Air Conditioning/Pressurization

Question 1

How many fans are used to cool the E/E compartment? When are they working?

Answer 1

Radio Rack= Primary and Secondary (2)

On the ground= Both fans operate
Inflight= Only primary fan operates

Question 2

What happens when one of the Radio Rack fans fail?

Answer 2

On the Ground= RADIO FAN OFF annunciator illuminates only when the Primary fan fails

In the Air= If Primary fan fails, Secondary fan will activate
If both fans fail, RADIO FAN OFF illuminates and Venturi valve opens to cool E/E compartment

Question 3

When will a pack automatically shut down?

Answer 3

• Thermal (overheat)= Supply Press Reg and Flow Control valves close
• Pneumatic (loss of cooling air)= Flow Control valve closes
• AUTO (engine failure sensed)= Both engines Supply Press Reg valves and both engines Flow Control valves close. Initiates when there’s 70 psi differential between 13th stages and cabin pressure of less than 1.3 differential

Question 4

What does the FLOW light mean on the Pressurization panel?

Answer 4

The system is unable to maintain cabin pressurization due to insufficient airflow

Question 5

On digital pressurization panel, what does the AUTO INOP light mean?

Answer 5

Both pressurization computers are inoperative

Question 6

When will the CABIN ALT and Master Warning illuminate?

Answer 6

Approx 10,000 ft

Question 7

Do the Pneumatic crossfeed valves have to be open for the packs to receive air from the engines? APU? Ground air cart?

Answer 7

Engines= No (not for the respective side)
APU= Yes
Ground air cart= No

Question 8

When will the recir fan operate? (if installed)

Answer 8

Inflight only, no controls or indications in the cockpit

Question 9

How are the Packs cooled on the ground?

Answer 9

Each pack has a cooling fan that operates on the ground only, with supply switches in HP Bleed Off/Auto, and normal AC power available

• left cooling fan draws air through the ram air intake
• right cooling fan draws air from the tail compartment

Question 10

Which systems use pneumatic air?

Answer 10

• engine starting
• cabin pressurization
• air conditioning
• ice protection
• potable water tank pressurization

Question 11

Where does the water separator get its heated air when its required?

Answer 11

Turbine compressor