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? :rly:

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?

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

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

nah.. just you hahahaha

Hmmm ... did you consider all aspects?

Engines?

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

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

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

i like that theory alot

http://media.mlxxfc.net/Fly-NotFly.gif
Yep.

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

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

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

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

I just nearly choked on my sandwich! :shock:

couldda been worse.. couldda been your sausage

:whistle:

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

Dave

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

seeing as we're off topic anyway ;) you could read my blog :D

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

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?

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?

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