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Since nosewheel centering prior to gear re-
traction depends on air pressure in the strut,
proper inflation of the strut is important. As
with the main gear, the nose strut is serviced
to a specified pressure with the airplane on
jacks. When the airplane weight is on the strut,
the amount of strut extension varies with air-
plane load.
The nose gear also incorporates a weight-on-
wheels switch for nosewheel steering func-
tions, discribed later in this chapter.
Nose Gear Wheel and Tire
The nose gear is fitted with an 18 x 4.4 inch
aluminum wheel. The tire is 10 ply rated chined
tubeless (210 mph/182 knots rated), serviced
to 104-114 psi loaded, or 105 +5 psi on jacks.
The dual chines on the nose gear tire deflect
water spray to reduce the potential for engine
water ingestion.
LANDING GEAR OPERATION
Four valves are contained within the landing
gear control valve module (Figures 14-10 and
14-11). They are used to control normal gear
retraction and extension, emergency exten-
sion, and hydraulic fluid source selection.
Normal landing gear operation requires 28
VDC power, which is supplied through the
GEAR circuit breaker, located on the pilot’s cir-
cuit breaker panel. The circuit breaker receives
power from the airplane’s emergency battery
bus, which allows normal landing gear exten-
sion in the event of a dual generator failure.
Normal Retraction
A f t e r b e c o m i n g a i r b o r n e a n d t h e s q u a t
switches have transitioned to the air mode,
positioning the landing gear control switch
to the UP position energizes the door control
valve to the open position. This directs hy-
draulic pressure to release the inboard main
gear door latches and opens the inboard doors.
The three gear advisory lights illuminate as
soon as the landing gear control switch is
moved to UP.
When the inboard doors are fully open, the gear
control valve is energized to the retract posi-
tion. This directs hydraulic pressure to the re-
tract side of the landing gear actuators (Figure
14-10). The green DOWN lights extinguish as
soon as the down locks are released and the
gear begins to retract.
When the nose gear reaches full up, the uplock
roller is engaged and the uplock switch ex-
tinguishes the nose gear advisory light. When
both main gear are fully retracted, the door
control valve is again energized, but now to the
closed position. Hydraulic pressure is then
applied to close the inboard main gear doors.
The main gear advisory lights extinguish as
soon as the main inboard gear doors are up.
As the inboard doors close, the door uplatches
engage and the gear control valve repositions
to remove hydraulic pressure from the main
gear actuators, allowing the main gear to rest
against the latched inboard gear doors. The
door control valve then removes hydraulic
pressure from the door actuators. The normal
retraction cycle takes less than 11 seconds to
complete with both engine-driven hydraulic
pumps operating.
14-10
FOR TRAINING PURPOSES ONLY
L E A R J E T 4 5
P I L O T T R A I N I N G M A N U A L
FlightSafety
international
L E A R J E T 4 5
P I L O T T R A I N I N G M A N U A L
FlightSafety
international
Figure 14-10. Control Valve Operation
SOL
SOL
SOL
SOL
SOL
SOL
EXTEND
NEUTRAL
RETRACT
RETURN LINE
PRESSURE/SUPPLY LINE