Air Conditioning

Question 1

How is cargo hold temperature controlled?

Answer 1

With air from the air conditioning system?

Question 2

How many air conditioning packs are there?

Answer 2

2

Question 3

How many Air System Control Units are there?

Answer 3

One per pack.

Question 4

How many channels per ASCU are there?

Answer 4

2

Question 5

How is air supply managed in the case of a dual pack failure?

Answer 5

In case both packs fail, the mixer unit can directly receive air from outside the aircraft, through the emergency ram air inlet.

Question 6

What does it mean if a pack operates in bypass mode?

Answer 6

The Air Cycle Machine is bypassed and cooling is carried out by the heat exchangers only.

Question 7

If a pack controller fails, what are the consequences for the pack?

Answer 7

The associated pack is lost.

Question 8

What is the purpose of the recirculation fans?

Answer 8

Recirculation fans provide cabin air to the premixer unit for mixing with cold pack air.

Question 9

In the event of a dual pack failure in flight how is air supply managed?

Answer 9

By allowing air to enter through the ram air inlet supplying the mixer unit.

Question 10

What is the pressure requirement to enable the ram air valve to open?

Answer 10

The differential pressure must be less than 2 psi.

Question 11

When is a pack flow controller automatically set to high (HI)?

Answer 11

When:

• If only one pack operates.
• If the APU supplies bleed air.

Question 12

What is the flow rate for an Air Flow selector of MAN (manual mode)?

Answer 12

AIR FLOW selector set to MAN: The pack airflow is at a default value

The default value corresponds to an airflow rate for a typical three-class cabin layout with all seats occupied.

Question 13

What is the flow rate for an Air Flow selector of HI (manual mode)?

Answer 13

AIR FLOW selector set to HI: The pack airflow is equal to or more than 120 % of the MAN value.

Question 14

What is the flow rate for an Air Flow selector of LO (manual mode)?

Answer 14

AIR FLOW selector set to LO: The pack airflow is 80 % of the MAN value.

Question 15

With the AIR FLOW selector set to NORM, what factors dictate the airflow?

Answer 15

• The number of passengers entered into the FMS MFD.
• The aircraft flight level.
• The temperature regulation of the forward cargo compartment on the CARGO AIR COND panel.

Question 16

How is air supply to the bulk cargo hold managed?

Answer 16

Some cabin air is recycled into the bulk hold via the ‘bulk cargo extraction fan’.

There is also a dedicated heater.

Question 17

What is the supplemental cooling system?

Answer 17

The Supplemental Cooling System (SCS) is a fully electrical system which supplies cooling to the galleys.

Question 18

How does the Supplemental Cooling System (SCS) chill the galleys.

Answer 18

The Supplemental Cooling System (SCS) uses two cooling units to chill fluid that is then distributed to the galleys.

When the COOLG button is in auto the system runs as soon as power is applied the aircraft.