The case of the plane and conveyor belt

R. · 23 Oct 2007, 21:17

This isn't actually new, in fact it's quit old. But is has baffled everyone from web bloggers to pilots and Mythbusters will try to find out on Dec. 19.

Here's the problem: "A plane is standing on a runway that can move (some sort of band conveyer). The plane moves in one direction, while the conveyer moves in the opposite direction. This conveyer has a control system that tracks the plane speed and tunes the speed of the conveyer to be exactly the same (but in the opposite direction).

Take your time and think about this for a few moments.

Now, does the plane take off?

samurai7 · 23 Oct 2007, 21:20

I wouldn't have thought so, as the air isn't as 'mobile' as it would be if the plane were hurtling through it, no?

*AndyK* · 23 Oct 2007, 21:27

Instinct tells me no, as I'd assume that there'd be no airflow around the wings and hence no lift could be created.

LucyK! · 23 Oct 2007, 21:30

Is anyone else doing planes and bands with their hands?!

duke knooby · 23 Oct 2007, 21:32

nah.. just you hahahaha

R. · 23 Oct 2007, 21:37

Hmmm ... did you consider all aspects?

R. · 23 Oct 2007, 21:39

Engines?

R. · 23 Oct 2007, 21:45

No, the conveyor is fine and there are no helicopter engines.
Why do you think the plane does not move forward?

daveake · 23 Oct 2007, 21:52

Yes.

The wheels are just holding the plane up. It'll take slightly longer to get up to take-off speed, because of increased friction and rolling resistance losses in the wheels/tyres (which are rotating twice as fast as normal), but that's it.

Dave

duke knooby · 23 Oct 2007, 21:54

Quote:

Originally Posted by R.

No, the conveyor is fine and there are no helicopter engines.
Why do you think the plane does not move forward?

female pilot.... she forgot to remove the handbrake

duke knooby · 23 Oct 2007, 21:56

Quote:

Originally Posted by daveake

Yes.

The wheels are just holding the plane up. It'll take slightly longer to get up to take-off speed, because of increased friction and rolling resistance losses in the wheels/tyres (which are rotating twice as fast as normal), but that's it.

Dave

i like that theory alot

R. · 23 Oct 2007, 22:01

Quote:

Originally Posted by knooby

female pilot.... she forgot to remove the handbrake

Quote:

Originally Posted by daveake

Yes.

The wheels are just holding the plane up. It'll take slightly longer to get up to take-off speed, because of increased friction and rolling resistance losses in the wheels/tyres (which are rotating twice as fast as normal), but that's it.

Dave

Yep.

duke knooby · 23 Oct 2007, 22:03

your both very smart.. well done you two.. that had never occurred to me

samurai7 · 24 Oct 2007, 00:59

Quote:

Originally Posted by AndyK

Instinct tells me no, as I'd assume that there'd be no airflow around the wings and hence no lift could be created.

that's what I said, albeit not quite so straightforward

anyway, it would appear we're both wrong; Daveake is a bit of a brainiac by all accounts

*AndyK* · 24 Oct 2007, 01:01

Well you can't have looks and too much brains can you?

samurai7 · 24 Oct 2007, 01:03

Quote:

Originally Posted by AndyK

Well you can't have looks and too much brains can you?

I just nearly choked on my sandwich!

duke knooby · 24 Oct 2007, 01:03

couldda been worse.. couldda been your sausage

*AndyK* · 24 Oct 2007, 01:04

daveake · 24 Oct 2007, 01:06

Quote:

Originally Posted by samurai7

Daveake is a bit of a brainiac by all accounts

Yeah, I couldn't even spell 'engineer' when I went to university, but now I is one.

Dave

samurai7 · 24 Oct 2007, 01:07

this went a bit off topic, didn't it lads?

seeing as we're off topic anyway

you could read my blog

daveake · 24 Oct 2007, 01:07

Quote:

Originally Posted by AndyK

Well you can't have looks and too much brains can you?

I think I know which side of that equation I sit ...

Dave

**Monstro** · 27 Oct 2007, 02:30

Quote:

Originally Posted by daveake

Yes.

The wheels are just holding the plane up. It'll take slightly longer to get up to take-off speed, because of increased friction and rolling resistance losses in the wheels/tyres (which are rotating twice as fast as normal), but that's it.

Dave

Ok, I don't get that, I'll admit to not being the brightest bulb in the box but that goes straight over my head.

Now if it was propeller driven I'd understand it (wind flow over the wings creating positive uplift and all that) but not if it was jet engined........or have I got my muppet head on?

daveake · 27 Oct 2007, 09:37

Nothing to do with jet vs prop propulsion.

Think of this scenario ... plane is sat on this conveyor belt, engines off, brakes off (that's the important bit), and someone turns on the belt which is now running backward at 200mph. What happens to the plane?

