What is Dutch roll and what causes it?

Dutch roll is a lateral-directional oscillatory mode involving combined yawing and rolling motion, named for its resemblance to ice skating. It occurs because an aircraft with strong directional stability but weak lateral (roll) stability tends to oscillate when disturbed. The aircraft yaws, creating sideslip, which generates a rolling moment through dihedral effect, leading to a coupled oscillation. Dutch roll is uncomfortable for passengers and can be problematic if poorly damped. Yaw dampers (automatic rudder inputs) are used on most transport aircraft to suppress Dutch roll.