Emergency Extension System
(Free-Fall)
The emergency landing gear extension system
is a mechanically controlled, gravity free-
fall system. It provides for landing gear ex-
tension in the event the airplane experiences
a hydraulic system failure or electrical mal-
functions that preclude a normal extension.
The system is activated by pushing the free-
fall lever, located on the copilot’s side of the
center pedestal, to the full down position
(Figure 14-13).
Operation
Pushing the free-fall lever full down me-
chanically opens the free-fall valve located
in the landing gear control valve module.
This opens a return path for hydraulic fluid
from both sides of the gear and gear door ac-
tuators, reducing hydraulic resistance and
eliminating the possibility of a hydraulic lock
(Figure 14-14).
Activation of the free-fall lever releases the
nose gear uplock and the inboard gear door
latches. The inboard main gear doors open
from the weight of the main gear, and all three
landing gear extend by gravity. Fully extended,
the landing gear are held in the down-and-
locked position by mechanical downlocks in-
side each gear actuator. When configured, all
three green DOWN lights illuminate, and the
nose gear advisory light is extinguished. The
main landing gear advisory lights remain il-
luminated since the inboard gear doors do not
close after free-fall extension. Free-fall ex-
tension should take no more than 1 minute
after the lever is placed down.
Auxiliary Hydraulic Extension
If the main hydraulic system fails inflight,
procedures call for use of the gear free-fall sys-
tem to lower the gear. However, should the
free-fall system fail to fully extend the gear,
the gear can also be lowered using the auxil-
iary hydraulic system and the HYD XFLO
switch (Figure 14-15).
If the AUX HYD pump and HYD XFLO are
to be used to operate the gear or gear doors,
the LANDING GEAR FREE-FALL LEVER
must be up. If it is down, the FREE-FALL
VALVE (Figure 14-14) will prevent any hy-
draulic pressure from reaching the gear or
gear door actuators.
The auxiliary hydraulic pump is automati-
cally turned on when the gear control switch
is placed down, but can also be selected on by
depressing the AUX HYD switch on the
GEAR/HYD switch panel. Depressing the
HYD XFLOW S/I energizes the hydraulic
crossflow valve, providing auxiliary pump
pressure for gear and flap operation.
Should fluid levels within the auxiliary hy-
draulic system become low (AUX HYD QTY
LO CAS message), the hydraulic crossflow
valve is automatically de-energized to the
CLOSED position to conserve remaining fluid
for the brake system.
If the landing gear is operated with the auxil-
iary hydraulic system, the sequence is identi-
cal to the normal extension sequence, except
it may take approximately 30 seconds to ex-
tend the landing gear.
14-14
FOR TRAINING PURPOSES ONLY
LEARJET 45 PILOT TRAINING MANUAL
FlightSafety
international
LEARJET 45 PILOT TRAINING MANUAL
FlightSafety
international
Figure 14-13. Landing Gear Emergency
Extension Lever
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