

But if the wheels turn fast enough, their motion will approach the speed of light and they will gain enormous mass, making the airplane too heavy to take off. :D

RI830 02-07-2017 11:50 AM


Originally Posted by tomgoodman (Post 2296775)
But if the wheels turn fast enough, their motion will approach the speed of light and they will gain enormous mass, making the airplane too heavy to take off. :D

Post of the week!!! Well played sir!


Reminds me of a guy who told me he greased on every landing.
He flies the plane to within a few millimeters of the ground. The heat created between the small gap of the ground and tires would cause the tires to slightly expand and bazinga.......a grease job every time.

JohnBurke 02-07-2017 06:53 PM


Originally Posted by tomgoodman (Post 2296775)
But if the wheels turn fast enough, their motion will approach the speed of light and they will gain enormous mass, making the airplane too heavy to take off. :D

If they get going that fast, they go past light speed to plaid.

Everyone will be fine as long as they don't try to stop suddenly.

tomgoodman 02-07-2017 08:22 PM


Originally Posted by JohnBurke (Post 2297085)
If they get going that fast, they go past light speed to plaid.

Everyone will be fine as long as they don't try to stop suddenly.

But they will stop suddenly, when the plaid speed causes a gigantic time reversal, and the wheels vanish because they have not yet been invented. :eek:

RI830 02-08-2017 09:42 AM


Originally Posted by tomgoodman (Post 2297130)
But they will stop suddenly, when the plaid speed causes a gigantic time reversal, and the wheels vanish because they have not yet been invented. :eek:

But only if 1.21 gigawatts was acheived in the flux capacitor

trip 02-08-2017 10:44 AM


Originally Posted by FallingWithStyle (Post 2287169)
Ok it's 2017 and yes I saw the mythbusters episode.

What if each wheel of the plane was placed on a non electric treadmill?

That was my original thought when first ever hearing this question. If the plane doesn't get forward momentum how could it take off?

In the show it clearly moves along the conveyor belt allowing air to flow over the wings so of course it will take off.

I thought though that the conveyor belt would be fast enough to basically keep the wheels spinning in place. In that scenario it seems the plane could not take off.

Yes there are some really light planes whose thrust could maybe produce enough airflow to get it off the ground, but I'm talking about the 747 in the original question.

So, if a 747 has each wheel on a non electric treadmill, will it off?

Arrgggg...

CrimsonEclipse 02-08-2017 01:57 PM


Originally Posted by tomgoodman (Post 2297130)
But they will stop suddenly, when the plaid speed causes a gigantic time reversal, and the wheels vanish because they have not yet been invented. :eek:


Originally Posted by RI830 (Post 2297448)
But only if 1.21 gigawatts was acheived in the flux capacitor

Just don't cross the streams!@!@!

(it would be bad)

JohnBurke 02-08-2017 03:21 PM


Originally Posted by tomgoodman (Post 2297130)
But they will stop suddenly, when the plaid speed causes a gigantic time reversal, and the wheels vanish because they have not yet been invented. :eek:

If the wheels vanish, that should solve most of the problem. The treadmill should vanish about the same time, and quite likely, the airplane with it. Now, if a cheetah is nearby waiting, it becomes an issue of who's faster on foot.

That's when it gets interesting.

Only the cheetah needs to worry about being the fastest, and then only faster than the slowest occupant of the non-airplane. The rest of us only need to worry about being faster than the slowest person. Other than that, everything will sort itself out in short order.

tomgoodman 02-08-2017 08:48 PM


Originally Posted by JohnBurke (Post 2297668)
If the wheels vanish, that should solve most of the problem. The treadmill should vanish about the same time, and quite likely, the airplane with it. Now, if a cheetah is nearby waiting, it becomes an issue of who's faster on foot.

That's when it gets interesting.

Only the cheetah needs to worry about being the fastest, and then only faster than the slowest occupant of the non-airplane. The rest of us only need to worry about being faster than the slowest person. Other than that, everything will sort itself out in short order.

So there you have it, Kids.
Fool around with treadmills and there will be nothing left but a fat cheetah. :p

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