tom17

Imagine a plane is sitting on a massive hypothetical conveyor belt, as wide and as long as a runway. The conveyor belt is designed to match the speed of the plane exactly but moves in the opposite direction. The engines are running at take-off thrust, the brakes are off, etc. Everything is normal save for the fact the plane is on a treadmill.

Can the plane take off?

Discuss

Tom...

Atlantic Xpat

Not much to discuss. No, where would the lift come from as the plane would not be moving through the air?

Tuppence

Will it take off vertically, and as soon as the wheels leave the conveyor, it will move forward??

My head still hurts from reading the "secret" thread, and this isn't helping

tom17

Excellent, it's working

End of the working day now, gotta go, but i'll check on your progress later

Tuppence

Bugger, that sounds right.

Tuppence

I hate you.

Steve_P

Yes because the movement of the aircraft is generated by the thrust from the engines.

The treadmill makes no difference whatsoever other than to make the landing gear wheels spin even faster than they normally would as the aircraft does its take-off roll.

Oakvillian

I think you're right, Steve. If the treadmill is moving as fast as the aircraft but in the opposite direction, the wheels will simply rotate twice as fast as normal and the aircraft will take off.

If the treadmill is programmed to move the same speed as the wheels then AX's scenario arises and the aircraft doesn't move forward no matter how much thrust the engines generate, so the wings generate no lift and it can't take off.

Almost Canadian

What a clever man

hot wasabi peas

So, essentially the plane is still. No, it can't take-off.

hot wasabi peas

Is there a ZOOM discount code for this flight?

Steve_P

But the thrust from the engines acts on the surrounding air and would push the aircraft forward no matter what the treadmill does, for the aircraft to remain still wouldn't the wheels have to be driving wheels like a car?

The question is how do you get the aircraft on the treadmill in the first place and to get it to stay at the end of the runway (treadmill) before applying the thrust?

Atlantic Xpat

The thrust from the engines may be acting on the surrounding air but unless the airplane is not actually in contact with the treadmill e.g. actually flying, then, using the Oakvillian assumption about the treadmill it would still not go anywhere. The thrust aft is counterbalanced by the speed of the treadmill so, <he pontificates, dredging up half remembered A level physics?>... surely the two thrusts or energies cancel each other out.

If your scenario is valid then why hasn't someone developed this system for short take off for small planes then?

I'm sure IainK will be along in a moment to set us all right. Him being an engineering type.

MikeUK

what's the wind speed and direction !!!!

as takeoff is entirely dependant on 'air speed' not 'ground speed' !!!!

Jingsamichty

No it won't take off.

If the thrust from the engines force the plane forward at 200mph, the treadmill will run backwards at 200mph. The wheels of the plane are doing 400mph, but the plane isn't moving. No movement = no lift.

I think!