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• 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.
LANDING GEAR/BRAKES
Description
Vol. 2 15−10−3
REV 76, Jul 17/09
CL−604 Operating Manual
PSP 604−6
LANDING GEAR (CONT'D)
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 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.
WARNING
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.
LANDING GEAR/BRAKES
Description
Vol. 2 15−10−4
REV 66, Feb 01/07
CL−604 Operating Manual
PSP 604−6
LANDING GEAR (CONT'D)
Nose Gear
Figure 15−10−3
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.
LANDING GEAR/BRAKES
Description
Vol. 2 15−10−5
REV 75, Feb 17/09
CL−604 Operating Manual
PSP 604−6
LANDING GEAR (CONT'D)
Gear Retraction
During gear retraction, the nose landing gear (NLG) retracts forward against the airflow, and the
main landing gear (MLG) retracts inward. Maximum retraction speed is 197 KIAS (0.6M).
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 MLG are
held by their respective close/uplock mechanisms.
Downlock Release
The landing gear lever is equipped with a solenoid lock, which prevents UP selection of the
landing gear with the airplane on the ground. After takeoff , if the solenoid lock or a PSEU
malfunction occurs, a downlock release button (DN LCK REL) on the landing gear control
　
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