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United 737 > Pressurization > Flashcards

Flashcards in Pressurization Deck (37):
1

Pressurization and ventilation are primarily controlled by which two valves?

Outflow valve and the Overboard Exhaust Valve.

2

Where is the outflow valve?

Rear of the aircraft

3

Where is the overboard exhaust valve?

underneath the aircraft kind of aligned with forward doors.

4

How many automatic pressurization controllers are there?

2 installed.

5

The outflow valve is controlled automatically when in either ____ or _____ pressurization modes.

AUTO or ALTN.

6

When does the CLOSE/OPEN switch for pressurization?

Only when the selector switch is in MAN.

7

T/F: The outflow valve indicator always shows the position of the outflow valve

true.

8

T/F: The initial planned cruising altitude should be set in the Flight Altitude indicator prior to takeoff.

true.

9

Every click of the Flight Altitude selector knob adjusts indication by _____feet over a range of _____ to ______feet.

500, -1000 feet, 42,000 feet.

10

T/F: The intended landing airport altitude should be set before takeoff.

True

11

What lights come on for a single failure of a pressurization controller?

AUTO FAIL AND ALTN (green light) lights come on.

12

What lights come on for a dual failure of pressurization controllers?

Just the amber AUTO FAIL light comes on.

13

What pilot action causes the green ALTN light to come on?

moving the pressurization selector switch to ALTN.

14

What causes the amber OFF SCHED DESCENT light to come on?

the aircraft descends prior to reaching the preset cruise altitude.

15

What causes the green MANUAL light to come on?

moving the pressurization selector switch to MAN.

16

What causes the intermittent cabin altitude warning horn to come on.

Cabin altitude exceeds 10,000 feet. The horn can be silenced by pressing the ALT HORN CUTOFF button.

17

How many positive pressure relief valves are there and what do they do?

2 valves in the right rear of aircraft. They limit the max pressure differential to 9.1 PSI.

18

How many negative pressure relief valves are there and what do they do?

1 valve in right rear of aircraft. Prevent atmospheric pressure exceeding internal cabin pressure which can sometimes occur with a very rapid descent from altitude.

19

What types of motors are used to control the outflow valve in all cabin pressure controller modes?

DC motors. Ensure operation in event of AC failure.

20

Where do the Cabin Pressure Controllers get their info from? What info do they use?

Air Data Inertial Reference Units (ADIRUs).

Ambient static pressure,
barometric corrected altitude
non-corrected altitude
calibrated airspeed.

Other inputs:
Throttle position via both stall management computers
Signals from the Air ground sensing system.

21

How does cabin air normally leave the aircraft in flight?

conditioned cabin air exits through foot grills and is then routed to provide heating for aft cargo compartment and then to the outflow valve.

22

What two things cause the overboard exhaust valve to open or close

differential pressure and air/ground status.

23

If there is low differential pressure in air or ground, how is the Overboard Exhaust valve positioned?

open and warm air exits from the E&E bay overboard.

24

If there is high differential pressure in air, how is the Overboard Exhaust valve positioned?

valve is closed and air is diffused to the lining of the forward cargo compartment.

25

If either pack is in ____ and the ___ RECIRC FAN is OFF, the overboard exhaust valve is driven ____ to provide increased ventilation in the smoke removal configuration.

HIGH, R, open.

26

What modes on pressurization do the FLT ALT and LAND ALT need to be set before flight?

AUTO and ALTN.

27

The outflow valve is fully open to depressurize the aircraft on the ground during ________________.

lower power settings.

28

When does cabin pressurization begin?

on the ground with higher power settings.

29

If you make a return to your takeoff airport before reaching planned cruise altitude, do you need to set the landing altitude?

No, the altitude is retained in memory.

30

When does the pressurization controller transition to the cruise phase of flight?

When the a/c reaches an altitude within 0.25 PSI of the selected flight altitude.

31

The pressurization controller always strives to maintain the cabin altitude slightly below the selected____________.

landing altitude. IF not possible, a target differential pressure and cabin altitude based on selected flight altitude.

32

When does the pressurization controller switch to the descent phase?

when the plane descends 0.25 PSI below the selected flight altitude.

33

T/F: you land slightly pressurized?

True.

34

What causes the AUTO FAIL light to come on?

Loss of DC Power
Controller Fault
Outflow valve control fault
Excessive diff pressure (>8.75 PSI)
Excessive rate of cabin pressure change (+/-2000 sea level feet/min)
High cabin altitude (above 15,800 feet)* if controller not responding properly.

35

What is the difference in MAN mode vs AUTO or ALTN for pressurization?

Full control. MAN has a separate DC motor powered by the DC standby system. The rate of change of the valve is slower in MAN mode. Full travel range time is 20 seconds.

36

T/F: Control of cabin altitude may be regained by increasing thrust on ensure a sufficient supply of air.

True.

37

If cabin altitude is not controllable:

Don mask and set regulators to 100%
Establish crew communication

If cabin altitude might or has exceeded 14,000 ft:
PASS OXYGEN switch ON
Passenger signs ON
Do Emergency Descent Checklist.