Flaperon
Control surface combining flap and aileron functions.
A flaperon is a control surface on an aircraft wing whose name blends "flap" and "aileron," as it performs the duties of both. Some kitplanes use flaperons to simplify construction, while large airliners like the Boeing 747, 767, 777, and 787 may place a flaperon between the flaps and aileron. The 787 features a SpoileFlaperon, which merges spoilers, flaps, and ailerons into a single surface.
In addition to controlling roll (like standard ailerons), both flaperons can be lowered together to lower stall speed, similar to flaps. Pilots still have separate controls for ailerons and flaps, but the flap control adjusts the flaperon’s range of motion. A mechanical mixer combines pilot inputs for the flaperons. Although using flaperons instead of separate ailerons and flaps might seem simpler, the mixer adds some complexity.
Some aircraft, such as the Denney Kitfox, mount flaperons below the wing—like slotted flaps—to keep airflow smooth at high angles of attack or low speeds. When hinged below the wing’s trailing edge, they are sometimes called "Junkers flaperons," after the doppelflügel (double wing) trailing edge surfaces on 1930s Junkers aircraft like the Ju 52 airliner and the Ju 87 Stuka dive bomber.
Research aims to coordinate flight control surfaces (ailerons, elevators, elevons, flaps, and flaperons) to reduce weight, cost, and drag, improving control response, reducing complexity, and lowering radar visibility for stealth. Drones and advanced fighters could benefit. Approaches include flexible wings and fluidics.
In flexible wings, much or all of the wing surface changes shape in flight to redirect airflow. Examples are NASA’s X-53 Active Aeroelastic Wing and the Adaptive Compliant Wing (military and commercial). This echoes the Wright brothers’ wing warping.
In fluidics, forces on vehicles come from circulation control: larger mechanical parts are replaced by smaller fluidic systems (slots emitting air flows), where larger fluid forces are diverted by smaller jets or flows to change direction. This promises lower mass and costs (as little as half), faster response, and simplicity.
- Aircraft with flaperons
- Boeing 747, 767, 777, 787; Denney Kitfox; Junkers Ju 52; Junkers Ju 87 Stuka
- Related research programs
- X-53 Active Aeroelastic Wing; Adaptive Compliant Wing
- Alternative name
- Junkers flaperons (for hinged below trailing edge)
- Related aircraft type
- Denney Kitfox
Lore & Background
Some kitplanes have flaperons for simplicity of manufacture, while large commercial aircraft such as the Boeing 747, 767, 777, and 787 may have a flaperon between the flaps and aileron. The 787 has a SpoileFlaperon that combines the action of spoilers, flaps and ailerons into one control surface. In addition to controlling the roll or bank of an aircraft, as do conventional ailerons, both flaperons can be lowered together to reduce stall speed, similarly to a set of flaps.
On a plane with flaperons, the pilot still has the standard separate controls for ailerons and flaps, but the flap control also varies the flaperon's range of movement. A mechanical device called a 'mixer' is used to combine the pilot's input into the flaperons. While the use of flaperons rather than ailerons and flaps might seem to be a simplification, some complexity remains through the intricacies of the mixer. Some aircraft, such as the Denney Kitfox, suspend the flaperons below the wing (rather in the manner of slotted flaps) to provide undisturbed airflow at high angles of attack or low airspeeds.
When the flaperon surface is hinged below the trailing edge of a wing, they are sometimes named 'Junkers flaperons', from the doppelflügel (lit., 'double wing') type of trailing edge surfaces used on a number of Junkers aircraft of the 1930s, such as the Junkers Ju 52 airliner, and the iconic Junkers Ju 87 Stuka World War II dive bomber.
Reader's Guide
Research seeks to coordinate the functions of aircraft flight control surfaces (ailerons, elevators, elevons, flaps, and flaperons) so as to reduce weight, cost, and drag, and thereby achieve improved control response, reduced complexity, and reduced radar visibility for stealth purposes. Beneficiaries of such research might include drones (UAVs) and the latest fighter aircraft. These research approaches include flexible wings and fluidics. In flexible wings, much or all of a wing surface can change shape in flight to deflect air flow. The X-53 Active Aeroelastic Wing is a NASA effort. The Adaptive Compliant Wing is a military and commercial effort. This may be seen as a return to the wing warping used and patented by the Wright brothers. In fluidics, forces in vehicles occur via circulation control, in which larger, more complex mechanical parts are replaced by smaller simpler fluidic systems (slots which emit air flows), where larger forces in fluids are diverted by smaller jets or flows of fluid intermittently, to change the direction of vehicles. In this use, fluidics promises lower mass and costs (as little as half), and response times, as well as simplicity.
Did You Know?
- The term 'flaperon' is a portmanteau of flap and aileron.
- The Boeing 787 has a SpoileFlaperon that combines spoilers, flaps, and ailerons.
- Some flaperons are hinged below the trailing edge and called 'Junkers flaperons', used on the Ju 52 and Ju 87 Stuka.
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