The series mode solenoid valve is energized, porting flight system hydraulic pressure to the electrohydraulic servo valve. Input signals from the AFCS amplifier are applied to the coils of a torque motor in the servo valve, regulating flow from the valve to the servo ram. The servo ram is connected to the auxiliary lever. Movement of the lever moves the mechanical input lever floating-pivot point. This movement causes mechanical input lever rotation about the manual input point and moves the power shuttle valve, causing a valve error.
Mechanical feedback is provided by the differentiating lever, as in the manual mode.
When operating in the series mode, control surface displacement is not reflected at the control stick. In this mode, stabilizer movement is controlled by input signals from the AFCS alone. Both series and parallel mode solenoid valves are energized. Flight system pressure is ported to the electrohydraulic servo valve and the mechanical input lockout piston. Fluid pressure stabilizes the lockout piston and holds the mechanical input lever.