Paul_J
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Registered: 6th Jun 02
Location: London
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quote:
Originally posted by Paul_J
People are getting confused between the fact it says the CONVEYOR and PLANE SPEED WILL BE MATCHED.
IT DOES NOT SAY THE FORCE OF PLANE AND CONVEYOR will be matched. Since the wheels are free wheeling the only force given by the conveyor is a % depending on the friction between things like wheel bearings.
The thing pushing the plane is a constant at max (not including time to warm up engines) - 16000 thrust will constantly be pushing out the back, despite the fact that the the conveyor is going backwards at 1 mph. The plane will move forward - albeit accelerate slightly slower than before.
Notice also the plane takes longer to take off on conveyor than normal - the conveyor forces are just a estimate. The conveyor force would only be equal if wheels were locked on the plane. Even then the friction between the tires and tarmac on conveyor would break and the plane would skid forward.
NOTICE SPEEDS ARE THE SAME (which is what the question says)
BUT THE FORCES ARE NOT EQUAL - HENCE PLANE ACCELERATES!
GET THIS IN YOUR HEAD ALREADY.
[Edited on 24-05-2006 by Paul_J]
You say they are in equillibrium live lee - that'd require 26400 from the conveyor belt to combat the thrust 26400 coming from the engines.
when the plane is stationary it has this thrust, but the conveyor belt is giving 0 force against it? SO THE PLANE WILL MOVE FORWARD.
when the plane is doing 1 mph, the conveyor belt will be going backwards at 1 mph.
The plane will still be pushing 26400 force backwards. TO keep the plane still the conveyor would have to have 26400 force opposing it.
however at 1 mph, there's no way even with the wheels locked it would apply that much force. If the wheels were locked or it was in skies, it'd just scrape up the conveyor as the force from engines at full thrust beats the friction co-efficent of tyres.
Thankfully the TYRES are not locked. they are freewheeling, so the resistance is merely, how much the thing weighs on the bearings etc. so say 5% resistance as it freewheels.
IF the conveyor can actually get to a speed that'd be applying 26400 force backwards (which it'd have to be travelling v.fast) - they'd still only be like 2000 force against the plane.
>>> THRUST versus <<< resistance from conveyor
if thrust is higher than resistance - plane will move forward no? but only slightly slower.
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SVM 286
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Registered: 13th Feb 05
Location: pain
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quote:
Originally posted by bradfincham
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?
No it wouldn't. 
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John
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Registered: 30th Jun 03
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You've stated the incorrect answer twice in 2 pages now SVM.
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RichR
Premium Member
Registered: 17th Oct 01
Location: Waterhouses, Staffordshire
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"Conveyor force is an estimate"
based on what?
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DarrenGSi
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Registered: 11th Jul 05
Location: East Ayrshire Drives: Civic Jordan 381
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i still think it would not take off, if it is effectivly stationary, then if they tried to pull the nose up to take off, there would be no wind force to lift the wings.
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Steve
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Registered: 30th Mar 02
Location: Worcestershire Drives: Defender
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 haha here we go again, i look and pity the people saying it wont
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John
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Registered: 30th Jun 03
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quote:
Originally posted by DarrenGSi
i still think it would not take off, if it is effectivly stationary, then if they tried to pull the nose up to take off, there would be no wind force to lift the wings.
Thats not the way to think about it.
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Greg_M
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Registered: 2nd Sep 03
Location: Grantham, Lincolnshire
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no it wouldnt tak eoff as there wouldnt be air passing over the wings
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Hammer
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Registered: 11th Feb 04
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quote:
Originally posted by Greg_M
no it wouldnt tak eoff as there wouldnt be air passing over the wings
i swear to god im now starting to lose the will to live 
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SVM 286
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Registered: 13th Feb 05
Location: pain
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quote:
Originally posted by John
You've stated the correct answer a number of times now SVM, but everyone's too drunk or silly to understand it.
I know John. 
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John
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Registered: 30th Jun 03
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People who don't have a clue in general should refrain from commenting.
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RichR
Premium Member
Registered: 17th Oct 01
Location: Waterhouses, Staffordshire
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right then once and for all - someone post in Leyman's terms and not something simply copied off someone else - or a useless graphic that could easily be made up to show either option with meaningless figures
why will the plane take off?
