Plane on a Conveyor Belt
02-07-2017, 08:57 AM
#21
Organizational Learning
Joined APC: Nov 2005
Position: Directly behind the combiner
Posts: 4,948
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.The question is:
Will the plane take off or not?
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.
.
02-07-2017, 11:50 AM
#23
Gets Weekends Off
Joined APC: Mar 2011
Position: Left seat on a kite
Posts: 1,884
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.
02-07-2017, 06:53 PM
#24
Disinterested Third Party
Joined APC: Jun 2012
Posts: 6,124
Everyone will be fine as long as they don't try to stop suddenly.
02-07-2017, 08:22 PM
#25
Gets Weekends Off
Joined APC: Feb 2006
Position: 767A (Ret)
Posts: 6,248
02-08-2017, 09:42 AM
#26
Gets Weekends Off
Joined APC: Mar 2011
Position: Left seat on a kite
Posts: 1,884
02-08-2017, 10:44 AM
#27
Gets Weekends Off
Joined APC: Sep 2009
Posts: 2,245
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?
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?
02-08-2017, 01:57 PM
#28
Banned
Joined APC: Feb 2007
Posts: 461
(it would be bad)
02-08-2017, 03:21 PM
#29
Disinterested Third Party
Joined APC: Jun 2012
Posts: 6,124
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.
02-08-2017, 08:48 PM
#30
Gets Weekends Off
Joined APC: Feb 2006
Position: 767A (Ret)
Posts: 6,248
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.
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.
Fool around with treadmills and there will be nothing left but a fat cheetah.
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