It's Friday..

[Timbo]

zero airspeed = zero lift =zero fly

[stevechesh]

Originally Posted by David G

Here is a totally pointless banal debate for you:

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?

David.

Originally Posted by tiggerbiker

no because the wings require air speed to produce the required lift.
as the plane is effectivly stationary, there would be no lift from the wings.


same as, if you were travelling at the speed of light in your car and you switched your headlights on - what would happen?
answer - nothing, the lights would glow but wouldnt project any light as you would be catching up with the edge of the projected beam the instant it left the headlamp filament.

Yep, speed of the aircraft is irrelevant using the criteria of the first post. Speed of airflow over the wing is what creates the lift. When you are next on a plane, try and look at the wings. As you start down the runway, you'll see the wings start to flex upwards. In laymans terms, when they reach the point where they don't bend up anymore, then 1 of two things can happen. They either snap or they'll lift the body of the aircraft and away you go. Fortunately the latter happens most of the time

[Timbo]

Nice one people !!
Just swotting up for the L.A.S.A.C quiz night tomorrow ???

[David G]

Originally Posted by tiggerbiker

no because the wings require air speed to produce the required lift.
as the plane is effectivly stationary, there would be no lift from the wings.


same as, if you were travelling at the speed of light in your car and you switched your headlights on - what would happen?
answer - nothing, the lights would glow but wouldnt project any light as you would be catching up with the edge of the projected beam the instant it left the headlamp filament.

Umm, the wheels aren't driven..........

The engines create thrust through the air not driven through the wheels therefore the plane moves; the conveyor belt just moves twice as fast .....

So it will move and take off..................

See I said it was banal.

[Sooty Stoo]

Originally Posted by David G

Umm, the wheels aren't driven..........

The engines create thrust through the air not driven through the wheels therefore the plane moves; the conveyor belt just moves twice as fast .....

So it will move and take off..................

See I said it was banal.

No it won't.

The wings will remain stationary, therefore they will NOT have any form of lift.

Logically then stationary wings = plane on the ground.

[Simon TW]

now explain the Harrier

[Tunicates]

Originally Posted by Simon TW

now explain the Harrier

Downwards thrust created by a hundred invisible chickens all flapping their wings furiously. Obvious.

NEXT.

[Frankie Price]

Originally Posted by Sooty Stoo

No it won't.

The wings will remain stationary, therefore they will NOT have any form of lift.

Logically then stationary wings = plane on the ground.

Doesn't matter how fast the conveyor moves if the aircraft is stationary relative to the ground, as soon as the engines create thrust the aircraft will move forward and take off. If however the aircraft is stationary relative to the conveyor and moving in reverse relative to the surrounding ground then the aircraft will need to produce take off velocity plus backward momentum velocity to get into the air.
Shit Frosty, I reckon thats almost worth a RED let alone a green.

[Sooty Stoo]

Originally Posted by Simon TW

now explain the Harrier

It's a type of hawk, isn't it?

[Jay_Benson]

Originally Posted by David G

Here is a totally pointless banal debate for you:

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?

David.

The thrust from the engines is not being applied to the conveyor belt but to the air. So the plane will move off relative to its starting point in the normal way. Granted the wheels will move twice as fast as normal but the air will still move over the wing creating lift. So, yes it will take off.