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Initial Ground School - E145 > Systems - AC and Pressurization > Flashcards

Systems - AC and Pressurization Flashcards

1
Q

Where does Engine Bleed Air Come from?

A

9th and 14th stages of the N2 compressor.

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2
Q

What does the Pre-Cooler located in the Pylon do?

A

Takes N1 air to pre-cool the very hot N2 air and dumps N1 air back into the atmosphere.

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3
Q

What do the bleed buttons in the cockpit control? What happens when you unstripe the buttons?

A

Control the engine bleed valves. When you unstripe, you are opening the bleed valve.

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4
Q

What are some terms an AC Pack will sometime be refered to as?

A

1) Environmental Control Unit (ECU)
2) Envronmental Control System (ECS)
3) “Air Cycle Machine”

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5
Q

What is the purpose of a “Pack”

A

To condition air by taking it from an extremely hot state and cooling to a more tolerable temperature.

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6
Q

What controls the pack valve?

A

The pack buttons in the cockpit (when striped, the pack valve is closed).

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7
Q

How does the pack condition air?

A

Takes air from the compressor, runs it through some heat exchangers, removes the moisture with a condenser and then sends reletivly cooler air to the cockpit and or cabin.

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8
Q

Which pack primarily feeds the cockpit? Which one primarily feeds the passenger cabin?

A

1 - Cockpit

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9
Q

What does the re-circulation fan do? How is it controlled?

A

picks up air from under the floorboards and recycles it back through the A/C system. It is controlled by the recirc button in the cockpit.

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10
Q

What is the proper way to use the recirculation fan?

A

Should be used all the time unless it is hotter in the airplane than it is outside.

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11
Q

What does the Gasper Fan do

A

Takes air from below the floorboards and routes it through the “eyeball” vents in the cockpit and cabin.

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12
Q

Will the Gasper fan shut off on the ground? Why or why not?

A

Will not shut off on the ground because it cools the aft electronics.

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13
Q

What happens if the RAM air door is in the emergency position?

A

Outside air enters the duct and bypasses the pack entirely.

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14
Q

What happens when the RAM air door is in the “Normal” position

A

Allows RAM air to move through the pack normally.

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15
Q

When will the RAM air doors move to the Emergency Position?

A

In flight when both packs are off line.

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16
Q

What needs to happen before Emergency Ram air pressure can enter the cabin?

A

Pressure inside the cabin needs to be equal to pressure outside the cabin.

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17
Q

What will result if a pack overloads?

A

The pack will go off line.

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18
Q

What causes a pack to overload?

A

Over pressure downstream of the pack valve (PRSV) and over temp downstream of the compressor.

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19
Q

How could the crew induce a pack overload?

A

By asking for too rapid of a temp change in too short a time.

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20
Q

To avoid Pack Overloads, what is the proper way to bring packs online and change the temp?

A
  • Turn the temp control knob to 12 O’Clock poistion and wait 30 sec
  • Select the pack and adjust temp slowly.
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21
Q

How do you manually control temperature, are there any temp restrictions when manually controlling?

A

Pull the temp control knob. There will be no temp restrictions.

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22
Q

When temp control is in the Automatic mode, are there any restrictions to the temp output?

A

Yes, 18°-29°C

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23
Q

How do you give control of the passenger cabin temp to the Flight Attendent?

A

Move the cabin temp knob all the way to the left to ATTD notch.

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24
Q

What is the recommended practice on the ground to ensure that the cabin temperature sensor does not accumulate frost?

A

Move the cabin temp controller knob to full hot for about 30 seconds every 30 mins.

25
Q

How will you know if you get a bleed leak?

A

EICAS message and a “leak” inscription on the on the overhead bleed buttons

26
Q

What is the only way for leak inscriptions (overhead and EICAS) to go away?

A

Associated temp probe(s) that detetected the leak must cool.

27
Q

How do you determine which side of the Engine Bleed Valve the leak is on?

A

If the Leak is downstream of the EBV, the warning will go out after you stripe the EBV button.

28
Q

When you stripe the EBV button, what will result and what are you limited to?

A

The associated pack will be lost and you are limited to 25,000 feet or lower and must completely stay out of icing conditions.

