OXIGENO

The cockpit oxygen pressure gauge reads:

• The oxygen pressure which is present at the crew masks

• Electrically derived system low pressure

• Bottle pressure

• Electrically derived system high pressure

Passenger masks are automatically dropped when the:

• Oxygen selector is in NORMAL and cabin altitude exceeds 13,500 feet.

• Cabin altitude exceeds 13,500 feet, regard- less of oxygen selector

  position.

• Oxygen selector is in MANUAL DROP, regardless of altitude.

• A and C.

If DC power fails, placing the oxygen selector in:

• MANUAL DROP deploys the passenger masks, regardless of the cabin

  altitude.

• MANUAL DROP deploys the passenger masks only if 13,500 feet

  cabin altitude is exceeded.

• CREW ONLY does not restrict oxygen to the crew only if the cabin

  altitude is above 13,500 feet.

• Any of the three operating positions will not route oxygen to the

  passengers—they have their own oxygen.

The purpose of the altitude pressure switch is to:

• Bypass oxygen flow directly to the passengers regardless of oxygen

  selector position

• Open a solenoid at 13,500 feet cabin altitude, allowing oxygen flow to

  the passenger oxygen distribution system

• Close a solenoid valve at 13,500 feet cabin altitude, stopping oxygen

  flow to the passengers

• Restore cabin altitude to 8,000 feet so that oxygen is not required

If the oxygen selector is placed in CREW ONLY:

• The passenger masks cannot be dropped automatically.

• The passenger masks will not deploy automatically, but they can still be

  dropped manually.

• The passengers will still receive oxygen if the cabin altitude is above

  8,000 feet.

• Normal DC power is removed from the passenger mask door actuators,

  thus pre- venting them from dropping the masks.

If normal DC power is lost with the oxygen selector in NORMAL:

• The passenger masks will deploy immediately, regardless of the cabin

  altitude.

• The passenger masks cannot be dropped manually.

• The oxygen pressure gauge on the copilot’s panel will be inoperative.

• Automatic dropping of the passenger masks will not occur.