I'll make one last comment before leaving this subject to be discussed off-list. The first I heard of the "moves air down" theory of lift was in Wolfgang Langewische's outstanding book about flight called "Stick and Rudder." First published in the later 1940s, this book is still in print and to my knowledge has never been equalled in its easy-to-understand descriptions of why planes fly and how they are controlled. In explaining lift, Langewische acknowledges all the theories and principles like the Bernoulli effect, but says simply that all the pilot really needs to know is that a wing flies because it moves air down. On the advice of my first flight instructor, I read this book before taking my first lesson. I was very familiar with the Bernoulli theory of why a wing generates lift and I understood it, so when I saw the passage in Stick and Rudder about lift, it made no sense to me. After all, the book had been written in the 1940s, which to me at the time was the stone ages. Wings flew because of the pressure differential between the upper and lower surfaces. End of story. During the past ten years, I've been exposed more and more to the moves-air-down reason a wing generates lift. I've described some of the sources in other posts. But since nobody could give me an easy-to-undersand reason why a wing moves air down, I stuck with Bernoulli. The convincer was when I saw the numbers. I may still have the industry journal where I first saw these numbers and the accompanying diagrams in my office. I'll try to find it. I can't do the math, and I wouldn't understand the calculations if I saw them. But I do understand the end result. If you calculate the actual pressure differential across a wing as a result of the Bernoulli effect, and thus measure the actual amount of lift that's being generated, the results are rather startling. The calculations take into account the curvature of the wing surfaces, the shape and dimensions of the wing, the speed at which the wing is moving through the air, the angle the wing is meeting the air, the area of the wing surfaces, the temperature and density of the air, and on and on and on. The numbers I first saw were for several airplanes in several conditions of flight. Slow flight, cruise, maximum speed, etc. It's been several years, so I don't remember all the planes used in the calculations, except one was a 747 and one was a general aviation plane, I think a Cessna 206. The bottom line is that the calculations show that in all flight conditions, on all the wings used as examples, the amount of lift that would be generated by the Bernoulli effect alone was a mere a fraction of the total amount of lift required to support the airplane in flight. I don't remember the specific percentages, but I recall most if not all of the percentages were but a single digit. So if the Bernouli effect by itself can generate only seven percent of the lift a 747 needs to sustain level flight (to use one of the typical percentages calculated- this is probably the wrong one for the 747) where does the other 93 percent of the required lift come from? Using seven percentage as an example, if a fully loaded 747 weighs 800,000 pounds, in cruise flight the Bernouli effect alone will generate 56,000 pounds of lift. So where does the other 744,000 pounds of lift come from? This is what finally convinced me that Bernoulli was a convenient way to explain lift, but in fact is the wrong way. The accompanying diagrams showing what the cross section of a wing would have to look like in order to generate enough pressure differential on the surfaces to generate the required lift simply reinforced the fact that wings fly because of Newton, not Bernoulli. It was a hard thing to give up something I completely understood for something I don't really understand at all. But the fact that organizations like the Smithonian National Air & Space Museum and NASA are switching their explanations of lift on public-access websites and things from Bernoulli to moves-air-down indicates that while I may not understand it, at least I now know the right reason the de Havilland Beaver I fly stays up. _______________ C. Marin Faure GB36-403 "La Perouse" Bellingham, WA