SVM 286
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quote:
Originally posted by bradfincham
Question:
If an aeroplane is taking off but is on a conveyor belt that is moving at the same speed as the plane, would the plane take off?
Just would like to see peoples responses
Its a question to get everyones minds thinking for once 
I don't think it would Brad.
The craft would be static and therefore have no air pressure on the wings to produce lift. 
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RichR
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my last word on this:
Lift is equal to 1/2*p*S*(V^2)*Cl
p is the pressure of the fluid in which the body is present - in the case of a P(atmospheric) = 1.25kg/m^3
S = frontal planform area
Cl is the coefficient of lift
V^2 is velocity of the body
in my opinion of course; the plane will not achieve the necessary velocity of forward advance in relation to the groundplane to produce the necessary lift to take off
twinned with the fact that, in my opinion and understanding of the question, there will be no forward motion, as the groundplane counteracts any forward motion there will be no airflow over the aerofoils and velocity of advance will be zero - as the above formula is a multiplication formula; if any component is zero - the product will be zero!
[Edited on 24-05-2006 by LiVe LeE]
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SVM 286
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quote:
Originally posted by gianluigi
YOU HAVE NO IDEA ABOUT AVIATIONOLOMOFLI 
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3CorsaMeal
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how about if you got two planes
turned 1 upside down and face it the opposite way, and put it under the other plane, (they on top of each other, one upside down, wheels touching)
they both went full throttle
would the two planes just sit still and the wheels spin?
no do it with two cars
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Cosmo
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quote:
Originally posted by 3CorsaMeal
how about if you got two planes
turned 1 upside down and face it the opposite way, and put it under the other plane, (they on top of each other, one upside down, wheels touching)
they both went full throttle
would the two planes just sit still and the wheels spin?
no do it with two cars
now your talking about two things that move which is totally different. The conveyor belt, although it spins round, doesnt actually move anywhere.
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RichR
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if you could ensure perfect balance and allignment then yes they should - but if one was on a down bank of the other ones wheels then no
infact you want a long and short wheelbase car
have the long on the bottom and the short on top - so the wheels sit in side the bottom ones
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3CorsaMeal
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the conveyor belt would have to be like rollers, I.e: loose, no power/mechanics
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3CorsaMeal
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i don't wanna bother anymore, but basically i know what i think, and how energy is transferred
[Edited on 24-05-2006 by 3CorsaMeal]
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SVM 286
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I haven't read the whole of this thread yet, but I have read the first four pages, so I apologise if I am about to re-quote something someone else has already stated.
I am very surprised that this discussion has gone on this long.
I'm not sure if it is naivety or misunderstanding of the question on the part of some folks, but the issue has been clouded by statements like ''the wheels on a plane aren't driven'' being made.
This is like saying ''custard doesn't taste like gravy''
It's painfully obvious and just causes more arguments.
Method of propulsion asides. The fact remains that an aircraft generates forward momentum with it's engine/s.
Forward momentum is what generates air pressure on the wings, and as a result, the lift that is required for flight.
If the craft is on full throttle on a conveyor belt and even if it had 1000 engines fitted, it would make no difference as the conveyor belt is matching the the craft's speed.
It's quite simple realy.
If it were possible to launch an aircraft at full throttle from a stationary position, the world's airports would be littered with conveyor belts rather than miles of air strip, and all aircraft carriers would be equipped with the same rather than a short runway and a steam catapult.
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Cybermonkey
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yes jim, i mentioned the aircraft carrier bit on page 5 i think
steve is going to kick himself when he realises.
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RichR
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I've gone too far - I think I've matematically proved my point; two sheets of A4!! - might post it up in a bit although its not that understandable - just meaningless numbers
oh what does the average 737 weigh? with full tanks, passengers, crew and effects
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Cybermonkey
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about 150,000lbs lee
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Jules S
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quote:
Originally posted by SVM 286
I haven't read the whole of this thread yet, but I have read the first four pages, so I apologise if I am about to re-quote something someone else has already stated.
I am very surprised that this discussion has gone on this long.
I'm not sure if it is naivety or misunderstanding of the question on the part of some folks, but the issue has been clouded by statements like ''the wheels on a plane aren't driven'' being made.
This is like saying ''custard doesn't taste like gravy''
It's painfully obvious and just causes more arguments.
Method of propulsion asides. The fact remains that an aircraft generates forward momentum with it's engine/s.
Forward momentum is what generates air pressure on the wings, and as a result, the lift that is required for flight.
If the craft is on full throttle on a conveyor belt and even if it had 1000 engines fitted, it would make no difference as the conveyor belt is matching the the craft's speed.
It's quite simple realy.
If it were possible to launch an aircraft at full throttle from a stationary position, the world's airports would be littered with conveyor belts rather than miles of air strip, and all aircraft carriers would be equipped with the same rather than a short runway and a steam catapult.
