think about this...

[Mars357]

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If the plane is not moving, no air is being forced under its wings. If no air is being forced under its wings, there is no lift. So it stays grounded.

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When did I say the plane wasn't moving?

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you essentially gave us two velocity vectors of equal magnitude that work in exactly opposite directions. the plane has zero velocity relative to somebody standing on the ground observing it. it is going nowhere.


i think.

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Everyone seems to be figuring this from the standpoint that the plane's wheels are where the thrust is comming from. The wheels do not push the plane forward, the props do.

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Why is that relevant? The thrust from the props = X. The "thrust" from the moving conveyor-runway = -X. The aircraft is not moving relative to the air. Hence, no airspeed, so no lift.

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I agree, ground speed has nothing to do with it. It's all about airspeed (the speed at which air passes over the wing). Nothing else matters.

If an plane is moving forward at 50 MPH into a headwind of 100 MPH, the net airspeed is 150 MPH BUT the plane would actually be moving backwards at a rate of 50 MPH groundspeed....