An aileron is a hinged control surface on the trailing edge of each wing, near the wingtip, that allows a pilot to roll the aircraft and initiate turns. Every fixed-wing airplane has a pair of them, and they work in opposite directions: when one goes up, the other goes down. This creates an imbalance in lift between the two wings, causing the plane to bank to one side.
Where Ailerons Sit on the Wing
Ailerons are located on the outboard (outer) portion of each wing, right at the rear edge. They’re relatively small compared to the total wing area, but their position far from the aircraft’s centerline gives them strong leverage to rotate the plane. If you’re watching an airliner from the ground, you can distinguish ailerons from spoilers by their location: ailerons move at the very trailing edge of the wing, while spoilers pop up from the middle of the wing’s surface.
How Ailerons Make an Aircraft Turn
Ailerons control the aircraft around its roll axis, an imaginary line running from nose to tail. When a pilot turns the control wheel (or pushes a stick) to the right, the right aileron deflects upward and the left aileron deflects downward. The downward aileron increases the curve of that wing’s cross-section, which generates more lift. The upward aileron does the opposite, reducing lift on its wing. Because one wing is now producing more lift than the other, the aircraft rolls toward the side with less lift.
This roll is what actually sets up a turn. Banking the wings tilts the total lift force to one side, pulling the airplane along a curved path. So while ailerons don’t directly steer the plane left or right, they’re the primary tool a pilot uses to enter and control turns. The connection between pilot input and aileron movement is straightforward: turn the wheel left, and the left aileron goes up while the right goes down. Turn right, and the reverse happens.
The Adverse Yaw Problem
Ailerons come with a built-in quirk called adverse yaw. When you roll to the right, the airplane’s nose briefly swings to the left, the opposite direction of the intended turn. This happens because the downward-deflected aileron, while producing more lift, also creates more drag. It works like a small flap: lowering it increases the wing’s effective angle of attack, which raises both lift and a type of drag tied to lift production. The upward aileron, meanwhile, creates less of both. That drag imbalance momentarily twists the nose the wrong way.
Pilots compensate for adverse yaw with rudder input, pressing the rudder pedal in the direction of the turn to keep the nose coordinated. But aircraft designers have also developed mechanical solutions to reduce the effect in the first place.
Design Variations That Reduce Adverse Yaw
The most common solution is differential ailerons. In this design, the upward-deflecting aileron travels through a larger angle than the downward-deflecting one. The extra upward deflection on the descending wing adds drag on that side, helping to balance out the excess drag from the rising wing’s lowered aileron. This doesn’t eliminate adverse yaw entirely, but it reduces it significantly.
Another approach is the Frise aileron, where the leading edge of the upward-deflecting aileron protrudes slightly below the wing surface, adding drag to that side and further evening out the imbalance. Many modern aircraft combine both strategies.
What Determines Aileron Effectiveness
Three factors control how quickly and forcefully ailerons can roll an aircraft: their size, how far they deflect, and how far they sit from the airplane’s centerline. A larger aileron span or a greater maximum deflection angle produces a stronger rolling moment. Positioning them near the wingtips, far from the fuselage, gives them more leverage.
Airspeed matters too. At higher speeds, the air flowing over the aileron exerts more force, so a small deflection produces a strong roll. At low speeds, like during takeoff and landing, ailerons are at their least effective. This is actually the critical condition engineers design around: the aileron has to be large enough to provide adequate roll control at the slowest speeds the airplane will fly. Federal regulations set specific limits on how much force a pilot should need to apply, with stick-controlled ailerons capped at 100 pounds of maximum force and 40 pounds minimum.
Once deflected, an aileron accelerates the roll until air resistance on the spinning wings balances out the rolling force. At that point the aircraft settles into a steady roll rate that continues as long as the ailerons stay deflected.
Hybrid Surfaces: Flaperons and Elevons
Some aircraft combine the aileron’s job with other control functions into a single surface. Flaperons act as ailerons when they deflect in opposite directions for roll control, but can also lower together symmetrically to work like flaps, increasing lift at slow speeds. This is common on aircraft with simpler wing designs where there isn’t room for separate flaps and ailerons.
Elevons, found on delta-wing and flying-wing aircraft, merge aileron and elevator functions. When both move up or down together, they control pitch (nose up or down). When they move in opposite directions, they control roll. Fighter jets and some advanced drones rely heavily on elevons.
From Wing Warping to Modern Ailerons
The concept behind ailerons predates the surfaces themselves. The Wright brothers achieved roll control by physically warping their wingtips in opposite directions, twisting the flexible fabric-covered wings to create the same kind of lift imbalance that ailerons produce. This was one of their most important technical contributions to flight. Within a few years, rigid hinged ailerons replaced wing warping because they were simpler, more durable, and worked on stiffer wing structures. Every conventional airplane built since has used some version of the same principle.