Air Systems Flashcards
Air Systems
In how many temperature zones is the 787 divided ?
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.
Air Systems
How many Packs are there ?
2
Air Systems
How many electric Cabin Air Compressors per Pack ?
2
A single CAC provides enough air to operate its Pack in all operating modes.
Air Systems
How is air supplied to the 4 CACs (Cabin Air Compressors) ?
Through 2 dedicated air inlets located in the Wing/Body fairings.
Air Systems
How are the CACs (Cabin Air Compressors) air inlets protected ?
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.
Air Systems
What do the CACs (Cabin Air Compressors) do ?
They pressurize and flow-regulate the incoming air before supplying it to their dedicated Pack.
Air Systems
How are Packs controlled ?
By 2 identical pack control units (PCUs).
If one system fails, pack control automatically switches to the other system.
Air Systems
Ground operations :
When running on APU, how many CACs (Cabin Air Compressors) are running ?
2 in normal operations as only one CAC on each side will run.
4 during cold weather as both CACs are commanded ON.
Air Systems
Can Air Conditioning be used during ENG start ?
NO.
All CACs are commanded OFF during normal start.
Air Systems
When do PACKS restart after ENG start ?
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.
Air Systems
How do pilots manage the Standby cooling mode of a Pack ?
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.
Air Systems
What does an EICAS message PACK MODE (L,R) mean ? What action(s) can be done ?
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.
Air Systems
What do recirculation fans do ?
They assist the Packs to maintain a constant ventilation rate through the cabin.
Air Systems
How do recirculation fans work ?
They draw cabin air through filters, then reintroduce the air into the condition air distribution system.
Air Systems
What type of air does the flight deck receive ?
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.
Air Systems
What type of air does the passenger cabin receive ?
The passenger cabin receives a mix of outside air and recirculated air.
Air Systems
Can cabin attendants reduce outside air to the cabin based on the number of occupants?
Yes, but this reduction is limited to ensure a minimum airflow to the cabin.
Air Systems
Which temperature range can be selected for cabin and flight deck ?
18°C to 29°C
Air Systems
Can flight attendants change the temperature in the cabin ?
YES
± 6°C from the cockpit-selected temperature.
Air Systems
In normal pack operating mode, when is ECONOMY mode triggered ?
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.
Air Systems
How are Pack temperatures controlled ?
1- By modulation of the pack control valves.
2- By opening or closing ram doors of the ram air heat exchanger.
Air Systems
What prevents smoke from entering the flight deck ?
The flight deck is kept at a slightly higher pressure than the cabin.
Air Systems
What is the purpose of the Alternate Ventilation System (AVS) ?
To provide an alternate means of ventilation to the flight deck and cabin if both packs become inoperative.
Air Systems
Which zone controls the pack temperature ?
The zone supplied by that pack that is set to the lowest temperature (white on synoptic).
Air Systems
Can Air Conditioning be used on the ground without APU running ?
Only if all 3 GND power supplies are used.
Air Systems
What conditions will cause the Equipment Cooling System to automatically reconfigure to OVRD mode?
- 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.
Air Systems
How is temperature regulated with the TRIM AIR system OFF?
- The flight deck temperature is maintained between 18-29 °C
- The cabin temperature controllers attempt to maintain all zones at the average target temperature.
Air Systems
If a pack is in Standby Cooling mode and the other operates normally, will it stay on throughout the flight?
No, the pack in Standby Cooling mode will shutdown at lower altitudes and higher outside air temperatures.
Air Systems
What provides additional cooling in the lower recirculation ducts ?
Liquid-to-Air heat exchangers.
What is the air source for the packs?
Outside air
How many Cabin Air Compressors (CACs) are there?
Four
What is the purpose of the CACs?
Pressurize and regulate the flow of outside air to the packs.