A plane on a conveyor belt

MTA99 · 12 Feb 2008 at 12:35

andyp said:
Oh - the OP makes it look like the plane is standing still.

So the concept is flawed in it's intent to deceive from the very beginning.

If the plane accelerates to V2 of course it will take off.

If the plane doesn't accelerate enough to get to V2, it won't take off.

Simple as.

Don't try using terms like "V2" to regain some face

andyp · 12 Feb 2008 at 12:36

Blinkz said:
I do fly the 737-800 yes, altho I believe chrismox also flys the 800 as well!

Ah, very good.

Two questions for you.

1) What's a ballpark figure for the fuel consumption of the APU on the 738?

2) Assumed temperature t/o - have you any idea of the parameters of the calculations the FMC makes when you enter an assumed temperature? I've been trying to work out where the figures come from, and been failing quite miserably.

MookJong · 12 Feb 2008 at 12:37

Dr House · 12 Feb 2008 at 12:37

Felix Da Housecat said:
No because there is no air moving over the wings.

The engines only provide thrust, where as the wings provide lift, so if there is no air flow over the wing the plane wont fly.

/thread

What he said, I can’t see how anyone can think it can take off without the air movement just because the wheels are spinning lol

MTA99 · 12 Feb 2008 at 12:37

MookJong said:

HAHAHA! Genius

andyp · 12 Feb 2008 at 12:38

MTA99 said:
Don't try using terms like "V2" to regain some face

lol, I won't rise to that

MTA99 · 12 Feb 2008 at 12:38

Paras said:
What he said, I can’t see how anyone can think it can take off without the air movement just because the wheels are spinning lol

Have you read any of the page 4?

Dave M · 12 Feb 2008 at 12:39

Helium_Junkie said:
So even though the wheels will be spinning at twice the speed they should be (or some other such hypothetical nonsense), the plane will still move forward and take the wheels with it, because the conveyer is only moving at the same speed as the plane - not the spinning speed of the wheels...

So if the conveyer were to be moving at a speed to directly counter the spin of the wheels as the engines pushed the plane, then I think what I was picturing before would be true...

But this conveyer isnt doing that, this conveyer is moving at the speed of the plane.

I think I get it... I misunderstood the scenario.
Unless I'm still not quite right?

Either way, thanks Scuzi That helped.

Still not quite right. The plane isn't connected to the belt at all.

The wheels spin freely, so aside from negligible friction in the bearings the movement of the wheels won't move the plane.

Would you expect a hovercraft to be moved by the belt? It has less friction than the wheels but nothing that won't be overcome by the forward thrust of the engines.

hamesy · 12 Feb 2008 at 12:39

Paras said:
What he said, I can’t see how anyone can think it can take off without the air movement just because the wheels are spinning lol

But for the wheels to spin, the plane needs to move forwards

Helium_Junkie · 12 Feb 2008 at 12:44

Telescopi said:
Still not quite right. The plane isn't connected to the belt at all.

The wheels spin freely, so aside from negligible friction in the bearings the movement of the wheels won't move the plane.

Would you expect a hovercraft to be moved by the belt? It has less friction than the wheels but nothing that won't be overcome by the forward thrust of the engines.

Hmm, good example. My first reaction was "yes, because the surface it is moving over is simultaneously moving the other way", but then I think that in fact the craft would still move at the same speed in relation to its static surroundings, but the speed between it and the surface is doubled... which is actually irrelevant because as you say, its not connected...
Crikey! Really wouldnt have thought about it that way

"andy" · 12 Feb 2008 at 12:44

andyp said:
If it made the question clear in the first place it would be easy to answer.

It's a resonable assumption to make that they're saying the plane will stay still.

lmao

thats the whole point of the question

you have to "think" about it !

anyway the wheel bearings will probably wear out after a few conveyor belt take offs because theyl be spinning at twice the rated speed

Von Luck · 12 Feb 2008 at 12:46

My god there are some thickies around. Having the wheels spun by a conveyor would have a negligible impact on the forward motion of the aircraft, as there's no link between the wheels and the propulsion.

It would take off. Fact.

neodude · 12 Feb 2008 at 12:50

Yep, plane will take off. With wheels spinning twice as fast due to the conveyor going the same speed backwards.

Anewbe4u · 12 Feb 2008 at 12:51

How are people not getting this?

Peter Diffey · 12 Feb 2008 at 12:52

Well this thread proves that a lot of OCUK are dumb, go buy a physics GCSE book.

and:

I
B
T
L

http://youtube.com/watch?v=tPFu7shIN3g

WillyNelson · 12 Feb 2008 at 12:52

Thrust from the engines will cause the plane to move forwards.
It will continue accellerating up to it's usual take-off velocity.
The wheels will turn twice as fast as they would on a 'static' runway.*
The plane will take off when it reaches it's normal take off velocity.

The only thing which changes is the rate at which the wheels turn as it moves down the runway.

*if, under normal circumstances, at take-off velocity the wheels rotate at speed r (the wheels are 'driven' by the velocity v of the plane). Therefore v=r

In the case in question the wheels are also being driven by the 'conveyor belt' moving in the opposite direction, -r. So v-r=r or v=2r

AFK_Matrix · 12 Feb 2008 at 12:52

Lol love this thread makes the brain hurt

But instead of all this talk you know how this can all be cleared up!! You need someone with a model plane, a treadmill or factory conveyer belt and a camera

. Problem solved if there is video evidence and you can all stop arguing. I actually might know a few people with model planes, must ask if they can get access to a conveyer belt.

andyp · 12 Feb 2008 at 12:53

"andy" said:
lmao

thats the whole point of the question

you have to "think" about it !

It's a ridiculous concept in the first place, which doesn't make itself clear. What's the point of mulling it over?

Commercial aircraft + lift = flying. If it can generate enough to fly, it will take off. If it can't, it won't.

End of, surely? I see no value in adding silly factors into the equation.

I'm sure if there were 600,000 chimpanzees sellotaped to a 747, it would struggle to take off - see my point?

Peter Diffey · 12 Feb 2008 at 13:01

AFK_Matrix said:
But instead of all this talk you know how this can all be cleared up!! You need someone with a model plane, a treadmill or factory conveyer belt and a camera . Problem solved if there is video evidence and you can all stop arguing.

Plane Conveyor Belt Mythbusters Bigger Plane Scene

youtube.com

Peter Diffey · 12 Feb 2008 at 13:04

andyp said:
It's a ridiculous concept in the first place, which doesn't make itself clear. What's the point of mulling it over?

Commercial aircraft + lift = flying. If it can generate enough to fly, it will take off. If it can't, it won't.

End of, surely? I see no value in adding silly factors into the equation.

I'm sure if there were 600,000 chimpanzees sellotaped to a 747, it would struggle to take off - see my point?

Its a concept to test you on the basic laws of physics.........failboat?