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activate the system and the ON annunciator will illuminate. When nose
steering has been activated, the system can be disengaged by depressing
either the pilot’s or copilot’s MSW or by depressing the NOSE
STEER switch a second time. A disconnect tone will sound.
The following CAS illuminations are specific to the nose steering
system:
CAS Color Description
NWS FAIL Amber The nose wheel steering system has failed.
NWS FAULT White A fault is detected in the nose wheel steering
system. The system will operate in degraded
mode.
Pilot’s Manual
PM-126A 3-17
WHEEL BRAKE CONTROL /ANTI-SKID SYSTEM
The wheel brake control /anti-skid system is a brake-by-wire system
that electronically controls hydraulic brake pressure. The system is designed
to maximize braking efficiency and reduce tire wear by modulating
brake pressure to each of the four wheels at the time of an
impending skid. Major components of the system include: a brake control
unit, four wheel-speed transducers, two hydraulic shutoff valves,
four two-channel pedal transducers, five hydraulic fuses, a pressure
switch, an emergency/parking brake valve assembly, an emergency/
parking brake accumulator, four brake control valves, four brake pressure
transducers, four brake shuttle valves, a source shuttle valve, and
four brake assemblies.
The brake control unit is divided into two independent channels for the
inboard and outboard wheels. Each channel applies brake pressure
commands to the respective left or right brake control valves. The brake
control valves regulate actual brake pressure to each corresponding
brake. Brake pressure commands from the brake control unit are determined
from the combination of pilot/copilot pedal commands, and
anti-skid, locked-wheel protection and touchdown protection functions.
Hydraulic fuses, located in the main gear wheel wells, will close
to prevent pressure loss if fluid flow exceeds normal brake actuation
rate.
Power is supplied by 28-vdc provided through the 3-amp INBD
BRAKES circuit breaker located on the pilot’s circuit breaker panel
(GEAR/HYDRAULICS group) and the 3-amp OUTBD BRAKES circuit
breaker located on the copilot’s circuit breaker panel (GEAR/HYD
group). The wheel brake control /anti-skid system is active whenever
power is present on the right essential bus and the emergency battery
bus, the circuit breakers are engaged, and hydraulic pressure is present
at the source shuttle valve.
TOUCHDOWN PROTECTION
Braking is enabled after touchdown when wheel spin-up is achieved
(≥50 knots) or after the main gear weight-on-wheels switches are in the
ground mode and time-out has elapsed. This prevents landing with the
brakes engaged and allows spin-up time for traction to be established.
The time-out function is a safety feature in the event of a wheel-speed
transducer failure. Locked-wheel protection is provided by the brake
control unit so that brake pressure is removed from a wheel if that
wheel’s velocity is less than or equal to 30% of the velocity of the fastest
wheel. Removal of brake pressure from the slow wheel allows traction
to be re-established.
Pilot’s Manual
3-18 PM-126A
The following CAS illuminations are specific to the brake system:
EMERGENCY/PARKING BRAKE
The emergency/parking brake component of the brake system utilizes
the emergency/parking brake valve assembly, emergency/parking
brake accumulator. An EMERGENCY/PARKING BRAKE handle and
cable system is used to apply emergency braking or to set the parking
brakes. Emergency braking works independently of the main braking
system and the brake accumulator is charged from the auxiliary hydraulic
system.The EMERGENCY/PARKING BRAKE handle is located
on the pedestal below the thrust levers. The handle is mechanically
connected to the emergency/parking brake valve assembly. A switch
within this assembly senses on/off condition and provides the signal
for illumination of the EMER/PARK BRK red and white CAS. The
parking brake is engaged by pulling the EMERGENCY/PARKING
BRAKE handle and rotating clockwise or counterclockwise to the locking
position. Rotating back to center position and releasing park brake
handle disengages the parking brake. Emergency braking is controlled
by pulling the EMERGENCY/PARKING BRAKE handle with a force
proportional to the amount of emergency braking desired. Releasing
the handle to the off position will disengage the emergency brake.
CAS Color Description
NORM BRK FAIL Red All four brakes (normal system) have failed.
CPLT BRK FAULT Amber One or more of the copilot’s brake LVDTs has
　
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