Would the plane take off?



Neil- 'The thrust produced by the engines does not produce lift,
'

Neil, Charlie did not say engine thrust produce lift,

charlie - 'Add wings... and more mates (For greater thrust) And u have flight!'

faction you are mixing fixed values for conditions with impossible theories, stop the values and come up with some of these theories 'Now I put some clever-engine technology on my aircraft, meaning the wheels can drive it up to oh, 180 knots. My clever engine-technology also means I can cut the jets in at 100% thrust in an instant.'

this must be the most serious thread i have read on here lol
 
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faction you are mixing fixed values for conditions with impossible theories, stop the values and come up with some of these theories 'Now I put some clever-engine technology on my aircraft, meaning the wheels can drive it up to oh, 180 knots. My clever engine-technology also means I can cut the jets in at 100% thrust in an instant.'

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OK, that's just a daft way to illustrate the point that regardless of where propulsion comes from, you do need some to get the air moving over the wing before it works and you break ground.

You have to take constant atmospheric conditions (even if you used realistic constants, qnh29.92. 20 degrees. calm wind (these conditions do happen you know), as there's a) no information of these conditions in the question b) they ARE exceedingly relevant for flight (specifically the operation of a conventional-wing), c) there's no frame of reference to use for the question (I've never seen a real-life try-out of this with a 747 on a conveyor-belt/rolling-road), so you need to be able to compare _somehow_, and to do that with any hope of reliability, you need to consider those values.

Still, I think the winged-Veyron is quite a basic, plausible, and simple to understand illustration of the point...

Regards,

Rob.
 
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charlie - 'Add wings... and more mates (For greater thrust) And u have flight!'

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You see, this requires 'more mates' pushing the car off the rollers (or along the conveyor) to get it airborne, for that to happen, forward motion beyond the inverse motion of the rollers has to occur...

...The conveyor-belt/rollers in the question continue to match the wheel-speed, you'd need the engines to be able to push harder than the conveyor/rollers can resist to begin to gain forward momentum (like the car being pushed off the rollers) and build airspeed in order for the wing to begin to function.

Regards,

Rob.
 
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charlie - 'Add wings... and more mates (For greater thrust) And u have flight!'

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You see, this requires 'more mates' pushing the car off the rollers (or along the conveyor) to get it airborne, for that to happen, forward motion beyond the inverse motion of the rollers has to occur...

...The conveyor-belt/rollers in the question continue to match the wheel-speed, you'd need the engines to be able to push harder than the conveyor/rollers can resist to begin to gain forward momentum (like the car being pushed off the rollers) and build airspeed in order for the wing to begin to function.

Regards,

Rob.

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The fact that the planes needs airflow over the wings to produce wings is not in doubt.

Yes, the plane wil need to push harder to counter the conveyor, but by a very, very small ammount. This is just the extra friction caused by the wheels moving twice as fast. When you're talking about a car reaching a max speed, people talk about it's drag coefficient, and it's power. They don't say, "wheel bearings are stopping us pusing it further!"

The wheels would have to be strong enough to cope, but if we're talking about a conveyor belt runway, i don't think that's really the point.

The engines would push the car forward relative to the air speed, not the ground speed.


Lots of people have argued the no argument, but so far nobody is close to convincing me it won't take off.
 
All the thrust from the engines needs to do, it take the weight of the aircraft...i.e produce enough thrust, to counteract the 'drag' its experiencing on the ground. This will not be hard to achieve! Afterall... There is no force acting on the aircraft itself (head wind) which will stop it moving. The drag from the wheels will be so insignificant it just wont matter! Its that hard a principle to get your head around.

Think about this.

Your on your 747 or something lined up on the runway. The captain applies the brakes and winds the engines up to near full power, and then releases the brakes (in some instances anyway). The aircraft catapults forward at quite a rate... Now, if the runway was moving backward at the same rate as the aircrafts WHEELS were moving forwards, then it would take a little logner to get upto speed...but it will still happen! All the wheels do is support the aircraft on the ground, until there is sufficient airflow over the top of the wing to product....At take off, they serve absolutely no other purpose!

airflow matters... nothing else does!
 
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airflow matters... nothing else does!

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Exactly!.. It will fly.

This situation would never happen in the true world. Its purley hyperthetical!. Hence, you have to ignore little factors such as bearing resistance.

You also have to look at this as a simple model.
Forward movement of the plane RELATIVE to the AIR will product upwards lift! Thats it!.... ignore how fast you need to be going to get lift, all systems are ideal (i.e. no resistance or mechanical losses).
Like the others have said.. The wheels are there pureley to lift the aircraft from the ground. Essentially, the craft is sitting on a bed of air (as the wheel bearings have zero resiatance).

