Aircraft rely on various control surfaces to maneuver through the air. Among these, ailerons play a central role in changing an aircraft’s lateral orientation, which is fundamental for initiating turns.
Ailerons: The Basics
Ailerons are hinged control surfaces found on the trailing edge of an aircraft’s wings, typically located near the wingtips. Their primary function is to control the aircraft’s roll, which is its movement around the longitudinal axis that extends from the nose to the tail. These surfaces always work in interconnected pairs, ensuring coordinated movement. This differential movement is what enables the aircraft to tilt or “bank” from side to side.
How Ailerons Initiate a Turn
When a pilot intends to turn an aircraft, the ailerons move in opposite directions to create a rolling motion. To initiate a turn to the right, the aileron on the right wing moves upward, while the aileron on the left wing moves downward. The upward deflection of an aileron disrupts the smooth airflow over that wing, reducing its camber and consequently decreasing the lift it generates. Conversely, the downward deflection of the opposing aileron increases the wing’s camber and its angle of attack, leading to an increase in lift on that wing.
This creates an imbalance in lift between the two wings; one wing generates more lift, and the other generates less. The wing with increased lift rises, while the wing with decreased lift drops. This differential lift produces a rolling moment around the aircraft’s longitudinal axis, causing the aircraft to bank in the desired direction of the turn.
Understanding Adverse Yaw
A side effect of aileron operation is a phenomenon known as adverse yaw, where the aircraft’s nose momentarily yaws in the opposite direction of the desired roll. This occurs because the aileron that deflects downward to increase lift also creates more induced drag on that wing. The increased drag on the rising wing pulls that wing back, causing the aircraft’s nose to swing away from the direction of the turn.
Aircraft designers mitigate adverse yaw through various methods. One common design involves “differential ailerons,” where the upward-moving aileron deflects through a greater angle than the downward-moving one. This increases the drag on the wing with the upward-deflected aileron, helping to balance the drag created by the downward-deflected aileron and reducing the adverse yaw effect. Pilots also manage adverse yaw by applying coordinated rudder input in the direction of the turn, which generates a side force to align the aircraft’s nose.