The Theory of FlightThe ForcesSir George Cayley first separated the forces involved with flight. They are lift, the upward acting force; weight, or gravity, the downward acting force; thrust, the forward acting force; and drag, the backward acting, or retarding force of wind resistance. |
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To design and build a flying airplane people needed to understand these basic theories. As will be seen in the History of Flight section, this was not always the case.
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| Drag and weight are forces
which are natural for anything lifted from the earth and moved through
the air. Thrust and lift are artificially created forces used to
overcome the forces of nature and enable an airplane to fly. The engine
and propeller combination is designed to produce thrust to overcome
drag. The wing is designed to produce lift to overcome the weight (or
gravity) of the aircraft.
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Lift opposes gravity. |
