In swept wing aircraft, what initiates a Dutch roll?

In swept wing aircraft, a Dutch roll is initiated by an asymmetrical lift due to yaw. This maneuver combines both rolling and yawing motions that result from the aircraft's aerodynamic characteristics, particularly in the presence of swept wings. When a swept wing aircraft experiences a yawing moment, one wing generates more lift than the other due to a change in angle of attack, leading to an imbalance. This causes the aircraft to roll towards the direction of the yaw.

As the aircraft rolls, the wing experiencing the greater angle of attack (and thus more lift) will also start to climb, creating a scenario where one wing rises and the other descends. The interaction between the lateral and directional stability characteristics of the aircraft, compounded by the effects of swept wings, further amplifies this motion, creating a oscillating cycle characteristic of a Dutch roll.

This dynamic behavior is intrinsic to swept wing designs, which are prone to yaw-induced rolling moments more so than straight wing designs due to their aerodynamic design.