FactionOne, the length of the aircraft carrier runway has nothing to do with this situation.... You need the length, because off the acceleration rate of the craft.

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EDIT: And to just quickly further deal with any point regarding the wheels of the aircraft not providing the power, it's irrelevant where the power comes from until you've gained the magic 150 knots airspeed. Lets imagine that my wing as I mentioned, generates lift at 150 knots, but that's only when you have some extension of flaps, if the flaps are retracted, we need 180 knots


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It is not irrelevant where the power comes from.
If the wheels power the plane, the forward motion is coming from the wheels pushing against the runway!.. If the engines powers the plane, the forward motion comes from the reaction of the thrust (newtons 3rd law)

Yet another example.
You are on a treadmill.... Running at the same pace as the belt. (Hence not moving forward). Imagine that the running speed increases and the belt matches the speed of your feet. (Still stationary).
Now comes your supposed best mate, who pushes you forward.
What happens?.. You still move forward. This is because your body and legs are treates seperatly.
Obviously your legs would have to do much more work when you are pushed forward.
 
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Yet another example.
You are on a treadmill.... Running at the same pace as the belt. (Hence not moving forward). Imagine that the running speed increases and the belt matches the speed of your feet. (Still stationary).
Now comes your supposed best mate, who pushes you forward.
What happens?.. You still move forward. This is because your body and legs are treates seperatly.
Obviously your legs would have to do much more work when you are pushed forward.

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I've changed my mind about this one more over the past couple of days than any other time I've come across it in the past...

I see all the points about power being disconnected from the wheels (and surface underneath them), but I'm struggling with mass and gravity...

We've been analysing treadmill type scenarios here too...

Let's imagine that you're at the bottom end of a treadmill at a standstill, and you're wearing roller-skates and a jetpack...

You hold the remote for your jetpack in your hand and start to gradually increase the power...

If the reverse motion is matched identically to the moment (and I mean the EXACT MOMENT, so there's no intertia / latency in the speed-matching whatsoever), surely the mass of the object (aeroplane, jet-car, Audi-Sport.net Rollerskating Jetpack-Pioneer), would held on the spot by gravity?

Regards,

Rob.
 
Right...Here is a brilliant example

Your standing on a treadmill, moving at 10mph, with skates one. The wheels on the skates match the speed of the belt. Now, if you were to pull on the bar in front of you, you will still go forwards... Now put this into context. rollerskates are the undercarriage, treadmill is the runway, and your arms, the thrust from the engines... You can pull yourself forward, no matter how fast the belt and you wheels are turning, as they cancel each other out! Therefore thrust is n action which will push (pull) you forward.

Rich
 
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Right...Here is a brilliant example

Your standing on a treadmill, moving at 10mph, with skates one. The wheels on the skates match the speed of the belt. Now, if you were to pull on the bar in front of you, you will still go forwards... Now put this into context. rollerskates are the undercarriage, treadmill is the runway, and your arms, the thrust from the engines... You can pull yourself forward, no matter how fast the belt and you wheels are turning, as they cancel each other out! Therefore thrust is n action which will push (pull) you forward.

Rich

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Good work RIch! better than all my examples.

Now surely, everyone agrees! /ubbthreads/images/graemlins/beerchug.gif
 
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I see all the points about power being disconnected from the wheels (and surface underneath them), but I'm struggling with mass and gravity...

We've been analysing treadmill type scenarios here too...

Let's imagine that you're at the bottom end of a treadmill at a standstill, and you're wearing roller-skates and a jetpack...

You hold the remote for your jetpack in your hand and start to gradually increase the power...

If the reverse motion is matched identically to the moment (and I mean the EXACT MOMENT, so there's no intertia / latency in the speed-matching whatsoever), surely the mass of the object (aeroplane, jet-car, Audi-Sport.net Rollerskating Jetpack-Pioneer), would held on the spot by gravity?

Regards,

Rob.


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You have to seperate the verticle from horizontal components. Therefore gravity and mass has zero effect on backwards and forwards motion.

Back to the treadmill example.... You have to look at it in a ideal world. i.e. zero resistance at the wheel bearings. Therefore if you had rollerscates on you would not need any forward force to keep you stationary. Adding an external force, would therefore move you in that direction.
 
lol, time to stop the brain from hurting and read from the experts:

Ask A Scientist

Aviation Web

Looks like the plane will take off "Perfectly Normally", but the wheels will not be rotating...
 
