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Nose Landing Gear (NLG)
The nose gear consists of:
• Nose gear shock strut (Nitrogen-charged/oil-filled)
• Nose gear actuator
• Drag brace with downlock
• Steering actuator
• Axle and wheel assembly
• Uplock pin
• NLG doors
• Weight-On-Wheels proximity sensors
NLG Uplocks and Downlocks
The nose gear is held in the up-and-locked position by a mechanical uplock. With the
gear extended, an overcenter locking mechanism in the drag brace holds the gear in the
down-and-locked position. On the ground, a NLG ground locking pin can be inserted
in the drag brace mechanism.
Nose Doors
With the NLG up and locked, the nose gear compartment is fully enclosed by nose
doors. When the gear is up, the aft nose door, mechanically attached to the landing
gear assembly, provides partial enclosure of the gear. Left and right forward nose
doors are electrically controlled by the PSEU and hydraulically actuated by hydraulic
system 3.
When the landing gear is selected down, the forward doors open to allow passage of
the gear assembly. When the gear is down and locked, the forward doors close to
minimize drag.
When the landing gear lever is selected up, the forward doors open to allow passage of
the gear assembly and then close after the gear is mechanically locked in the up
position.
The nose landing gear forward doors’ actuation, sequencing, and position sensing are
controlled and continuously monitored by the PSEU. Any nose door faults or detection
of a door position deviation is annunciated by the NOSE DOOR OPEN warning
EICAS message and “NOSE DOOR” aural warning.
A maintenance access switch is installed on the external service panel to open and
close the nose doors for ground servicing if hydraulic system 3 pressure is available.
LANDING GEAR / BRAKES
For Training Purposes Only
May 03
15-5
P I LOT T R A I N I N G GU I D E
PRIOR TO ACTIVATING HYDRAULIC SYSTEM 3, ENSURE
THAT THE NOSE GEAR COMPARTMENT IS CLEAR OF
PERSONNEL AND / OR SERVICING EQUIPMENT.
NLG WOW Sensors
Two WOW proximity sensors are incorporated in the nose gear assembly. They
prevent landing gear retraction when the aircraft is on the ground, and they provide
“ground” or “air” status for other aircraft systems via the PSEU.
Nose Gear
Figure 15-3
WARNING
P604_15_026
Downlock Assist
Springs
Aft Nose Door
Steering Actuator
WOW Proximity Sensor
Nose Gear Strut
Nose Gear Centered
Proximity Sensor
Uplock Pin
Nose Oleo Extension Range
Maximum: 11.25 in (28.6 cm)
Minimum: 2.5 in (6.4 cm)
NOSE GEAR DOORS
NOSE LANDING GEAR DOOR SWITCH
Left Nose
Door
Nose Gear
Actuator
Drag Brace
Downlock
Mechanism
Right Nose
Door
Ground
Safety Pin
LANDING GEAR / BRAKES
15-6 For Training Purposes Only
May 03
P I LOT T R A I N I N G GU I D E
Operation
Normal retraction or extension of the landing gear is initiated by selecting the LDG
GEAR lever UP or DN. The retraction or extension signal is sent to the PSEU, which
monitors landing gear proximity sensor and weight-on-wheel (WOW) inputs. If the
correct proximity sensor and WOW parameters are met, the PSEU sequentially
energizes the appropriate selector valves to retract or extend the landing gear using
hydraulic system 3 pressure.
Gear Retraction
During gear retraction, the nose landing gear (NLG) retracts forward against the
airflow and the main landing gear (MLG) retract inward. Maximum retraction speed is
197 KIAS (0.6 M).
During landing gear retraction (aircraft in “air” mode / no WOW signal), the PSEU
commands and monitors the following events:
• landing gear lever solenoid lock is released to allow the landing gear lever to be
selected up
• NLG door selector valve is energized to open the forward nose landing gear doors
• NLG and MLG selector valves are energized to direct hydraulic fluid to release the
respective downlocks and retract the NLG and MLG. Hydraulic pressure from the
nose gear up line is directed to the brake control valves to stop main wheel rotation
(in-flight braking)
• when the gear is fully retracted, uplocks for the NLG and MLG are mechanically
engaged to secure the landing gear in the retracted position
• NLG door selector valve is energized to close the forward NLG doors
• on completion of the retract sequence, NLG, NLG door and MLG selector valves
are de-energized and hydraulic pressure is removed. The NLG, NLG door and
　
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