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nose gear is retained while in the extended position.
The nose hydraulically actuated doors, sequencing and position sensing are controlled
and continuously monitored by the LGECU. Any fault or position deviation detected
is annunciated on EICAS.
NOSE GEAR DOWNLOCK SAFETY PIN
A downlock safety pin is installed within the drag brace assembly to secure the nose
landing gear in position while on ground.
LANDING GEAR ELECTRONIC CONTROL UNIT (LGECU)
The Landing Gear Electronic Control Unit (LGECU) consists of two subsystems
which perform:
• All landing gear control and indication, including WOW
• Landing gear and landing gear door operations
• Control and indication and fuselage door status functions. For fuselage door
indications, refer to Chapter 1, AIRPLANE GENERAL
REMOVE
GHT
BEFORE FLI
Downlock
Assist
Spring
Ground
Locking
Pin
GX_14_006
For Training Purposes Only
Sept 04
14-9
P I LOT T R A I N I N G GU I D E
LANDING GEAR AND BRAKES
LGECU SYSTEM SCHEMATIC
LGECU CONTROL
The LGECU receives gear position commands from the landing gear control handle in
the flight compartment. The handle is compared with actual gear position and WOW
for each landing gear assembly. The landing gear system includes proximity sensors
for gear and door positioning, and locked position monitoring.
GX_14_007
LANDING GEAR
ELECTRONIC CONTROL
UNIT (LGECU)
CONTROL SEQUENCING
MAIN / NOSE
GEAR
AND
DOOR
POSITIONS
WEIGHT-ON-WHEELS
LOGIC PROCESSING
GEAR
POSITION
AND
LOCKED
INDICATION
MAIN / NOSE
GEAR AND DOOR
CONTROL VALVES
NOSE GEAR ASSEMBLY
MAIN GEAR ASSEMBLY
AIRPLANE
SYSTEMS
UP
DN
DN LCK
RELEASE
LDG GEAR
P I LOT T R A I N I N G GU I D E
LANDING GEAR AND BRAKES
14-10 For Training Purposes Only
Sept 04
The EICAS monitors the information received from the LGECU and generates status
and warning messages when certain conditions are met.
The landing gear door, control and indications system provides three basic functions:
• Landing gear sequencing control – The system performs logic on handle position,
landing gear and door positions, WOW and gear lock inputs. It provides the
signals that command the landing gear, landing gear door and lock actuators that
change the position of the landing gear based on this input logic
• Landing gear, door and fuselage door position indication – The system monitors
door position inputs, landing gear door inputs, landing gear position inputs and
provides indication of the position status of airplane doors and landing gear
• Weight-On-Wheels indication – The system monitors landing gear strut
compression (sensor input) and provides indication of the air or ground status of
the airplane. Weight-On-Wheel sensors on each landing gear assembly report to
the LGECU and are divided into two classifications, WOW 1 and WOW 2 inputs.
In addition, the system monitors its own circuitry and provides fault information to
the Central Aircraft Information Maintenance System (CAIMS) and/or EICAS
system
The LGECU is divided into two subsystems which provide control and indication to
the landing gear system.
Subsystem A functions include:
• WOW 1 (WOW sensor input logic)
• Landing gear control and secondary position indication
• Landing gear door control
Subsystem B functions include:
• WOW 2 (WOW sensor input logic)
• Landing gear primary position indication
• Landing gear door indication
• Fuselage door status
For Training Purposes Only
Sept 04
14-11
P I LOT T R A I N I N G GU I D E
LANDING GEAR AND BRAKES
LGECU CONTROL SCHEMATIC
GX_14_008
LANDING
GEAR
AND GEAR
DOOR
CONTROL
WOW
GEAR UP
AND
DOWNLOCK
BITE
(Built-In-Test)
BACKUP
DOWNLOCK
INDICATION
PRIMARY
DOWNLOCK
INDICATION
WOW
AND
DOWNLOCK
BITE
(Built-In-Test)
SUBSYSTEM A SUBSYSTEM B
EICAS
• Landing Gear Control
• Landing Gear Up Indication (Primary)
• Landing Gear Unsafe
Indication (Primary)
• Landing Gear Up Indication
(Secondary)
• Landing Gear Unsafe
Indication (Secondary)
• Landing Gear In Transition
Indication (Primary)
• Landing Gear Down
Indication (Secondary)
• Door Indication
• Landing Gear In Transition
中国航空网 www.aero.cn
航空翻译 www.aviation.cn
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