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PCA -power control actuator
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pos -position
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PSI -pounds per square inch
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RVDT -rotary variable differential transformer
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WES -warning electronic system
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xdcr -transducer.
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777 AIRCRAFT MAINTENANCE MANUAL
STEERING -INTRODUCTION
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NOSE GEAR STEERING SYSTEM -INTRODUCTION
Purpose
The nose gear steering system supplies the primary ground directional control of the airplane.
Inputs
Steering inputs are from the steering tillers or the rudder pedals.
Cable Loops
Steering inputs move an upper cable loop. This loop connects to a lower cable loop. The lower cable loop makes inputs to a NLG steering metering valve module.
Hydraulic Supply
The center hydraulic system supplies the pressure to operate the nose gear steering system.
Limits
Steering tiller input turns the nose gear up to 70 degrees in each direction.
Rudder pedal input turns the nose gear approximately 7 degrees in each direction.
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NOSE GEAR STEERING SYSTEM -INTRODUCTION
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NOSE GEAR STEERING SYSTEM -COMPONENTS
Upper Cable Loop Components
These are the nose gear steering components on the upper cable loop:
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NLG steering tiller and gearbox (2)
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NLG drum mechanism (2)
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NLG steering centering and rudder interconnect mechanism
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NLG steering broken cable compensator
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NLG steering pivot link.
Lower Cable Loop Components
These are the nose gear steering components on the lower cable loop:
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NLG steering centering mechanism
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NLG steering summing mechanism
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NLG steering metering valve module
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NLG steering actuator (2)
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Nosewheel steering collar.
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NOSE GEAR STEERING SYSTEM -COMPONENTS
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NOSE GEAR STEERING SYSTEM -NLG STEERING TILLER, GEARBOX, AND DRUM MECHANISM
Purpose
Two NLG steering tillers control nose gear steering up to 70 degrees in each direction.
Physical Description
The tillers mechanically connect to each other through the upper cable loop.
Each tiller attaches to a gearbox assembly. The gearbox assembly has a bevel gear to change the angle of rotation from the tiller.
The gearbox decreases tiller motion and increases tiller input torque by a ratio of 3.9 to 1. Maximum tiller rotation is 350 degrees in each direction.
A torque shaft connects the gearbox to the drum mechanism. The cable drums move the upper cable loop. The torque shaft and drum mechanism can turn 90 degrees in each direction.
Location
The captain’s tiller is forward and to the left of the captain. The first officer’s tiller is forward and to the right of the first officer.
The drum mechanisms are below the steering tillers. You get access to the drum mechanisms through the forward equipment center access door.
Training Information Point
Zero-position indicators are at the base of each tiller. These show when the steering tiller is in the neutral position.
NLG steering tiller position transducers are at the base of each drum mechanism. These transducers supply the input to operate the main gear steering system.
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NOSE GEAR STEERING SYSTEM -NLG STEERING TILLER, GEARBOX, AND DRUM MECHANISM
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NOSE GEAR STEERING SYSTEM -NLG STEERING CENTERING AND RUDDER INTERCONNECT MECHANISM
Purpose
The NLG steering centering and rudder interconnect mechanism connects the rudder pedals to the upper cable loop. It also moves the steering system to the neutral position when there are no inputs.
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