Air Systems

Question 1

Air Systems

In how many temperature zones is the 787 divided ?

Answer 1

7
Flight deck + 6 passenger cabin zones.
Only 5 are depicted on the synoptic.
Nitpicking: zones A and B contain sub-zones A1 and B1, not depicted on the air synoptic.

Question 2

Air Systems

How many Packs are there ?

Answer 2

2

Question 3

Air Systems

How many electric Cabin Air Compressors per Pack ?

Answer 3

2

A single CAC provides enough air to operate its Pack in all operating modes.

Question 4

Air Systems

How is air supplied to the 4 CACs (Cabin Air Compressors) ?

Answer 4

Through 2 dedicated air inlets located in the Wing/Body fairings.

Question 5

Air Systems

How are the CACs (Cabin Air Compressors) air inlets protected ?

Answer 5

During normal ground ops and the landing phase, deflector doors deploy in front of the CAC inlets to prevent debris from entering the CACs. These deflectors may retract on the ground when ambient temp is below 2°C or above 35°C.

Question 6

Air Systems

What do the CACs (Cabin Air Compressors) do ?

Answer 6

They pressurize and flow-regulate the incoming air before supplying it to their dedicated Pack.

Question 7

Air Systems

How are Packs controlled ?

Answer 7

By 2 identical pack control units (PCUs).

If one system fails, pack control automatically switches to the other system.

Question 8

Air Systems

Ground operations :
When running on APU, how many CACs (Cabin Air Compressors) are running ?

Answer 8

2 in normal operations as only one CAC on each side will run.
4 during cold weather as both CACs are commanded ON.

Question 9

Air Systems

Can Air Conditioning be used during ENG start ?

Answer 9

NO.

All CACs are commanded OFF during normal start.

Question 10

Air Systems

When do PACKS restart after ENG start ?

Answer 10

2 minutes limit from start of sequence.

If both engines are started together, immediately after the second engine is started and the 2 minutes limit is met.

Question 11

Air Systems

How do pilots manage the Standby cooling mode of a Pack ?

Answer 11

They don’t !
The entire process is automatic.
The EICAS displays a PACK MODE (L,R) message and STBY COOLING is displayed in amber on the AIR synoptic.

Question 12

Air Systems

What does an EICAS message PACK MODE (L,R) mean ?
What action(s) can be done ?

Answer 12

A significant fault or overheat was detected and the pack was shut down automatically.
An attempt to restore pack operation may be made by pressing the AIR CONDITIONING RESET switch.

Question 13

Air Systems

What is the purpose of the Recirculation Fans ?

Answer 13

To assist the Packs in maintaining a constant ventilation rate through the cabin.
They draw cabin air through filters, then reintroduce the air into the condition air distribution system.

Question 14

Air Systems

What type of air does the flight deck receive ?

Answer 14

The flight deck receives 100% conditioned outside air.
Some recirculated air is supplied to the flight deck if one pack is off and its associated lower recirculation fan is on.

Question 15

Air Systems

What type of air does the passenger cabin receive ?

Answer 15

The passenger cabin receives a mix of outside air and recirculated air.

Question 16

Air Systems

Can cabin attendants reduce outside air to the cabin based on the number of occupants?

Answer 16

Yes, but this reduction is limited to ensure a minimum airflow to the cabin.

Question 17

Air Systems

Which temperature range can be selected for cabin and flight deck ?

Answer 17

18°C to 29°C

Question 18

Air Systems

Can flight attendants change the temperature in the cabin ?

Answer 18

YES

± 6°C from the cockpit-selected temperature.

Question 19

Air Systems

In normal pack operating mode, when is ECONOMY mode triggered ?

Answer 19

Economy cooling mode is a normal mode of operation that occurs regularly above FL290.
The Economy Cooling Valve is opened, bypassing the condenser and 1st stage turbine of the Pack.

Question 20

Air Systems

How are Pack temperatures controlled ?

Answer 20

1- By modulation of the pack control valves.

2- By opening or closing ram doors of the ram air heat exchanger.

Question 21

Air Systems

What prevents smoke from entering the flight deck ?

Answer 21

The flight deck is kept at a slightly higher pressure than the cabin.

Question 22

Air Systems

What is the purpose of the Alternate Ventilation System (AVS) ?

Answer 22

To provide an alternate means of ventilation to the flight deck and cabin if both packs become inoperative.

Question 23

Air Systems

Which zone controls the pack temperature ?

Answer 23

The zone supplied by that pack that is set to the lowest temperature (white on synoptic).

Question 24

Air Systems

Can Air Conditioning be used on the ground without APU running ?

Answer 24

NO, use of external power to power air conditioning packs is not recommended.

Question 25

Air Systems

What conditions will cause the Equipment Cooling System to automatically reconfigure to OVRD mode?

Answer 25

• The FWD/AFT EQUIP COOLING switch is selected to OVRD
• SMOKE is detected
• The FWD/AFT CARGO FIRE ARM switch is ARMED
• Both supply fans fail in flight
• Low airflow is detected in flight
• Excessive Temperature in flight
• Both Flow sensors fail.

Question 26

Air Systems

How is temperature regulated with the TRIM AIR system OFF?

Answer 26

• The flight deck temperature is maintained between 18-29 °C

- The cabin temperature controllers attempt to maintain all zones at the average target temperature.

Question 27

Air Systems

If a pack is in Standby Cooling mode and the other operates normally, will it stay on throughout the flight?

Answer 27

No, the pack in Standby Cooling mode will shutdown at lower altitudes and higher outside air temperatures.
Note: For certain internal malfunctions, pack control automatically uses standby cooling mode as a backup to normal mode.

Question 28

Air Systems

What provides additional cooling in the lower recirculation ducts ?

Answer 28

Liquid-to-Air heat exchangers.