Landing Gear
Citation Bravo Developed for Training Purposes 5I-17
March 2009
Brake
System
Each main landing gear wheel has
hydraulically or pneumatically oper-
ated multiple disc brakes. The pneu-
matic braking system provides a
back-up if hydraulic braking fails.
During normal braking, the anti-skid
system provides maximum braking
efficiency and prevents skidding on
wet, dry, or icy runways.
The parking brake system uses
trapped hydraulic pressure to lock
the brakes.
The brake system receives electrical
power through a 20 amp SKID
CONTROL CB on the left CB panel.
The brake anti-skid system and the
power brake hydraulic pump receive
power from this CB. When disen-
gaged, the SKID CONTROL CB
disables the power brake system;
braking is then available only by
means of the backup pneumatic
braking system.
Anti-Skid/Power
Brake System
The anti-skid system provides
power-assisted braking with protec-
tion against skidding. Components
are as follows:
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two wheel speed generators
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a power brake relay/anti-skid valve
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control module
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reservoir accumulator
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electrically driven hydraulic pump
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hydraulic filter
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pressure and control switches
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indicator lights.
A wheel speed generator is bolted to
each main gear axle. As the wheel
turns, the generator creates a 36Hz
signal for each wheel revolution.
These signals are sent to the control
module as a variable frequency. The
control module converts these sig-
nals to a DC voltage directly propor-
tional to wheel speed.
The control module averages the
voltages from the left and right
wheels to create a reference voltage.
Any significant variation between
either wheel speed voltage and the
reference voltage produces an error
signal in the control module.
The control module activates the
power brake and anti-skid valve,
which controls the amount of brak-
ing applied to each wheel.
The anti-skid control module incor-
porates test circuitry that continu-
ously monitors the anti-skid system.
If a fault is detected, the ANTI-
SKID INOP annunciator on the con-
trol panel illuminates. If hydraulic
pres-sure in the power system drops
below 750 PSI, the LO BRK PRESS
annunciator illuminates.
When the control module produces
an error signal, the servo valve seg-
ment of the power brake and anti-
skid valve energizes. The servo
valve modulates the braking effort
applied by the pilot to maintain the
reference and wheel speed voltages
within skid limits; this prevents skid-
ding. When the aircraft speed drops
below approximately 12 kts, the
anti-skid function disengages.
A switch on the instrument panel
allows the pilot to select anti-skid on
or off. When the switch is in ON, the
anti-skid function is operational.
With the control switch in OFF, the
ANTI-SKID INOP annunciator illu-
minates; in this situation, the pilot
has power braking available without
the anti-skid function. If the power
brake system fails, braking is avail-
able only through the backup pneu-
matic system.
NOTE: To ensure proper braking,
the pilot must apply maximum effort
to the brake pedals through-out the
braking run. When the system antici-
pates a skid and releases the applied
brake pressure, any attempt by the
pilot to modulate braking can result
in an interruption of the applied
brake signal; this may increase brak-
ing distance significantly.
NOTE: If anti-skid is turned off
prior to or during taxiing, it must be
turned on prior to takeoff. The anti-
skid self-test sequence must be com-
pleted when the air-craft is stationary;
failure to do so renders the anti-skid
inoperative during takeoff.
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