What a great thread, i was going to reply YES but its run its course. you could also prove thinking about conservation of momentum, or a force diagram thinking ONLY about the force on the plane, big force from engines, small backwards force from bearing resistance, therefore large resultant force forwards. it will be fun (?) to ask my A level physics students this for a homework..
chas
 
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What a great thread, i was going to reply YES but its run its course. you could also prove thinking about conservation of momentum, or a force diagram thinking ONLY about the force on the plane, big force from engines, small backwards force from bearing resistance, therefore large resultant force forwards. it will be fun (?) to ask my A level physics students this for a homework..
chas

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That brings back memories!
 
"If the forward acceleration of the plane's wings is opposed by a negative accelertion of the
conveyer belt then there will be no sufficent forward movement of the wing relative to the air
around it and hence it will not produce lift."

Thats exactly what i meant, lol, if no forward movement, no air pressure under wings for lift....

Imagaine this.....what would the plane do if it had no wings during the flight.....lol
 
also remeber the zero air pockets ie no air pressure.....some airports in the states have this problem, espically on landings etc.. which result in the plane falling a good few ****** feet....
 
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Looks like the plane will take off "Perfectly Normally", but the wheels will not be rotating...


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The wheels HAVE to be rotating, if the plane is physically moving along the runway. What you will actually observe is that the wheels are spinning twice as fast.
 
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"If the forward acceleration of the plane's wings is opposed by a negative accelertion of the
conveyer belt then there will be no sufficent forward movement of the wing relative to the air
around it and hence it will not produce lift."


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If you read back through the other posts and the original question. The converyer belt is not acting on the planes wings. Only on the wheels.
 
OK - there is something which I think most of you have missed.

Firstly - the plane would take off. Period. No question, no doubt.

BUT! It would not take off "vertically", which is what most people think of when confronted with this (IE they see the plane sitting still and then launching directly up in the air) - it would basically accelerate along the conveyer belt runway as normal, and when it has enough airspeed, will take off as normal. The wheels would be spinning at conveyerbelt speed+airspeed, so much faster than on a conventional runway. Therefore, the conveyer belt is the misleading part, becuase although its moving, the actual actions of the aircraft whilst grounded will not change.

So as far as the aircraft is concerned, from the outside looking at the aircraft, take off would look exactly the same as if the runway was not moving.....

PS - did I ever mention I used to be an avionics and aerodynamical engineer? /ubbthreads/images/graemlins/grin.gif
 
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Looks like the plane will take off "Perfectly Normally", but the wheels will not be rotating...


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The wheels HAVE to be rotating, if the plane is physically moving along the runway. What you will actually observe is that the wheels are spinning twice as fast.

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Exactly what i said in a previous post

"the plane will take off it just means that the wheels will be roatating at twice the speed at which they normally would be during take off!"
 
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charlie - 'Add wings... and more mates (For greater thrust) And u have flight!'

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You see, this requires 'more mates' pushing the car off the rollers (or along the conveyor) to get it airborne, for that to happen, forward motion beyond the inverse motion of the rollers has to occur...


Regards,

Rob.

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You what? Turn that roller into a conveyor, put wings on you car and produce enough thrust from ur mates and you'll get it to fly...


I like the treadmill/skates idea thats good!
Especially when u ignore all frictional values etc.
 
I think the wheels would have to skid across the belt for the duration of the takeoff a breakdown of friction between the tyre and the belt surface.
 
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I think the wheels would have to skid across the belt for the duration of the takeoff a breakdown of friction between the tyre and the belt surface


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Why would they have to skid??.. There is nothing stopping the wheels fro spinning. They are free to rotate.
 
NOOOOOO this post is just not natural, LEAVE IT and get up the pub
 
There is nothing stopping the wheels from spinning, but there is something stopping them from
making ground forwards, the belt moving backwards. No air speed no lift.

Only when the tyres of the wheels loose grip with the belt does the plane begin to move
forwards. The tyres wouldnt last very long like this so I guess the thing would crash
somewhere halfway up the runway of the belt. So not the thing would not fly.
 
HAHAHA this is turning out to be hilarious...keep them rolling in if you excuse the pun! /ubbthreads/images/graemlins/laugh_roll.gif
 
Christ people..The simple fact of the matter is that the plane will take off... People saying it wont, your wrong... sorry! lol

Lets go back to a kids theory.

Youve got your toy plane on the checkout of a supermarket while you sit in mummy's trolly... The conveyor is moving, and you put your plane on it..the wheels are turning, but the plane is not moving forwards as you are holdig it still... But, your arm is the equivalent of thrust from the engines, and you can STILL push the plane forwards on the belt and build up airspeed. This is a fact, not an opinion!!

