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NLG EXTENSION-RETRACTION -INTRODUCTION
Purpose
The NLG extension-retraction system extends and retracts the nose landing gear and opens and closes the NLG doors.
Components
These are the NLG extension-retraction components:
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NLG-operated sequence valve
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NLG door actuator
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NLG door-operated sequence valve
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NLG retract actuator
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NLG lock actuator
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NLG locking mechanism.
General Description
The center hydraulic system supplies pressure to operate the nose landing gear. The pressure goes through the NLG selector/bypass valve. The NLG door-operated sequence valve controls hydraulic pressure to the NLG retract actuator and the NLG lock actuator.
The NLG-operated sequence valve controls hydraulic pressure to the NLG door actuator.
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777 AIRCRAFT MAINTENANCE MANUAL
NLG EXTENSION-RETRACTION -INTRODUCTION
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NLG EXTENSION-RETRACTION -COMPONENT LOCATIONS
General
These are the components in the NLG wheel well:
*
NLG retract actuator
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NLG-operated sequence valve
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NLG lock actuator
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NLG lock mechanism
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NLG door-operated sequence valve
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NLG door actuator.
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NLG EXTENSION-RETRACTION -COMPONENT LOCATIONS
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NLG EXTENSION-RETRACTION -NLG RETRACT ACTUATOR
Purpose
The NLG retract actuator supplies the force to retract the nose landing gear.
Physical Description
The NLG gear retract actuator is a two-position piston-type actuator. The actuator retracts to raise the NLG and extends to lower the NLG.
A flow restrictor controls the gear extension rate.
Snubbers at both ends of the actuator control speed at the ends of the actuator stroke.
The NLG retract actuator is unpressurized during gear extension.
The dry weight of the actuator is approximately 95 pounds (43 kilograms).
Location
The NLG retract actuator is in the right top corner of the aft bulkhead in the NLG wheel well.
The head end of the actuator attaches to a bracket in the top, aft, right outboard corner of the wheel well.
The rod end attaches to the right side brace for the NLG.
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NLG EXTENSION-RETRACTION -NLG RETRACT ACTUATOR
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NLG EXTENSION-RETRACTION -NLG LOCKING MECHANISM AND NLG LOCK ACTUATOR
Purpose
The NLG locking mechanism holds the NLG in the extended or the retracted position.
The NLG lock actuator unlocks the NLG locking mechanism at the start of an extension or retraction. It also locks the mechanism when the NLG is fully extended or fully retracted.
Physical Description
The NLG locking mechanism uses over-center locking to lock the NLG in either the extended or retracted position. The locking mechanism has a forward and an aft lock link which connect by a hinge. Two lock springs keep the lock links in position.
The NLG lock actuator is a hydraulic piston-type actuator. Flow restrictors control the hydraulic flow rate in both directions of actuator motion.
Location
The nose gear locking mechanism is directly above the nose gear shock strut. The forward lock link attaches to the drag strut hinge. The aft lock link attaches to the NLG wheel well aft bulkhead.
The NLG lock actuator is at the aft end of the NLG locking mechanism. The rod end of the actuator attaches to the NLG wheel well aft bulkhead. The head end attaches to the aft part of the locking mechanism.
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NLG EXTENSION-RETRACTION -NLG LOCKING MECHANISM AND NLG LOCK ACTUATOR
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NLG EXTENSION-RETRACTION -NLG LOCKING MECHANISM AND NLG LOCK ACTUATOR -FUNCTIONAL DESCRIPTION
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