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re: Will an airplane on a treadmill be able to takeoff?
 by Saraesa / Liesje on 2008/09/08 15:02
A plane is standing on a runway that can move (like a giant conveyor
belt). This conveyor has a control system that tracks the plane's
speed and tunes the speed of the conveyor to be exactly the same (but
in the opposite direction).
Will the plane be able to take off?
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Derdriu.EoL-Veteran Likes forums
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re: Will an airplane on a treadmill be able to takeoff?
by Derdriu. on 2008/09/08 15:05
no, no it wont.
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re: Will an airplane on a treadmill be able to takeoff?
by Saraesa / Liesje on 2008/09/08 15:10
| Thrizie wrote: | | no, no it wont. |
Why not?
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wowTallisEoL-Veteran Likes forums
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re: Will an airplane on a treadmill be able to takeoff?
by wowTallis on 2008/09/08 15:14
because the plane needs the airflow to take off
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MerkeEoL-Veteran Ever so eager to reply
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re: Will an airplane on a treadmill be able to takeoff?
by Merke on 2008/09/08 15:14
NOT ENOUGH SPEED!
Well, thrust, and yeah.
Last edited by Merke on 2008/09/08 15:21; edited 1 time in total
_________________ 
“I believe the single most significant decision I can make on a day-to-day basis is my choice of attitude. It is more important than my past, my education, my bankroll, my successes or failures, fame or pain, what other people think of me or say about me, my circumstances, or my position. Attitude keeps me going or cripples my progress. It alone fuels my fire or assaults my hope. When my attitudes are right, there is no barrier too high, no valley too deep, no dream too extreme, no challenge too great for me.” - Charles R. Swindoll
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re: Will an airplane on a treadmill be able to takeoff?
by Saraesa / Liesje on 2008/09/08 15:40
But the planes movement doesn't come from it's weels. It's from the thrust from the engines. So the conveyor belt might make it a tad harder for the airplane to get the needed acceleration but it will go forward, cause of the thrust, right?
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LightmaneEoL-Veteran Chatterbox
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re: Will an airplane on a treadmill be able to takeoff?
by Lightmane on 2008/09/08 15:42
her her u said 'thrust'
(oh dear)
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AirshaEoL-Veteran Forum Pet
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re: Will an airplane on a treadmill be able to takeoff?
by Airsha on 2008/09/08 15:53
| Quote: | A plane is standing on a runway that can move (like a giant conveyor
belt). This conveyor has a control system that tracks the plane's
speed and tunes the speed of the conveyor to be exactly the same (but
in the opposite direction).
|
Is the conveyor speed ALWAYS the same?
If yes it means the conveyor belt must move faster and faster because plane thrust produces force to accelerate the plane. So if the speed is the same conveyor's engines must produce the same AMOUNT of force to accelerate belt. It means PLANE Net Force will be 0 and the plane won't accelerate at all - will stay in the same play. So no lift force will be produces (no opposition force to the wings - no force to lift the plane).
So generally speaking the plane won't take off. More of it if control system works perfectly (adjust conveyor's belt at the same time as plane accelerates) plane will stay in one place and won't move at all. It's velocity will be 0 km/h.
Other thing is friction on the wheels would be too great and basically would tear them off. What would happen later I don't know. But for sure plane wouldn't be in air ;).
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AeolthelwenEoL-Veteran Chatterbox
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re: Will an airplane on a treadmill be able to takeoff?
by Aeolthelwen on 2008/09/09 2:31
I can only describe how i'm reading this thread as the following: 
_________________ Don't Doubt! Pounce - Mangle - Shred them all!
You still feel like doubting? Pooh on all!
Call me Kittie Humpalot!
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DidaDida/NaoyaEoL-Veteran Chatterbox
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re: Will an airplane on a treadmill be able to takeoff?
by Dida/Naoya on 2008/09/09 3:46
| Aeolthelwen wrote: | | I can only describe how i'm reading this thread as the following: |
It's quite easy actually. If you look at a plains wings you can see that it's curved on the top. Thats means that the air have to travel faster over the wing than under it when the plain moves forward.
That against leads to less dense air and so less pressure over the wing than under it. Since the air always try to move from a place with high pressure to a place with less pressure it will push the plane upwards. When the plain goes fast enough the upwards pressure will be enough to lift the plane enough for flying.
If the plain is standing on a threadmill that moves so fast that the plain is infact standing still, the pressure under and over the wings will be the same wich means you got no force pushing the plain upwards and so the plain can't fly.
Rockets useses another principle, so they can do vertical liftoffs.
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re: Will an airplane on a treadmill be able to takeoff?
by Teeboppity on 2008/09/09 4:08
Right, an airplane needs airflow over the wings to get airborne.
This airflow is generated by the airplane moving forward. Depending on the type of airplane, this airflow has to be about 150 mph. This is what is called in pilot term "Vr" (aka Velocity Rotate) Don't ask me where the term came from...
For the purpose of this discussion we will set Vr as "+1>" with the ">" symbol denoting direction.
We will set the corresponding airflow as "<+1" (or greater. But +1 would do)
So, a plane on a threadmill would reach "+1>" but with the threadmill keeping it in one spot the airflow over the wings would not reach "<+1".
Hence, the airplane will not take off.
That the airplane reaches it's Vr through engine thrust and not by driving wheels is not the point of this discussion. The point is that the threadmill keeps the plane stationary, thus negating any airflow over the wings.
Which allows us to spot the error in this premise; can you actually stop something from moving by using a conveyor-belt, if the force for driving it forward is not grip+motion (a.i. powered wheels) but thrust?
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re: Will an airplane on a treadmill be able to takeoff?
by Saraesa / Liesje on 2008/09/09 4:35
| Teeboppity wrote: | | Which allows us to spot the error in this premise; can you actually stop something from moving by using a conveyor-belt, if the force for driving it forward is not grip+motion (a.i. powered wheels) but thrust? |
Indeed, that is the question!!
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re: Will an airplane on a treadmill be able to takeoff?
by Teeboppity on 2008/09/09 4:38
Hence, the whole premise to the conundrum is wrong! Only thing this puzzle teaches us is to every once in a while question the question, not look blindly for the answer.
/flex
Gawd I'm good...
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BorgrimmEoL-Veteran Forum Pet
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re: Will an airplane on a treadmill be able to takeoff?
by Borgrimm on 2008/09/09 4:42
Bad troll cant be bothered to pretend to be intelligent.....
http://www.kottke.org/06/02/plane-conveyor-belt
_________________ In WotLK sap will work on pretty much everything with a brain. It"s a huge nerf to Horde Rogues, since they won"t be able to use it against Alliance in PvP any more.
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AirshaEoL-Veteran Forum Pet
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re: Will an airplane on a treadmill be able to takeoff?
by Airsha on 2008/09/09 4:47
Hahaha I don't believe it :D
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