Will it take off?

[threehills]

This is blatantly stolen from another board, but I curious as to what some of the real "minds" over here at MS have to say about the subject.



A plane is standing on a movable runway( something like a conveyor).as the plane moves the conveyor moves but in the opposite direction.the conveyor has a system that tracks the speed of the plane and matches it exactly in the opposite direction.

The question is, will the plane take off or not?

[feather]

Re: Will it take off?

No I don't think so. You're saying the conveyor cancels out the plane's forward vector. So your plane is stationery.

If I'm not wrong the plane has to gather enough speed for the air/wind to work on those wings to lift it up.



Dynamics of flight

[Troklo]

Re: Will it take off?

Mythbusters did this, and yes it takes off

[threehills]

Re: Will it take off?

^ but myth busters was crap. The "treadmill" was not countering the speed of the plane as the plane is clearly acclerating forward.

http://mythbustersresults.com/episode97

[Garrick]

Re: Will it take off?

i've heard a bunch of different responses and i'd have to see it for myself because i don't know who to believe. i think the answer is no, the plane will not take off if it is solely using the treadmill to gain momuentum and not moving forward. as soon as it goes up in the air, i would think there isn't enough resistance against the air to keep it afloat. part of the reason the planes fly is the air it distributes under and above its wings to balance itself. when it takes off, it doesn't have the force against the plane it would have if it were moving forward and i'd think it'd just come back to the ground.

[Kamal]

Re: Will it take off?

I'm with feather, the plane is in fact stationery (conveyor canceling the forward motion of the plane) and you need airspeed to lift the wings/plane. Can't see how the plane took off.

[Kamal]

Re: Will it take off?

^ but myth busters was crap. The "treadmill" was not countering the speed of the plane as the plane is clearly acclerating forward.

http://mythbustersresults.com/episode97

This is because the thrust of the airplane engines acts on the air, not on the ground.

that doesn't sound right, even if the engines are providing the forward thrust, wont the reversing direction of the treadmill reverse the airflow (by moving the plane backward at the same speed) thereby providing nearly no "lift"

[feather]

Re: Will it take off?

Actually ... if those engines are there to provide thrust from sucking air in and thus over and under the wings (I always assumed the engines were there to propel the plane forward on the runway, but Kamal makes an illuminating point or whoever he quoted), the plane might end up lifting off or hovering. But I don't think it will maintain its flight as there is no forward motion here, the conveyor has cancelled it.

[Garrick]

Re: Will it take off?

i guess it might depend on how much thrust the engine emits. i'd think it'd take a helluva lot more thrust to keep a plane up in the air from a standstill (how much more thrust? is it possible?) than if it were already moving at normal takeoff speed.

[lilsensa]

Re: Will it take off?

Mythbusters did this, and yes it takes off

Fucking Mythbusters! The ruin everything...Fucking assholes.

[Kamal]

Re: Will it take off?

but Kamal makes an illuminating point or whoever he quoted), the plane might end up lifting off or hovering

thats quoted from the mythbusters link that threehills posted. If the "thrust" from the engines is in fact lifting the plane, then premise of the experiment is inaccurate imo because the wind speed through the engines far exceeds the reversing speed of the treadmill.

[Huggie Smiles]

Re: Will it take off?

if its a harrier jumpjet it will take off - no problem

[Kamal]

Re: Will it take off?

if its a harrier jumpjet it will take off - no problem

[srbbnd]

Re: Will it take off?

Yes it will take off. Think of yourself running on a treadmill. The faster you run the more air resistance you have. IMO

[threehills]

Re: Will it take off?

Yes it will take off. Think of yourself running on a treadmill. The faster you run the more air resistance you have. IMO

Not so my friend. Runner's world suggests always running at a +1% incline to what you would normally do to simulate the MISSSING air resistance.

The only air resistance encounterd while on a treadmill is from your arms swinging through the air...not whole body air resistance from running normally.