EMB-120 Environmental Control System Flashcards Preview

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Flashcards in EMB-120 Environmental Control System Deck (31):
1

The maximum operating altitude with one engine bleed deferred closed (EECs ON) is what?

FL250

2

Illumination of a DUCT OVERHEAT light closes what valves?

None

3

On the descent, the ALT SET knob on the cabin pressurization should be set to what?

-300' field elevation

4

With the pressurization in AUTO and the rate knob in the detent, the scheduled climb rate is ______ and the descent rate is ______.

• Climb rate = 650 FPM
• Descent rate = 450 FPM

5

At FL 230 you transfer to Electrical Emergency Mode. How will the pressurization system respond?

• Engine bleed valves close.
• Aircraft will slowly depressurize.
• Must descend below FL200 and 135-200 KIAS to start APU.

6

What will happen to the PNEUMATIC/AIR CONDITIONING panel in emergency mode?

Nearly everything on the panel is powered by the main buses. Therefore, when we are in the emergency mode, everything will be depowered except for the ram air valve. That is powered of an Emergency Bus and will continue to operate.

7

Why do we call our bleed air P2.5 and P3?

We draw bleed air from the two stages of compression in the engine. One bleed source comes off of the low speed compressor at station 2.5 so we will refer to that bleed pressure as P2.5.
The second bleed source comes off the high speed compressor at station 3. We will refer to that bleed pressure as P3.

8

What is P3 always available for?

P3 is always available for pressurizing the Hydraulic Reservoir and for inflating the De-ice Boots. However,P3 air may or may not get past the High Stage Shutoff Valve depending on the bleed switch position and the power on the engine.

9

BLEED AIR SWITCH POSITIONS WILL PROVIDE WHAT P AIR?
CLOSE:
LOW:
AUTO: HIGH POWER / LOW POWER

With the bleed air switch in CLOSE, the bleed air valve and the high stage shutoff valve will be closed.
With the bleed switch in LOW, the bleed valve will be open, the high stage shutoff valve will be closed, and the line will see P2.5.
The same is true for the bleed air valve in the AUTO position and a high power setting.
If the power setting is low the high stage and bleed valves will be open and you will be using P3 air.

10

What is happening during a Bleed Overheat?
Will anything automatically close?

If the temperature sensor downstream of the bleed valve overheats, it will generate a Bleed Overheat light on the overhead, an air conditioning light on the MAP, and a single chime. It will also automatically close the bleed shutoff valve.

11

DUCT LEAK:
What is happening and what will the QRH have you do?

There is a leak in the bleed ducting. The side with the leak will annunciate a DUCT LEAK warning light and audio.
The QRH will have you close the bleed valve and the crossbleed valve in an effort to isolate the leak. If the light does not go out: the QRH will direct you to shut down the engine, since the leak is presumed to be upstream of the bleed valve.

Note: If the leak is on the left side, make sure the APU bleed valve is closed before shutting down the engine. Remember that when the QRH asks if we are pre or post mod, we are pre-mod on this modification only.
FYI: The duct leak sensors are individual units wired in parallel and distributed along the hot ducting. Failure of one does not affect the others.

12

If the electrical system transfers to emergency mode and the APU generator is not available what will occur regarding the pressurization system?

The bleed valves will close and the aircraft will depressurize.

13

Which component receives power from the emergency bus system?

The ram air valve.

14

If a bleed valve sensor overheats:

The BLEED OVERHEAT caption will illuminate and the bleed valve will close automatically.

15

When are the heat exchangers used?

When the packs are operating with the aircraft on the ground, the heat exchangers are cooled by ambient air with a ground cooling fan. It operates automatically with weight on wheels any time the packs are not off.

16

What pressure of bleed air does LOW and NORM let to PACK?

The Low setting on the Pack knob lets in 15 psi of bleed air pressure to the air cycle machine (Pack).
The NORM position lets in between 15 and 35 psi.

17

When will you get a DUCT OVERHEAT?

If the temperature going to the cabin is greater that 188 degrees C, it will generate a DUCT OVERHEAT caution.
Check the QRH. Make it cooler.

18

What is happening during a PACK FAIL?
Will anything automatically close?

Pack fail occurs when the compressor outlet overheats. This may be due to demanding too much hot or cold air.
If the air downstream from the compressor is too hot, the temperature sensor will generate a PACK FAIL caution light and the pack inlet valve will automatically close. This is one of only two lights in the environmental system that cause an automatic valve closure.
What is the other one?
[Bleed Overheat closes the bleed valve].
Check the QRH.

19

During a descent with the bleed and pack switches in AUTO and NORM, respectively, the aircraft experiences a PACK FAIL condition at 16,257’. Why?

A bleed position of AUTO with reduced power selects for P3 air which increases in temperature during the descent.

20

With the bleed switch and pack valve in AUTO and HIGH, respectively, the pressure source is:

Always P3.

21

With the gasper fans off will there be any air coming out them with the packs running?

With the gasper fan switch in the off position, the gasper shutoff valve is open and whatever pressure or temperature is delivered from the packs is what is felt at the gasper nozzles.
With the switch to MIX, the shutoff valve is open and the gasper fan (underneath the floor) is in low. The mixture is sent to the gasper nozzles.
In auto, the valve and fan settings are temperature dependent. With the air temperature from the packs less than 75 degrees F, it is the same as the Gasper switch OFF – that is the shutoff valve will be open and the gasper fan will be off.
With the temperature above 75, the shutoff valve will be closed and the gasper fan will be on high.
The auto position cycle the fan on and off. This tends to annoy the passengers even thou it is supposed to supply colder air out of the gaspers.

22

Where does cold and hot air exit the environmental system in the cabin?

When duct temperature is greater than 75 deg F, air is ducted to the HOT outlets on your feet.
When duct temperature is less than 75 deg F, air is ducted to the COLD outlets by your head.

23

Ensure the aircraft is ____________ before selecting the RAM AIR SWITCH to OPEN.

Ensure the aircraft is UNPRESSURIZED before selecting the RAM AIR SWITCH to OPEN.
The purpose of RAM AIR is to provide ambient air to the cabin, if desired, when conditioned PACK air is unavailable. This presumes that the cabin is unpressurized and the PACKS are OFF (or bleed valves are CLOSED). Attempts to use RAM AIR when the PACKS are operating will result in a PACK FAIL condition because the inlet to the heat exchanges will be closed.

24

What would be good reasons to have the Ram Air valve open in flight?

To eliminate smoke once the cabin is depressurized below 10,000.
To do an unpressurized takeoff

25

What is the purpose of Ram Air?

The purpose of RAM AIR is to provide ambient air to the cabin, if desired, when conditioned PACK air is unavailable. This presumes that the cabin is unpressurized and the PACKS are OFF (or bleed valves are CLOSED). Attempts to use RAM AIR when the PACKS are operating will result in a PACK FAIL condition because the inlet to the heat exchanges will be closed.

26

RAM AIR should be used when:

The cabin is unpressurized and the bleed valves are closed.

27

The COOLING FANS operate when:

The aircraft is on the ground and the pack valves are not closed.

28

A takeoff with the Ram air switch OPEN and the air conditioning packs ON will result in:

A PACK FAIL condition for both systems.

29

Which statement is true concerning ram air?

Ram air routes ambient air to the cabin.

30

What does the vacuum do for the environmental system?

Vacuum allows the outflow valves to change.

31

What happens if there is a loss of vacuum in the environmental system?

Both outflow valves close and cabin pressurizes to 7.2 psi. Descend below 10,000 and turn off packs.