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LANDING GEAR POSITION LIGHTS
The landing gear position lights, consisting of a set of three UNSAFE/
DOWN lights arranged in a triangular pattern, are located on the
LANDING GEAR control panel to the left of the LANDING GEAR selector
switch . The UNSAFE portion of each light is red in color and
equipped with dualbulbs. TheDOWN portion of each light is green in
color and equipped with dual bulbs. The location of each light in the triangular
arrangement corresponds to the location of the gear on the aircraft.
An UNSAFE (red) indication signifies that the corresponding
gear is not in the down and locked position or that the corresponding
main gear inboard door is open. A DOWN (green) indication signifies
the corresponding gear is down and locked. During the gear retraction
sequence, the three UNSAFE lights will illuminate when the sequence
is initiated, remain illuminated throughout the retraction cycle, and
thenextinguish when the nose gear is up and locked and the main gear
inboard doors close. During the gear extension sequence, the three UNSAFE
lights will illuminate when the sequence is initiated, remain illuminated
throughout the extension cycle, and then extinguish when the
nose gear is down and locked and the main gear inboard doors close.
The lights are operated by the same switches that control the landing
gear extension and retraction cycles . The lights are dimmed when the
navigation lights are on.
The lights maybe tested at any time by depressing the light test switch
(under glareshield) or by using the GEAR function of the system test
switch . When the system test switch is used, all of the landing gear panel
indicator lights will illuminate and the landing gear warning horn
will sound.
The landing gear position indicator lights operate on 28 VDCsupplied
through the 7.5-amp WARN LT'S circuit breakers on the pilot's and copilot's
circuit breakerpanels . The position indicator lights are operative
during EMER BUS mode. In the event of a complete DC electrical failure,
the landing gear position lights will be powered by the emergency
power system when the EMER BAT1 Switch is in the On position.
PM-121
3-7 Change 3
Pilot's Manual
Learjet 31A
LANDING GEAR WARNING SYSTEM
A landing gear warning system is installed to warn the flight crew of
potentially unsafe flight conditions with the landing gear retracted. The
system consists of the landing gear warning horn, a thrust lever position
switch, and flap position switches. The warning system also uses
the landing gear position switches and UNSAFE lights . The air data
computers provide airspeed/ altitude bias for the system. The gear
warning horn is operative during EMER BUS mode.
Depending upon the flight condition encountered, one of two distinct
warnings will be given as follows:
Warning horn sounds and UNSAFE lights illuminate - This indicates
that the landing gear is not locked down, airspeed is below approximately
170 KIAS, altitude is below approximately 14,500 feet, and at
least one thrust lever is below the 55% to 65% N1 position. When the
horn sounds under these conditions, the horn can be silenced by depressing
the MUTE switch on the LANDING GEAR control panel or
depressing the MUTE button in the right thrust lever knob. Whenever
the warning horn has been muted, theMUTEbutton on theLANDING
GEAR control panel will illuminate amber. TheUNSAFE light indication
will continue until either the landing gear is extended or one ofthe
above conditions is corrected.
Warning horn sounds - The warning horn will sound whenever the
landing gear is not locked down and the flaps are lowered beyond 25°.
When the horn sounds because the flaps are lowered, the horn cannot
be silenced by the mute switch . The horn will continue to sound until
either the landing gear is extended or the flaps are retracted.
LANDING GEAR ALTERNATE EXTENSION
In the event of a main hydraulic system failure or an electrical system
malfunction, the landing gear can be extended pneumatically. Pneumatic
gear extension can be accomplished by using the alternate gear
blow down system . Air pressure to operate the blow down system is
supplied by the emergency air bottle and is controlled by the EMER
GEAR lever on the right side of the pedestal. Whenever alternate gear
extension is to be selected, theLANDING GEAR selector switch should
be placed in the DN position and the GEAR circuitbreaker on the copilot's
circuit breaker panel should be pulled . This will prevent inadvertent
gear retraction in the event electrical or hydraulic power to the
system is regained. When the EMER GEAR lever is pushed down, air
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