How do Airplanes fly? Well, if you're like, what seems, most people, you've probably been told that it has to do with Bernoulli's Principle. In a nutshell, people who use Bernoulli's Principle make the following arguments to justify using Bernoulli as the explanation for flight.
1. Pressure above the airfoil (wing) is lower than the pressure below the airfoil, so creating LIFT
2. The top surface of the foil is longer than the lower surface, so the air above has to move faster so that the two streams of air meet at the same point at the trailing end of the foil
3. Faster moving air stream creates lower pressure, slower, greater pressure
Sound good, right? Well, none of the above is true...yikes! Yet, it continues to be the popular way to explain how airplanes fly in school textbooks today.
I guess not all of the ideas presented are false, but the fundamental premise presented are not correct. For one thing, the application of Bernoulli's Principle is not appropriate. Bernoulli's Law is in reference to a SINGLE stream of fluid, not two or more, as the traditional explanation for flight clearly tries to do.
Second, there is no scientific principle that says that the travel of two independent streams of air should meet at the same point. NONE. It simply begs the question, why should they? In fact, in air tunnel tests of airfoils, the air on the upper, longer surface always reaches the trailing end of the foil before the bottom stream.
Third, it turns out, that pressure is what affects the air particles, streams forcing them to move faster/slower. So, it is atmospheric pressure that affects speed and not speed creating the pressure differential. Huh?
Okay, so here is the real reason why airplanes fly. Coanda anyone? What about Newton's 3rd Law of Motion? Other details, observations that make Bernoulli untenable. So, not Bernoulli.
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