Oxygen Flashcards
What is the purpose of the oxygen supply solenoid?
On each system, a pressure regulator is connected directly to the cylinder. A supply solenoid valve located downstream of the pressure regulator is used to shut off the flow of oxygen to the masks. This can be used to prevent oxygen leakage from the masks when the aircraft is on the ground for an extended period of time. Each solenoid is controlled using the CREW SUPPLY pb on the overhead OXYGEN panel.
What were to happen if the oxygen cylinder or regulator pressure becomes too high?
The system includes an overpressure safety system which vents the oxygen overboard through a discharge line and relief port if pressure in the cylinder or regulator becomes too high. A green disc covers the relief port and absence of this green disc indicates the oxygen cylinder may have been depleted due to overpressure, notify MX.
When does the CKPT OXY indication change to amber?
- Cylinder pressure is below a certain threshold
- Low oxygen pressure is detected
- When the CREW SUPPLY pb is set to OFF
On the ground, an amber half frame appears around the indication when pressure in the cylinder is less than a certain threshold, depending on the aircraft. If oxygen pressure is below 50 PSI in any system, REGUL LO PR appears in amber.
What is the purpose of the EMERENCY pressure selector oxygen control?
The EMERGENCY pressure selector creates an overpressure which eliminates condensation or fogging of the mask and prevents smoke, smell, or ashes from entering the mask. Pressing the selector generates a brief overpressure which purges the mask. The selector is normally left in the non-emergency position, requiring the pilot to inhale to obtain oxygen. When rotated to the EMERGENCY position, continuous positive oxygen pressure is supplied to the mask. If the cabin altitude exceeds 30,000’, positive oxygen pressure is automatically supplied to the mask regardless of selector position. This is only available when the N/100% selector is set to the 100% position.
What is the purpose of the N/100% oxygen control?
The N/100% selector is a two position rocker switch that is normally positioned in the 100% position and delivers 100% oxygen in this position. In the N position, a mixture of ambient air and oxygen is delivered, the content of which varies with cabin altitude.
When does oxygen begin supplying to the crewmembers mask?
When the left door of the oxygen stowage box is opened, oxygen is supplied to the mask, and the mask microphone is activated. The OXY ON flag appears when the mask is supplied with oxygen and the door is closed. The flag indicates that the mask’s oxygen supply valve is open and oxygen is flowing to the mask.
What is the purpose of the RESET/TEST slide oxygen control?
The RESET/TEST slide is used to test the operation of the system, pressing the slide initiates a short flow of oxygen which causes the blinker to flash yellow. Pressing the RESET/TEST slide after the mask has been used also resets the system by closing the oxygen supply valve and deactivating the mask microphone.
What are the steps to test a crewmembers oxygen mask?
- Ensure CREW SUPPLY pb is ON
- Loudspeakers ON
- INT reception knob and INT on INT/RAD switch (Inform ground crew)
- Press and hold RESET/TEST slide - Yellow blinker should be visible for a short time before going black
- Simultaneously Hold RESET/TEST and the EMERGENCY pressure selector - Yellow blinker should be visible, listen for oxygen flow
- Check that the RESET/TEST slide returned to the up position and 100% is selected
- Press the EMERGENCY pressure selector and verify that the yellow blinker does not turn yellow
- Verify that the REGUL LO PR message is not displayed
When stowing the oxygen mask, check that the OXY ON flag has completely disappeared. Don’t forget the jumpseaters mask!
How are the passengers provided oxygen?
Chemical generators provide oxygen for passengers and flight attendants for a period of about 15 minutes. These are located in each lavatory, each cabin crew station, and in the galley area. Each compartment is equipped with a storage door that is normally owned by an electrical latching mechanism which automatically releases if the cabin altitude exceeds approximately 14000’ (+250’, -750’). The PASSENGER SYS ON light illuminates on the overhead panel when the deployment signal is sensed. The cabin masks can be manually deployed with the MASK MAN ON pb. If a compartment fails to open, a manual release tool may be used to manually open the storage doors.
A rise in cabin temperatures and the presence of light smoke and odors are considered normal when the oxygen generators are activated.
