Air Conditioning

Question 1

How many cabin zones are there?

Answer 1

There are 6 cabin zones.

Question 2

How is the Air Conditioning demand from the cockpit sent to the Pack Controllers?

Answer 2

The Zone Controller (ZC) sends the demand from the cockpit to the Pack Controllers (PC).

Question 3

What valves do the Pack Controllers (PC) control?

Answer 3

The Pack Controllers control the Pack Flow Control Valves.

Question 4

What components does the Zone Controller (ZC) control?

Answer 4

The Zone Controller controls the trim air valves and trim air pressure regulating valves.

Question 5

Where are the safety valves installed, and how many are there?

Answer 5

There are three safety valves installed on the rear pressure bulkhead.

Question 6

Where is the negative-pressure relief valve located, and how many are there?

Answer 6

There is one negative-pressure relief valve installed on the forward fuselage.

Question 7

How many outflow valves are there, where are they located, and what controls them?

Answer 7

There are two outflow valves, one forward of the wings and one aft of the wings. Both are controlled by the Cabin Pressure Controllers.

Question 8

How many motors are on each outflow valve, and what are they used for?

Answer 8

Each outflow valve has three motors: one for each Cabin Pressure Controller (CPC) and one for manual operation.

Question 9

Where does position feedback from the outflow valves come from, and how is it activated?

Answer 9

Position feedback from the outflow valves comes from CPC 1, which is activated by pin programming.

Question 10

What does the Residual Pressure Control Unit (RPCU) do after landing?

Answer 10

The Residual Pressure Control Unit (RPCU) fully opens the outflow valves after landing (after 70 seconds if the valves aren’t already open).

Question 11

Where are the Cabin Pressure Controllers installed?

Answer 11

The Cabin Pressure Controllers are installed on the 800VU rack.

Question 12

What happens when the Ditching switch is pushed?

Answer 12

Pushing the Ditching switch closes the outflow valves and the emergency ram air inlet flap.

Question 13

What pressure does the trim air system maintain, and why?

Answer 13

The trim air system maintains around 4 psi to ensure a positive air flow.

Question 14

How does the Vent Controller (VC) ensure redundancy in case of failure?

Answer 14

The Vent Controller has two lanes, so if one fails, full VC functionality is still maintained.

Question 15

What additional function do the two cabin re-circulation fans serve?

Answer 15

The two cabin re-circulation fans are also used for Avionics Equipment Ventilation.

Question 16

What controls the turbofan for pack compartment cooling, and when does it operate?

Answer 16

The AEVC (Avionics Equipment Ventilation Controller) controls the turbofan for pack compartment cooling, which operates only on the ground when the packs are running.

Question 17

What component is installed in the AEV duct to monitor for sufficient cool air?

Answer 17

The Cooling Effect Detector (CED).

Question 18

How are the main batteries cooled?

Answer 18

The main batteries have their own cooling via a venturi.

Question 19

What does the fault light on the Extract pushbutton indicate?

Answer 19

A fault light on the Extract pushbutton indicates an extract fan fault.

Question 20

What causes airflow through the lavs and galleys while in the air?

Answer 20

Differential pressure via an overboard venturi causes airflow through the lavs and galleys while in the air.

Question 21

What causes airflow through the lavs and galleys while on the ground?

Answer 21

An extract fan causes airflow through the lavs and galleys while on the ground.

Question 22

What controls the Lav and Galley ventilation system?

Answer 22

The Vent Controller.

Question 23

What does the Vent Controller use to determine air/ground status?

Answer 23

The Vent Controller communicates with LGCIU 2 for an air/ground signal and also receives a discrete signal from a differential pressure switch.

Question 24

What protects the Lav and Galley Extract fan in case of overheat conditions?

Answer 24

A thermal switch protects the Lav and Galley Extract fan in case of overheat conditions.

Question 25

What monitors for excessive high and low pressure in the Lav and Galley ventilation duct?

Answer 25

A safety switch inside the Lav and Galley ventilation duct.

Question 26

What happens to the zone controllers if the Vent Controllers or fan become unserviceable?

Answer 26

If the Vent Controllers or fan become unserviceable, the cabin temperature sensors are no longer reliable, so the zone controllers switch to a fixed duct temperature based on the TAT probe indication.

Question 27

What conditions must be met for Aft Galley Heating to be active?

Answer 27

The galley heating switch must be on, at least one pack must be on, and cargo loading must be off.

Question 28

What are the two temperature settings for Aft Galley Heating, and how do they function?

Answer 28

The Aft Galley Heating has two temperature settings: 1- Low: Heats one element. 2- High: Heats all three elements.

Question 29

What happens to the Avail light if the Aft Galley Heating system’s thermal protection is active?

Answer 29

If the Aft Galley Heating system’s thermal protection is active, the Avail light will be off.

Question 30

What are the two automatic pressurization modes?

Answer 30

The two automatic pressurization modes are External and Internal.

Question 31

What does External Pressurization Mode use to pressurize the cabin?

Answer 31

External Pressurization Mode pressurizes the cabin according to data from the FMGEC.

Question 32

What does Internal Pressurization Mode use to pressurize the cabin?

Answer 32

Internal Pressurization Mode pressurizes the cabin according to ambient parameters.

Question 33

What monitors the three safety valves?

Answer 33

The three safety valves are monitored by the Cabin Pressure Controllers (CPCs).

Question 34

What happens to the outflow valves if the cabin altitude exceeds 15,000 feet?

Answer 34

A pressure switch on each outflow valve's automatic actuator will close the outflow valve if the cabin altitude exceeds 15,000 feet.

Question 35

How are the outflow valve actuators powered?

Answer 35

The two automatic actuators are AC powered, while the manual actuator is DC powered.

Question 36

What is the maximum cabin altitude for flights less than 2.5 hours?

Answer 36

The maximum cabin altitude for flights less than 2.5 hours is 8,000 feet.

Question 37

What is the maximum cabin altitude for flights longer than 2.5 hours?

Answer 37

The maximum cabin altitude for flights longer than 2.5 hours is 7,350 feet.

Question 38

What is the maximum vertical speed for cabin altitude changes?

Answer 38

The maximum vertical speed for cabin altitude changes is 1,000 feet per minute.

Question 39

When does the pressurization system revert to Internal mode?

Answer 39

The pressurization system reverts to Internal mode in two cases: 1- During a long level off at the top of climb. 2- At the start of descent for 30 seconds while waiting for FMGEC data validation.