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| 2.14. SUMMARY Daniel Bernoulli, born 1700, discovered the principle bearing his name. Giovanni Venturi, in 1822, noted the effects of constricting a passage through which fluid flowed. The Venturi tube was invented by Clemens Hershel, an American engineer. He named it in honor of G. B. Venturi. Newton's three laws on force and motion are applicable to aerodynamics. The four forces acting on an aircraft are weight, lift, thrust, and drag. Flight becomes possible when lift overcomes weight and thrust overcomes drag. The two kinds of airfoils used on Army aircraft are symmetrical and asymmetrical. An airfoil uses low-pressure air on top of the wing and high-pressure air under the wing to produce lift. When the wing's angle of attack is increased, the deflection of the airstream over the wing's upper surface creates more lift. However, if the angle of attack is too great the airstream breaks away from the upper surface and burbles. At this point, the aircraft can stall. Ailerons control the aircraft about its bank or roll (longitudinal) axis. Flaps are used to increase the lift capability of a wing and are used mostly in landing and takeoff. A true cantilever wing derives its strength from internal wing-design. The boundary layer is that air closest to the surface of an aircraft's wings, and flows in layers called laminae. |