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(1)  Engaging the autopilot actuates a solenoid to open the autopilot shutoff valve. The shutoff valve directs hydraulic pressure to the autopilot engage mechanism and the autopilot control valve. Actuating the engage mechanism holds the main control valve closed by locking the manual input crank. The engage mechanism is spring-loaded to allow manual override of the autopilot system. A control wheel input will allow the input crank to override the engage mechanism spring pressure. Hydraulic pressure at the autopilot control valve, displaces the spring-loaded control valve slide and applies pressure to the transfer valve. The transfer valve slide is displaced by position signals from the roll channel of the autopilot. Hydraulic pressure is thus directed through the control valve to extend or retract the main actuator piston. When the transfer valve slide moves in the extended direction, the retract port is opened to return. As the main actuator moves, a balancing signal is generated by a linear transducer which assists in nulling the transfer valve electrically. Extension of the main actuator piston displaces hydraulic fluid from the retract side of the piston to return. Disengaging the autopilot de-energizes the solenoid and closes the shutoff valve. Hydraulic bleed at the transfer valve depressurizes the autopilot system and allows the control valve to close. The control valve prevents loss of pressure through the transfer valve when the power control unit is operating with the autopilot disengaged.
12. Operation
A.  The ailerons may be actuated either hydraulically or mechanically. For normal operation, hydraulic pressure from both systems A and B is utilized (Fig. 9). Motion is initiated by the aileron control wheels and aileron trim control wheel (Ref Fig. 2). Rotation of either aileron control wheel initiates motion in the aileron control cables which connect the control wheel drum to the aileron control quadrant. The cable motion is transferred from this quadrant through control linkage to the power control units. Motion of the main control valves in the power control units delivers hydraulic power to the actuator pistons which rotate cranks on the shaft connected to the bus drums. Rotation of the bus drums is 40 degrees in each direction from neutral, this is transferred through the bus system cables and aileron bus quadrants to rotate the ailerons 20 degrees in each direction from neutral position. Power control unit movement also provides spoiler system input through the aileron spring cartridge. Movement of the ailerons actuates the balance tabs. Hydraulic system A and B pressures to the aileron power control units are controlled by the flight controls shutoff valves in the flight controls hydraulic modular packages. A shutoff valve switch for each system is located on the overhead panel. Each hydraulic modular package is equipped with a low pressure warning switch which controls an amber light for each hydraulic system on the overhead panel. In the event of failure of either hydraulic system A or B, normal powered operation of the ailerons will be retained. In the event of failure of both hydraulic systems A and B, manual operation wil1 take place. During manual operation, the aileron trim knob will not provide aileron trim.
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B.  The aileron trim control knob on the control stand is connected by aileron trim cables to the trim gearbox. Rotation of the knob alters the position of the centering spring mechanism through the trim gearbox. This provides an input to the aileron control linkage which changes aileron neutral and thus providing aileron trim. The available aileron trim provides 15 degrees aileron travel in both directions from neutral. The centering spring mechanism also provides artificial feel. The artificial feel force increases as the control wheel is rotated to obtain maximum aileron deflection.
C.  If trim is adjusted with both aileron power control units depressurized, the drag of the unpowered aileron system will allow the system to remain out of center. This will force the trim and centering mechanism cam follower out of the cam detent. Then, when hydraulic power is applied, the control wheels and ailerons will rapidly move to the newly trimmed position.
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AILERON AND AILERON TRIM CONTROL SYSTEM - TROUBLE SHOOTING
1. General
A.  Forces at the control wheels are generated by two areas in the aileron control system during operation with hydraulic power on.
(1)  
Left Side - From the control wheels, through the left body cables AA and AB and the centering spring and trim mechanism, to the two power control unit main control valves. In a control system within rigging tolerance, all control wheel forces are generated by the "left side."
　
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