DSC Air conditioning - Press - Vent

Question 1

What compose the air conditioning system ?

Answer 1

• two pack control valves
• two packs
• one mixing unit

Question 2

What is the purpose of the mixing unit ?

Answer 2

mix air from the cabin and the air coming from the packs

Question 3

What is the purpose of the trim air valve and the hot air ?

Answer 3

optimize the temperature by adding hot air tapped upstream of the packs

Question 4

What is the purpose of the pack flow control valve ?

Answer 4

It is controlled by the ACSC and regulate the air flow

Question 5

When will the pack flow control valve close ?

Answer 5

• pack overheat
• low pressure
• fire PB
• engine start

Question 6

What is the purpose of the emergency RAM air ?

Answer 6

provide ambient air to the mixing unit.
Can be use to remove smoke and in case of dual pack failure

Question 7

When will the emergency ram air inlet open ?

Answer 7

• when PB pressed and
• delta P is less than 1PSI and
• Outflow valve in automatic control mode (will open at 50%)

Question 8

How does the ACSC control the temperature of the pack ?

Answer 8

It adjust the temp by modulating bypass valve and the ram air inlet flap.

Question 9

When will the pack flow automatically adjust ?

Answer 9

• single pack
• use of APU bleed
• normal flow if in LO and temp cannot be satisfied

Question 10

What compose the ACSC ? and how will it work in case of failures ?

Answer 10

Composed of two lanes per ACSC
Single lane failure => no effect the other takes over
Both lanes failure => pack lost, hot air valve close and associated trim air valve close

Question 11

What compose the cabin press system ?

Answer 11

• two CPC
• one residual pressure control unit
• one outflow valve with an actuator with 3 motors
• one control panel
• two safety valves

Question 12

In normal cabin press operation what control the system ?

Answer 12

Only one CPC at a time, this other is on standby

Question 13

When will the transfer between CPC happen ?

Answer 13

failure
70sec after landing
Can be forced by selecting Mode sel to MAN for 10sec or more and back to auto

Question 14

What is the normal cabin pressure limit ?

Answer 14

8000ft

Question 15

How is the outflow valve operated and by what ?

Answer 15

3 differents motors
- two for automatic mode associated with their CPC
- one for manual mode
In manual mode the N°1 CPC backup section signal the position to ECAM

Question 16

How many safety valves ? when will they activate ?

Answer 16

too high above 8,6PSI
too low -1PSI

Question 17

Avionic vent, what are the normal configurations ?

Answer 17

• open circuit config
• closed circuit config
• intermediate config

Question 18

Avionic vent, In the open circuit config how is the avionic cooled ?

Answer 18

by ambiant air, the skin heat exchanger is not used (closed)

Question 19

Avionic vent, in the closed circuit config how is the avionic cooled ?

Answer 19

skin air inlet and outlet closed, cooled by skin heat exchanger

Question 20

Avionic vent, when can the open circuit be used ?
what about the closed ?

Answer 20

on the ground only
for the closed can be used:
- ground when takeoff power or below ground threshold
- in flight when BELOW in flight threshold (around 33°c)

Question 21

Avionic vent, what is the intermediate configuration ? and when can it be used ?

Answer 21

Same as the closed config but some of the air is extract overboard via a partially open skin air outlet valve.
In flight when skin temp is ABOVE inflight threshold (around 35°C)

Question 22

Avionic vent, what is the smoke configuration ?

Answer 22

blower and extract are set to override, the air conditioning is supplying cooling air which is then exhausted overboard via a partially open skin air outlet valve.
The skin heat exchanger is not used

Question 23

In case of the loss of both FMGC how does the Press system obtain the landing elevation ?

Answer 23

Manually selected via the rotary selector

Question 24

With the loss of CPC 1+ 2 how is the cabin altitude controlled ?

Answer 24

Mode sel MAN and use toggle to adjust cabin alt.
Two ways to manage this failure:
- Manually select a cabin VS of 300ft/min and 0 when leveling off or
- Keep current cabin alt and once at this cabin altitude fully open outflow valve => Once fully depressurized monitor closely the rate of descent of AC has it will impact directly the rate of descent of the cabin alt.

Question 25

When in MAN mode for the cabin alt, what happen to the outflow valve when the toggle is selected up ?

Answer 25

open the outflow valve => Makes the cabin alt climb

Question 26

On takeoff why does the press system slightly pressurise the cabin ?

Answer 26

to avoid a surge on takeoff

Question 27

Avionic vent, What is the effect of pressing Blower to overide, Extract to overide, what will cool the A/C and which config does the system goes into ?

Answer 27

Blower overide => Stop running
Extract overide => Keep running
A/C is cooled by air from the air conditioning
The system goes into the closed config

Question 28

What is the recommended maximum time without Air conditioning supply with pax on board ?

Answer 28

20min

Question 29

On the ground what is the avionics ventilation limit for normal avionics ventilation system config ?

Answer 29

OAT <= 49°c // No limitation
49°c < OAT <= 55 // 2h
Some additional limitation with temp exist but 55°c is rarely exceeded (ref to FCOM if required)

Question 30

Cabin pressure, what is the max positive differential pressure ? negative ? safety relief valve ?

Answer 30

Max 9PSI
Min -1PSI
Safety relief valve 8.6PSI
the tolerance is +/-7hPA (0,1PSI)

Question 31

At what altitude will the cabin altitude warning trigger ?

Answer 31

9550ft +/- 350ft

Question 32

What is the max normal cabin altitude ?

Answer 32

8000ft