Imagine a plane is sitting on a conveyor belt, can it take off?

[aubiegirl]

If i am not mistaken, this is gonna be a prop plane. The function of the prop is not to generate the airflow over the wings - the function of the prop is to generate forward thrust by pushing the surrounding air backward, so that the wing picks up enough forward speed for the airflow required to take off. Since the prop is pushing against air and not the treadmill, the plane will move forward. The plane should take off.

[DWarrior]

Originally Posted by aubiegirl

If i am not mistaken, this is gonna be a prop plane. The function of the prop is not to generate the airflow over the wings - the function of the prop is to generate forward thrust by pushing the surrounding air backward, so that the wing picks up enough forward speed for the airflow required to take off. Since the prop is pushing against air and not the treadmill, the plane will move forward. The plane should take off.

But the wings won't be gaining any forward speed as the plain will remain motionless horizontally.

PS, if propeller generates airflow to the wings, then how does a jet engine plane (with the jet in the back) get lift?

Imagine a jet plane on this conveyor belt. The jet's in the back, so it has no effect at all on the wings. The jet pushes the plane forward, while the conveyor belt pushes the plane back. The two forces are equal and opposite, so the plane doesn't experience any horizontal motion. I don't see any way for the plane to lift off, and I think the other engines (propeller in the front, or the larger commercial jets with engines on the sides) work the same way.

[Grapist]

Originally Posted by aubiegirl

If i am not mistaken, this is gonna be a prop plane. The function of the prop is not to generate the airflow over the wings - the function of the prop is to generate forward thrust by pushing the surrounding air backward, so that the wing picks up enough forward speed for the airflow required to take off.

You are, indeed, mistaken.

[Grapist]

Originally Posted by DWarrior

PS, if propeller generates airflow to the wings, then how does a jet engine plane (with the jet in the back) get lift?

Good question. As I have pointed out before, the plane, WILL move down the treadmill, but under the thrust created by the jet pushing air molecules (matter) out of the back. This will do 2 tings, 1) also pull air over the air foils of the plane, and 2, Physically move the plane down the treadmill runway. The only difference is in the speed the wheels spin.

[mrdahonay]

Originally Posted by aubiegirl

If i am not mistaken, this is gonna be a prop plane. The function of the prop is not to generate the airflow over the wings - the function of the prop is to generate forward thrust by pushing the surrounding air backward, so that the wing picks up enough forward speed for the airflow required to take off. Since the prop is pushing against air and not the treadmill, the plane will move forward. The plane should take off.

Assuming it's a prop plane and all else you say is true (you are infallible in my book!) then if the treadmill is synchronizing precisely with the wheels, how can the plane move forward? Until lift is generated, it will still be limited by the movement of the wheels against the ground.

Mythbusters- my 2nd dream job, next to Steve on Blues Clues

[Grapist]

Originally Posted by DWarrior

The jet pushes the plane forward, while the conveyor belt pushes the plane back. The two forces are equal and opposite,

This statement is incorrect.

[Grapist]

Originally Posted by mrdahonay

Assuming it's a prop plane and all else you say is true (you are infallible in my book!) then if the treadmill is synchronizing precisely with the wheels, how can the plane move forward? Until lift is generated, it will still be limited by the movement of the wheels against the ground.

Mythbusters- my 2nd dream job, next to Steve on Blues Clues

It's actually irrelavant if it is a prop or jet.

[DWarrior]

Originally Posted by Grapist

This statement is incorrect.

You're right, I completely mis-visualized the setup. I think this explanation makes it clear and is valid:

http://www.straightdope.com/columns/060203.html

[typicallistener]

who cares.

[DWarrior]

Originally Posted by Lord of the Cock Rings

DoctorRon! Good post. I too am exhausted by dealing with this rumor.


Wrong, MPH has everything to do with lift.




Wrong again. A bus on a treadmill will not go anywhere either. No movement = no air resistance = no lift on an airplanes wings

Thrust means shit. Would a sailboat in the middle of the ocean [with NO wind] move if you mounted a huge fan on the back?

It wouldn't, it's thrusting against itself. Just like the jets are thrusting against the conveyer. No Newtonian language. Simple enough for you?

As the link explains though, there's a difference between a car moving on a treadmill and a plane. The car's wheels move it forward by spinning, so if they're spinning at 60mph and then the conveyor is moving back at 60mph, then the car will remain in place.

However, the wheels on a plane don't propel it forward, they just keep it from falling into the ground. If the plain is being propelled by the propeller (or jet engine) at 60mph forward and the conveyor spins back 60mph, the wheels will just move at 120 mph (since they're completely free to rotate, they're not what drives the plane), and the plane will move forward as normal.