Ailerons and spoilers are two different flight-control surfaces that influence an airplane's roll, but they work in contrasting ways. Ailerons are hinged panels near each wingtip that move up and down: when one aileron goes down lift on that side rises, and when the opposite aileron goes up lift there falls, so the airplane rolls toward the wing with reduced lift.
Spoilers are panels mounted on the top of each wing that reduce lift by disrupting the airflow; when raised, they ‘spoil’ the lift on that side and let the wing drop. Spoilers can therefore assist ailerons or replace them entirely. When used alone for roll control they are called spoilerons, positioned on the outer wing to create the same lift-differential effect. Unlike ailerons, spoilerons generate only small changes in roll rate between low and high speeds, giving pilots more a consistent response across the speed range.
Expert behind this article
Jim Goodrich
Jim Goodrich is a pilot, aviation expert and founder of Tsunami Air.
What is the difference between ailerons and spoilers?
Ailerons are hinged panels at the trailing edge of each wingtip and they move up and down in opposite directions to create differential lift that banks the aircraft. Spoilers are flat plates on the upper wing surface that, when raised, spoil lift and add drag.
Spoilers can replace or augment ailerons for roll control. When the pilot commands a roll, spoilers rise on the down-going wing only. Lift on that side suddenly drops, so the aircraft banks. Because spoilers simultaneously increase drag on the down-going wing, they also generate proverse yaw that reduces the need for rudder coordination and avoids the adverse yaw normally created by ailerons.
Large or fast aircraft often combine both devices: ailerons handle gentle low-speed rolls, while spoilers provide extra authority at high speed where outboard ailerons are locked out to prevent control reversal. Spoilerons - spoilers used asymmetrically - maintain nearly the same roll rate at low and high speeds, whereas pure ailerons lose effectiveness as airspeed drops.
What is the difference between ailerons and elevons?
An aileron is a dedicated surface that creates a rolling moment by moving one wing up and the opposite wing down. An elevon is the combination of the elevator and the aileron into a single control surface. Two elevons are placed at the trailing edge of each wing. Inputs of the two controls are mixed either mechanically or electronically to provide the appropriate position for each elevon. When the stick is moved sideways, the elevons deflect differentially like ailerons, and when the stick is moved fore and aft both elevons move together like an elevator.
Elevons combine the functions of the elevator and the aileron in one panel, so a tailless aircraft can be controlled as though the pilot still has separate aileron and elevator surfaces at their disposal. The term elevon is not relevant to the horizontal control surface mounted at the tail of a conventional aircraft design that has a wing and a horizontal tail. That separate surface is typically called a stabilator when it serves only pitch control.
Can ailerons be used as elevators?Ailerons are not designed to control pitch and thus cannot be used as elevators. A special surface called a taileron can take over that job. Because tailerons combine functions of elevators and ailerons, the same panels that roll the aircraft can also tilt the nose up or down.
On a conventional airplane the elevators are the primary control surfaces used to control pitch. These hinged panels are located on the horizontal stabilizer at the tail. When they move up the nose rises, and when they move down the nose drops. Ailerons are situated on the outer wing: the right aileron moves up while the left aileron moves down to bank the aircraft. Separating these jobs keeps flight simple and predictable.
When designers want extra agility they fit tailerons that work as both roll and pitch controls. Thus, while ordinary ailerons cannot replace elevators, a taileron can.
