A rudder assist mechanism for operable interconnection with a rudder control system of an aircraft rudder control surface, the rudder assist mechanism comprising: a control spring assembly; and a linkage assembly which operably connects the control spring assembly to the rudder control system, the linkage assembly including a null position which defines a dead zone of rudder control surface deflection within a selected range of right and left rudder control surface deflection angles whereby substantially no spring force of the control spring assembly is transferred to the rudder control system, and an actuator unit which is operably capable of moving the control spring assembly and the linkage assembly connected thereto between a thrust symmetrical mode condition and into a thrust asymmetrical mode condition in response to receiving a signal from an engine monitoring system of an abnormal engine thrust condition, characterised in that (i) in response to the linkage assembly being moved by the actuator unit into the TSM condition, the linkage assembly causes the control spring assembly to exert right and left spring forces to the rudder control system at rudder deflection angles in excess of a predetermined maximum deflection angle to thereby establish a rudder deflection stop whereby additional manual pilot input to the rudder control system results in substantially no additional rudder deflection beyond the predetermined maximum deflection angle, and wherein (ii) in response to the linkage assembly being moved by the actuator unit into the TAM condition, the linkage assembly prevents the right and left spring forces from being exerted by the control spring assembly to the rudder control system at rudder deflection angles in excess of the predetermined maximum deflection angle to thereby allow rudder deflection beyond the predetermined maximum deflection angle in response to additional manual pilot input to the rudder control system. a control spring assembly; and a linkage assembly which operably connects the control spring assembly to the rudder control system, the linkage assembly including a null position which defines a dead zone of rudder control surface deflection within a selected range of right and left rudder control surface deflection angles whereby substantially no spring force of the control spring assembly is transferred to the rudder control system, and (i) in response to the linkage assembly being moved by the actuator unit into the TSM condition, the linkage assembly causes the control spring assembly to exert right and left spring forces to the rudder control system at rudder deflection angles in excess of a predetermined maximum deflection angle to thereby establish a rudder deflection stop whereby additional manual pilot input to the rudder control system results in substantially no additional rudder deflection beyond the predetermined maximum deflection angle, and wherein (ii) in response to the linkage assembly being moved by the actuator unit into the TAM condition, the linkage assembly prevents the right and left spring forces from being exerted by the control spring assembly to the rudder control system at rudder deflection angles in excess of the predetermined maximum deflection angle to thereby allow rudder deflection beyond the predetermined maximum deflection angle in response to additional manual pilot input to the rudder control system.