Groan.
Its fcuking simple. The plane has jet engines. Thrust is developed through the surrounding air. The conveyor belt has no influence on the air.
The plane moves forward, it takes off.
Honestly, its not all that difficult to grasp is it?
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SVM 286
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quote:
Originally posted by 3CorsaMeal
would the two planes just sit still and the wheels spin?
No 3CM, because the wheels are static.
If the wheels of the two planes in your example were tethered together, the planes would act as a giant Catherine wheel. If they weren't the planes would merely fly away from each other.
The conveyor belt in the example that Brad gave however, would be driven and preventing any forward progress of the craft.
A good parallel would be to think of the conveyor belt theory as a runway in a vacuum.
There would be no air at all to generate lift so the craft would simply not be able to take off.
Actually, the craft wouldn't move at all as the engines would have no air to work against and the engines wouldn't run either and even if they could the pilot would have died from suffocation but i'm sure you can see where i'm coming from.
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Cosmo
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quote:
Originally posted by Jules S
Groan.
Its fcuking simple. The plane has jet engines. Thrust is developed through the surrounding air. The conveyor belt has no influence on the air.
The plane moves forward, it takes off.
Honestly, its not all that difficult to grasp is it?
but it moves forward by the wheels turning (as its on the ground not in the air yet - and yes the wheels arent driven but it makes no difference on the ground), so as it gets faster the wheels turn faster, but so does the conveyor belt....so the plane moves nowhere.
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RichR
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quote:
Originally posted by Cybermonkey
about 150,000lbs lee
must be more than that - that equates to 68.2 tonnes - that cant be heavy enough
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Jules S
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FFS forget the bloody converyor belt, it could be on iceskates for that matter.
the plane uses thrust to move NOT its wheels. The plane is moving through the air not along the tarmac/conveyor.
The conveyor is not matching the thrust of the engines.
The plane moves forward regardless of the conveyor belt.
It takes off.
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gianluigi
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Jules good point, its like those aircrafts that take off on water 
[Edited on 24-05-2006 by gianluigi]
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RichR
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u eegit - before take off - there is contact between the wheels and groundplane - the wheels are attached to the plane, if the wheels are in a static location, the plane has no forward momentum - oh I cant be arsed read my replies above
your whole argument lacks any merit
when its on the ground the forward momentum is translated through the wheels to the groundplane
if these can not move to or fro - then the plane can not inhibit signs of forward momentum and as such cant produce lift,
your argument only works if the wheels are never in contact with the groundplane - in which case it doesnt matter if its over a fucking conveyor or paddling pool full of ky jelly and dime bars
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Cosmo
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quote:
Originally posted by Jules S
FFS forget the bloody converyor belt, it could be on iceskates for that matter.
the plane uses thrust to move NOT its wheels. The plane is moving through the air not along the tarmac/conveyor.
The conveyor is not matching the thrust of the engines.
The plane moves forward regardless of the conveyor belt.
It takes off.
Once again, your thinking of the plane when its in the air, not when its on the ground.
When its on the ground it doesnt matter what is providing the thrust (jet engine, engine powering the wheels, elastic bands, etc) the fact is that the wheels are touching the conveyor belt...the plane is not 'in the air'.
To move forward its wheels MUST move faster than the conveyor belt but this wont happen as the speed will always be matched, the jet engines can thrust as much as they want but while its on the ground its not moving anywhere.
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RichR
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the ice skates argument doesnt hold up either - because the forward momentum could be achieved - but with a conveyor the two are acting simultaneously and opposite
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RichR
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quote:
Originally posted by gianluigi
Jules good point, its like those aircrafts that take off on water
nothing to do with it - the groundplane equilibrium can be overcome]
with a conveyor - the groundplane is acting in the opposite direction at the same velocity of advance - hence there will be no forward momentum
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Steve
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SVM 286 your painfully wrong, i know you cant launch planes off stationary position, but the conveyor belt would still have to be as long as a normal runway CANT YOU LOT FCUKING SEE!! the plane would still have to travel as far as normal, the conveyor belt would have no effect,
i cannot believe some of you are arguing this, i would actually place a bet on my house that i am right
[Edited on 24-05-2006 by Steve]
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Steve
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quote:
Originally posted by LiVe LeE
quote:
Originally posted by gianluigi
Jules good point, its like those aircrafts that take off on water
nothing to do with it - the groundplane equilibrium can be overcome]
with a conveyor - the groundplane is acting in the opposite direction at the same velocity of advance - hence there will be no forward momentum
cant you see that the opposite direction of force has no effect on the forward direction of force applied by the jets because the force of the conevyor belt is simply just running under the freehwling wheels on the plane
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Hammer
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im quite bored in the office, i shall gather the specific components and build a scale model, i also may take live lees lead and jot down 2 pages of random numbers saying i have worked it out then ask the weight of a plane
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