32-53-00
ALL ú ú 01 Page 2 ú Jun 10/92
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400 MAINTENANCE MANUAL
BODY GEAR
RETURN LINE STEERING
PRESSURE ELECTRONIC CHECK
LINE CONTROL UNIT VALVE SOLENOID VALVE
SEE H CONNECTION TO ARMING SWITCH
SOLENOID LEFT
AND AIRCRAFT
VALVE BODY POWER SUPPLY
BODY GEAR
GEAR STEERING
SERVO VALVE CONTROL
CONNECTION TO MODULE
ELECTRONIC
CONTROL MODULESEE E SERVO
VALVE ACTUATOR LOCK SWITCHES
PRESSURE SWITCH CONNECTION TO PRESSURE INDICATION FILTER
MESSAGESTEERING PRESSURE
ACTUATORS SWITCH
INBD SEE F LEFT ACTUATOR EXTEND PORT
RIGHT ACTUATOR
D EXTEND PORT RETRACT PORT
FWD
LEFT INSTALLATION BODY GEAR STEERING CONTROL MODULE
GREASE FITTINGS UP
(RIGHT INSTALLATION E
GREASE FITTINGS DOWN)
A
SEE G
STEERING PRIMARY STEERING
ACTUATORS LOCK SWITCH
CYLINDER LOCK SWITCH
YOKE SPINDLE ASSEMBLY
CONNECTORASSEMBLY
A
LOWER
ALTERNATE TORSION LINK
LOCK SWITCH
TILT SENSOR
BRACKET
ELECTRONIC
CONNECTOR BODY
STEERINGFWD
GEAR FWD
ACTUATOR TRUCK
G
BODY GEAR STEERING ACTUATOR (LH SHOWN)
F
Body Gear Steering System - Component Location Figure 1 (Sheet 2)
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A 747-400 MAINTENANCE MANUAL
PLUNGER
ELECTRONIC CONTROL UNIT
Body Gear Steering System - Component Location
Figure 1 (Sheet 3)
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400
MAINTENANCE MANUAL
Body Gear Steering System Schematic BSCU Figure 2
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
U23301
A
747-400 MAINTENANCE MANUAL
B. The shaft of the transducer is sleeved to the shaft of the nose wheel steering pivot link drum located at the aft nose wheel well bulkhead. Any motion caused by the nose wheel steering cable is transmitted to the transducer through the cable drum shaft.
3. Electronic Control Unit (Fig. 1)_______________________
A. A command signal from the nose wheel is compared in the electronic control unit with position signals from the right and left trucks. Any deviation of either truck from the desired position produces an electrical error signal. This signal is amplified in the electrical control unit and then transmitted to right and left electrohydraulic servo valves where electrical signals are converted to proportional hydraulic fluid flows. The unit is contained in a metal box with built-in test switches and indicator on the top. An interlock in the control unit prevents application of reverse polarity electrical signal to the electrohydraulic valves when the trucks are being steered.
4. Control Module (Fig. 1 and Fig. 3)______________
A. The control module consists of pressure switch, solenoid valve, servo valve, filter element and mounting brackets with reinforcing angles installed in main wheel well. The control module has an amplifier and follow-up system which control the servo valve and hence the cylinder position. The servo valve is a jet type valve with the secondary spool capable of 10 gallons per minute flow.
B. A slide valve is included in the module for easy on and easy off pressure operation in obtaining the required flow of hydraulic fluid without going through the solenoid valve. The second stage of the servo valve has an open center position so that fluid returns from the cylinders at any time the current is removed from the servo valve. This is true at any time the nose wheel steering angle is reduced below the 20-degree position as a result of actuation of the arming switch.
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