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50Calibre
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Registered: 13th Dec 04
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i know this has already been stated by steve... however,
if you were on a bike on a treadmill and youre pedalling at 10mph with the treadmill set to 10mph.. then once your wheels are moving if you pull on the bars at the front of the treadmill its pretty much the same as pulling a rope while on a stationary surface
therefore the plane would move forward and take off...
also if the plane was still on the runway travelling at 50knots and the treadmill was travelling faster than that then the wheels would just spin faster apart from the friction caused by this the speed of the plane wouldnt be effected...
the same as holding the toy car on the treadmill and then increasing the speed of the treadmill, your still effectivly just supporting the weight of the car the force required to do this wouldnt increase too much
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John
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Registered: 30th Jun 03
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The rollerskates/treadmill example was quite a good one I think.
I'd be very interested in a proof either way though.
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J da Silva
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Registered: 10th Apr 03
Location: The FACTory
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I've read 15 pages and I'm still unsure, however, I decided to ask the people in the know and hopefully shed some light on it all........
"The plane will not take off. If maximum thrust is applied(it doesnt even have to be max thrust, whatever thrust you want) it will only counteract the backward motion of the conveyor. No airflow over the wings will occur, no lift. I hope I did not just dork this up and miss the whole joke or something."
"Ok, Ill bite. (Unless this is some sort of trick question) As I recall, two things make an airplane fly. 1. Lots of money, and 2. Bernoulli's Principle. Since all the money has been spent already on the above conveyor contraption, that rules out option one. And since there is no air flow over the airfoil (wind or realitive wind), there is not lift. Don't quote me on this but I think I heard once that you need lift to get an airplane to take off. Hmmmm. Here is another riddle: If a pilot is out in the forest and a tree falls on him (her), will the pilot make a noise?"
"Ah yes... this one has been around a few boards lately... I was like you guys, until I too was turned. At first glance it seems easy- but once you figure it out and are convinced of the physics, you slap your head.
Here's a "pro's" article on the subject:
The Pilot's Lounge #94: It's The Medium, Manfred
There's a new aviation myth running around the Internet. It involves a conveyer-belt runway and misuse of aerodynamics and ... well, it's better if AVweb's Rick Durden explains it all himself in The Pilot's Lounge.
By Rick Durden
Columnist
The Pilot's Lounge "
So if you would like to rubbish these comments, then fair enough, but I'm too curious on this one.
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Paul_J
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Registered: 6th Jun 02
Location: London
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There would be air passing over the wings - as the plane would accelerate, just not as quick as usual.
Simple maths, One force is larger than another working against it.
Live Lee - estimate is based on the fact that the resistance within the wheel bearings will not be 100% (otherwise the wheels would be locked, like the brakes are on) and not rolling at all. Even if the brakes were locked - if the plane was on fucking skies for fuck sake with 26400 Lbs of Thrust shooting out the back of the air craft it'd quite easily drive up a conveyor.
I don't understand Why people are finding it so hard to grasp.
that the question does not say the plane has a equal force acting against it, it jsut say's the conveyor is going the same speed in the opposite direction as place.
SPEED - NOT FORCE.
so at 0 mph, the conveyor belt has no force on the plane, but the plane is shooting 26400 lbs ft of thrust out of the back - so how is the plane going to stay stationary?
then at 1 mph - the conveyor is only doing 1 mph. Still I somehow think 26400 lb ft of thrust would over come this.
I think people have an image in their head of a tiny conveyor belt about the length of the plane, and the plane sitting there stationary. IDIOTS.
that's not the idea at all. the conveyor could be miles and miles long. Providing the plane is accelerating which it would considering it has huge forces pushing out of the back it would lift off when it hits the speed required MOVING FORWARD. NOT SITTING STATIONARY.
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Greg_M
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Registered: 2nd Sep 03
Location: Grantham, Lincolnshire
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quote:
Originally posted by Sxi04
quote:
Originally posted by Greg_M
no it wouldnt tak eoff as there wouldnt be air passing over the wings
i swear to god im now starting to lose the will to live
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
That kinda implys everyones answer to the question so i did.
Does it say i have to read all 15pages first NO.
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John
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Registered: 30th Jun 03
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Because somebody is a pilot I wouldn't take their word on it.
And there have been RAF pilots somewhere who say it would.
There has to be an actual proof which would most likely have to be mathematical to prove it either way.
