Actuator,
SB 45-55-6 for the lear 45 will "install straps of the trailing edge" of the rudder and rudder trim tab assembly. The "reason" was that "Learjet has received reports of yaw fluctuations (dutch roll) during flight. Accomplishment of this SB will reduce the dutch roll tendency of the aircraft during flight"
From the AFM; "aircraft not modified must have yaw damper engaged for all flight operations except take off and landing. On modified aircraft the yaw damper use is not required"
so the mod somehow negates the requirement for the use of the yaw damper.
Perhaps Cessna did the same?
Hawk