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 ALL  ú ú 01 Page 5 ú Oct 18/01
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400
MAINTENANCE MANUAL

 A. Hydraulic Control Module
 (1)  
The hydraulic control module is located at the Pilots' Overhead Panel, P5. The module provides control of all four hydraulic systems and system fault and status indications.

 (2)  
The push-on/push-off type switch/lights at the bottom of the module are used to turn on and off the engine-driven pumps (EDPs). The ON light at the top half of each pushbutton illuminates white when pushed. The PRESS light at the bottom half of each pushbutton illuminates amber to indicate low EDP output pressure.

 (3)  
The demand pump control switches are above the EDP control switches. Air-driven pumps (ADPs) are the demand pumps for systems No. 1 and No. 4. AC motor-driven pumps are the demand pumps for systems 2 and

 3. When the switch is set to OFF, the demand pump is off. When the switch is set to ON, the demand pump runs continuously. When the switch is set to AUTO, the demand pump operates whenever the system pressure is reduced due to system demand or if fuel is shut off to the engine. The PRESS light above each demand pump control switch illuminates amber to indicate low demand pump output pressure.

 (4)  
The SYS FAULT indicators are at the top of the hydraulic control module. These lights illuminate amber when any of the following conditions is detected:

 (a)  
System pressure is low

 (b)  
System temperature is high

 (c)  
Hydraulic reservoir quantity is low

 B. Flight Control Hydraulic Power Module
 (1)  
The flight control hydraulic power module is located at the Pilots' Overhead Maintenance Panel, P461. The shutoff switches operate shutoff valves in shutting off parts of the flight control system for leak isolation or maintenance activity, when the system cannot be shut off completely.

 (2)  
The WING shutoff switches control pressure to all flight control components in the wings, including actuators and servos for ailerons and spoilers.

 (3)  
The TAIL shutoff switches control pressure to all flight control components in the tail, including feel computers, rudder ratio changers, actuators and servos for elevators and rudders.

 (4)  
The VALVE CLOSED light below each shutoff switch illuminates amber when the selected shutoff valve is closed and hydraulic pressure to the selected areas has been isolated.

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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400
MAINTENANCE MANUAL

 C. Stabilizer Trim Cutout Switches
 (1)  
Two stabilizer trim cutout switches (No. 2 and No. 3) are located on Pilots' Control Stand. These cutout switches operate cutout valves, which are part of the stabilizer trim control modules, to isolate hydraulic power to stabilizer trim components in the tail. This enables trouble shooting and ground maintenance activity on the stabilizer trim drive hydraulic motors without removing hydraulic system power.

 (2)  
The switches are guarded to the ON position; placing the switches in CUTOUT position closes the cutout valves.

 5. Flight Deck Flight Controls (Fig. 4)
___________________________
 A. Primary Flight Control Inputs
 (1)  
Primary flight control inputs are made using the control column, control wheels, rudder pedals, and control surfaces trim switches on the Aft Electronics Control Panel, P8.

 (2)  
The captain's and first officer's control column and control wheel provide the manual control cable input for pitch and roll control respectively. The captain's and first officer's rudder pedals provide the manual cable input for yaw control.

 (3)  
Each flight control computer of the autopilot system provides control input for pitch, roll, and yaw control through dedicated servos. The yaw damper system also provides control input for yaw control.

 (4)  
Aileron and rudder trim switches provide arm and control signals to trim motors for trimming of the ailerons and rudders.

 B. Secondary Flight Control Inputs
 (1)  
Secondary flight control are made using stabilizer trim switches (thumb operated) on each control wheel, alternate electric trim switches, speed brake control lever, and flap control lever on the Pilots' Control Stand.
　
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