Rich
 
Rich that is because the checkout belt speed is constant and does not match the
rotation of the wheels when you apply force to push the plane forwards.
Therefore you can push the plane up the checkout belt because the wheels are moving faster
than the speed of the belt.

The original statement says the belt speed changes in accordance with the planes wheels
speed so this analogy is wrong.
 
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Rich that is because the checkout belt speed is constant and does not match the
rotation of the wheels when you apply force to push the plane forwards.
Therefore you can push the plane up the checkout belt because the wheels are moving faster
than the speed of the belt.

The original statement says the belt speed changes in accordance with the planes wheels
speed so this analogy is wrong.

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aaaaaaaaaaaaarrrrrrrrrrrrghhhhhhhhhhhh

Ok, now imagine the checkout speed was faster than the plane was moving!!! It still ****** works!
 
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Planes can fly backwards?

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Even if the belt was going faster, the plane won't move backwards. The wheels will just spin faster.
 
If there was NO friction on the wheel bearings and no engine thrust the plane would stand still no matter what the speed of the conveyor. If the thrust is bigger than the friction of the wheel bearing then the plane will ACCELERATE forwards. as the plane goes faster the wheel turns faster and the whhel bearing friction increases but the thrust is still bigger than the friction so the plane still accelerates.
EVENTUALLY the combined air resistance and bearing friction will equal the thrust of the engine but this is when the plane is going way over take off speed.
chas
 
Ok its friday so weekday passes from the mental institute are void ...everybody get back to your rooms /ubbthreads/images/graemlins/lol.gif

Guys does it really matter! Lifes too short /ubbthreads/images/graemlins/beerchug.gif
 
No i dont... This is annoying me now..can you tell? hahahahah

all the plane needs to go, is produce enough thrust to hold itself stationary... past this, the thrust oversomes the firctional losses rom the wheels, the wheels speed up and away you go. The conveyor belt and the wheels are more or less irrelevent!! As has been said OVER and OVER and then OVER again, the wheels are NOT driven, so do NOT affect the FACT that the plane is 'floating' on the wheels, and doesnt matter that they are being rolled by the conveyor. The plane will take off.

Are we done?
 
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No i dont... This is annoying me now..can you tell? hahahahah

all the plane needs to go, is produce enough thrust to hold itself stationary... past this, the thrust oversomes the firctional losses rom the wheels, the wheels speed up and away you go. The conveyor belt and the wheels are more or less irrelevent!! As has been said OVER and OVER and then OVER again, the wheels are NOT driven, so do NOT affect the FACT that the plane is 'floating' on the wheels, and doesnt matter that they are being rolled by the conveyor. The plane will take off.

Are we done?

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So rich what you're saying is the plane will stay stationary? /ubbthreads/images/graemlins/lol.gif

good to know we're all on the same page isn't it!
 
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No i dont... This is annoying me now..can you tell? hahahahah

all the plane needs to go, is produce enough thrust to hold itself stationary... past this, the thrust oversomes the firctional losses rom the wheels, the wheels speed up and away you go. The conveyor belt and the wheels are more or less irrelevent!! As has been said OVER and OVER and then OVER again, the wheels are NOT driven, so do NOT affect the FACT that the plane is 'floating' on the wheels, and doesnt matter that they are being rolled by the conveyor. The plane will take off.

Are we done?

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So rich what you're saying is the plane will stay stationary? /ubbthreads/images/graemlins/lol.gif

good to know we're all on the same page isn't it!

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/ubbthreads/images/graemlins/laugh_roll.gif
 
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Are we done?

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Doubt it Rich.... /ubbthreads/images/graemlins/laugh.gif
 
Asked Jeeves and got the folowing quote from a site....

"The airplane will sit on the conveyer belt with engines blasting, tires rolling, and to the outside observer, standing in place. While tremendous forward force is being generated, there is no increase on the airflow over the wings.

So, if there is is no increased airflow over the wing, there is no lift. Without lift, the airplane CANNOT take off and fly. "
 
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Asked Jeeves and got the folowing quote from a site....

"The airplane will sit on the conveyer belt with engines blasting, tires rolling, and to the outside observer, standing in place. While tremendous forward force is being generated, there is no increase on the airflow over the wings.

So, if there is is no increased airflow over the wing, there is no lift. Without lift, the airplane CANNOT take off and fly. "

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Ok, everyone is just intentionally winding me and Rich up now!

/ubbthreads/images/graemlins/fuck_you.gif
 
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