Differences Between Ailerons, Flaps, and Spoilers

If you look outside a commercial jet’s window out at the wing, you’ll probably see a variety of different panels and surfaces rise, lower, and shift as the plane takes off, flies, and lands. But what do these different panels do, and why are they used in one situation over another?       

The first and most commonly used control surface on an aircraft wings are the ailerons. Aircraft ailerons are panels on the trailing edge (back) of the wing near the tips that move up and down. This alters the wing’s airfoil and how air travels under and over it. When an aileron tips down, lift increases, and when it tips up, lift decreases. By causing lift to increase on one wing and decrease on another, the entire plane banks to one side or another, causing it to roll to the pilot’s desired bank angle and turn in the same direction it is banking in. By returning to a neutral position on the flight stick, the ailerons return to their normal positions, causing the plane to return to a level flight path. Ailerons always work in opposition, meaning that as one is deflected up, the other is deflected down.

Airplane Flaps are movable panels on the trailing edge of the wing, mounted closer to the fuselage than ailerons. Flaps are used to increase lift at lower speeds—during takeoff and landing.  Similar to ailerons, flaps increase an aircraft’s lift when they are lowered, making it easier to get the aircraft off the ground. However, flaps also cause drag due to the altered airfoil, so they are elevated to a neutral position during cruising altitude. 

Spoilers are panels on the wing’s top surface that are used to reduce lift. When raised, they interrupt airflow over the wing, increasing drag and reducing lift at the same time. Aircraft Wing Spoilers can be used alongside or in lieu of ailerons for roll control by raising the spoilers only on one wing. Spoilers are also used during landings to reduce lift as much as possible, keeping the plane on the ground, and improving braking and traction on the runway.