Learjet 60 - ANTI-SKID Lights; Anti-Skid System

Learjet 60

Pilot's Manual
ANTI-SKID SYSTEM
An anti-skid
system is integrated into the hydraulic brake system to
provide maximum
braking efficiency under all runway surface condi-
tions without
skidding the tires . The system consists of the ANTI-
SKID control
switch, anti-skid control box, two anti-skid control
valves, monitoring lights, four
wheel-speed transducers (one in each
main wheel axle), and associated aircraft
wiring . Each anti-skid con-
trol valve is a dual unit capable of individually
modulating brake
pressure
for both associated brakes . As the transducers
are driven by
the
main wheels, a frequency proportional to the
wheel speed is in-
duced and
forwarded to the control box . The control box
converts the
wheel-speed frequency to
an analog signal and compares the analog
to a reference representing
the normal deceleration limits . Should the
wheel speed deviate from the
normal deceleration limits, the control
box will signal the affected
wheel's control valve to reduce
braking
pressure on the affected
wheel . Braking pressure
is reduced by by-
passing some of the
hydraulic system pressure into a
return line by
means of a servo controlled
valve in the control valve . As the
wheel
speed increases,
normal braking pressure is restored .
To ensure full
manual control
of the hydraulic braking system
and to prevent pres-
sure loss when the
parking brake is set, a
solenoid-operated shutoff
valve at each
control valve return port is
de-energized closed when
the
ANTI-SKID switch is OFF or the parking
brake is set . Electrical
power for the anti-skid system control circuits is
28 VDC supplied
through
the 7 .5-amp ANTI-SKID circuit breaker
in the hydraulics
group on the
copilot's circuit breaker panel .
ANTI-SKID
LIGHTS
Four
amber ANTI-SKID lights on the pilot's subpanel
provide a con-
tinuous
cockpit indication of the anti-skid system
control circuits . The
two
lights labeled L represent control circuits
for the left main gear
brakes
and the two lights labeled R represent
control circuits for the
right main gear brakes . The anti-skid control
box continuously moni-
tors
the system circuits and will illuminate the
applicable light(s)
should any
of
the following conditions arise :
loss of input power,
open and short transducer circuits, open
or short control valve cir-
cuits, and failure of control box circuits .
Also, the lights will be illumi-
nated
any time the gear is down and locked,
power is on the aircraft,
and
the ANTI-SKID switch is off .
PM-123
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3-19
Original