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MLG EXTENSION-RETRACTION -RETRACTION SEQUENCE

Pressure through the MLG door-operated sequence valve also goes to brake system components for the gear retract braking function. See the wheels and brakes section for more information (SECTION 32-40).
Door Closes
Pressure also goes to the close side of the MLG door actuator and the lock side of the MLG door lock actuator. The door starts to close.
When the door is almost closed, a roller on the door starts to move the MLG door uplock mechanism to the locked position. Pressure in the MLG door lock actuator moves the uplock mechanism over-center to the locked position.
Final Position
Final main gear conditions are:
*
MLG -UP and LOCKED

*
MLG door -CLOSED and LOCKED

*
MLG truck position actuator -STOW

*
MLG drag brace-operated sequence valve -NOT DOWN

*
MLG uplock-operated sequence valve -LOCKED

*
MLG door-operated sequence valve -NOT OPEN.

Pressure stays in the retract lines until the auto-off function moves the MLG selector/bypass valve to OFF.
EFFECTIVITY BEJ ALL  32-32-00 
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MLG EXTENSION-RETRACTION -RETRACTION SEQUENCE

EFFECTIVITY BEJ ALL  32-32-00 
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777 AIRCRAFT MAINTENANCE MANUAL

THIS PAGE IS INTENTIONALLY LEFT BLANK

32-32-00

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MLG EXTENSION-RETRACTION -EXTENSION SEQUENCE

General
Main gear extension is the same for both left and right main gear.
These are the start conditions:
*
MLG -UP and LOCKED

*
MLG door -CLOSED and LOCKED

*
MLG truck positioner actuator -STOW

*
MLG Drag brace-operated sequence valve -NOT DOWN

*
MLG uplock-operated sequence valve -LOCKED

*
MLG door-operated sequence valve -NOT OPEN.

Control
When you select DOWN with the landing gear lever, the MLG selector/bypass valve moves to the down position. This permits hydraulic pressure to go to the extend lines.
Door Opens
Pressure goes through the MLG drag brace-operated sequence valve and the MLG uplock-operated sequence valve. This pressure goes to the MLG truck positioner actuator to hold the MLG truck in the STOW position.
This pressure also goes to the MLG door lock actuator to unlock the MLG door. The MLG door actuator then gets extend pressure through the MLG door priority/relief valve. The MLG door starts to open.
EFFECTIVITY
BEJ ALL

Gear Extends -Truck Tilts
When the MLG door is almost all the way open, the MLG door-operated sequence valve moves to OPEN. Pressure then goes to the MLG uplock actuator to unlock the MLG uplock.
The MLG extends by its own weight and by airloads. It is not pressurized during extension.
When the main landing gear is 20 degrees from fully extended, the MLG drag brace-operated sequence valve moves to DOWN.
Hydraulic pressure then retracts the MLG truck positioner actuator which moves the MLG truck to the TILT position.
Hydraulic pressure also goes to the MLG drag brace and MLG side brace downlock actuators to lock the gear down.
Door Closes
Pressure from the MLG drag brace-operated sequence valve goes through the MLG uplock-operated sequence valve and the MLG door release/safety valve module. This pressure goes to the MLG door actuator and the MLG door lock actuator. The MLG main gear door closes.
32-32-00

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MLG EXTENSION-RETRACTION -EXTENSION SEQUENCE

When the door is almost closed, a roller on the door starts to move the MLG door uplock mechanism to the locked position. Pressure in the MLG door lock actuator moves the uplock mechanism over-center to the locked position.
Final Condition
These are the final conditions of the MLG:
*
MLG -DOWN and LOCKED

*
MLG door -CLOSED and LOCKED

*
MLG truck positioner actuator -TILT

*
MLG drag brace-operated sequence valve -DOWN

*
MLG uplock-operated sequence valve -UNLOCKED

*
MLG door-operated sequence valve -NOT OPEN.

These actuators stay pressurized when the MLG is down and the center hydraulic system is pressurized:
*
MLG door actuator

*
MLG door lock actuator

*
MLG truck positioner actuator

*
MLG side brace actuator

*
MLG drag brace actuator

*
MLG uplock actuator.

EFFECTIVITY BEJ ALL  32-32-00 
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MLG EXTENSION-RETRACTION -EXTENSION SEQUENCE
　
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