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Old Mar 11, 2012, 07:47 PM
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The 'Wack, BC, Canada
Joined Oct 2002
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Herkm I am SOOOOO in agreement with you on the aspect of the downwash coming off the trailing edge being what is left after the airfoil does its job. To my mind it was the reason why I told the originator of that last thread why I was totally done more then once.

I guess I just can't say "no" to a good mind puzzle....

Aeronaut, the whole conservation of momentum seems like a good principle. But since the airplane develops its lift by reacting with the air mass and not neccesarily by pushing against the earth I'm not sure the whole argument holds water, so to speak. Is it really a crime if the earth is "falling" towards a plane in flight? It's not like it's enough to make the earth shift to any significant degree in it's orbit. And in truth the earth does not revolve around the true geometrical center anyway. The distribution of the plates that make up our landmasses both above and below the water of our oceans ensure that the center of mass of this ball of dirt is anything but centered on the overall average spherical center. Tossing in a few planes in flight wouldn't cause more than an undetectable blip in the gravitational "noise" level.

Balloons and fish at their balance point, in other words neither rising nor falling, don't add or subtract to the whole picture as their volumes at that point are of the same density as the air around them. They simply become part of the homogenious mass of the water or air of the globe.... unless you want to look at them as providing an increase to the overall volume of water or atmosphere and by being part of the water or air mass raising the height of the oceans or atmosphere and thus contributing to some change and effect of such a change.

Ya know... thinking along those lines we're getting back dangerously close to the age old mystery of how many angels are able to dance on the head of a pin.....

The whole conservation of momentum certainly applies to someone that jumps off the earth and then they suck themselves back together and "impact" to a landing. But I'm not so certain that it applies to an airplane which is able to develop lift in various directions (but mostly "up") by interacting with the air around it to re-direct air in such a way as to create reaction like thrust through the action of wing surfaces. But I'll freely admit that it's all a feeling and that I don't know enough to say either way with authourity.
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