Ailerons are fundamental components of an aircraft’s flight control system, serving as hinged surfaces located on the trailing edge of each wing. They are among the primary controls that enable an aircraft to maneuver through the air, facilitating directional changes and maintaining stability during flight.
Controlling Aircraft Roll
Ailerons primarily govern the aircraft’s roll, which is the rotational movement around its longitudinal axis, extending from the nose to the tail. This motion is also commonly referred to as banking. This banking action is essential for initiating and executing turns in the air.
When a pilot inputs a command to roll the aircraft, the ailerons work in opposition to create an imbalance in lift. One wing experiences an increase in lift while the other experiences a decrease. This differential lift generates a rotational force, causing the aircraft to tilt.
The degree of this tilt directly influences the aircraft’s turning radius and direction. Without the ability to control roll, an aircraft would be limited to straight-line flight. The precise control over banking provided by ailerons allows for dynamic and controlled changes in the aircraft’s flight path.
How Ailerons Work
Ailerons are typically positioned on the outer portion of the wing’s trailing edge. They operate in interconnected pairs: when one aileron moves upward, the corresponding aileron on the opposite wing simultaneously moves downward. This synchronized, opposing movement is crucial for their function.
When an aileron deflects downward, it effectively increases the curvature, or camber, of that section of the wing, as well as its angle of attack relative to the airflow. This alteration in shape and angle causes the wing to generate more lift. Conversely, when an aileron deflects upward, it reduces the camber and angle of attack, resulting in a decrease in lift on that wing.
This creation of unequal lift between the two wings produces a net rolling moment. The wing with increased lift rises, while the wing with decreased lift descends, causing the entire aircraft to rotate around its longitudinal axis.
Ailerons and Coordinated Turns
While ailerons effectively control an aircraft’s roll, their sole use can introduce “adverse yaw.” This effect causes the aircraft’s nose to momentarily swing in the direction opposite to the intended turn. Adverse yaw occurs because the wing generating increased lift from the downward-deflected aileron also experiences a corresponding increase in aerodynamic drag.
This additional drag on one wing pulls it slightly backward, causing the aircraft’s nose to yaw away from the desired turn direction. To counteract adverse yaw and achieve a smooth, “coordinated” turn, pilots must apply the rudder in conjunction with the ailerons. The rudder, located on the vertical tail fin, helps align the aircraft’s nose with its flight path, ensuring a balanced turn.
Without proper coordination between aileron and rudder inputs, an aircraft can enter an “uncoordinated” turn, manifesting as either a “slipping” or “skidding” motion. A slipping turn occurs when the aircraft banks too steeply for its rate of turn, causing it to slide sideways toward the inside of the turn. Conversely, a skidding turn happens when the aircraft’s turn rate is too high for its bank angle, causing it to slide sideways away from the center of the turn.
Pilots monitor a “slip indicator,” often referred to as “the ball,” on their instrument panel to ensure coordinated flight. Keeping the ball centered indicates that the forces acting on the aircraft are balanced, providing an efficient turn. The coordinated use of ailerons and rudder is fundamental for precise and stable flight control.