What is the intake source for the CAC's?
Two dedicated inlets located in the wing/body fairings.
When are the deflector doors deployed?
During normal ground operations and landing phases of flight.
The airplane is divided in to how many temperature zones?
7. Flight deck + 6 cabin zones (A, A1, B, B1, C, D)
How many CAC's are running on the ground using the APU as the power source? What happens during cold weather ops?
Normally only one CAC per side. Both CAC's commanded on during cold weather ops. (Below -1C)
During engine start, the CAC's are commanded off. How soon after engine start do the packs restart?
Packs do not restart until at least 2 minutes after the start sequence is initiated and the engine is running.
If both engines are started together, when do the packs restart?
Packs restart immediately after the second engine is running if the two minute limit is met.
It may be possible to draw fresh, unpressurized air into the airplane. If so, under what circumstances?
Only when the airplane is unpressurized.
What determines the pack outlet temperature?
The temperature zone requiring the coolest temperature controls the pack outlet temperature.
Describe how the trim valves function as cabin temperature regulators?
Hot trim air is added to the conditioned air to control the temperature in each zone.
How many trim air systems are there? Are there any manual controls?
2 trim air systems, left and right. System is automatic but the flight deck controls are the trim air switches and temp control switches.
How many CAC's feed each pack? What happens in the event of ONE CAC failure?
2 CAC's feed each pack. A single CAC is sufficient to operate the associated pack in all modes.
What does the EICAS message "PACK L/R" indicate?
- Pack Overheat - Other significant pack fault - Pack switches selected off
Is there any situation where some recirculated air will be supplied to the flight deck?
If one pack is OFF and it's associated recirculating fan is ON.
What is standby cooling mode?
An automatic built-in redundancy in the packs for certain internal malfunctions provides continued service. ACM is bypassed and air goes directly from primary heat exchanger to compact mixer.
How is a standby cooling mode of a pack indicated?
EICAS advisory "PACK MODE L/R" "STBY COOLING" in amber on AIR synoptic.
Which zones get recirculated and which get 100% fresh air?
100% to the flight deck. Recirculated air mixed with fresh to the cabin zones.
What temperature will be maintained in FWD and BULK cargo with the switches in AUTO?
Approximately 21 C
Lower deck air either goes overboard or into the lower recirculating system. What happens there?
Lower recirculating ducts contain liquid-to-air heat exchangers capable of additional cabin cooling, reducing the power required by the CAC's. Lower recirculating cooling provided by the ICS.
What services uses engine bleed air?
Thermal Engine Anti-ice system only
Should live animals be carried in the aft cargo compartment? If not, why?
No. Compartment is only kept above freezing.
Why is the air pressure supplied to the flight deck higher than that supplied to the cabin?
To prevent smoke from entering flight deck.
How is the forward cargo compartment temperature controlled?
Automatically controlled by: -Forward E/E exhaust air -An in-line electric heater -Forward cargo exhaust fan
How many recirculating fans are there?
3 in total. 1 upper and 2 lower.
If the FWD and BULK switches are off, what will the temperature in respective compartment be?
How is the bulk cargo compartment heated?
Ventilation and heat provided by: -Cabin air passing through a supply fan -In line electric heater -Residual heat from AFT E/E exhaust.
How many supply fans drive the airflow for FWD equipment cooling? How many fans are available?
One primary supply fan drives the airflow, with a backup fan operating automatically in case of failure. One vent fan. 3 fans available in total.
Is there any flight deck control of the ICS?
No, system is automatic.
When does the forward equipment cooling system go into override mode?
-FWD EQUIP COOLING switch selected to OVRD -In flight, both supply fans fail -In flight, low airflow is detected -Both flow sensors fail -In flight, excessive temperature is detected -Smoke detected in the system or the FWD cargo area -FWD CARGO FIRE ARM switch is ARMED
What happens when the FWD equipment cooling system is in override mode?
-Forward cargo heat and overboard vent valves close. -Both supply fans and and the vent fans commanded off -Forward equipment cooling override valve to override position Cabin diff pressure draws air through panels and forward E/E equipment, creating a reverse flow that exits through the override valve to an overboard venturi.
Exhaust air from the FWD equipment cooling system has two possible destinations. Where?
-Forward cargo heat -Forward outflow valve