LANDING GEAR AND
BRAKES
AIRPLANE
OPERATIONS
MANUAL
2-12-10
Page
2
Code
01
REVISION 40
AOM-145/1114
NORMAL BRAKE SYSTEM
Normal brake system is operated by rudder pedal inputs. The brakes
are powered by two independent hydraulic systems. It is controlled
and monitored by the Brake Control Unit (BCU). The BCU receives
signals from the pedal position transducers and commands the four
Brake Control Valves (BCV) to modulate required pressure to the
wheel brakes. BCVs 1 and 4 control the hydraulic pressure from
system 1 to the outboard wheels. BCVs 2 and 3 control the hydraulic
pressure from system 2 to the inboard wheels.
The hydraulic system 1 and the ESS DC BUS 1 supply the main brake
system for the control of the outboard wheels. The hydraulic system 2
and the ESS DC BUS 2 supply the main brake system for the control
of the inboard wheels.
Pressure and wheel speed transducers send signals to the BCU so
that it can monitor brake performance and send the appropriate
signals to the crew alerting system and other systems. The BCU also
receives signals from the landing gear position and condition,
air/ground situation, and hydraulic system status. The system displays
messages on the EICAS to indicate a failure in one pair of brakes or a
failure in a single wheel brake (brake degraded performance). In the
event of brake system failure, the BCU will shut down the affected
hydraulic system through the shutoff valves. The shutoff valves are
energized whenever the landing gear is extended and de-energized
after landing gear retraction.
Protective functions controlled by the normal braking system include
anti-skid protection, locked wheel protection, and touch-down
protection.
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