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Flight Manual for instrument limit markings.
LANDING GEAR SYSTEM
The landing gear is hydraulically retractable, conventional tricycle gear
with air-hydraulic shock strut-type nose and main gear. The main gear
has dual wheels and brakes on each strut. Each main gear wheel is
equipped with two fusible plugs which will melt and release tire pressure
in the event wheel temperature reaches 360°F (182°C) to prevent a
wheel explosion. The brake system incorporates four power-boosted
disc-type brakes with an integral anti-skid system. The nose gear utilizes
a chined tire to prevent splashing into the engine inlets . Nose wheel
steering is electrically controlled by the rudder pedals. Hydraulic pressure
for gear retraction and extension is transmitted by a system of tubing,
hoses, and actuating cylinders, and is electrically controlled by
limit switches and solenoid valves. Alternate extension can be accomplished
pneumatically in case of hydraulic or electrical system failure.
Two doors enclose each main gear after retraction. The inboard doors
are hydraulically operated and the outboard doors are mechanically
operated by linkage connected to the main gear struts. The nose gear
doors operate mechanically with linkage attached to the nose gear
shock strut.
3-4
PM-121
Change 3
Learjet 31A
Pilot's Manual
' Priority valveremoved on aircraft 31-060 &subsequent .
TRMWucet
t fwn"
__
NOTE: THE ABOVE SCHEMATIC DEPICTS THE
LANDING GEAR EXTENSIOWRETRACTION SYSTEM
AT THE END OF THE EXTENSION SEQUENCE
(GEAR DOWN AND LOCKED).
LANDING GEAR EXTENSION/RETRACTION SCHEMATIC
Figure 3-2
PM-121
3-5
Change 2
Pilot's Manual
Learjet 31A
LANDING GEAR SELECTOR SWITCH
The LANDING GEAR switch, located on the copilot's instrument panel,
is a lever-lock type switch and must be pulled aft before selecting the
UP or DN position . The switch controls the position of the gear selector
valve and the door selector valve through gear and door position
switches. Electrical power for the control circuits is 28 VDC supplied
through the 2-ampGEAR circuit breaker on the copilot's circuit breaker
panel. The landing gear is operative during EMER BUSmode.
Landing gear retraction cycle: When the LANDING GEAR switch is
placed in the UP position and the squat switches are in the air mode,
the following sequence of events will occur:
1. 28 VDC will be applied to the "open" solenoid of the door selector
valve and hydraulic pressure will be applied to both inboard
main gear door uplock actuators and door actuators.
2. When the inboard main gear doors open, door open switches
will complete a circuit from the LANDING GEAR switch to the
"up" solenoid of the gear selector valve. Hydraulic pressure
will be applied to the main and nose gear actuators and the gear
will retract.
3. When the main gear retract, gear up switches will complete a
circuit from the LANDING GEAR switch to the "dose" solenoid
of the door selector valve. Hydraulic pressure will be
applied to the inboard main gear door actuators to raise the
gear doors. Additionally, a gear down safety switch will complete
a circuit to the "up" solenoid of the gear selector valve to
maintain continuous hydraulic pressure in the gear actuators.
4. The inboard main gear doors and nose gear are latched by
uplatch actuator spring tension.
Landing gear extension cycle. When the LANDING GEAR switch is
placed in theDN position the following sequence of events will occur.
1. 28 VDCwill be applied to the "open" solenoid of the door selector
valve and hydraulic pressure will be applied to both inboard
main gear door uplock actuators and door actuators.
2. When the main gear doors open, door open switches will complete
a circuit from the LANDING GEAR switch to the "down"
solenoid of the gear selector valve. Hydraulic pressure will be
applied to the main and nose gear actuators and the gear will
extend.
3. When the main gear are full down, gear down switches will
complete a circuit from the LANDING GEAR switch to the
"close" solenoid of the door selector valve. Hydraulic pressure
will be applied to the inboard main gear door actuators to raise
3-6
PM-121 Change 3
Learjet 31A
Pilot's Manual
the gear doors. Additionally, a gear down safety switch will
complete a circuit to the "down" solenoid of the gear selector
valve to maintain continuous hydraulic pressure in the gear
actuators.
4. The inboard main gear doors are latched by uplatch actuator
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