Airplane on a Conveyor conundrum

[progrob]

If you say it's a helicopter there will be a disorderly queue to slap you

or a jumpjet!

[That Ruddy Squirrel]

well yes there will as dont planes measure windspeed anyway, therefore a planes 10miles per hour is a wind speed of 10miles per hour , therefore it will take off

And WHERE does the wind come into this ?

And NO saying the Yeti is visiting !!!!

[RodLeach]

yes it will fly, because its the thrust from the engines that gets the plane moving and they are not driven by the wheels , therefore no matter how fast the conveyor belt is moving, the wheels will be spinning faster and faster but will not be slowing the plane down
so for the plane to be doing 10mph for example, it must be phisically moving through the air, not have its wheels moving that fast!
therefore there will be lift and the plane will take off

i thought it needed windspeed to lift? would there be any?

Thats what i thought, the aerodynamics of the plane force air underneath to create lift, the trust is just what gets the plane to the speeds needed for the air to 'lift the plane'

Im thinking of that top gear episode where they put a 2cv an a mondeo behind a 747 - that was on the ground, engines running at point full blast - but it was stationary and didnt take off- if the wheels were rolling, its still 'motionless'

[animal]

what im trying to say is the plane is moving forward at 10mph, the conveyor is moving backwards at 10mph, the wheels will be turning at 20mph as they are free wheeling on the conveyor belt,
therefore the plane is actually moving (not staying still) and it will create lift due to the air moving over and under the wings, and so it will take off,
when its moving at 20mph, the conveyor is moving at 20mph in the opposite direction, the wheels will be turning at 40mph due to the speed of the plane and the speed in the oposite direction of the conveyor,
the plane is physically moving through the air, and will take off when it reaches take of speed,

[RodLeach]

what im trying to say is the plane is moving forward at 10mph, the conveyor is moving backwards at 10mph, the wheels will be turning at 20mph as they are free wheeling on the conveyor belt,
therefore the plane is actually moving (not staying still) and it will create lift due to the air moving over and under the wings, and so it will take off,
when its moving at 20mph, the conveyor is moving at 20mph in the opposite direction, the wheels will be turning at 40mph due to the speed of the plane and the speed in the oposite direction of the conveyor,
the plane is physically moving through the air, and will take off when it reaches take of speed,

aha, i see your logic there!


so yeah, the plane will take off, in probably half the distance required according to your theory

im still lost an regret voting so fast

[BUSHWHACKER]

Wow, just think of the size of that conveyor belt!

[progrob]

what im trying to say is the plane is moving forward at 10mph, the conveyor is moving backwards at 10mph, the wheels will be turning at 20mph as they are free wheeling on the conveyor belt,
therefore the plane is actually moving (not staying still) and it will create lift due to the air moving over and under the wings, and so it will take off,
when its moving at 20mph, the conveyor is moving at 20mph in the opposite direction, the wheels will be turning at 40mph due to the speed of the plane and the speed in the oposite direction of the conveyor,
the plane is physically moving through the air, and will take off when it reaches take of speed,

still not sure about that - keep thinking of running machine - if you put a remote control car on one would it not stay in same place? can someone try?
maybe i'm being really thick- its been a long day...

[animal]

still not sure about that - keep thinking of running machine - if you put a remote control car on one would it not stay in same place? can someone try?

but on a running machine, you are not actually moving forward at 10mph, the running machine is moving at 10mph, your just keeping up with it, not actually moving anywhere,
a plane does not measure its speed through its wheels , it measure the speed at which it is actually moving through the air,
therefore to be doing 10mph, it must be actually physically moving through the air at 10mph, the wheels could be spinning at 300mph and the plane still only moving at 10mph

[MOTRAV]

OK, here is a thought experiment/conundrum for all the clever-clogs on here.

You have an airplane sat on a huge conveyor belt. The conveyor belt is computer controlled such that its speed is always the same as that of the aircraft - only backwards. I.e. If the aircraft is moving forwards at 10mph, then the conveyor will move backwards at 10mph. Will the aircraft be able to take off?

Assumptions:
1. The aircraft is otherwise normally capable of flying just fine, and the pilot is normally capable of flying this aircraft just fine.
2. The conveyor belt runway is more than long enough that if the belt didn't move the aircraft would have ample room to achieve take-off. There are no obstructions that would affect a normal take-off.
3. The runway is at sea level, the air is still, and the conditions are perfect.

