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indication when the alternate extension system is used. During alternate
extension, the EICAS message GEAR DOOR is displayed because all the
hydraulically powered gear doors remain open.
Following an alternate extension, the landing gear can be retracted by the normal
system, if it is operating. Select DN then UP to retract the landing gear using the
normal system.
Nose Wheel Steering
The airplane is equipped with nose wheel steering powered by the center hydraulic
system.
Primary steering control is provided by a nose wheel steering tiller for each pilot.
Limited steering control is available through the rudder pedals. The tillers can turn
the nose wheels up to 70 degrees in either direction. A pointer on the tiller
assembly shows tiller position relative to the neutral setting. The rudder pedals can
be used to turn the nose wheels up to 7 degrees in either direction. Tiller inputs
override rudder pedal inputs.
787 Flight Crew Operations Manual
Landing Gear -
System Description
Boeing Proprietary 14.20.3
Brake System
Each main gear wheel has a multiple disc carbon brake. The nose wheels have no
brakes. The brake system includes:
Electric Brake System
The brake system is powered by four electric brake power supply units. The brake
pedals provide independent control of the left and right brakes.
Four Electric Brake Actuators (EBAs) are provided on each main landling gear
wheel brake to control the application of braking force to the carbon disc. The
EBA’s are controller by an Electric Brake Actuator Controller (EBAC). There are
four EBACs that control all eight main wheel brakes, each EBAC controlling the
brake force of a fore-aft wheel pair.
Antiskid Protection
Antiskid protection is provided on an individual main gear wheel basis. When a
wheel speed sensor detects a skid, the braking force is reduced until skidding
stops.
Touchdown and hydroplaning protection is provided using airplane inertial
ground speed. Locked wheel protection is provided using a comparison with other
wheel speeds.
The EICAS advisory message ANTISKID is displayed if an antiskid fault
affecting the brake system is detected, or if parking brake force is applied with the
parking brake lever released, or if the system is completely inoperative.
Autobrake System
The autobrake system provides automatic braking at preselected deceleration rates
for landing and full pressure for rejected takeoff. Antiskid system protection is
provided during autobrake operation.
The EICAS advisory message AUTOBRAKE is displayed if the autobrake system
is disarmed or inoperative.
The EICAS advisory message AUTOBRAKE is displayed if the autobrake system
is disarmed or inoperative, the autobrake selector is OFF but the system is armed,
or an RTO is initiated above 85 knots but autobraking has not been applied.
• electric brake system
• antiskid protection
• autobrake system
• parking brake.
787 Flight Crew Operations Manual
Landing Gear -
System Description
14.20.4 Boeing Proprietary
Rejected Takeoff
Selecting RTO (rejected takeoff) prior to takeoff arms the autobrake system. The
RTO mode can be selected only on the ground. The RTO autobrake setting
commands maximum braking pressure if:
• the airplane is on the ground
• groundspeed is above 85 knots, and
• both thrust levers are retarded to idle.
Maximum braking is obtained in this mode. If an RTO is initiated below 85 knots,
the RTO autobrake function does not operate.
Taxi Brake Release
During each taxi brake application, the antiskid system releases the brakes of one
axle pair of each main landing gear (if wheel speeds are less than 45 knots). The
system sequences through the axle pairs at each brake application, thereby
reducing the number of brake applications by each brake. This extends service life
and reduces brake sensitivity during taxi.
All active brakes are applied for a heavy brake application, landing rollout, RTO,
or when setting the parking brake.
Landing
Five levels of deceleration can be selected for landing. However, on dry runways,
the maximum autobrake deceleration rate in the landing mode is less than that
produced by full pedal braking.
After landing, autobrake application begins when:
• both thrust levers are retarded to idle, and
• the wheels have spun up.
Autobrake application occurs slightly after main gear touchdown. If MAX AUTO
is selected, deceleration is limited to the AUTOBRAKE 4 level until pitch angle
is less than one degree, then deceleration is increased to the MAX AUTO level.
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787机组操作手册Flight Crew Operations Manual 3(108)
