3 0.2 6.0 2000
4 0.2 7.5 2400 MAX 0.2 11.0 3000 RTO 0.0 MAX** 3000
*No delay if the system is armed after touchdown. **Maximum braking applied. Actual deceleration depends on airplane weight and runway conditions. _________________________________________________________________________
E. A malfunction of the selector switch can be isolated using the CMC to test the autobrake system. The panel can be removed and replaced using a procedure in this section. The steps that follow the installation are a test of the switch operation. A test is also done on the switch as a part of the Brake Control System Adjustment/Test. No adjustments or repairs are done on the switch when it is installed in the airplane.
9. Autobrake Pressure Control Module (Fig. 7)
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A. The autobrake-pressure-control module is installed on the aft bulkhead of the right-wing-gear-wheel well. It is connected to a hydraulic system 4 pressure line and the normal brake system. The autobrake-pressure-control module contains these parts:
-pressure control valve
-solenoid shutoff valve
-two 750 psi pressure switches
-an inlet-pressure-fluid filter.
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A 747-400 MAINTENANCE MANUAL
SEE A
SYSTEM 4 RETURN LINE
SOLENOID VALVE PRESSURE SWITCH
VALVE SERVO CONTROL SYSTEM 4 PRESSURE
SOLENOID VALVE
BRAKE PRESSURE LINE FILTER
A Figure 7 Autobrake Pressure Control Module Location
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400
MAINTENANCE MANUAL
B. Hydraulic fluid at 3000 psi is supplied to the autobrake-pressure-control module from hydraulic system 4. Pressure is released from the module into the hydraulic system 4 return lines as necessary by the valves. This module supplies hydraulic pressure for the operation of all 16 wheel brakes when an automatic braking selection is made by the flight crew.
C. The solenoid shutoff valve is a two-stage, three-way solenoid operated valve. This valve opens to supply hydraulic fluid to the pressure control valve when the solenoid is energized by the brake control unit. The valve closes off the hydraulic supply and releases pressure in the module to the return line when the solenoid is not energized.
D. The pressure control valve is a two-stage-pressure-control-servo valve installed in the autobrake-pressure-control module downstream of the solenoid valve. This valve operates on signals from the brake control unit to control pressure supplied to the brakes.
E. The solenoid-valve-pressure switch is installed between the solenoid valve and the control valve and monitors the operation of the solenoid valve. When the switch is closed, pressure between the solenoid valve and the servo control valve is greater than 750 psi. When the switch is open the pressure is less than 750 psi. The switch signals the control unit when the solenoid valve malfunctions.
F. The control-valve-pressure switch monitors the output pressure of the autobrake-pressure-control module. This switch signals the brake control unit when the servo-pressure-control valve malfunctions. When pressure downstream of the servo-control valve is less than 750 psi the switch is open. When pressure downstream of the servo-control valve is greater than 750 psi the switch is closed.
G. For more data on the operation of the autobrake-pressure-control module refer to the applicable component maintenance manual.
H. This module may be removed and serviced in a shop or these components may be removed and replaced or serviced without removing the autobrake-pressure-control module from the airplane:
-
The solenoid components of the shutoff valve
-
The servo components of the control valve
-
The pressure switches
-
The filter.
10. Autobrake Shuttle Valve (Fig. 8)
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