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Aileron—A control surface set into or near the trailing edge of an airplane wing, extending, when in the wing, toward the tip and usually within the contour of the wing, and used to control the longitudinal axis of an airplane.

Airborne—Of an airplane or other winged craft: Supported entirely by aerodynamic forces; flying.

Airfoil—A surface or body, as a wing, propeller blade, rudder, or the like, especially designed to obtain a reaction, as lift or thrust, from the air through which it moves.

Angle of attack—The acute angle between the chord of an airfoil, and a line representing the undisturbed relative airflow. Any other acute angle between two reference lines designating the cant of an airfoil relative to oncoming air.

Aspect ratio—The ratio between the span of an airfoil and its chord.

Camber—The curve of an airfoil section from the leading edge to the trailing edge. Camber is usually expressed as the distance from the chord line to the upper or lower surface of an airfoil.

Center-of-pressure travel—The movement, or the amount of movement, of the center of pressure along a chord of an airfoil as the latter is inclined through its normal angles of attack.

Chord—An assumed straight-line tangent to the lower surface of an airfoil section at two points, or a straight line between the leading and trailing edges of an airfoil section, or between the ends of the mean line of an airfoil section; the distance between the leading and trailing edges of an airfoil section.

Drag—A resistant force exerted in a direction opposite to the direction of motion and parallel to the relative gas or air stream.

Dynamic lift—The lift given an airplane by the aerodynamic force produced from an adequately designed airfoil.

Glider—A fixed-wing aircraft having no power plant and constructed so as to glide and soar.

Gliding—The art, science, and activity of moving through the air in a glider.

Heavier-than-air aircraft—Any aircraft weighing more than the air it displaces.

Lift—That component of the total aerodynamic forces acting on an airfoil or on an entire aircraft or winged missile, perpendicular to the relative wind, and exerted, normally, in an upward direction opposing the pull of gravity.

Lighter-than-air aircraft—An aircraft that rises and is supported in air by virtue of a contained gas weighing less than the air displaced by the gas.

Nose dive—A steep dive by, or in, an aircraft.

Power plant—The complete engine or engines in an aircraft, together with propeller or propellers (if any), accessories, fuel and oil tanks and lines, etc.

Powered aircraft—An aircraft having one or more engines, as distinguished from a glider.

Tailspin—A spin, so named in reference to the characteristic spiral action of the tail when the airplane is in a spin.

Warp—To change the shape of something, especially an airplane's wing, by twisting. To give lift or drop to a wing by twisting it at the ends.

Wind tunnel—A chamber through which air is forced at controlled velocities, up to several thousand miles an hour, and in which airfoils, airplanes, missiles, scale models of airplanes, or other objects are mounted in order to observe and study the airflow about such objects, as well as the aerodynamic effects upon them.

Wingspan—The span of a wing, measured or taken between the tips or outermost extremities of either a single-piece wing or a wing that is separated by other aircraft components.

Wing-warping—The action of warping a wing, or a control system for warping the wings at will.

Yaw—An angular displacement or motion to the left or right about the vertical axis of an airplane.


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