*
Overdoor and lowered ceiling boxes -two masks
*
Lavatory boxes -two masks.
Latches attach the outboard and center PSUs to the airplane structure. Release the latches and lower the PSU for access to the oxygen generators.
Lower the overdoor panel for access to the oxygen generators above those panels. To get access to the generators in the lavatories or lowered ceiling panels, remove the adjacent lowered ceiling panel.
See the equipment and furnishings chapter for more information about the PSUs, overdoor panels, and lowered ceiling panels (CHAPTER 25).
Passenger Oxygen Mask
The masks are continuous-flow units. A plastic tube connects the oxygen box manifold to a mask reservoir bag. A flexible facepiece with two check valves attaches to the reservoir bag. An elastic strap holds the facepiece in place over the user’s nose and mouth. A lanyard connects the mask to the release cable in the oxygen box.
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PASSENGER OXYGEN -PASSENGER OXYGEN BOX AND PASSENGER OXYGEN MASK
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PASSENGER OXYGEN -DOOR LATCH/ACTUATOR -INTRODUCTION
The latch part of the door latch/actuator holds the oxygen door closed. The actuator causes the latch to release the door.
Physical Description
The latch/actuator has these parts:
*
Electrical connector
*
Housing
*
Spring
*
Lever arm with metal plate.
The housing contains a permanent magnet with an electric coil around it.
There is a spring-loaded latch pin on the oxygen door. It fits into a notch on the bottom of the lever arm to hold the door closed.
The hinge on the mask box in the lavatory at door one left has a design that is different from the other boxes. When the door is released and moves to open, the hinge separates and lets the door fall. It hangs on lanyards. In this position, the box door will not interfere with the operation of the lavatory bifold door.
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PASSENGER OXYGEN -DOOR LATCH/ACTUATOR -INTRODUCTION
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PASSENGER OXYGEN -DOOR LATCH/ACTUATOR -FUNCTIONAL DESCRIPTION
Either of these two conditions releases the oxygen masks:
*
The passenger oxygen switch on the P5 is set to the ON position
*
Two of the three cabin pressure sensors give a signal that the cabin pressure altitude is above 13,500 feet (4115 meters) and the airplane is in the air with an airspeed more than 80 knots.
Functional Description
When you operate the passenger oxygen switch, a signal goes from OPAS to the ELMS. The ELMS latches a ground for the channel A and B oxygen deployment relays for fifteen seconds. (The channel B relay is not shown. It is redundant with the channel A relay.) The relays let 115v ac energize the oxygen module door latch/actuators.
When the deployment relays energize, the ELMS sends a signal to these systems:
*
AIMS
*
Cabin services system (CSS)
*
OPAS.
The OPAS turns on the light in the passenger oxygen switch. The AIMS shows an advisory message.
The CSS causes these events in the passenger compartment:
*
Aural alert
*
The passenger compartment lights come on bright
*
The no smoking and fasten seat belt signs come on
*
Passenger address volume increases to maximum.
The ELMS cancels the oxygen on signal two minutes after the airplane lands.
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PASSENGER OXYGEN -CHEMICAL OXYGEN GENERATOR
The chemical oxygen generators supply oxygen for the passengers and flight attendants.
Physical Description
The size of the generator has a relation to the number of oxygen masks that connect to it. The masks connect to a manifold at one end of the generator.
A firing pin is at the other end. A release pin holds the firing pin against the spring force. A release cable connects to a lanyard that goes to the mask. A safety pin holds the firing pin when the release pin is not installed.
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