Air Systems

Question 1

What are the sources of air the Bleed Air System?

Answer 1

Engines, Auxiliary Power Unit (APU), or an external pneumatic/conditioned air source

Question 2

What is the purpose of the Air Supply Controller (ASC)?

Answer 2

The ASC is a subsystem of the Integrated Air Supply Controller (IASC), and digitally controls the output of 4th- and 10th-stage pneumatic air in response to bleed air demands. The ASC also controls the Pressure Regulating Shutoff Valve (PRSOV) and the High Pressure Shut off Valve (HPSOV).

• The NG does not have an ASC, and bleed air is provided by the 5th and 9th stage of the compressor. Bleed air is regulated via a engine bleed shutoff valve which opens and closed based on the pressure of the air.

Question 3

What causes the engine bleed air valve to automatically close?

Answer 3

• closes for high temp or over pressure relief
• will also close when the associated engine start lever is positioned to CUTOFF.

Question 4

What does the illumination of the BLEED light indicate?

Answer 4

*bleed air valve has closed for over-temperature
or excessive pressurization of the bleed duct, or
* a failure within the Bleed Air System that may not be resettable, or
* an incorrect bleed configuration after takeoff or go-around

Question 5

What causes the automatic closure of the APU bleed valve?

Answer 5

The valve will automatically close when the APU is shut down, regardless of switch position

Question 6

What is the position of the isolation valve with the ISOLATION VALVE switch in AUTO?

Answer 6

Closed

Question 7

What does the illumination of the DUAL BLEED light indicate?

Answer 7

The DUAL BLEED light illuminates when two sources of bleed air (Engine and APU) could be
pressurizing the left bleed duct

Question 8

In the event of a single pack failure at altitude, the remaining pack is capable of
maintaining cabin pressure and comfort up to what altitude?

Answer 8

41,000 ft with a single pack in high airflow mode

Question 9

What causes a pack to automatically switch to high airflow?

Answer 9

-If a pack or an engine fails when
the aircraft is airborne with Flaps UP and both engine BLEED switches ON, the operating pack
will automatically switch to high airflow mode.
- Additionally, positioning a PACK switch OFF in
flight with the Flaps UP will also cause the remaining pack to go into high airflow mode.

Question 10

How many controllers does each pack have?

Answer 10

Each pack has adual channel pack/zone electronic controller.
Each controller has a digital primary channel to control its respective pack and an analog channel
that provides backup control for the opposite side pack.

Question 11

What does the illumination of the PACK light indicate?

Answer 11

• failure of both the primary and standby pack controls for the same pack; the pack will
  continue to operate uncontrolled unless tripped off by excessive temperature
• failure of the pack valve to open when commanded
• an incorrect PACK switch configuration after takeoff, or
• a pack overheat
• in the NG the PACK light only indicates pack controller failure or excessive temperature of a pack

Question 12

Do the Flight Attendants have any control of cabin temperature?

Answer 12

• Temperature set points for the forward and aft passenger cabin zones can be adjusted ± 3°
  from the Flight Attendant panel in the cabin.
• In the NG they have no control of cabin temp

Question 13

How is the failure of either the primary or standby pack controller indicated on the
ground?

Answer 13

MAINT light will illuminate

Question 14

What provides cooling air for the pack systems?

Answer 14

The Ram Air System provides cooling air for the air conditioning pack heat exchangers.

Question 15

How is a supply duct overheat indicated?

Answer 15

ZONE TEMP lights indicate a supply duct overheat of the associated temperature zone or
failure of both the left and right IASC (Integrated air system controller)

Question 16

What is the primary source of conditioned air for the Flight Deck?

Answer 16

The Flight Deck receives air directly from the left pack

Question 17

What is the purpose of the recirculation fans?

Answer 17

• reduces the Engine Bleed Air and Pack
  System demands and increases engine efficiency.
• also helps to maintain humidity in the cabin from the very low humidity air from the
  engine bleeds

Question 18

Can pre-conditioned air temperature be controlled by the packs?

Answer 18

No.Conditioned air temperature is controlled at the external air source,therefore, the packs have no temperature control of this
air source.

Question 19

What does the Equipment Cooling System cool?

Answer 19

electronic equipment in the Flight Deck and
Electrical Equipment Bay (E & E Bay).

Question 20

Which cargo compartment is heated by warm air from the Equipment Cooling System’s
exhaust fans?

Answer 20

The forward cargo compartment

Question 21

What does the EQUIP COOLING OFF light indicate?

Answer 21

Loss of airflow due to the failure of a fan

Question 22

What does the illumination of the EQUIP SMOKE light indicate?

Answer 22

Smoke detected in the E & E bay

Question 23

How is the alternate pressurization controller selected?

Answer 23

Selecting ALTN on the Cabin Pressurization
panel will switch control to the standby controller

Question 23

How are pressurization controller failures indicated?

Answer 23

Amber AUTO FAIL light

Question 24

What would cause the OFF SCHED DESCENT light to illuminate?

Answer 24

Should a descent begin prior to the aircraft reaching the set FLT ALT

Question 25

The CABIN ALTITUDE light and altitude warning horn activate at approximately what altitude?

Answer 25

If the cabin altitude exceeds 10,000 ± 1000 ft

Question 26

Can the cabin altitude warning horn can be silenced using the ALT HORN CUTOUT switch above 10,000 ft?

Answer 26

Yes, but lights will remain illuminated until cab high condition is resolved