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flightoffancy wrote in news:MPG.2172cb3db6410d90989680
@news-server.hot.rr.com: In article . com, says... Now, in Chapter 3, section about airfoils, it actually says: "In addition to the lowered pressure, a downward-backward flow of air also is generated from the top surface of the wing. The reaction to this downwash results in an upward force on the wing which demnstrates Newtons' third law of motion. This action/reaction principle also is apparent as the airstream strikes the lwoer surface of the wing when inclinded at a small angle (the angle of attack) to its direction of motion. The air is forced downward and therefore causes an upward reaction resulting in positive lift." IMHO, the latter part of this paragraph is correct, but the former part is wrong. JC, you're confusing yourself. Instead of focusing on "fixed" wing, think for a moment about helicopter blades and propellers. These are airfoils not fundamentally different than one attached to the side of an aircraft. Anyone who has ever seen video of a helicopter hovering or has been near a helicopter hovering knows that air is being pushed down by the blades with massive force and that is the equal and opposite force exerted by the mass of air on the bottom of the blades that keeps the helicopter from falling out of the sky. A fixed wing aircraft is only different in that it pushes air under it by moving forward, rather than in a circle. The bottom line is simple: an airplane can only stay aloft by pushing air down. Yes, the angle of attack gives the greater impulse to knock the air downward. But a curved upper surface gives even more downard force to the air. Nit-picking Jeppensen's watered down description, which was not authored for aeronautical engineers (which I note you are NOT), will not advance your piloting skills in any significant way. Nope, wrong. Bertie |
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