NOSE GEAR STEERING SYSTEM -NLG STEERING SUMMING MECHANISM AND METERING VALVE MODULE
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NOSE GEAR STEERING SYSTEM -NLG STEERING ACTUATORS AND NOSEWHEEL STEERING COLLAR
Purpose
The NLG steering actuators supply the force to turn the nose gear.
The nosewheel steering collar transmits the actuator steering forces to the nose gear.
Steering Actuators
The NLG steering actuators are trunnion-mounted between the upper and lower steering plates.
The rod ends of the actuators attach to the steering collar.
Steering Collar
The nosewheel steering collar is trunnion-mounted on the nose gear shock strut. Torsion links connect the steering collar to the inner shock strut cylinder.
Training Information Point
A protractor scale is on the aft side of the steering collar.
Quick disconnect fittings permit easy torsion link disconnection.
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NOSE GEAR STEERING SYSTEM -NLG STEERING ACTUATORS AND NOSEWHEEL STEERING COLLAR
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NOSE GEAR STEERING SYSTEM -FUNCTIONAL DESCRIPTION
General
The NGS system uses center hydraulic system pressure to turn the nose gear.
Steering inputs move the upper and lower cable loops. This makes an input through the summing mechanism to move the NLG steering metering valve. This permits hydraulic pressure to go through the swivel valves to the steering actuators.
The actuators get pressure on the extend side, the retract side, or both sides to move the nose gear from 0 -70 degrees.
Rotation: 0 -27 Degrees
One actuator gets pressure to its head end and the other actuator gets pressure to its rod end. This causes one actuator to extend and the other to retract.
This rotates the nose gear through the torsion links.
Rotation: 27 -70 Degrees
When the nose gear turns to approximately 27 degrees, the swivel valve for the retracting actuator sends pressure to both sides of that actuator.
Both actuators now extend and permit nose gear rotation to the 70 degree limit.
Feedback
When the nose gear gets to the commanded position, the summing mechanism moves the metering valve back to neutral. This stops hydraulic pressure to the actuators and stops nose gear movement.
Training Information Point
To tow the airplane, you move the towing lever on the metering valve module to the tow position. This closes the towing shutoff valve to stop hydraulic pressure to the metering valve module. The towing lever also moves the dynamic load damper to let fluid flow between the steering actuators. This lets an external force move the nose gear wheels.
The bypass/relief valve lets fluid flow between the steering actuators when the pressure in either actuator is approximately 4000 psi. This lets an external force move the nose gear wheels if the tow lever is not in the tow position.
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NOSE GEAR STEERING SYSTEM -FUNCTIONAL DESCRIPTION
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777 AIRCRAFT MAINTENANCE MANUAL
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BOEING PROPRIETARY -Copyright # -Unpublished Work -See title page for details.
MAIN GEAR STEERING SYSTEM -INTRODUCTION
Purpose The MGSCU also supplies aft axle lock status to the warning
electronic system (WES). The WES uses this data to calculate The main gear steering system reduces tire scrub and airplane
the CONFIG GEAR STEERING takeoff configuration warning. turn radius.
Main gear steering also decreases the force necessary to turn the airplane.
Components
The main gear steering system components include:
*
NLG steering tiller position transducer (2)
*
Main gear steering control unit (MGSCU)
*
Main gear steering/locking power control actuator (2)
*
Main gear steering crank (2)
*
Main gear steering reaction link (2).
General Description
The NLG steering tiller position transducers supply steering tiller position data to the MGSCU.
The center hydraulic system supplies the hydraulic power for main gear steering operation.
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