elevon

An elevon is a control surface at the trailing edge of a wing or canard that combines the functions of an elevator and aileron. Found on tailless aircraft, delta-wing designs, and flying wings, it deflects to control both pitch (nose up and down) and roll (banking). The space shuttle orbiter used elevons extensively; the Concorde relied on them as primary pitch control at supersonic speeds.

On a conventional aircraft, the horizontal stabilizer at the tail provides pitch control while ailerons in the wings handle roll. A tailless design eliminates the tail entirely, so the trailing edge surfaces must do both jobs simultaneously. When both elevons on left and right deflect upward together, the aircraft pitches nose-down. When they deflect in opposite directions, the aircraft rolls. Mixing these commands allows a pilot or autopilot to achieve any combination of pitch and roll authority.

Elevons are typically actuated hydraulically or electrically and may be split into multiple segments for redundancy and fine control. The space shuttle had eight elevons across its wings and payload bay doors, with independent hydraulic systems to ensure control even if one system failed. On high-performance jets and experimental aircraft, elevon geometry and deflection rates are critical to handling characteristics and must be carefully tuned during design.

The term itself is a portmanteau of elevator and aileron, coined when designers first integrated these functions into single surfaces. It remains the standard terminology across aerospace engineering and maintenance documentation. Understanding elevon behavior is essential for flight control system troubleshooting, as asymmetric deflection or lag can cause unwanted roll or pitch tendencies that are harder to diagnose than problems with separate control surfaces.