Dave

**Monstro** · 27 Oct 2007, 11:45

Quote:

Originally Posted by daveake

Nothing to do with jet vs prop propulsion.

Think of this scenario ... plane is sat on this conveyor belt, engines off, brakes off (that's the important bit), and someone turns on the belt which is now running backward at 200mph. What happens to the plane?

Dave

Inertia of the plane would make it go backwards?

daveake · 27 Oct 2007, 13:29

Quote:

Originally Posted by Monstro

Inertia of the plane would make it go backwards?

Sorry, but I sense this could go on a while ...

No. Plane has no inertia 'cos it's not moving. When the conveyor starts up, the plane stays not moving*. So it's just the same as being on the runway. So if the engines are now turned on the plane can take off as normal.

* Actually it will start moving backwards a little. But not a lot. The wheels/tyres/bearings aren't perfect and will allow some of the conveyor movement to push on the plane a little.

I'm kinda out of explanation, so if you don't "get it" I think you'll stay not getting it.

Dave

23 Oct 2007, 21:17	#1
R. You dig. Join Date: 02.04.2002 Location: On the fothermucker Posts: 7,179	The case of the plane and conveyor belt This isn't actually new, in fact it's quit old. But is has baffled everyone from web bloggers to pilots and Mythbusters will try to find out on Dec. 19. Here's the problem: "A plane is standing on a runway that can move (some sort of band conveyer). The plane moves in one direction, while the conveyer moves in the opposite direction. This conveyer has a control system that tracks the plane speed and tunes the speed of the conveyer to be exactly the same (but in the opposite direction). Take your time and think about this for a few moments. Now, does the plane take off?

23 Oct 2007, 21:20	#2
samurai7 Rock Star Join Date: 09.05.2005 Location: The future... Posts: 2,928	I wouldn't have thought so, as the air isn't as 'mobile' as it would be if the plane were hurtling through it, no?

23 Oct 2007, 21:27	#3
AndyK Relentless Join Date: 21.11.2003 Location: Over the top..... seeing what's on the other side Posts: 18,694	Instinct tells me no, as I'd assume that there'd be no airflow around the wings and hence no lift could be created.

23 Oct 2007, 21:30	#4
LucyK! The Monster Is Luce Join Date: 14.04.2002 Location: Posts: 7,547	Is anyone else doing planes and bands with their hands?!

23 Oct 2007, 21:32	#5
duke knooby Mega Loafer Join Date: 24.06.2005 Location: belfast Posts: 17,884	nah.. just you hahahaha

23 Oct 2007, 21:37	#6
R. You dig. Join Date: 02.04.2002 Location: On the fothermucker Posts: 7,179	Hmmm ... did you consider all aspects?

23 Oct 2007, 21:39	#7
R. You dig. Join Date: 02.04.2002 Location: On the fothermucker Posts: 7,179	Engines?

23 Oct 2007, 21:45	#8
R. You dig. Join Date: 02.04.2002 Location: On the fothermucker Posts: 7,179	No, the conveyor is fine and there are no helicopter engines. Why do you think the plane does not move forward?

23 Oct 2007, 21:52	#9
daveake 200% is the new 110% Join Date: 13.03.2005 Location: Newbury Posts: 2,983	Yes. The wheels are just holding the plane up. It'll take slightly longer to get up to take-off speed, because of increased friction and rolling resistance losses in the wheels/tyres (which are rotating twice as fast as normal), but that's it. Dave

23 Oct 2007, 22:03	#13
duke knooby Mega Loafer Join Date: 24.06.2005 Location: belfast Posts: 17,884	your both very smart.. well done you two.. that had never occurred to me

24 Oct 2007, 01:01	#15
AndyK Relentless Join Date: 21.11.2003 Location: Over the top..... seeing what's on the other side Posts: 18,694	Well you can't have looks and too much brains can you?

24 Oct 2007, 01:03	#17
duke knooby Mega Loafer Join Date: 24.06.2005 Location: belfast Posts: 17,884	couldda been worse.. couldda been your sausage

24 Oct 2007, 01:04	#18
AndyK Relentless Join Date: 21.11.2003 Location: Over the top..... seeing what's on the other side Posts: 18,694

24 Oct 2007, 01:07	#20
samurai7 Rock Star Join Date: 09.05.2005 Location: The future... Posts: 2,928	this went a bit off topic, didn't it lads? seeing as we're off topic anyway you could read my blog

27 Oct 2007, 09:37	#23
daveake 200% is the new 110% Join Date: 13.03.2005 Location: Newbury Posts: 2,983	Nothing to do with jet vs prop propulsion. Think of this scenario ... plane is sat on this conveyor belt, engines off, brakes off (that's the important bit), and someone turns on the belt which is now running backward at 200mph. What happens to the plane? Dave