(b)  
When an error signal is applied, the motor armature rotates in proportion to the magnitude and direction of the input signal and moves the projector jet accordingly. The jet directs more hydraulic pressure to one end of the piston than the other, causing it to move and open the corresponding output port, to complete hydraulic pressure through the servo. When the error signal is nulled, the motor armature and jet return to center. This equalizes the pressure on the piston and, with the aid of the centering springs, causes the piston to recenter and close both output ports.

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747-400
MAINTENANCE MANUAL

ENGAGE SOLENOID VALVE
MOUNT POINTS (2) ELECTRO-HYDRAULIC SERVOVALVE (EHSV)
OUTPUT 
CRANK  ARM SOLENOID 
VALVE 

FILTER POINT
MOUNT AUTOPILOT LVDT
OUTPUT LVDT
ELECTROHYDRAULIC
SERVOVALVE PRESSURE REGULATORRETURN PORT
ENGAGE SOLENOID VALVE
AUTOPILOT
ARM SOLENOID LVDT
VALVE
PRESSURE AUTOPILOTDETENT
PORT ACTUATORENGAGE PISTONPISTONSFILTER OUTPUT ARM
OUTPUTCRANK OUTPUT LVDT
Lateral Autopilot Servo - Component Details Figure 4
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747-400
MAINTENANCE MANUAL

OUTPUT TO SPOILERS 
VALVE ENGAGE SOLENOID CONNECTOR ELECTRICAL 
SERVOVALVE ELECTROHYDRAULIC 
MOUNTING POINTS (4)  VALVE ARM SOLENOID 

OUTPUT TO  AUTOPILOT 
AILERONS  LVDT 
ELECTROHYDRAULIC 
RETURN  SERVOVALVE  PRESSURE 
PORT  DETENT ENGAGE  REGULATOR 
ENGAGE SOLENOID  PISTONS
VALVE  AUTOPILOT 
ACTUATOR 
PISTON 
ARM SOLENOID 
VALVE  AUTOPILOT 
LVDT 

FILTERS CONTROL VALVE
RETURN
INPUT LEVERPRESSURE FILTERPORT PRESSURE PORT
(TO SPOILER) (TO AILERON)
MAIN ACTUATOR ASSEMBLY
OUTPUT SUMMING LEVER MAIN ACTUATOR LVDT
Central Lateral Control Package - Component Details Figure 5
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747-400 MAINTENANCE MANUAL
OUTPUT CRANK
OUTPUT LVDT
ENGAGE SOLENOID VALVE
ELECTRICAL CONNECTOR
AUTOPILOT HYDRAULIC
LVDT RETURN
FILTER
ELECTROHYDRAULIC ARM SOLENOID
SERVOVALVEHYDRAULIC VALVE
PRESSURE
ELECTROHYDRAULIC 
PRESSURE  SERVOVALVE  ELECTRICAL  ENGAGE SOLENOID 
FILTER  PORT  CONNECTOR  VALVE 

PC CR PRC
ARM SOLENOID
VALVE
P
C P
PRESSURE
RR
REGULATOR LVDT RD
AUTOPILOT
D
RELIEF VALVE
AUTOPILOT
DETENT POSITION ACTUATOR
(SHOW ENGAGED) PISTON
OUTPUT ARM
OUTPUT CRANK OUTPUT LVDT
Rollout Power Control Package - Component Details Figure 6
D20496
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747-400 MAINTENANCE MANUAL
 (c)  
The EHSV is installed with four bolts and sealed with a gasket plate. Electrical pins are mated when the EHSV is bolted into position.

 (d)  
　
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