The primary control valve is an LRU. These components on the primary control valve are LRUs:
*
The shutoff solenoid

*
The extend solenoid

*
The retract solenoid

*
The low-speed solenoid

*
The bypass solenoid.

The low-speed solenoid is different than the other solenoids, but it is interchangeable with the low-speed solenoid on the flap primary control valve. All the other solenoids are interchangeable and they are interchangeable with the other solenoids on the flap primary control valve. The slat primary control valve is similar to, but not interchangeable with, the flap primary control valve.
Location

The slat primary control valve attaches to the keel beam in the left main landing gear wheel well.
Training Information Point
There is a small difference in the location of the mounting holes for the flap and slat primary control valves. This helps prevent the slat primary control valve from being installed where the flap primary valve should be. The reverse is also true.
The low-speed solenoid has a longer valve and different mounting hole locations. This helps prevent the low-speed solenoid from being installed where a different type of solenoid should be. This also helps prevent a different solenoid from being installed where the low-speed solenoid should be.

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LEADING EDGE SLATS -SLAT PRIMARY CONTROL VALVE

EFFECTIVITY BEJ ALL  27-81-00 
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777 AIRCRAFT MAINTENANCE MANUAL

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LEADING EDGE SLATS -PRIMARY CONTROL VALVE -FUNCTIONAL DESCRIPTION

General
The primary control valve has these components:
*
Shutoff valve

*
Shutoff solenoid valve

*
Low-speed solenoid valve

*
Low-speed piston

*
Flow regulator

*
Retract solenoid valve

*
Extend solenoid valve

*
Selector valve

*
Bypass solenoid valve

*
Bypass valve.

The FSEUs electrically control the solenoid valves in the primary control valve. All the solenoid valves are normally de-energized.
Shutoff Valve and Shutoff Solenoid Valve

The shutoff valve supplies hydraulic pressure and hydraulic flow to the selector valve.
The shutoff valve has three positions: closed, open, and low-speed. The shutoff valve is spring-loaded and hydraulically controlled to the closed position. It moves to the open or low-speed positions when the shutoff solenoid valve removes pressure from one side of the valve.
EFFECTIVITY
BEJ ALL

The shutoff solenoid valve controls the pilot pressure to the shutoff valve. The shutoff valve solenoid has two coils. When both coils are de-energized, the shutoff solenoid valve lets pilot pressure close the shutoff valve. When either coil is energized, the shutoff solenoid valve removes pilot pressure from the shutoff valve. Hydraulic system pressure then lets the shutoff valve open.
When the shutoff valve is closed, it removes hydraulic pressure from the selector valve. When the shutoff valve is open, hydraulic system pressure goes to the selector valve to move the slats at their normal rate. When the shutoff valve is in the low-speed position, the hydraulic flow to the selector valve is restricted.
Low-Speed Solenoid Valve, Low-Speed Piston, and Flow Regulator
The low-speed solenoid valve, the low-speed piston, and the flow regulator help to decrease the speed of the slat drive system.
The low-speed solenoid valve is a dual-coil solenoid valve that controls hydraulic pressure to the low-speed piston. The low-speed piston is a hydraulic piston that is spring-loaded to the retracted position.
When the FSEUs energize the low-speed solenoid valve, the low-speed piston extends. This limits the position of the shutoff valve to the low-speed position.
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LEADING EDGE SLATS -PRIMARY CONTROL VALVE -FUNCTIONAL DESCRIPTION

When the FSEUs de-energize the low-speed solenoid valve, the pressure in the low-speed piston decreases. An internal spring then forces the low-speed piston to retract. This lets the shutoff valve move to the open position.
The flow regulator limits the flow of hydraulic fluid to 35 gpm at high speed, and 7 gpm at low-speed.
Selector Valve

The selector valve controls the direction of operation of the hydraulic motor.
The selector valve is spring-loaded and hydraulically balanced to the center position and normally has pressure on both sides of the valve. The selector valve moves to the extend position when the extend solenoid valve removes pilot pressure from the extend side of the selector valve. The selector valve moves to the retract position when the retract solenoid valve removes pilot pressure from the retract side of the selector valve.
　
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