elevon

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elevon

delta wing aircraft (Precision Graphics)

n.
A control surface on an airplane that combines the functions of an elevator and an aileron.

[ELEV(ATOR) + (AILER)ON.]

A movable surface at the trailing edge of a tailless airplane that provides pitch and roll control. Elevons hinged on each side of the rear wing surface (see illustration) nose the airplane up or down, and roll one wing up and the other down. The term elevon is derived from elevator and aileron, and, in effect, elevons provide the same control as conventional elevators and ailerons. An example of an airplane employing elevons is the orbiter vehicle for the space shuttle. See also Aileron; Elevator (aircraft); Space shuttle.

Elevons on the trailing edge of a delta wing.

When the elevons on both sides of the wing are deflected upward, they combine to produce a nose-up pitching moment on the wing and, hence, on the tailless airplane. If the elevon on the right wing is deflected upward and the one on the left wing downward, the differential movement does not result in any pitching moment, since the nose-up and nose-down pitching moments produced by the two elevons cancel each other. However, the lift on the right wing decreases, and that on the left wing increases; the combined effect produces a moment on the airplane tending to roll it to the right. Deflecting the elevons in the opposite directions causes the wing to roll to the left, and deflecting both elevons downward produces a nose-down moment. See also Airplane; Wing.

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