Normally, the pilot and CPG flight controls are mechanically linked. The mechanical linkages are protected by shear pins and mis-track sensors to prevent a control jam or severance from affecting both sets of flight controls. If the flight controls are decoupled by the shear pin, or a mis-track is otherwise sensed, the Back-Up Control System is automatically activated. The BUCS is a single-channel, four-axis, non-redundant electric fly-by-wire (FBW) system. The FBW system is designed to replicate the feel of the hydromechanical controls but does not replicate SCAS functionality. BUCS can only be active for the pilot or the CPG station. Either the pilot or the CPG can transfer BUCS control to their station if necessary, depending on the nature and location of the jam or severance within the flight controls.
