(2)
Solenoid Valves
(a) Each solenoid valve (SV1 and SV2) is an electrically operated open-close valve which completes hydraulic pressure through the servo when autopilot arm and engage logic circuits are completed. The valve is installed with 4 bolts and sealed with a gasket plate. Electrical pins are mated when the solenoid valve is bolted in position.
YAW DAMPER
SUMMING LEVER
RUDDER POWER
YAW DAMPER CONTROL ACTUATORS
SERVOS
SECONDARY PRIMARY CONTROL
CONTROL PATH
PATH
RATIO CHANGER
MECHANISM
A/P ROLLOUT CABLES TO
GUIDANCE SERVOS (3) RUDDER PEDALS
SEE A RUDDER FEEL, CENTERING
AND TRIM MECHANISM
A/P ROLLOUT GUIDANCE SERVOS A
ARGS Location and Linkage Figure 4
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HYDRAULIC SOLENOID VALVE
RETURN NO. 1
HYDRAULIC PORT ELECTROHYDRAULIC
PRESSURE SERVO VALVE
FILTER SCREEN PORT AND VALVE NO. 2 SOLENOID
OUTPUT
(SURFACE
POSITION) ELCTRICAL
LVDT CONNECTOR
OUTPUT CRANK
TO PCA
ACTUATOR (SERVO) POSITION LVDT
PRESSURE REGULATOR AND REFIEF VALVE
ELECTROHYDRAULIC SERVO VALVE
SOLENOID SOLENOID
VALVE NO. 1 VALVE NO. 2
FILTER SCREEN ELECTRICALHYDRAULIC CONNECTOR
PRESSURE
PORT
PCR RC2C1P PCR
PRESSURE REGULATOR P
AND REFIEF VALVE HYDRAULIC PRESSURE
R C
RETURN PORT RESTRICTOR
ACTUATOR (SERVO) POSITION LVDT
ACTUATOR PISTON
DETENT ROLLER CENTERING SPRING
PISTON ACTUATOR
DISENGAGE
PISTON
SPRING
DISENGAGE OUTPUT (SURFACE) SPRING
INTERNAL
POSITION LVDT OUTPUT CRANK
CRANK TO PCA
Autopilot Servo Components (ALCS and ARGS)
Figure 5
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(b) Solenoid valve number 1 (SV1) opens when the autopilot is armed. It ports hydraulic pressure to solenoid valve number 2 (SV2) and the electrohydraulic servo valve (EHSV). Solenoid valve number 2 opens when the autopilot is engaged, and ports hydraulic pressure to the detent pistons. The detent pistons clamp the output linkage crank and transmit actuator piston position to the output linkage.
(3)
Electrohydraulic Servovalve (EHSV)
(a)
The EHSV is controlled by the output command signal from the FCC. The EHSV contains a sealed torque motor, a feedback spring, a projector jet and a piston. Hydrualic pressure through the valve can be applied to either of two output ports. When no command signal is applied to the torque motor, a small amount of hydraulic fluid flows through a flexpipe attached to the torque motor armature and out of the projector jet. From the jet, equal pressure is applied to opposite ends of the piston holding it at center.
(b)
When a command 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 command signal is nulled, the motor armature and jet return to center. This equalizes the pressure on the piston and, with the aid of the feedback spring, causes the piston to recenter and close both output ports.
(c)
In response to the FCC output command, the EHSV ports hydraulic pressure to the right or left side of the actuator piston. Feedback from the actuator piston LVDT (linear variable differential transducer) nulls the command signal at the FCC and piston movement stops.
(d)
The EHSV is installed with four bolts and sealed with a gasket plate. Electrical pins are mated when the EHSV is bolted in position.
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