Air Con And Ventilation Flashcards
When do the packs operate automatically in HI flow?
When in single pack operation or when the APU is supplying bleed air.
How does the air con system regulate the temperature?
The conditioned air from both packs enters the mixer unit where it is mixed with recirculated cabin air. Before being fed to the cockpit and cabin zones hot trim air is mixed with each individual air flow to regulate the temperature.
How is cabin pressurisation achieved?
By regulating airflow out of the aircraft through the outflow valve (and ensuring the outflow valve is fully open on the ground).
What happens if the controlling Cabin Pressurisation Controller (CPC) fails?
The other CPC will automatically assume control
When does the CABIN ALT indicator change to red?
9,550 ft cabin altitude
What happens when the avionics ventilation system is in the SMOKE configuration?
The blower fan stops and the exhaust fan continues to run.
The air conditioning inlet valve opens to allow air conditioning air to supply cooling air which is then exhausted overboard through the partially open outlet skin air valve!!
When do both Packs operate automatically and independently of each other?
When both Pack 1 and Pack 2 are ON
How do the TRIM AIR valves optimise individual zone temperature?
By adding hot air
What does the pressurisation system comprise?
2 cabin pressure controllers
1 outflow valve
2 safety valves
Maximum permitted positive differential pressure?
9.0 psi
How do crew take manual control of the cabin pressurisation?
Set MODE SEL pb to MAN on the CABIN PRESS panel
Crew can then control the position of the outflow valve using the MAN V/S CTL switch
When the Avionic Ventilation system BLOWER pushbutton is set to OVRD what happens?
The system goes into Closed circuit configuration
The blower fan stops
Air is added from the air conditioning system to the ventilation air
With smoke or a dual pack failure what action could improve ventilation?
Press the RAM AIR pb
What controls pack operation
Packs operate automatically and independently
Operation is controlled by signals from pack controller or Air Conditioning System Controller (ACSC)
Which ACSCs control what temperature zone?
Concept temp: ACSC 1
Cabin zones: ACSC 2
What happens after a single lane failure in the ACSC (Air conditioning System Controller)?
No obvious effect, the second lane takes over
Amber FAULT light on the ENG 1(2) ANTI ICE pb sw?
The valve position disagrees with the selection
How many CPCs?
2 Cabin Pressure Controllers
What conditions are required for the RAM AIR INLET to function
Below 10,000ft
Ditching NOT selected
If delta P is equal to or greater than 1PSI
What controls the avionics ventilation system?
The AEVC (Avionics Equipment Ventilation Computer) controls the system automatically
In flight when does the intermediate configuration operate?
In flight when skin temp above the inflight threshold - mid point
In the air when does the close circuit configuration operate?
In flight valves close when skin temp beneath the inflight threshold
On the ground when does the closed circuit configuration operate?
On ground valves close when skin temp is beneath the on ground threshold
On the ground when does the open circuit configuration operate?
On ground valves open when skin temp is above the on ground threshold
What is the purpose of the two independent pneumatic safety valves?
They prevent cabin pressure from going too high (8.6 PSI above ambient) or too low (1 PSI below ambient)
