Environmental System Flashcards
Which system provides conditioned air to the flight deck and passenger cabin?
The environmental control system (ECS) does, via two air conditioning units (PACKs)
What’s an ACSC?
It’s an “air conditioning system controller”
How many air conditioning system controllers (ACSC’s) do we have
2
Are the ASCS’s dual channel?
Yes, an A and B channel.
How often do the ACSC channels switch?
Daily
Is there any indication of which ACSC channel is active?
No
What do the ACSC’s do?
They regulate the aircrafts pressure (by operating the HPV and engine bleed valves) and temperature (controls the output temperature of the packs)
What does PACK stand for?
Pneumatic air conditioning kit
How many PACK’s do we have?
2
Where are the PACK’s located?
In the aft equipment bay
Which pack usually supplies air to the passenger cabin?
Right pack
Which pack usually sends air the flight deck?
The left PACK
What controls airflow through the packs?
The flow control valves (pack valves)
Will the pack valves automatically close when an engine start button is pushed?
Yes. After starter cutout, the pack valves will go the their previous position.
Which valve is modulated to adjust the temperature of the air?
The temperature control valve
What is used to cool the bleed air that’s sent to the cabin?
Three heat exchangers (pre-cooler, primary heat exchanger, and secondary heat exchanger) and an air cycle machine
What’s the flow of air through the PACK’s?
From the bleed air manifold —> pre-cooler —> flow control valve —> either the primary heat exchanger or the temperature control valve —> from the primary heat exchanger to the —> air cycle machine —> secondary heat exchanger —> reheated —> ACM —> mixed with metered, warm air from the temperature control valve —> condenser (removes excess water) —> fuselage
Where does conditioned air enter the cabin?
Ceiling, sidewalls, and gaspers
How is cabin air exhausted?
At the floor level
Is there another way for the galley to recieve heat?
There’s supplementary galley heat provided at the galley control panel
What is the backup cooling for the EICAS and EFIS displays?
The conditioned air from the left PACK
Is cabin air recycled?
Yes
Is galley or lavatory air recycled?
No, it’s exhausted
What aids in recirculating air throughout the cabin?
Dedicated, left and right, recirculation ducts and fans
What does the RECIRC toggle switch do?
In the ON position it allows air throughout the cabin to be recirculated
What controls the mixing of hot and cold air?
ACSC (air conditioning system controller)
Where can we see the cockpit and cabin air temperature?
ECS synoptic page
Apart from the ECS synoptic page, can the cabin temperature be seen anywhere else?
EICAS status page
How is the temperature usually controlled?
Automatically by setting the CKPT and CABIN temperature knobs to the desired temperature
How do you manually control the aircraft temperature?
Selecting MAN on the AC overhead panel. Temperature increase or decrease can be achieved by adjusting the hot/cold toggle switch. This will not display a selected temperature. You can try and achieve a particular temperature by watching the PACK discharge temperature vis the ECS synoptic page.
In manual mode, when will you get a L(R) PACK message?
When the discharge temperature is <= 5ºC or >=85ºC
What will happen if you have an overtemperature in auto mode?
The ACSC automatically closes the PACK valve, the pack shuts down, a L(R) PACK TEMP message will be displayed, and FAULT will illuminate on the L(R) air conditioning pack switchlight.
What the highest you can fly single PACK?
FL310
What does it indicate if FAULT is illuminated on the left or right air-conditioning pack switchlights?
Pack overtemperature or over-pressure condition exists. The pack valves close automatically and must be manually reset per the QRH.
What does the RAM air SOV do?
Supplies RAM air to the right side of the mixing manifold
What does the RAM-AIR guarded switchlight do?
Allows RAM air to circulate in the cabin. Used when the aircraft is unpressurized. This is limited to 15,000’.
What happens to the aft cargo bay if the aircrafts RECIRC overhead switch is turned off and the CARGO switch is selected to COND AIR?
Cool, un-recirculated air is sent to the aft cargo bay from the mixing manifold
What does OFF do when selected on the CARGO switch?
Intake SOV and Exhaust SOV are closed
What does the CARGO switch do the the AIR position?
Allows recirculated air (or conditioned air if the RECIRC switch is off or the RECIRC fan has failed) to flow through the aft cargo bay
What happens when the CARGO switch is set to COND AIR?
Automatically provides temperature control to the aft cargo bay via an electric heater
How many smoke detectors are in the forward cargo bay?
3
How many smoke detectors are in the aft cargo bay?
2
How are the display screens cooled?
