LANDING GEAR AND
BRAKES
AIRPLANE
OPERATIONS
MANUAL
2-12-10
Page
8
Code
01
REVISION 40
AOM-145/1114
EMERGENCY/PARKING BRAKE SYSTEM
The emergency/parking brake system is used when parking the
airplane or when the normal braking system has failed. The
emergency/parking brake system is mechanically commanded and
hydraulically actuated. It is totally independent of the BCU, so it has
none of the normal braking system protections.
The emergency/parking brake is controlled through a handle located
on the left side of the control pedestal. This modulates the
Emergency/Parking Brake Valve. When the Emergency/Parking Brake
Valve is actuated, hydraulic pressure coming from a dedicated
accumulator is equally applied to the four main landing gear brakes.
Braking capacity is proportional to the handle displacement. A BRAKE
ON indicating light illuminates to indicate that pressure is being applied
to the wheel brakes. A locking device allows the handle to be held in
the actuated position, for parking purposes.
The accumulator is supplied by hydraulic system 2. A caution
message is displayed on the EICAS in case of accumulator hydraulic
low pressure. After the message is displayed, if no leakage exists, at
least one full emergency/parking brake application is available. If
overpressure occurs due to overheating, a thermal relief valve allows
hydraulic system communication with the return. A refilling connection
is provided to allow pressurization of the accumulator.
The accumulator allows 6 complete emergency actuation or at least 24
hours of parking brake actuation.
NOTE: To prevent transfer of hydraulic fluid from one system to the
other, normal braking should be applied and held while the
parking brake is fully applied or released.
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