A question someone has asked on CS

clio200cup

clio200cup

hi all.

see here - http://www.cliosport.net/forum/showthread.php?142784-Question-If-an-aeroplane-is-taking-off...


the question is, 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?

some of the answers are worth a chuckle, lol.

here's the explanation - http://www.straightdope.com/columns...the-opposite-direction-can-the-plane-take-off

just make sure you think about it and come up with your answer before reading the explanation, lol.
 
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ill be first then, ill say the plane wont take off, surely it needs wind to create lift to go anywhere. If its going the same speed as the conveyor belt it wont be moving forward at all. :closedeyes:
 
as above, the wings require air speed to hit the wing to creat the push up.
 
haha but there IS airspeed isn't there.

the forward motion on a jet engined plane, comes from thrust from the engines. this creates the increase in speed of the aircraft which causes the air to flow over the wings faster. lower pressure above the wing and higher pressure below the wing means the aircraft will lift. there is still air rushing over the wings, it's just not being caused by thrust.
think of it as removing the 1 mile long conveyor belt, would it go then...?
if you click on the second link, perhaps that can do a better job of explaining my point than i seem to be able to, lol.

btw - what's half of 99...?

*edit* - i see how i have worded it poorly in the first post. think of it as a never ending conveyor belt (same distance as a runway lets say). rather than a conveyor belt which is the same length as the aicraft itself.
 
The conveyor has nothing to do with it, the plane is propelled by it's propeller/engine to create it's forward motion. If it was driven by it's wheels then it would be a different story
 
I feel i might be being a bit thick, but surely a plane can only take off if the air is travelling over its wings is fast enough. So i suppose the plane will take but only if it gets enough air speed which due to the conveyor belt going in the opposite direction will just take more thrust????????
The wording is bit iffy, if the conveyor belt and plane were both travelling at x mph then would the plane not then be stationary????? i.e tread mill????
 
clio200cup said:
haha but there IS airspeed isn't there.

the forward motion on a jet engined plane, comes from thrust from the engines. this creates the increase in speed of the aircraft which causes the air to flow over the wings faster. lower pressure above the wing and higher pressure below the wing means the aircraft will lift. there is still air rushing over the wings, it's just not being caused by thrust.
think of it as removing the 1 mile long conveyor belt, would it go then...?
if you click on the second link, perhaps that can do a better job of explaining my point than i seem to be able to, lol.

btw - what's half of 99...?

*edit* - i see how i have worded it poorly in the first post. think of it as a never ending conveyor belt (same distance as a runway lets say). rather than a conveyor belt which is the same length as the aicraft itself.
Click to expand...


surely its irrelevant the size of the conveyor belt? If its going the same speed as the plane is you could use a rolling road? Are you saying the plane could take off on a rolling road? :bored:
 
Graeme GTR said:
surely its irrelevant the size of the conveyor belt? If its going the same speed as the plane is you could use a rolling road? Are you saying the plane could take off on a rolling road? :bored:
Click to expand...

how could the aeroplane take off on a rolling road...? it isn't wheel powered....

read the explanation link :smile:
 
you've misunderstood me. i replied with that, as you asked me that i must think it could take off on a rolling road.

read the solution :smile:
 
Pretty sure it would still take off unless the conveyor went at such a speed that the friction on the wheels caused the plane to stay in the same place, otherwise it would still move forward and generate lift in the same way as anything else.

The was a slightly ropey mythbusters episode on this (apologies if thats what one of the links is anyway i havent clicked!)
 
depends which way the conveyor belt is going!?

and where we're measuring speed from?

my brain hurts and my notepad has doodles..

Just read the link..
ahhhhhhh
 
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No it wouldn't take off I would have thought. Presuming:
The conveyor belt is going the opposite direction to the plane
The friction on the wheels holds the plane (It should if the force of the engines <= friction of the tyres on the conveyor, which as you said are turning at the same speed.)
There is no ridiculous wind or the conveyor unit isn't being moved or anything else ridiculous.

The reason the plan takes off (to my knowledge) is due to the imbalance of air travelling over/under the wings creating lift. If the plane is not actually moving and its wheels just spinning on the conveyor there'll be no air running past the wings.

In short: It'll stay still until the engines overheat and blow up due to lack of cooling.

.... I think :smiley:

Edit: **** I just read the link in the OP! :smiley:
 
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I've not read the links yet, but I think...

1. The plane will roll straight off the conveyor and continue on down the runway and take off.

BECAUSE... The wheels aren't driven, the engines thrust will push the plane off the conveyor and it'll conitinue on it's way.

2. If the plane IS teatherd to the floor/conveyor then it WON'T take off.

BECAUSE... The wings wouldn't be able to generate the lift required because there'd be no air passing over them as the plane wouldn't be physically travelling forwards and ALSO the jet engines woudn't be working properley as they need a constant flow of air feeding through them in order to compress it properley and in turn create thrust.

Now I'll go read the links and see how wrong I am hahaha!!! :smiley:
 
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