25. AIR COND Panel

Question 1

What computers monitor and control the pneumatic system?

Answer 1

2 Bleed Monitoring Computers (BMC)

Question 2

If one BMC fails, can the other take over?

Answer 2

Yes

Question 3

How is the PACK FLOW switch set during cockpit preparation?

Answer 3

Select
 LO: If the number of occupants is below 138
 HI: For abnormally hot and humid conditions
 NORM: For all other normal operating cases

Question 4

What would cause an amber PACK FAULT light to illuminate?

Answer 4

o Pack Overheat or

o Switch position disagreement with pack flow control valve

Question 5

What does the amber FAULT light in the APU BLEED pb indicate?

Answer 5

Bleed leak

Question 6

What causes the amber FAULT light on the ENG BLEED PB?

Answer 6

o Engine bleed temperature or pressure limit exceeded
o Switch / Valve Position disagreement
o Bleed Leak detected

Question 7

What happens when the Ram Air pb is pressed?

Answer 7

This pb is used to open the emergency ram air inlet. In the normal position (lights out), the emergency ram air inlet is closed. When the guard is lifted, and the pb depressed, “ON” illuminates blue, and the ram air inlet opens. “RAM AIR ON” is displayed in green on the memo display. Once the cabin differential pressure is less than 1 psi, the outflow valve will automatically open (if the cabin MODE SEL pb is in AUTO). The emergency ram air inlet and the outflow valve will not open if ditching has been selected.

Question 8

What logic controls the X‐Bleed valve when the X‐BLEED switch is in AUTO?

Answer 8

o When APU bleed valve is OPEN, the X‐Bleed valve is OPEN.

o When APU bleed valve is CLOSED, the X‐Bleed valve is CLOSED.

Question 9

What is the function of the HOT AIR pb?

Answer 9

o The hot air valve controls the supply of hot air to all of the trim air valves which maintain the selected temperature in each zone.
o Valve position is controlled by the HOT AIR pb. The valve automatically closes in the event of a fault.

Question 10

What does the amber HOT AIR FAULT light indicate?

Answer 10

Duct overheat. The Hot Air valve closes automatically.

Question 11

How does the system optimize the temperature in each of the three zones?

Answer 11

Trim Air Valves
 To maintain the selected zone temperature, the trim air valves under control of the zone regulator, add hot air, if necessary, to the air flowing from the mixing unit.
 This allows for air temperatures to be controlled independently in each zone.

Question 12

What effect will the engine start sequence have on the pack flow control valves?

Answer 12

The pack flow control valve will close automatically.

Question 13

After engine start with the APU BLEED pb ON, what source is supplying bleed air to the packs?

Answer 13

APU Bleed