The crew oxygen mask/regulator assembly lets the flight crew breathe oxygen.
The stowage box components have these purposes:
*
Mask stowage

*
Communications connection

*
Oxygen connection

*
Oxygen flow control

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Oxygen flow indication.

Location
A crew mask/regulatory assembly and stowage box is adjacent to each crew position.
Physical Description
These components are on the front of the storage box:
*
Quick release fastener (4)

*
Doors (2)

*
Flow indicator

*
Reset test lever.

These components (not shown) are inside the box:
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Oxygen shutoff valve

*
Oxygen jack

*
Microphone jack.

There are connections (not shown) on the back of the box that connect the oxygen and microphone jacks to the oxygen supply line and communications systems.
The mask/regulator assembly has these components:
*
Pneumatic harness

*
Mask

*
Vent Valve

*
Push-Pull Control

*
Diluter/demand regulator with controls

*
Oxygen plug connection

*
Microphone plug connection.

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CREW OXYGEN -CREW OXYGEN MASK AND STOWAGE BOX

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CREW OXYGEN -OPERATION

Pull on the release levers of the diluter/demand regulator to remove the mask from the box. The shutoff valve opens when the left door opens. You hold the left release lever (inflation control) in as you hold the mask by the diluter/demand regulator. This makes oxygen inflate the pneumatic harness.
You put the harness around your head with the mask over your nose and mouth. When you release the release levers, the oxygen that inflates the harness shuts off and bleeds from the harness. Elastic in the harness pulls the mask tight to the face.
Normally you breathe a mixture of oxygen and compartment air when you set the oxygen dilution control to N (normal). The percent of oxygen has a relation to the pressure altitude in the flight deck. At or above a preset pressure altitude the regulator gives you 100 percent oxygen. You breathe only oxygen at any pressure altitude when you set the dilution control to 100 percent.
Normally, oxygen flows only when you breathe (on demand). The flow indicator shows flow each time you breathe. If you set the emergency demand control to emergency, oxygen will flow continuously (pressure breathing). The flow indicator shows continuous flow.
The vent valve (not shown) is part of the mask. The valve lets air and oxygen flow from the mask into the goggles (not shown).
You manually open and close the vent valve with the push-pull control (not shown).
If you close the left door on the box, the oxygen on indicator shows.
You can turn oxygen off at the oxygen box with the shutoff valve. Close the left door and push the reset/test lever sets the valve to the close position.
Mask Storage
To return the mask to the box, set the test and emergency demand control to the normal position. Put the wire, hose, and harness into the box. Place the mask into the box so the tabs are against the upper stop and the mask is against the lower stop in the box. Close the left door. Push down on the reset/test lever to close the shutoff valve and retract the oxygen on indicator. Move the mask to the left. Close the right door.
Test
Push down and hold the reset/test lever. The flow indicator should show a momentary flow.
Push down and hold the reset/test lever. Push in on the test and emergency demand control. The flow indicator should show a continuous flow.
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777 AIRCRAFT MAINTENANCE MANUAL

CREW OXYGEN -OPERATION

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777 AIRCRAFT MAINTENANCE MANUAL

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CREW OXYGEN -FUNCTIONAL DESCRIPTION

The cylinder supplies oxygen through the shutoff valve, pressure regulator, and supply line to the masks in the flight deck. The supply line pressure regulator decreases the bottle pressure to 70 psi. The diluter/demand regulator/mask supplies the flow and pressure that the crew needs.
Remote Fill Port
You use the remote fill port to fill the oxygen cylinder in the airplane. The check valve will not let oxygen go from the cylinder to the panel.
Indications
　
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