Learjet 60 - Nose Wheel Steering System

Pilot's Manual
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Learjet 60
NOSE WHEEL
STEERING SYSTEM
The digital nose
wheel steering system is a steer
by wire system that
receives pilot commands
through dual rudder
pedal
position and
dual rudder pedal force
sensors . The computer processes
information
from the rudder pedal
position and force sensors and
three anti-skid
wheel speed
generators and steering
authority is modified as a func-
tion of aircraft
ground speed . For low speed
ground operations 60° of
steering
authority either side of
neutral is available . At low speed and
large
rudder pedal deflection
the
nose
wheel displacement will be
large
for high maneuverability
. Once a rudder pedal has reached
its
stop, further nose
wheel displacement is generated
by additional
force being applied
to that rudder pedal . As ground speed
increases,
the maximum wheel
deflection is reduced to zero . At 90
knots 28
VDC is removed
and the system disengages . Above 90 knots the
nose
wheel is allowed
to castor . Nose wheel steering engage
circuits are
controlled
through the momentary-action
pedestal-mounted ARM/
NOSE
STEER switch and the Control
Wheel Master Switches (MSW) .
When the squat
switches are in the ground
mode, depressing and re-
leasing the ARM/NOSE
STEER switch will
activate the computer
when AC and DC
power are available, the nose gear
is down and
locked, and no faults
are detected by the system monitor
. When the
system is active the
STEER ON annunciator on
the glareshield and
the ARM
annunciator on the ARM/NOSE
STEER switch will illumi-
nate . At90
knots, when the system
disengages, the glareshield STEER
ON
annunciator will extinguish .
When the nose gear is no longer in
the down and locked position, the
ARM annunciator on the ARM/
NOSE STEER switch will extinguish,
however ; the computer is still
powered and system monitor
circuitry remains active . When the nose
gear is down and
locked for landing the ARM annunciator on
the
ARM/NOSE STEER
switch will illuminate provided no faults have
been detected . After
touchdown, when ground speed decreases to 90
knots, the STEER ON light on
the glareshield will illuminate and
steering authority will increase as
ground speed decreases .
If the system cannot be armed,
limited authority steering (24° either
side
of neutral) is available by depressing
and holding either MSW . It
should
be noted that in some instances, even though a fault has been
detected, the system
will continue to function normally until shut-
down . After that, however
; it will not be possible to operate the sys-
tem with full steering
authority until the fault has been corrected . If
the system cannot be
accessed by either MSW, sufficient control is still
available by differential
braking .
3-14
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PM-123
Change 2