OLA Air Conditioning, Pressurization and Ventilation Flashcards
Briefly summarise the air conditioning system
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
How many air conditioned zones are there?
3 - cockpit, forward cabin and aft cabin
Describe the flow of hot air
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
What does ACSC stand for?
Air Conditioning System Controller
How many ACSCs are there? What do they do?
2
System 1 regulates cockpit temperature
System 2 regulates the temperature of the two cabin zones
What air enters the mixer unit?
Recirculated cabin air
Temperature regulated air from packs
External air conditioning air
Ram air (providing ditching pb not selected)
What air exits the mixer unit?
Air to be mixed with pneumatic air and distributed into the three zones
What can ram air be used for?
During emergencies to supply cabin with external air for cabin smoke removal or when both packs fail
How is the required pack outlet temperature decided?
It is the lowest commanded temperature for each of the three temperature controlled zones
How much air flow is given when selecting LO, NORM and HI on the pack flow selector?
LO - 80%
NORM - 100%
HI - 120%
What happens if the air flow selector is on LO, but the cooling demand cannot be satisfied?
100% is automatically selected
When does the aircraft prepressurise for departure?
When thrust levers are set for take off
Why does the aircraft prepressurise?
To prevent a pressure surge at rotation
How many configurations does the avionics equipment ventilation system have? What are they called?
Three
Open circuit
Close circuit
Intermediate
Describe airflow in the open configuration
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
Describe airflow in the closed configuration
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.
What happens in the closed configuration if AEVC detects greater than required airflow?
Part of the hot air is ducted below the floor of the forward cargo compartment, through the skin exchanger inlet bypass valve
Describe airflow in the intermediate configuration
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
