A plane on a runway, how smart is r3vlimited?

[Axxe]

OK, I got this off a local forum, I thought it created great debate, and proved that people who have engineering degree's are not as smart as they claim to be.

Here is the question :

A plane is sitting on runway that can move (some sort of giant conveyer belt). 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 opposite direction).

The question is:

Will the plane take off or not? Will it be able to run up and take off?

[Teaguer]

No the plane will never lift off .

There will not be any air moving over the wings to generate the needed lift .

[Rigmaster]

No the plane will never lift off .

There will not be any air moving over the wings to generate the needed lift .

+1

But......somehow I'll bet someone will make a strong argument for the plane taking off.



Bret.

[Erick]

^ What they said.


Unless you have a 500mph headwind. :)

[Teaguer]

^ What they said.

Cheater . ;)

[Ray Smoodiver]

Plane does not take off.

The engines provide forward motion on the ground --> minimum groundspeed (air travelling over the wings) required to induce lift.

If there is no forward motion - no lift - no flying.

The only way this conveyer system would work, would be if the engines were designed in such a way as to provide the required amount of airflow over the wings, which planes of this current day and age, aren't.

Edit: Last time I checked (which was today, btw) a plane doesn't suddenly start rising up when it is at rest - lift being caused by a lower pressure on the top of the wing ---> seldom seen when the plane isn't moving.

Edit 2: A plane's lift is caused to due the bernoulli effect ---> If there is no motion relative to the air, the plane ain't going anywhere.

Think of an excercycle in the gym ---> you might be peddling fast, but there is no wind in your hair, so to speak.

Unlike a helicopter, where the helicopter blades (wings) provide lift, it is actually the wings that provide lift. Shocking I know.

[Erick]

Cheater . ;)

You just beat me to it. :p

[golde30]

unless its a vertical lift plane, in which case the conveyer belt wouldnt be moving at all, and this questions perameters would be completely in-applicable...:D

[Axxe]

Hahaha, just what I expected. Keep them coming.

Also, state exactly why the plane will / will not take off.

[trent]

I Do my research first.

http://www.google.com/search?hl=en&safe=off&rls=com.microsoft:en-us&sa=X&oi=spell&resnum=0&ct=result&cd=1&q=plane+and+conveyor+belt&spell=1

There is LOTS of info out there about this.

[bwanac]

From what I read it is like being on a treadmill.

From a viewpoint outside of the plane/runway system the plane is not moving.

EDIT: I guess it can take off if the wheels are not important because they are supplying no force. Now if the belt is applying an equal and opposite force on the plane via its wheels, I dont see it taking off.

[erik325i]

+1

But......somehow I'll bet someone will make a strong argument for the plane taking off.



Bret.

I can't believe all you guys. Yes, the plane will take off.

Airplanes use jet engines that propel the plane forward. They are not powered by the wheels like cars.
Once you start the engines and try to take off, the speed of the ground has no effect. The Jet engines will still propell the plane forward enough to gain enough speed to fly.

Look at it this way, Let's say that the jet engines have the ability to push the plane 200mph upon take-off (I have no idea how fast they accually go, but that's irrellevant). The conveyor belt is also moving 200mph backward.
The plane is still traveling at 200mph, while the wheels are spinningh at 400mph.

-Erik

[trent]

http://txfx.net/2005/12/08/airplane-on-a-conveyor-belt/

Good explanation.

[Axxe]

Ding ding, we have smarties in the house.

[Ray Smoodiver]

http://www.airliners.net/discussions/tech_ops/read.main/136068/