Via fans that draw cool air from the flight compartment
What methods of cooling are available for the EIFS and EICAS CRT’s?
A ground fan, flight fan, and standby mode
What does the ground fan do?
Primary source of CRT cooling on the ground
What does the flight fan do?
Primary source of CRT cooling in the air?
What happens if both the ground and flight fans fail?
Conditioned flight deck air is used to ventilate the displays
What do the exhaust fans do?
Used to evacuate air from the avionics bay, and CRT display exhaust duct.
What does the ground valve do?
It ensures the aircraft is depressurized on the ground, improves the effectiveness of avionics cooling, and can help depressurization the aircraft on the ground.
When is the ground valve open?
It opens after touchdown. It closes again when the galley and passenger doors are closed. It can be opened on the ground when the EMERGENCY DEPRESURIZATION button is pushed.
What message is displayed if the ground valve fails to close?
OVBD COOL
What message is displayed if the ground valve fails to open?
OVBD COOL FAIL
How quickly does the ground valve open, on the ground, when the EMER DEPRESS button is pushed?
At full speed (approximately 2 seconds)
What controls the aircrafts pressurization?
Two cabin pressure controllers (CPC’s)
Ho is the cabin pressure regulated?
By modulating the outflow valve
How many motors does the outflow valve have?
3 electric motors
When do the cabin pressure controls (CPC’s) switch?
With weight on wheels (WOW) plus 3 minutes
Is there a way to manually switch the cabin pressure controllers?
Yes. By pressing the PRESS CONTROL switch twice.
What happens when you select the EMER DEPRESS switch in flight?
The outflow valve will open to depressurize the aircraft but it won’t depressurize to less than 14,500’+/-500’
How many safety valves do we have and what do they do?
There are two pneumatically operated safety valves which prevent overpressure and negative pressure conditions.
What does the cabin pressure acquisition module (CPAM) do?
- Automatically deploys the passenger oxygen masks at 14,000’ cabin pressure altitude.
- Limits cabin altitude to 14,500’ +/- 500’
- Controls the opening of the ground valve to avoid disturbance of the outflow valve.
Whats normal cabin differential pressure?
8.5psi
What’s the maximum relief differential cabin pressure?
8.7psi
What’s the maximum negative pressure?
-0.5psi
What’s the maximum differential pressure during taxi, takeoff, and landing?
0.1psi
What does ground mode do?
- drives outflow valve fully open for maximum ventilation
- closes when passenger and service doors are closed
What does pre-pressurization mode do?
- Activated on the ground when thrust levers are advanced for takeoff.
- Cabin is pressurized to 150’ below actual field elevation
- For a no bleed takeoff the outflow and ground valves are closed.
What does takeoff abort mode do?
- Altitude is drive back to field elevation at 500fpm for 20 seconds, then the outflow valve remains fully open. Returns to ground mode.
- Activates when thrust levers are retarded for an aborted takeoff
What does flight abort mode do?
-Retains pre-pressurization altitude for the first 10 minutes of flight in event of a return to the field.
What does climb mode do?
- Increases cabin pressure altitude, usually at 300-500fpm
- programmed according to the landing field elevation.
What does cruise mode do?
-Every cruise altitude has an assigned cabin pressure altitude that the aircraft will try and maintain
What does descent mode do?
- Increases the cabin pressure altitude, typically by about 300fpm, by restricting to the outflow valve.
- The rate is directly related to the aircrafts rate of descent
What does landing mode do?
- after touchdown the cabin pressure altitude is increased to landing elevation. Outflow and ground valve will be completely open.
- Entered when the active controller (CPC) receives the WOW signal and at least on thrust lever is at idle.
When will FAULT illuminate on the PRESS CONTROL switchlight?
When both CPC’s have failed
What happens when you select the PRESS CONTROL switchlight?
Will change the pressurization to manual mode and MAN will illuminate
What’s the manual pressurization procedure?
- Select UP or DOWN on the MAN ALT toggle switch to decrease or increase the cabin pressure altitude respectively. The rate can then be controlled by MAN rate switch.
- To hold your current pressure altitude select HOLD on the MAN ALT toggle switch
When will you get a cabin altitude caution message?
Cabin altitude above 8,500’
When will you get a cabin altitude warning message?
Above 10,000’. Additionally a voice can be heard saying, “CABIN PRESSURE”
How often is the pressurization system tested?
It’s continually tested throughout the flight
EPC memory checklists related to pressurization
RAPID DECOMPRESSION checklist items and CABIN ALT OR EMERGENCY DESCENT checklist memory items
