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When the autobrake system disarms after landing, the Autobrake selector moves
to DISARM position. Rotating the Autobrakes selector to OFF removes power
from the autobrake system.
When the autobrake system disarms during takeoff, the Autobrake selector
remains in RTO position, but moves to OFF after takeoff.
Parking Brake
The parking brake can be set with the normal or alternate brake hydraulic system
pressurized. If the normal and alternate brake systems are not pressurized, parking
brake pressure is maintained by the brake accumulator. The brake accumulator is
pressurized by hydraulic system 4. Accumulator pressure is shown on the brake
accumlator pressure indicator.
Sufficient pressure is stored in the accumulator to set and hold the parking brake,
but the accumulator is not designed to stop the aircraft.
The parking brake is set by depressing both brake pedals fully, while
simultaneously pulling the Parking Brake lever up. This mechanically latches the
pedals in the depressed position and commands the parking brake valve to close.
December 01, 1999
747 Operations Manual
Copyright © The Boeing Company. See title page for details.
14.20.6 D6-30151-425
Landing Gear -
System Description
When the parking brake is set, the first hydraulic system pressurized may supply
a small amount of fluid to the brake lines. When brakes are released, that small
amount of fluid returns to system 4. Pressurizing system 4 before pressurizing the
other systems precludes the transfer of hydraulic fluid from system 1 or 2 into
system 4.
The parking brake is released by depressing the pedals until the Parking Brake
lever releases.
Brake Temperature Indication
Wheel brake temperatures display on the GEAR synoptic display. Numerical
values related to wheel brake temperature display inside each wheel/brake
symbol.
December 01, 1999
747 Operations Manual
Landing Gear -
System Description
Copyright © The Boeing Company. See title page for details.
D6-30151-425 14.20.7
Normal Brake System Diagram
METERING
ANTISKID
CONTROLLER
PRESS
ALT BRAKE
VALVE
NORMAL
VALVE
NORMAL
HYD
SYS 4
DISARM
OFF MAX
AUTO
1
2
3
AUTOBRAKES
RTO
4
SHUTTLE
VALVE
AUTOBRAKE
CONTROL
MODULE SHUTTLE
VALVE
LEFT
LEFT
BODY GEAR BODY GEAR
RIGHT
ANTISKID VALVES
ANTISKID VALVES ANTISKID VALVES
ANTISKID VALVES
RIGHT
WING GEAR WING GEAR
ISOLATION
VALVE
ACCUMULATOR
RETURN
METERING
PARKING
BRAKE
VALVE
PARK
PULL
BRAKE
P
0
PSI X 1000
BRAKE PRESS
4 HYD
3
2 1
December 01, 1999
747 Operations Manual
Copyright © The Boeing Company. See title page for details.
14.20.8 D6-30151-425
Landing Gear -
System Description
Alternate Brake System Diagram
ALTN
METERING
VALVE
RETURN
LEFT
WING GEAR
RIGHT
WING GEAR
LEFT RIGHT
BODY GEAR BODY GEAR
SOURCE
SELECT
VALVE RETURN
ALTN
METERING
VALVE
RETURN
HYD SYS 2
SOURCE
SELECT
VALVE
RETURN
HYD SYS 1
ANTISKID
VALVES
ALTN
ANTISKID
VALVES
ALTN
ANTISKID
VALVES
ALTN
ANTISKID
VALVES
ALTN
ANTISKID
CONTROLLER
December 01, 1999
747 Operations Manual
Landing Gear -
System Description
Copyright © The Boeing Company. See title page for details.
D6-30151-425 14.20.9
Brake Source Selection Diagram
ANTISKID
HYD SYS 2
ANTISKID
PRESSURE
OPERATED
SELECT VALVE
SOURCE
NORMAL
METERING
VALVES
NORMAL
VALVES
ALTERNATE
METERING
VALVES
ISOLATION
HYD SYS 4
PRESSURE
OPERATED
SELECT VALVE
SOURCE
HYD SYS 1
ACCUMULATOR
VALVE
BRAKES
SHUTTLE
VALVES
RETURN RETURN RETURN
VALVES
ALTERNATE
ACCUMULATOR
P
P
P
December 01, 1999
747 Operations Manual
Copyright © The Boeing Company. See title page for details.
14.20.10 D6-30151-425
Landing Gear -
System Description
Intentionally
Blank
April 1, 2000
747 Operations Manual
Landing Gear Chapter 14
EICAS Messages Section 30
Copyright © The Boeing Company. See title page for details.
D6-30151-425 14.30.1
Landing Gear EICAS Messages
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波音747-441操作手册2(125)
