Plane and conveyor belt...

[Inky Pete]

A runner on a treadmill is pushing himself "forwards" by pushing backwards against his running surface (which is moving). An aircraft is not.
It's engines are pushing it forwards by pushing air backwards (Newtons Third Law "for every action there is an equal and opposite reaction"), and the wings are generating lift by moving through the same still air.

If it were the air which were moving, ie. a very strong tail wind which increases with the speed of the aircraft, then it would be a different story. But what the ground is doing is irrelevent because the aircraft is not pushing against it.

(The ground, the plane, and the air are actually all moving at about 1000mph anyway as the earth rotates, and at 67,000mph as the earth orbits the sun, and at an even greater speed as the solar system orbits the centre of our galaxy, etc. etc. etc. But all of that is irrelevent because everything in the model we are considering also shares these same speeds.
What matters to generating lift is the relative speed of wing to air. Nothing else.)

 

[wotan]

The plane will never take off, it's the airflow over the wings that provides the lift, Bernoulli's effect.
If the aircraft is on what is in effect a treadmill and keeps pace, then it's forward progress relative to the ground is zero, and lift will never be generated, because there is no airflow over the wings.


Wotan

 

[imamartian]

Nige F with respect, you don't need to be quite rude.

If this thread is not for you, move your sorry @sses somewhere else...

 

[Inky Pete]

The only reason that a runner on a treadmill - or a car on a rolling road - doesn't move forward is that they are both pushing themselves forward against a surface which is moving backwards at the same speed.

This is NOT the case with an aircraft. The engines are pushing AIR backwards to propel it forwards. There is NO thrust applied to the runway through the wheels.

 

[Nige F]

I`m off to the Plumbing forum where they are polite

 

[sooey]

There's a 200 mile an hour headwind....so the fckin plane takes off without even starting it's engine.

 

[snico]

The correct answer

 

[Inky Pete]

The correct answer

WRONG!!!!

The plane is no more affected by the motion of the conveyor than a hovercraft would be by travelling over a moving river. Any holding back of the plane due to rolling friction in the free spinning wheels is TINY compared to the thrust produced by the engines.

The driving force is NOT being applied to the moving conveyor, it is being applied to the STILL air.

 

[snico]

This debate has being going on for years now, the original question was if the airplane was stationary and the conveyor is moving, with the airplane static to its surroundings. If that was the case the airplane would not take off.....it is impossible as an airplane need air flow around the wings to lift....its basics physics.

The video on mythbusters is showing a different scenario all together.

conveyer, airplane stationary, conveyor moving....plane does not lift off....FACT

 

[wotan]

The original analogy was the runway, a moving conveyor, was been driven at a speed in the opposite direction to the effort being applied by the aircraft trying to accelerate forwards net result that the aircraft remained stationary, relative to the moving runway.

Without airflow over the wings no lift would be generated, the aircraft will not take off.

Wotan

 

[Norcon]

This debate has being going on for years now, the original question was if the airplane was stationary and the conveyor is moving

Wrong. In the original question the plane "moves". Thus it will take off.

 

[wotan]

The plane moves equally to the conveyor, so in effect it remainds stationary to the surrounding air mass, no lift no take off.

Wotan

 

[Norcon]

The plane "thrusts" forward" by the implementation of the propellors just as mythbusters showed it.
The wheels would have to be braking to prevent take off or the plane anchored by ropes.

Inky petes posts explains it well.

 

[snico]

In the original question the plane "moves". Thus it will take off.

Wrong, the plane moves in relation to the conveyor belt, but the airplane remains stationary to its surroundings.
It has been misquoted over the years, but in the original question....the plane would NOT take off.

 

[Norcon]

Your playing pedantics with the question I think.
Most would assume the plane is allowed to thrust with no braking or anchoring mechanisms in which case it will take off.

Which question incidentally are you referring too?

BTW how can a plane "move" yet remain stationary?