OLA Air Conditioning, Pressurization and Ventilation

Question 1

Briefly summarise the air conditioning system

Answer 1

Hot air comes from the pneumatic system. Some goes directly to the cabin, and some goes through the packs and into the mixer unit. Recycled cabin air also goes to the mixer unit. Air from the mixer unit it mixed with air from the pneumatic system to generate the new air for the air conditioning system

Question 2

How many air conditioned zones are there?

Answer 2

3 - cockpit, forward cabin and aft cabin

Question 3

Describe the flow of hot air

Answer 3

Comes from the pneumatic system, passes through the pack flow control valves, then splits, with some going to the packs and some passing through the hot air pressure regulating valve, directly to the cabin

Question 4

What does ACSC stand for?

Answer 4

Air Conditioning System Controller

Question 5

How many ACSCs are there? What do they do?

Answer 5

2

System 1 regulates cockpit temperature
System 2 regulates the temperature of the two cabin zones

Question 6

What air enters the mixer unit?

Answer 6

Recirculated cabin air
Temperature regulated air from packs
External air conditioning air
Ram air (providing ditching pb not selected)

Question 7

What air exits the mixer unit?

Answer 7

Air to be mixed with pneumatic air and distributed into the three zones

Question 8

What can ram air be used for?

Answer 8

During emergencies to supply cabin with external air for cabin smoke removal or when both packs fail

Question 9

How is the required pack outlet temperature decided?

Answer 9

It is the lowest commanded temperature for each of the three temperature controlled zones

Question 10

How much air flow is given when selecting LO, NORM and HI on the pack flow selector?

Answer 10

LO - 80%
NORM - 100%
HI - 120%

Question 11

What happens if the air flow selector is on LO, but the cooling demand cannot be satisfied?

Answer 11

100% is automatically selected

Question 12

When does the aircraft prepressurise for departure?

Answer 12

When thrust levers are set for take off

Question 13

Why does the aircraft prepressurise?

Answer 13

To prevent a pressure surge at rotation

Question 14

How many configurations does the avionics equipment ventilation system have? What are they called?

Answer 14

Three

Open circuit
Close circuit
Intermediate

Question 15

Describe airflow in the open configuration

Answer 15

Outside air is drawn in by the blower fan, through the skin air inlet valve.

Hot air is then discharged overboard by the extract fan through the skin air extract valve

Question 16

Describe airflow in the closed configuration

Answer 16

Extracted avionics air is cooled by the skin heat exchanger, then recirculated through the avionics ventilation system. The skin air inlet and skin air extract valves are closed.

Question 17

What happens in the closed configuration if AEVC detects greater than required airflow?

Answer 17

Part of the hot air is ducted below the floor of the forward cargo compartment, through the skin exchanger inlet bypass valve

Question 18

Describe airflow in the intermediate configuration

Answer 18

Same as closed configuration, except a small flap in the skin air extract valve is open.

The intermediate configuration is used when the skin temperature is high