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Paul_J
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Registered: 6th Jun 02
Location: London
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quote:
Originally posted by 50Calibre
i know this has already been stated by steve... however,
if you were on a bike on a treadmill and youre pedalling at 10mph with the treadmill set to 10mph.. then once your wheels are moving if you pull on the bars at the front of the treadmill its pretty much the same as pulling a rope while on a stationary surface
therefore the plane would move forward and take off...
also if the plane was still on the runway travelling at 50knots and the treadmill was travelling faster than that then the wheels would just spin faster apart from the friction caused by this the speed of the plane wouldnt be effected...
the same as holding the toy car on the treadmill and then increasing the speed of the treadmill, your still effectivly just supporting the weight of the car the force required to do this wouldnt increase too much
Exactly! and with 26400 lb ft of thrust out of the back of it, it'll quite easily push the plane forward.
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Paul_J
Member
Registered: 6th Jun 02
Location: London
User status: Offline
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quote:
Originally posted by Jizinho Silva 10
I've read 15 pages and I'm still unsure, however, I decided to ask the people in the know and hopefully shed some light on it all........
"The plane will not take off. If maximum thrust is applied(it doesnt even have to be max thrust, whatever thrust you want) it will only counteract the backward motion of the conveyor. No airflow over the wings will occur, no lift. I hope I did not just dork this up and miss the whole joke or something."
"Ok, Ill bite. (Unless this is some sort of trick question) As I recall, two things make an airplane fly. 1. Lots of money, and 2. Bernoulli's Principle. Since all the money has been spent already on the above conveyor contraption, that rules out option one. And since there is no air flow over the airfoil (wind or realitive wind), there is not lift. Don't quote me on this but I think I heard once that you need lift to get an airplane to take off. Hmmmm. Here is another riddle: If a pilot is out in the forest and a tree falls on him (her), will the pilot make a noise?"
"Ah yes... this one has been around a few boards lately... I was like you guys, until I too was turned. At first glance it seems easy- but once you figure it out and are convinced of the physics, you slap your head.
Here's a "pro's" article on the subject:
The Pilot's Lounge #94: It's The Medium, Manfred
There's a new aviation myth running around the Internet. It involves a conveyer-belt runway and misuse of aerodynamics and ... well, it's better if AVweb's Rick Durden explains it all himself in The Pilot's Lounge.
By Rick Durden
Columnist
The Pilot's Lounge "
So if you would like to rubbish these comments, then fair enough, but I'm too curious on this one.
This is all trash, as the picture these people have in their head of a little plane sitting on a treadmill thats about the size of the plane. The conveyor could be miles and miles and miles long in this example. IT WOULD HAVE TO BE TO WORK.
End of the day everyone on this post knows - unless the plane moves, there will be no air flow. and the plane won't take off. That's simple.
The question being debated here is whether or not the plane is moving or stationary.
People think the force is being matched but it isn't. It says speed of the plane. So if plane is doing 10 mph, conveyor is doing 10 mph, if plane is doing 100 mph FORWARD, not on the spot, then conveyor is doing 100 mph backwards.
Basically half the people on this forum have mis-read this question (as those quotes you posted) and have an image in their head of a tiny conveyor, same size as the plane, with the plane just sitting effectively in one spot with the conveyor whizzing round. hence no movement, no air flow and no lift.
This is not the right thing to picture in your head and not the scenerio described. the plane will move forward and the conveyor can be miles and miles long.
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Robin
Premium Member
Registered: 7th Jan 04
Location: Northants Drives: Clio 182 Cup
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what about if it was in a wind tunnel on a conveyor belt?
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John
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Registered: 30th Jun 03
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Even if the plane was on a tiny runway it would still be exactly the same, it would just end up coming off the runway onto whatever was after it very quickly.
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bradfincham
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Registered: 20th Sep 02
Location: East Of England Drives: Clio 172
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We shall fight them on the beaches
we shall fight them in the air (if the plane takes off:lol
and we shall fight them on corsasport
O what the fuck have I done here
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Paul_J
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Registered: 6th Jun 02
Location: London
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quote:
Originally posted by John
Even if the plane was on a tiny runway it would still be exactly the same, it would just end up coming off the runway onto whatever was after it very quickly.
Exactly
at least there's a few intelligent people who are open minded enough to see the truth on this board.
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SVM 286
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Registered: 13th Feb 05
Location: pain
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quote:
Originally posted by Paul_J
There would be air passing over the wings - as the plane would accelerate, just not as quick as usual.
It wouldn't Paul, the conveyor belt is travelling at the same speed as the plane but in the other direction.
The plane is effectively stationary, so any air around the plane would be effectively still, dependant on climatic conditions of course.
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