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pressure from the emergency air bottle is admitted to the blow down
3-g
PM-121
Change 3
Learjet 31A
Pilot's Manual
system through the lever actuated blow down valve. If the air pressure
is greater than the landing gear system hydraulic pressure, shuttle
valves in the landing gear system will reposition to admit air pressure
to the landing gear system inboard main gear door and door uplock actuators,
the main gear actuators, the nose gear uplock and gear actuators,
the gear control valve, and the door control valve. The gear and
door selector valves are positioned to "down" to prevent inadvertent
gear retraction. When the landing gear is down and locked, the three
green DOWN lights will illuminate. The LEFT and RIGHT red UNSAFE
lights will remain illuminated after gear extension due to the inboard
main gear doors remaining open. When emergency gear blow
down is selected, the EMER GEAR lever must be returned to the "up"
position in order to retain air pressure for emergency braking. The
EMER GEAR lever is returned to the "up" position by lifting the lever
ratchet release (small metal tab available through a small hole immediately
forward of the lever) and pulling the lever to the full up (latched)
position .
NOSE WHEEL STEERING SYSTEM - ANALOG
Analog nose wheel steering is accomplished by displacement of the
rudder pedals and is electronically controlled through a computer-amplifier,
nose-gear steering actuator, follow-up sensor, rudder pedal position
sensor, and associated aircraft wiring. Wheel rotation speed is
sensed by the two inboard and right outboard anti-skid transducers
and steering authority is modified as a function of aircraft ground
speed. From 0 to 10 knots, 45° of steering authority either side of neutral
is available. The steering authority tapers to 8° either side of neutral at
45 knots. Nose wheel steering engage circuits are controlled through
the STEER LOCK switch and the Control Wheel Master Switches
(MSW). When the squat switch is in the ground mode and the steering
circuits are engaged, the rudder pedal position sensor forwards a rudder
pedal displacement signal to the computer-amplifier. The computer-
amplifier accepts the rudder pedal displacement signal, modifies the
signal according to the aircraft ground speed, then forwards a steering
signal to the nose wheel actuator, which rotates the nose gear toward
the selected position. As the nose gear approaches the selected position,
a follow-up signal from the actuator follow-up to the computer-amplifier
cancels the rudder pedal displacement signal . The nose wheel
steering system is powered by 28 VDC supplied through the 7.5-amp
NOSE STEERcircuit breaker on the pilot's circuit breaker panel and 115
VAC supplied through the 2-amp NOSE STEER circuit breaker on the
pilot's circuit breaker panel.
PM-121
3-9
Change 3
Pilot's Manual
Learjet 31A
STEER ON LIGHT
The green STEERON light on the glareshield annunciator panel will be
illuminated whenever nose steering engage circuits have been
activated.
STEER LOCK SWITCH
Normally, the STEERLOCK switch on the pedestal trim switch panel is
used to lock in steering circuits for taxi operations . Momentarily depressing
the STEER LOCK switch will engage the nose wheel steering
system. When STEERLOCK has been selected, the nose wheel steering
system can be disengaged by depressing then releasing either the pilot's
or copilot's Control Wheel Master Switch (MSW).
CONTROL WHEEL MASTER SWITCH -NOSE STEERING FUNCTION
Normally, the Control Wheel Master Switches (MSW), on the outboard
horn of the pilot's and copilot's control wheels, are used to control nose
wheel steering engagement during the takeoff ground roll. Depressing
and holding either Control Wheel Master Switch (MSW) will engage
the nose wheel steering system and the system will remain engaged as
long as the Control Wheel Master Switch (MSW) is held. When STEER
LOCK is engaged, depressing and releasing either Control Wheel Master
Switch (MSW) will disengage STEER LOCK.
NOSE WHEEL STEERING SYSTEM - DIGITAL
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 function of aircraft
ground speed. For low speed ground operations 45° of steering
authority either side ofneutral is available. At low speed and large rudder
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