*
The MLG selector/bypass valve.

Location
The landing gear control lever is on the P2 center instrument panel.
The NLG selector/bypass valve is in the NLG wheel well.
The MLG selector/bypass valve is the right MLG wheel well.
General Description
Landing gear control is electrical. A two-position (UP and DOWN) landing gear control lever controls the extension and retraction.
When the airplane is on the ground, a landing gear lever lock solenoid locks the landing gear lever in the DOWN position. The solenoid releases the lock when the airplane is in the air.
Auto-off relays in ELMS remove the gear-up signal ten seconds after the landing gear retracts. This removes the pressure from the landing gear components.
Interfaces
The proximity sensor electronics unit (PSEUs) get landing gear lever position. The PSEUs also supply landing gear position data to the HYDIM cards.
The HYDIM cards control the auto-off relays in ELMS.
Air/ground relays control the landing gear lever lock solenoid.
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LANDING GEAR CONTROL SYSTEM -INTRODUCTION

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LANDING GEAR CONTROL SYSTEM -LANDING GEAR CONTROL LEVER MODULE

Purpose
The landing gear control lever module sends signals to the landing gear selector/bypass valves to extend and retract the landing gear and the tail skid (if applicable).
Physical Description
The module has these components:
*
Lever

*
Switches

*
Lock mechanism.

Location
The landing gear lever is on the P2 center forward panel.
Functional Description
The lever has two positions with detents: UP and DN. You must first pull the lever out before you can raise or lower the lever.
The lever has eight internal switches. Four of these switches control power and ground to the down solenoids in the NLG and MLG selector/bypass valves. Two switches go to the ELMS to control power to the up solenoids in the NLG and MLG selector/ bypass valves. One switch resets the gear door release/safety valve modules after an alternate gear extension or ground door operation. One switch provides a signal to the weather radar system. See the weather radar system section for more information (SECTION 34-43).
The module also has a solenoid controlled lever lock mechanism. The lever lock prevents accidental movement of the control lever from DN to UP when the airplane is on the ground. When the aircraft takes off, the solenoid gets electrical power and releases the lever lock.
Training Information Point
You can mechanically release the landing gear lever lock with the lever lock override switch.
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LANDING GEAR CONTROL SYSTEM -LANDING GEAR CONTROL LEVER MODULE

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LANDING GEAR CONTROL SYSTEM -LANDING GEAR SELECTOR/BYPASS VALVES -INTRODUCTION

Purpose
The NLG selector/bypass valve controls extend and retract pressure to NLG extension and retraction components.
The MLG selector/bypass valve controls extend and retract pressure to the left and the right MLG extension and retraction components.
The NLG and MLG selector/bypass valves operate the same way. The MLG selector/bypass valve is larger to permit higher hydraulic flow.
Location
The NLG selector/bypass valve is on the left bulkhead in the NLG wheel well.
The MLG selector/bypass valve is on the aft bulkhead in the right MLG wheel well.
Training Information Point
The solenoids on the selector/bypass valves are LRUs.
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LANDING GEAR CONTROL SYSTEM -LANDING GEAR SELECTOR/BYPASS VALVES -INTRODUCTION

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777 AIRCRAFT MAINTENANCE MANUAL

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LANDING GEAR CONTROL SYSTEM -LANDING GEAR SELECTOR/BYPASS VALVES -FUNCTIONAL DESCRIPTION

General
The landing gear selector bypass valves are solenoid-operated, three-position valves. These are the positions:
*
Retract

*
Off

*
Extend.

The landing gear selector/bypass valves have these components:
*
Dual coil UP solenoids

*
Dual coil DOWN solenoids

*
　
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