The position of the stabilizer is shown on the integrated position indicator located on the left side of the pilot’s instrument panel. When the stabilizer is in the “clean” configuration, the STAB window of the indicator shows the word CLEAN. When the stabilizer is in the “dirty” configuration, the window shows a picture of a stabilizer. The stabilizer actuator (fig. 9-7) is a tandem-type actuator powered by both flight and combined system pressures. It contains a power valve shuttle, two tandem-mounted power pistons, a servo ram, an electrohydraulic servo valve, a lockout actuator, and parallel and series mode solenoid valves. The actuator can operate in any of three modes-manual, series, or parallel. Refer to figure 9-7 to help you understand the three modes of operation, as described in the following paragraphs. MANUAL MODE.—In this mode, the pilot input alone controls the power valve. Inputs are transmitted through linkage to the mechanical input lever. The auxiliary lever is linked in neutral by the servo ram centering springs, causing the mechanical input lever to rotate about its pivot point, moving the power shuttle valve. As the valve shuttle is displaced from neutral, a valve error is established, and pressure is ported to the actuating pistons. The pressure moves the pistons and the attached stabilizer in proportion to the input. A mechanical feedback is transmitted through the differentiating lever, the load-relief bungee, and the mechanical input lever back to the power valve shuttle, causing it to return to the neutral position. For a constant velocity pilot input, a small constant valve error is established, and the stabilizer moves at a constant speed. When the pilot input stops, the power shuttle valve is returned to neutral, and the stabilizer stops until a new input is introduced. SERIES MODE.—In this mode, input signals from the automatic flight control system (AFCS) may be used independently or combined with manual input to control stabilizer movement. 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. A linear transduce, mounted on the servo ram center line, provides electrical feedback signals to the AFCS. 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. PARALLEL MODE.—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. The transducer mounted on the servo ram provides an electrical signal feedback to the AFCS. There is no mechanical feedback, since the mechanical input is locked. Additional electrical signal feedback is provided by a transducer, which is mechanically linked to the stabilizer actuating arm. In the parallel mode, the control stick follows the motion of the stabilizer. Should the pilot desire to override the AFCS, he/she can overpower the lockout actuator with a stick force of 24 pounds. Stop bolts are attached to the control stick pedal to limit fore-and-aft stick movement. The eddy current damper dampens out any rapid fore-and-aft stick movement. All joints between the pushrods and bell cranks or idlers contain self-aligning bearings to compensate for any misalignment during operation and airframe deflections in flight that might cause binding. Artificial feel is provided by the artificial-feel bungee. The bungee consists of two springs, which have different spring constants. The stick force caused by the bungee is proportional to stick displacement. At near neutral, the bungee provides a high stick force that decreases a short distance from neutral and gradually increases with the amount of stick displacement. The electric trim actuator is mechanically linked to the artificial-feel bungee, and varies the neutral position of the bungee to provide longitudinal trim of the aircraft. The actuator consists of one high-speed and one low-speed motor, a gearbox, a brake, a ball detent clutch, and a 9-8