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Turning the Airplane | |
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The position of the airplane over time is called the flight path. The flight path can be changed by increasing or decreasing the lift or thrust. In steady, level flight, the lift force exactly balances the weight force. The pilot can increase the lift on the plane by moving a control surface, such as the elevator. This will produce a nose-up motion. The pilot may also increase the thrust so that the plane moves faster through the air. In either case, the lift now exceeds the weight! The aircraft now starts climbing higher in the air. If a line were drawn for the flight path, it would show a curved section for this altitude change. When the lift exceeds the weight, there is an effect on the pilot and crew. The ratio of the lift to the weight is called the load factor. When the lift is equal to the weight, as in level flight, the load factor is 1 or 1 g (meaning the same as normal gravity). If the load facotr were 2 (the lift is twice the weight), then the pilot and crew would be experiencing 2 g's. Most small or commercial aircraft are not designed to experience high load factors; they rarely exceed 1.5 g's while turning or changing altitude. Military fighters, however, are designed for many more g's for tighter turns and increased speed. Obviously, these increased g's affect the pilot as well as the airplane; in fact, the latest generation of fighter airplanes can pull more g's than most human beings can withstand, without going unconscious. The computers that help control the airplane also prevent the pilot from attempting to pass the established g-limits. The pilots are trained to withstand high g forces. The direction of the lift force is perpendicular (straight up and down) to the wing of the airplane. The pilot can change the wing angle by using the ailerons to roll or bank the aircraft for a turn. This changes the direction of the lift force compared to the weight force. It adds a lateral (sideways) acceleration to the airplane, which causes the plane to turn. The flight path will show a curve as the plane turns.
The pilot must add thrust or a slight nose pitch as he or she turns, or
the plane will lose lift and altitude. Pilots experience g forces in
turns, too.
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