*
Both engines off
*
You start an engine.
The ELMS electronics unit (EEU) causes electrical power to go to a solenoid for 25 seconds. The solenoid opens the bleed valve to let oxygen pressure out of the line. If the cylinder shutoff valve is closed, the line will not repressurize when the bleed valve closes. The pressure transducer sends the line pressure information to the AIMS.
Overboard Discharge
The frangible disc breaks if cylinder pressure gets above safe limits (2500 -2750 psi). The oxygen flows overboard through the overboard discharge indicator.
Oxygen Shutoff Valve/Indicator
The oxygen shutoff valve/indicator supplies these functions:
*
On/off control
*
Flow indication
*
Starts the oxygen regulator/mask-mounted microphone.
The valve automatically opens when the left door (not shown) on the stowage box is open. The valve stays open until you close the door and push the RESET/TEST LEVER.
The valve supplies flow indication when oxygen flows through the valve.
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CREW OXYGEN -FUNCTIONAL DESCRIPTION
A switch in the valve supplies an oxygen ON signal to the audio management unit when there is oxygen pressure between the valve the regulator/mask. The audio management unit uses this signal to start the operation of the microphone. See the flight interphone system section for more information about the audio management unit (SECTION 23-51).
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CREW OXYGEN -FUNCTIONAL DESCRIPTION
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BOEING PROPRIETARY -Copyright # -Unpublished Work -See title page for details.
PASSENGER OXYGEN -INTRODUCTION
The passenger oxygen system supplies oxygen to the passengers and cabin attendants if the airplane loses cabin pressurization.
General Description
The passenger oxygen system uses chemical generators to make the oxygen. The passenger oxygen masks can drop automatically or manually.The masks drop automatically when all these conditions are true:
*
The airplane is in the air with an airspeed of more than 80 knots
*
The cabin altitude goes above 13,500 feet (4115 meters).
Push the passenger oxygen switch to drop the masks manually. The chemical reaction that generates oxygen starts when you pull down on the mask.
Location
The oxygen generators and masks are in these locations:
*
In passenger service units (PSU)
*
In the lavatory PSUs
*
In the overdoor panels.
Oxygen generators and masks can also be in lowered ceiling panels in cross aisles and in other areas of the airplane.
The control switch is on the P5 overhead panel in the flight compartment.
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PASSENGER OXYGEN -PASSENGER OXYGEN BOX AND PASSENGER OXYGEN MASK
The passenger oxygen boxes contain the oxygen masks for the passengers and flight attendants. The oxygen masks supply oxygen to the passengers and attendants if the airplane loses cabin pressure.
Location
Oxygen mask boxes are in these locations:
*
Center passenger service units (PSUs)
*
Outboard PSUs
*
Lavatory PSUs
*
On overdoor panels
*
On some lowered ceiling panels.
Passenger Oxygen Box
A chemical oxygen generator attaches to each box. The center PSUs have two generators if they supply oxygen to more than three seats. A manifold (not shown) in the box distributes oxygen from the generator to the masks. A door with an electrically operated latch keeps the masks in the box until the oxygen deployment circuit operates.
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