What's a Flaperon?

Flaperon
By Bruce C. Cooper (uploader) (Own work) [Public domain], via Wikimedia Commons

News reports about the discovery of a flaperon that might have come from MH370, a missing Malaysian Airlines 777, have people wondering: What, exactly is a flaperon?

You might have heard of an aileron before, and you might have heard about flaps. But a flaperon? Yes, it's exactly what it sounds 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, and the cost savings is important these days. But how do they work?

How Do They Work?

Well, 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.

Small Aircraft

On small aircraft, the flaperon might be the entire length of the wing, such as the flaperon found on a Kitfox. With the flaps retracted in this case, you have aileron control on the entire length of the wing, allowing for good roll authority - 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.