How do planes and helicopters fly? With the tremendous weight of an aircraft, one might conclude that sheer magic must surely be at work. But in fact, there are many solid principles that explain this magical phenomenon.
We owe our understanding of these aerodynamic principles to two famous people, Sir Isaac Newton and Daniel Bernoulli. Bernoulli's principle can be explained pretty simply. Wings are shaped with an upper surface that is curved, and a lower surface that is not curved as much. When an airplane is in flight, some air is going over the top surface, and some is going under the bottom surface. Because the air moving over the top part of the wing must move faster to cover more surface area than the air moving under the bottom part of the wing, the pressure of the air on top drops slightly. That pressure difference is the key to creating lift, because physics tell us that an area of high pressure tends to move toward an area of low pressure. In flight, that means the higher pressure below the wing tries to move toward the lower pressure above it. Because the body of the wing is in the way, the high-pressure air takes the wing along with it, lifting it as it goes. .
Sir Isaac Newton, a renowned philosopher, mathematician, and physicist also made outstanding contributions in the area of lift dynamics. Sir Isaac Newton wrote that for every action, there is an equal and opposite reaction. In other words, every action causes a reaction of equal force and in an opposite direction. To understand what this means in terms of airplane flight, think of a wing as a simple flat metal plate. If the plate was placed flat in a steady stream of moving air, such as in a wind tunnel, no lift will be created. But if the front end of plate were tilted upward in the air stream, some of the air will strike the bottom of the plate and deflect downward. The plate has acted on the air stream by changing its direction.
