Learjet 20 Series Pilot Training Manual page 272

The nose gear actuator incorporates an integral
downlock mechanism to maintain a positive
downlocked condition; therefore, a downlock
pin is not required. As with the main gear
actuator, the locking mechanism can be released
only by hydraulic pressure on the retract side.
When retracted, the gear is retained by a spring-
loaded uplock hook that engages the uplatch
roller on the forward side of the strut. The
uplock hook is released by a hydraulic actuator.
When retracted, the nose gear is enclosed by two
doors that are linked to, and travel with, the gear.
An improperly centered nosewheel may jam
in the wheel well; therefore, the nose strut
incorporates a self-centering mechanism. At
liftoff, two cams are forced together by air
pressure within the strut to center the wheel
(Figure 14-5).
Figure 14-5. Nose Gear Centering Cams
LEARJET 20 SERIES PILOT TRAINING MANUAL
FOR TRAINING PURPOSES ONLY
Since nosewheel centering depends on air pres-
sure in the strut, proper inflation of the strut is
especially important. With a full fuel load and no
passengers or baggage aboard, 5 1/4 to 5 3/4
inches of bright surface should be visible on the
lower portion of the nose gear strut.
If the nosewheel is swiveled 180º from its normal
position, the cams may not be able to center the
wheel prior to entering the wheel well. Therefore,
the nose gear should be checked during the exteri-
or inspection to ensure that the gear-uplock roller
(Figure 14-4) is facing forward.
Nose Gear Wheel and Tire
The nosewheel tire is chined to deflect water or
slush spray (up to 3/4-inch deep) away from the
engine intakes during takeoff or landing.
Nosewheel tire pressure should be maintained at
105 psi.
Squat Switch Functions
SNs 23-003 through 24-209 and
25-003 through 25-045
Left Switch
• Gear sequencing
• Pressurization
• Windshield overheat light
• Takeoff trim light
• Thrust reverser arming
• Antiskid (25 model)
• Stall warning test inhibit
(Century III wing)
Right Switch
• Gear sequencing
• Pressurization time delay (SNs 24-185,
-188, and -190 through -209, and 25-027
and -029 through -045)
• Windshield overheat light
• Stabilizer heat
• Thrust reverser arming
FlightSafety
international
14-5