OK, so, will it fly or not? Please explain your answers if possible.

Ya canae change the laws of physics captain !!!!!!!!!!!!!!!!!!!!!!!!!!
When the aircraft reaches V1 speed (approx 186 mph For a fully laden 747) although the conveyor belt will be moving backwards at the same speed it bears no relation to the forward movement of the plane . When the airflow over the wings reach the pint where the centre of gravity moves rearwards the nose will lift this takes one set of wheels out of the equation . when the aircraft reaces V2 (approx 206mph for a fully laden jumbo jet ) unstick will happen and the aircraft will fly .

Please refer to Boyles law of thermodynamics and Newtons 3rd law .


PICK THE BONES OUTTA THAT slugsie

Mo

[progrob]

but on a running machine, you are not actually moving forward at 10mph, the running machine is moving at 10mph, your just keeping up with it, not actually moving anywhere,
a plane does not measure its speed through its wheels , it measure the speed at which it is actually moving through the air,
therefore to be doing 10mph, it must be actually physically moving through the air at 10mph, the wheels could be spinning at 300mph and the plane still only moving at 10mph

but doesnt it measure speed through wheels when on the ground, like a car?
- thats what i was basing my thoughts on anyway - not air speed, in which case i see what youre saying

[animal]

but doesnt it measure speed through wheels when on the ground, like a car?
- thats what i was basing my thoughts on anyway - not air speed, in which case i see what youre saying

from what i can find out, the speed is not measured through the wheels at all, and is measured these days more by radar and satellite postioning, like how a sat nav tells you how fast you are moving, therefore if it moves 10miles in a hour it has moved at 10mph.

[CaptainBeaky]

Boyle's Law is gases - pressure and volume at constant temperature, not thermodynamics...

I think you mean the Bernoulli effect. Thermodynamics has nothing to do with this

Motrav has a point, though - the plane would actually move forward onthe belt irrespective of the belt, because it is not driven forward by it's wheels, but by the thrust of it's engines.

It would therefore reach v1 and v2 (or v(rot)), but it's apparent speed relative to the belt would be 2 x v2 at take-off.

So looking at it that way, yes it would fly.

Framing the question more closely might have made it simpler to answer (but wouldn't have lasted 3 pages)

[Vultch]

I thought the explanation would be something to do with a baggage handlers strike ...

[Andy Dawson]

Hum, going to have to type this carefully!!

Newton's 3 Laws of Motion

So the thrust of the engines is countered by the action of the conveyor belt and the aircraft will remain in one place relative to the ground.
No air will be moving over the wings and thus no lift will be generated.
The treadmill analogy holds true, you experience no flow of air whilst running 'on the spot' nor would an aircraft. A second analogy would be that of a car on a rolling road - it doesn't matter where the forward thrust is applied, either directly to the wheels or the exhaust from a jet engine, if a force counters the thrust you is going to stay in one place!
Finally (at last they say!)
Airspeed is measured via a probe (stop giggling at the back!) normally located on the nose of the a/c and indicates the speed of the air entering it, this does not allow for head winds or tail winds. Thus you hear people talk about 'airspeed' or 'true airspeed' - that which has been corrected for the wind. Lastly you have 'ground speed' and I'll let some one else explain that one to you all!!!

~I'm now going to lie down in a darkened room for a bit as my head hurts

[MOTRAV]

Boyle's Law is gases - pressure and volume at constant temperature, not thermodynamics...

I think you mean the Bernoulli effect. Thermodynamics has nothing to do with this

Motrav has a point, though - the plane would actually move forward onthe belt irrespective of the belt, because it is not driven forward by it's wheels, but by the thrust of it's engines.

It would therefore reach v1 and v2 (or v(rot)), but it's apparent speed relative to the belt would be 2 x v2 at take-off.

So looking at it that way, yes it would fly.

Framing the question more closely might have made it simpler to answer (but wouldn't have lasted 3 pages)

Since when has air not been a gas beaky EH EH air is a fluid hence the reference to Boyles law bernoulis theorum deals with pressure and tempearture through convergent and divergent ducts

Mo