An elevon is a combination of pitch and roll control surfaces used on aircraft without stabilizers and horizontal elevators. It provides roll inputs by moving controls on either side of the aircraft in opposite directions and pitch control by moving both elevons up or down. The elevon system is used on high-performance military delta-wing aircraft and some civil aircraft like the Concord.
An elevon is a combination of pitch and roll aircraft control surface on hang glider aircraft without stabilizers and horizontal elevators. An elevon supplies roll inputs by moving the controls on either side of the aircraft the same distance in opposite directions. Tone control is achieved by equally moving both elements up or down. Combined pitch and roll control is achieved by moving both elevons up or down to launch the aircraft; one control extends further than the other to induce roll. Pilot controls on elevon-equipped aircraft remain the same as conventional aircraft with the combined inputs facilitated by sophisticated flight control systems.
Conventional aircraft designs feature an empennage or tail section consisting of a vertical stabilizer and two smaller wing-shaped horizontal stabilizers. Mounted on the horizontal stabilizers are a set of movable control surfaces known as elevators that control the pitch or pitch of the aircraft. These pitch controls cause the aircraft to descend or climb. Mounted on the wingtips is a similar set of controls known as ailerons which, when moved in opposite directions, rotate the aircraft around its axis. Many aircraft, such as delta or flying wing designs, lack horizontal stabilizers or elevators and an alternate method of pitch control must be used.
The answer to this dilemma is the added functionality of ailerons to induce both roll and pitch motion. This combined function control surface is known as an elevon. In general, the ailerons only move in opposite directions in equal increments. In elevon designs, they can also move in the same direction and to different degrees. The result of this added range of motion is a multi-purpose control surface that can roll the plane up and down.
The theory and operation of the elevon is quite simple and capable of producing very precise flight control. When the elevons move equally in opposite directions to conventional ailerons, air traveling above and below the wing will push one wing down and the other up, causing the plane to roll on its axis. If both move up or down equally, air moving over or under the wing will cause the nose of the plane to go up or down to go up or down. Roll and pitch combinations are a bit more complex and require a compound movement. Both elevons move up or down to induce pitch motion with one control extended more than the other to induce roll motion.
This deviation from control surface standards does not affect the way the pilot controls the aircraft. Entries are still achieved using the familiar control column or side stick controls; Elevon’s only combo movements are controlled by the aircraft’s flight control systems. The elevon system is typically employed on high-performance military delta-wing aircraft such as the F-117 Nighthawk and F-102 Delta Dagger. Delta wing civil aircraft using elevons are not that common, the best known example being the Concord.
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