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actuator. The NLG lock actuator and lock springs move the NLG
lock links overcenter to the locked position. This locks the NLG
in the retracted position.
The landing gear lever is moved to the OFF position and the
normal landing gear hydraulic system is depressurized.
Extension
This is the extension sequence for the nose landing gear:
* Landing gear control lever moved to DOWN
* Lock actuator extends
* Lock mechanism unlocks
* Nose landing gear actuator retracts
* Nose landing gear extends
* Lock actuator continues to extend
* Lock mechanism locks.
When the landing gear control lever is in the DOWN position,
hydraulic pressure pressurizes the NLG down lines through the
selector valve to the NLG transfer cylinder and NLG lock
actuator. The transfer cylinder stroke delays full pressurization
to the NLG actuator until the lock actuator unlocks the lock links.
After the lock links unlock, pressure increases in the rod-end of
the NLG actuator and it retracts. The landing gear extends by
actuator force, landing gear weight, and airloads.
As the NLG landing gear gets to the down position, the restrictor
decreases the flow of fluid out of the head-end of the NLG
actuator. The lock actuator and lock springs move the lock links
to the locked position. This locks the NLG in the extended
position.
When the landing gear lever is in the down position, the lock
actuator, NLG actuator, and transfer cylinder remain
pressurized.
NLG EXTENSION AND RETRACTION - OPERATION
EFFECTIVITY
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NLG EXTENSION AND RETRACTION - OPERATION
NLG EXTENSION AND RETRACTION - OPERATION
EFFECTIVITY
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737-600/700/800/900 AIRCRAFT MAINTENANCE MANUAL
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Purpose
The nose landing gear actuator supplies the force to retract and
extend the nose landing gear.
Location
The nose landing gear actuator is in the nose landing gear
wheel well, forward of the upper drag brace. The head end
attaches to a fitting on the upper bulkhead of the wheel well. The
rod end attaches to a fitting on the upper drag brace.
Physical Description
The nose landing gear actuator is a two-position piston-type
actuator.
The actuator weighs 31 pounds (14 kg).
Functional Description
The actuator retracts to extend the nose landing gear. The
actuator extends to retract the nose landing gear.
The flow restrictor on the up pressure port of the actuator
decreases the flow of fluid from the actuator to 3 gpm (11 lpm)
during gear extension. This prevents an uncontrolled nose
landing gear extension if a hydraulic hose or tube fails.
NLG EXTENSION AND RETRACTION - NOSE LANDING GEAR ACTUATOR
EFFECTIVITY
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737-600/700/800/900 AIRCRAFT MAINTENANCE MANUAL
32-33-00-003
NLG EXTENSION AND RETRACTION - NOSE LANDING GEAR ACTUATOR
NLG EXTENSION AND RETRACTION - NOSE LANDING GEAR ACTUATOR
EFFECTIVITY
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BOEING PROPRIETARY - Copyright#- Unpublished Work - See title page for details.
737-600/700/800/900 AIRCRAFT MAINTENANCE MANUAL
32-33-00-003
Purpose
The NLG lock mechanism uses an over-center device to lock
the NLG in the extended or the retracted position. Two bungee
springs keep the lock links in these positions.
The nose landing gear (NLG) lock actuator unlocks the NLG lock
mechanism at the start of an extension or retraction sequence.
The lock actuator also locks the lock mechanism when the NLG
moves to the fully extended or retracted positions.
Location
The NLG lock mechanism connects to the upper and lower NLG
drag brace joint and to the aft bulkhead of the NLG wheel well.
The NLG lock actuator is on the aft bulkhead of the nose landing
gear wheel well, near the valve manifold.
Physical Description
The NLG lock mechanism has these components:
* Forward lock link
* Aft lock link
* Bungee springs (2).
The NLG lock actuator is a two-position hydraulic actuator.
Retraction
Before gear retraction, the NLG lock actuator retracts. This
unlocks the NLG lock mechanism and lets the NLG retract.
The hydraulic pressure stays on the retract side of the NLG lock
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