Normal Extension
Positioning the landing gear control switch to
the down position energizes the gear control
valve to the retract position. This action pro-
vides hydraulic pressure to hold the main land-
ing gear in the retracted position, relieving
the gear weight from the inboard main gear
doors.
The door control valves are then energized to
the open position and hydraulic pressure is
directed to release the inboard main gear door
uplatches and extend the doors. The three
landing gear advisory lights illuminate as soon
as the landing gear control switch is moved to
the DN position.
Placing the landing gear control switch to the
down position also energizes the auxiliary hy-
draulic pump. This insures auxiliary system
pressure is available to back up the main sys-
tem for brakes, and also insures that the brake
accumulator is fully charged.
When the inboard doors are fully open, the gear
control valve is energized to the extend posi-
tion (Figure 14-12). Hydraulic pressure is si-
multaneously directed to release the nose gear
uplock and extend all three landing gear.
When the gear are down, mechanical down
locks inside each gear actuator cause the re-
spective green DOWN lights to illuminate and
the nose gear advisory light to extinguish.
A signal, through the main gear downlock
switches, then energizes the door control valve
to the closed position. Hydraulic pressure then
closes the inboard main gear doors. As the in-
board doors close, and the uplatches are en-
gaged, the door control valve removes hydraulic
pressure from the gear door actuators, and the
main gear advisory lights extinguish. The gear
control valve remains in the extend position di-
recting hydraulic pressure to hold the gear
down. As an additional safety feature, the gear
actuator downlock is mechanically locked in
the extend position.
The auxiliary hydraulic pump remains on until
it is either manually turned off by the crew, or
until DC electrical power is removed from the
airplane. The pump should normally be on for
takeoff, landing and taxi. The normal gear ex-
tension cycle takes less than 11 seconds to
complete with both engine-driven pumps op-
erating.
14-12
FOR TRAINING PURPOSES ONLY
LEARJET 45 PILOT TRAINING MANUAL
FlightSafety
international
LEARJET 45 PILOT TRAINING MANUAL
FlightSafety
international
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