Pressurisation System

Question 1

How many cabin altitude controllers are provided?

Answer 1

• Two controllers, A and B. Each controller controls both outflow
valves.
FCOM, VOL 2; 2.30.1

Question 2

Can either outflow valve maintain cabin altitude and full ventilation?

Answer 2

• Yes

FCOM, VOL 2; 2.30.1

Question 3

What are the three modes controlled by the cabin altitude controllers?

Answer 3

• Climb, cruise, and descent

FCOM, VOL 2; 2.30.1

Question 4

How do the cabin altitude controllers calculate a cabin pressurization schedule?

Answer 4

• They use ambient pressure, and
• Flight plan data from the FMC
FCOM, VOL 2; 2.30.1

Question 5

Does cabin altitude continue to increase, or level-off, if there is a planned level segment during the climb phase?

Answer 5

• Continues to increase during the level segment.

FCOM, VOL 2; 2.30.2

Question 6

What is maximum cabin altitude in cruise mode?

Answer 6

• 8,000 feet

FCOM, VOL 2; 2.30.2

Question 7

When do the cabin altitude controllers enter descent mode?

Answer 7

• T/D, or
• An initial descent of approx. 1,000 feet from cruise altitude,
regardless of T/D.
FCOM, VOL 2; 2.30.2

Question 8

When in descent mode, do the cabin altitude controllers program a positive or a negative pressurization at touchdown?

Answer 8

• In descent mode cabin alt increases or decreases to slightly below the
FMC planned landing altitude, the small difference assures a small
positive pressurization at touchdown.

FCOM, VOL 2; 2.30.2

Question 9

When does the cabin rate limiter close both outflow valves?

Answer 9

• When cabin altitude exceeds 11,000 feet.

FCOM, VOL 2; 2.30.2

Question 10

How can you gain manual control of the landing altitude, if the airport for takeoff or landing is not in the data base?

Answer 10

• By pushing the Landing Altitude (LDG ALT) Switch on the overhead panel,
then set the airport elevation, with the Landing altitude selector.
• Landing altitude followed by MAN (amber) displays on primary EICAS.
FCOM, VOL 2; 2.10.23/26

Question 11

What altitude is assumed by the cabin altitude controllers if landing altitude is not available from the FMC, and MAN is not selected?

Answer 11

• 2,000 feet

FMC, VOL 2; 2.30.2

Question 12

Describe the NORM position of the Cabin Altitude Selector?

Answer 12

• Cabin altitude controller A or B selected automatically on alternate flights.
- Selected controller is primary, selects secondary controller if the primary fails.
- The cabin altitude controllers swap at each landing.
FCOM, VOL 2; 2.10.23

Question 13

What happens if the primary controller selected by the cabin altitude selector switch fails?

Answer 13

• The secondary controller is automatically selected.

FCOM, VOL 2; 2.10.29

Question 14

What action would allow you to gain manual operation of the pressurization system?

Answer 14

• Turn both Outflow Manual switches to ON.
• All automatic cabin altitude control functions are bypassed.
- In this config’ one pack is shut 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.

FCOM, VOL 2; 2.30.3

Question 15

Out flow valve MAN L,R switch ON/ OFF positions?

Answer 15

ON
- Outflow valve is controlled manually.
- System automatically bypasses automatic outflow valve and
cabin altitude limiter.
OFF
- Outflow valve controlled automatically.

Question 16

CABIN ALTITUDE CONTROL, AUTO SELECT, selector function?

Answer 16

NORM
- Cabin altitude controller A or B selected on alternate flights,
- Selected controller is the primary controller, selects secondary controller
if primary controller fails.
A
- Selects cabin altitude controller A as primary.
B
- Selects cabin altitude controller B as primary.