Air Conditioning And Pressurization / Oxygen

Question 1

What is normal and max pressure

differential

Answer 1

Normal 10.33 psi @FL420
( from cabin pressure chart )

Max. 10.73 psi
( AFM LIM and opening of
cabin safety valves )

note:
“CABIN DELTA P” msg. at 10.85 psi

Question 2

The BMC’s extract bleed air

from which engine stages

Answer 2

5th stage low-pressure

8th stage high-pressure

note:
PRV limits the bleed pressure supply
to 43 +/- 3 psi

Question 3

What occurs automatically when

a bleed leak is detected

Answer 3

The BMC isolates the effected manifold

by closing the appropriate valves

Question 4

How is a Bleed leak depicted

on the synoptic page

Answer 4

Flow line is amber and

corresponding valves are closed

Question 5

Can one engine supply two

AC packs simultaneously

Answer 5

No, The BMC prevents two packs

from being supplied by one engine

Question 6

What happens when the system

has only one operating pack

Answer 6

High flow schedule is automatically
selected by the BMC

The HASOV’s close automatically
turning off the trim air

Question 7

When do the packs automatically 
shut off ( FCV closed )

Answer 7

Bleed failure, shutdown
or engine starting

Ditching
( below 15,000’ )

Pack inlet overheat

Compressor discharge overheat

Pack discharge overheat
or under pressure

Question 8

Selecting the TRIM AIR PBA switch

to OFF closes which valves

Answer 8

2 HASOV’s and trim air valves

Question 9

What are the two modes of operation
with the cabin pressure control
system in AUTO

Answer 9

PRIMARY ( predictive ) uses FMS info
Autopilot on, VNAV engaged, and
Landing elevation source
selected to FMS

SECONDARY ( reactive ) uses airplane
altitude and vertical speed ( ADC )

Question 10

What are the caution/warning
messages and associated cabin
altitudes during a loss of
pressurization

Answer 10

Amber "CABIN ALT"  8200'
RED     "CABIN ALT"  9000'
note: when aircraft altitude goes below 
41,000' with the landing elev. set to 
7230' or higher the limits increase 
proportionately; 
caution at 1000' above landing field elev.
warning at 1800' above landing field elev.

Question 11

After selecting MAN pres. what
new info is displayed on
STATUS page

Answer 11

Both outflow valve position indicators

Cabin rate analog gauge

Cabin altitude and Delta P

note:
landing elevation is not displayed
( must monitor cabin alt )

Question 12

How long does it take the cabin
pressure controller to remain
scheduled at the pre-pressurization
altitude after takeoff

Answer 12

10 minutes

Question 13

What occurs when the EMER DEPRESS

switch is selected ON

Answer 13

Both outflow valves are
commanded open

Cabin altitude limited to 14,500’ +/- 500

Question 14

What does selecting Ditching switch

ON provide

Answer 14

Air conditioning pack flow is shut off

Cabin is de-pressurized

OFV’s are driven to the closed position

note: 
inhibited above 15,000'
manuall sequence;
Packs Off, Emer Depress On, 
both OFV's closed

Question 15

How many Oxygen bottles does the

system have

Answer 15

4

Question 16

When do the pax masks automatically

deploy

Answer 16

14,500’ ( +500 / -750 )

Question 17

How is the crew alerted when
the oxygen bottle drops below
75% ( < 1,400 psi )

Answer 17

Amber
“OXYGEN LO QTY” CAS

Note:
this cas will also appear if the oxygen
cylinder SOV is closed

Question 18

What is the minimum oxygen quantity

for dispatch

Answer 18

75%