Nudge the nose of a B-47 bomber sideways, and it wallows, again and again. Why won’t it settle? As the nose swings, the advancing swept wing faces the airflow more squarely; it gains lift, and the plane rolls. The fin pulls the nose back, but with weak damping, too far — swing and roll keep trading, out of step: a Dutch roll. Boeing’s fix was a yaw damper: a sensor feels the swing begin, and a servo moves the rudder against it, automatically. Now the same nudge fades: the rudder soaks up each swing as it starts — and swept-wing jets use yaw damping to this day.
Sources: FAA Pilot’s Handbook of Aeronautical Knowledge (FAA-H-8083-25C) and Airplane Flying Handbook (FAA-H-8083-3C); NACA TN 4310 (Rhyne, 1958); NASA SP-468 (Loftin, Quest for Performance); McRuer & Graham, ‘A Flight Control Century’ (AIAA JGCD 2004); W. J. Boyne, ‘The Long Reach of the Stratojet’, Air Force Magazine (1997). The 4-second cycle was measured with the yaw damper off. Illustrative 3D reconstruction of a B-47-type bomber, no markings; oscillation amplitudes (the same nudge before and after) and the drawn rudder deflection (×1.6) are exaggerated, and the explanation shots run in slow motion; airflow, arrows, wingtip trails and the schematic yaw-damper hardware are drawn, not simulated.
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This is what killed SHELL77
How does it affect a plane trying to land with a missing rudder?
The recent Fly Dubia flight lost the rudder when the copilot tried to crash the plane. The rudder came off in a dive. The passengers and deadheading pilots retook the cockpit and recovered the aircraft, but then had to deal with a missing rudder.
This happens due to high lateral stability and low directional stability of the plane