How Flaperons Work to Stabilize Airplanes

Airplane wing above clouds
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After Malaysia Airlines Flight 370 went missing in 2014, the first piece of debris to be discovered was a flaperon, prompting a lot of people to ask, "What exactly is a flaperon?" Flight 370 was a Boeing 777 that still had not been located as of 2018, with all 227 passengers and 12 crew members presumed dead.

The discovered flaperon is an example of the combination of an aileron and a wing flap. Ailerons are located on the outer trailing edges of airplane wings and help control roll, and wing flaps are located along the trailing edge of the wings to help with lift, both helping the pilot with navigation.

Flaperons are exactly what they sound like—an aileron and flaps combined into one, fluid flight control. Designers realized that by combining the two functions, weight is reduced. And weight in an aircraft equates to fuel and money, of course.

How Flaperons Work

Ailerons control roll about the longitudinal axis of an airplane. And flaps, as we know, are hinged controls on the wing that are retractable. Flaps change the chord line of the wing (an imaginary line that runs from the leading edge to the trailing edge) by increasing the camber of the wing when deployed, and they increase the lift coefficient during low-speed flight. Flap use increases the angle of attack, causing the required angle of attack to be less than usual for the same amount of lift produced.

On the Boeing 777 and other aircraft, flaperons are part of the primary flight control system and are located on the mid-section trailing edges of the wing. On the Boeing 777, the flaperon is a small but useful portion of the wing that is stowed for flight and used primarily during landing and slow flight configurations to help stabilize the roll of the aircraft. In the retracted position, the flaperon is flush with the wing, and when retracted, the flaperon creates a large amount of drag, often acting as a spoiler.

On small aircraft, the flaperon might be the entire length of the wing, such as the flaperon found on some kitplanes. With the flaps retracted in this case, you have aileron control on the entire length of the wing, allowing for good roll authority and quick, positive response from aileron input. With the flaps extended, the pilot will notice a lot of drag with a smaller amount of roll control.

Design Influences for the Flaperon

The development of the elements of airplane wings—including flaps, ailerons, and flaperons—can be traced to the flight feathers on birds. On the wings of birds, these are known as remiges. The way birds manipulate these remiges aid them in flight by giving them control over things like direction and lift. While birds do this instinctively, airplane wings (and their corresponding controls) in a lot of ways are designed to mimic the ways birds use their wings.