A plane is standing on a large treadmill or conveyor belt. The plane moves in one direction, while the conveyor moves in the opposite direction. This conveyor has a control system that tracks the plane speed and tunes the speed of the conveyor to be exactly the same (but in the opposite direction). Can the plane take off?


DISCLAIMER
It doesn't matter what colour the plane is and it does not have a gearbox

had this before on an Audi forum - what a row ensued

plane would take off, unless the wheel bearings burnt out/tyres blew due to double speed rotation. the plane would still travel at x mph whatever the runway/conveyor did.

thats one hell of a conveyor what colour is it? and what gearbox drives it, does the plane have a tow hook? caravan? At work
At home

"I can't always believe facts I read on the web" - Charles Dickens

winner by default of the tractor vs caravan race

Row....oh yes

The plane doesn't use the wheels for gaining speed during takeoff...
The plane's engines are "pushing air", not spinning wheels. Sorry my English, but you'll get my point.
So yes, the plane will gain speed vs. air as a reference system (the thing that's important here), the belt will do its job in moving in the opposite direction regarding plane's wheels rotational movement and finally the plane will take off.
The belt whatever it moves or not its just an support for the plane until it gains enough speed relativelly to air to form portance force and detach itself from the belt.

Last edited by alex_pescaru on 25th Jan 2012 9:38 pm. Edited 1 time in total

treadmill scenario, the air is stationary relative to the ground, so the plane has to move relative to the ground in order to gain flight. If it doesn't move, it simply won't fly. There will be no airflow over the wings, and there will be no lift. A lot of people get confused here, and think that the original thought experiment is some sort of trick question, and that the propeller of the airplane, or possibly the jet engines, will be blowing air backwards over the wings, which will create lift. While there will be a certain amount of airflow created by the propeller or engines, it is not enough to create flight. Former Mod/Member, with the most post & Chicken George Arch nemesis

What a wind up merchant you are Taz This one has got legs and will run for days

Moi

Take out the gravity from the equation and all will be clear...
Just like the rockets in outer space. Newton's third law.
In our case, by reduction to absurdity, imagine the plane's wheels just barelly touching the ground/belt or not touching at all.
The plane's engine will create enough motion based on the above law until the speed of the plane, relativelly to air, is enough to create portance / lift (vertical) motion.
Remember, the air is the reference system and not the ground/belt.

Well I carried out such an experiment on the planet Apple in the Andromeda Galaxy a couple of years back. The plane took off but in a parallel universe it didn't take off.

There we go, debate sorted.  LL.B (Hons) - University of Derby
LOT (Lord of Time) - University of Gallifrey

planes engine will push/pull through the air creating speed, the behaviour of the wheels/runway are irrelevant. At work
At home

"I can't always believe facts I read on the web" - Charles Dickens

winner by default of the tractor vs caravan race

no yorkshirsman will work that one out taz  rainy-city
xs

It's a Lancs thing Stewart

Only if its an Harrier Jump Jet will it take off, it needs air flowing under the wings to create lift, it will not happen if it is stationary. What if there were no hypothetical situations?

Last edited by Gunfa on 26th Jan 2012 11:30 am. Edited 1 time in total

No, no, no, it needs a pressure difference that is only got by movement of air over and under the wings, there will be no lift created, end of.

I told you Taz