Levons

Levons, often written elevons, are aircraft control surfaces that combine the functions of an elevator (pitch control) and an aileron (roll control) into a single trailing-edge surface. They are primarily used on tailless aircraft and flying-wing configurations where there is no separate horizontal stabilizer.

In operation, elevons are located along the trailing edge of the wing and deflect in coordinated ways to produce pitching moments and roll moments. A single outward deflection typically generates both lift and a turning moment, while differential deflection between left and right elevons controls roll. On modern aircraft, flight control computers often perform the required mixing of inputs from the pilot to produce the appropriate elevon deflection.

Historically, the concept emerged with tailless and flying-wing designs in the mid-20th century. Elevons became a standard solution for providing full flight control without a conventional tailplane. Notable examples include the Northrop Grumman B-2 Spirit, a tailless flying wing that relies on elevons for primary control, and the Space Shuttle orbiter, which used elevons on its wing for pitch and roll control during reentry and landing.

Terminology can vary, and while elevon is the widely accepted term, levon is sometimes encountered as an alternate spelling or misspelling in certain texts. Regardless of spelling, the concept refers to a blended control surface serving both elevator and aileron roles on suitable aircraft.

Related topics include control surfaces, ailerons, elevators, flaps, spoilers, and tailless or flying-wing aircraft designs.