Pressurization *** Flashcards
How many cabin altitude controllers are provided?Each Controller controls both ______?
• Two controllers, A and B. Each controller controls both outflow valves.
Can either outflow valve maintain cabin altitude and full ventilation?One pack is selected off to ensure ___-?
• Yes
• One pack is selected off to ensure cabin doors may be opened
regardless of the position of the outflow valves if an emergency
evacuation is required immediately after landing.
What are the three modes controlled by the cabin altitude controllers?
• Climb, cruise, and descent
How do the cabin altitude controllers calculate a cabin pressurization schedule?
- They use ambient pressure, and
* Flight plan data from the FMC
Does cabin altitude continue to increase, or level-off, if there is a planned level segment during the climb phase?
• Continues to increase during the level segment.
What is maximum cabin altitude in cruise mode?
• 8,000 feet
When do the cabin altitude controllers enter descent mode?
- T/D, or
* An initial descent of approx. 1,000 feet from cruise altitude, regardless of T/D.
When in descent mode, do the cabin altitude controllers program a positive or a negative pressurization at touchdown?
• Small positive pressurization at touchdown.
When does the cabin rate limiter close both outflow valves?
• When cabin altitude exceeds 11,000 feet.
How can you gain manual control of the landing altitude, if the airport for takeoff or landing is not in the data base?
• By pushing the Landing Altitude (LDG ALT) Switch on the overhead
panel.
• MAN (amber) displays on primary EICAS.
What altitude is assumed by the cabin altitude controllers if landing altitude is not available from the FMC, and MAN is not selected?
• 2,000 feet
Describe the NORM position of the Cabin Altitude Selector.
• Cabin altitude controller A or B selected automatically on alternate flights.
What happens if the primary controller selected by the cabin altitude selector switch fails?
• The secondary controller is automatically selected.
What action would allow you to gain manual operation of the pressurization system?
• Turn both Outflow Manual switches to ON.
• All automatic cabin altitude control functions are bypassed
.
Describe pressurization upon touchdown?
Small positive pressure
At touchdown, the outflow valves open to depressurize the cabin
What protection is lost when both outflow valves are operated manually?
Cabin Altitude Limiter
What happens is excessive cabin pressurization occurs?
Positive pressure relief valves OPEN and PACK 2 shuts down until pressure is relieved.
During climb, the cabin altitude gradually increases so that when cruise is reached a target differential pressure of ____ is achieved?
9.4 PSI
When does the cabin altitude controller enter cruise mode?
When within 200’ of cruise altitude or when the aircraft vertical climb falls below 100FPM for more than one minute.
When does CABIN ALT AUTO message appear on EICAS?
- Both cabin altitude controllers FAILED
- Both manual switches are on
When does EICAS Warning CABIN ALTITUDE and aural warning message sound?
10000’ cabin altitude
When do O2 masky automatically deploy in flight?
14000’ cabin altitude
When can pax oxygen system be reset?
Once cabin altitude has dropped to below 12000’
When do cabin warning messages re-arm after being triggered?
Below 9500’ cabin altitude. EICAS message CAB ALT returns to amber
If you forget to enter a CRZ altitude into FMC, what will controllers assume cruise altitude to be?
FL390
What is the cabin altitude sequence of events?
8500’ - Cabin Altitude Indicator turns amber
10000’ - Warning, Aural
11000’ - Outflow Valves Close
14000’ - Masks Drop
12000’ - Passenger O2 system can be reset
9500’ - Cabin Warning Messages Rearm
How many positive pressure relief valves? Location?
- 2 total
- In EE Compartment + FWD Left Fuselage
Max differential pressure 9.4 psi
Where are negative pressure relief valves located?
- Side cargo door
- FWD + AFT low Cargo Doors