29
Q

If you are operating under a single bleed and there are no leaks then what altitude are you restricted to in icing conditions?

A

15,000 feet.

30
Q

What happens if the leak is on the engine/ pylon side of the EBV and what will you need to do?

A

1) The warning light will not go out.
2) QRH will have you reduce the thrust and if this does not solve the issue then
3) The associated engine will need to be secured.

31
Q

Can APU and Engine Bleed air occupy the same plumbing at the same time? Why or Why not?

A

No it can’t becuase APU bleed air is pumped at a lower pressure and Eng Bleed will trump it.

32
Q

Can APU air be used to run the Anti Ice? Why or why not?

A

No it can’t becuase it does not have enought temp or pressure.

33
Q

What altitude are you limited to if you lose a pack?

A

25,000 feet.

34
Q

If you lose a pack, other than due to a bleed leak downstream of the EBV, what altitude are you restricted to in Icing conditions?

A

15,000’

35
Q

Where are the massive leak detectors located, how many are there and why are they there?

A

Three located in the aft electronics and in AFT electronics because the electronics are vital to the operation of the aircraft.

36
Q

What are the goals of the pressurization system?

A

1) Maintain S.L. pressure Alt (Primary)
2) If unable to do above - control the cabin alt rate of change to one that is comfortable (+- 600-700fpm).

37
Q

How many outflow valves do we have and what do they do?

A

We have 2 and they control the amout of air pressure we let out of the cabin.

38
Q

How is the Pneumatic Outflow Valve controlled when in manual operation?

A

Mechanically by the manual controller knob through a needle valve.

39
Q

How is the Electropneumatic outflow valve operated

A

Electrically commanded and pneumatically operated. Controlled by the digital controller on the center console (Brain).

40
Q

How are the outflow valves kept in the closed position?

A

Air pressure from the packs is consistently pushing against the outflow valves.

41
Q

What forces the outflow valves open?

A

Vacume pressure which is provided by a venturi syle ejector pump with air from the engine bleeds.

42
Q

How many outflow valves are normally moving in flight?How is this done?

A

1) 2 are moving
2) The electropneumatic valve “slaves” the pneumatic valve as long as the manual controller knob is fully to the left (DN position).

43
Q

What happens if you move the manual controller knob?

A

It will remove the pneumatic needle valve from the slaved position and over-ride allowing for manual control.

44
Q

When does the A/C start to pressurize, what pressure will it hold and until what point?

A

1) When you push the T.L. fwd.
2) To 300 ft below T.O field elevation for 15 mins OR
3) Until theoretical cabin alt is reached.

45
Q

What is theoretical cabin alt?

A

A function of fast (or slow) you are climbing

1) If you are in a slow or stagnant climb, the will be no change in cabin pressure until after the 15 min mark
2) If you are in a fast climb, there will be a faster change in the rate of cabin pressurization (likely before the 15 min mark).

46
Q

What is CPAM and how does it work?

A

Cabin Pressure Aquistion Module

1) Fed data by Pitot static 3
2) Takes data from outside and compares it to inside pressure to give you Cabin ALT, Cabin Delta P and Cabin Rate of Climb/ Descent.

47
Q

On your after T/O flow, what should you see on your Cabin ALT, Cabin Delta P and CAB rate of climb?

A

1) Cabin ALT = 300 feet below Field Elev (for 15 mins)
2) Cabin Delta P = slowly increasing (pressure outside is decreasing & inside is holding)
3) Cabin Rate of Climb = zero until you are in a climb.

48
Q

When will the Cabin Warning Horn Go off?

A

When the cabin gets to 10,000 feet (this should never happen since we are limited to 8,000 feet @ 37,000 feet).

49
Q

When will the pax O2 masks drop automatically?

A

14,500 feet (+-500 feet).

50
Q

When will the Dump Button on the digital controller work?

A

When you are in “Auto” pressurization mode.

51
Q

What happens when you push the Dump Button

A

Automatically dump pressure until you get to 14,500 feet.

52
Q

If you are 10,000 feet and you push the dump button, to what altitude will you be pressurized?

A

10,000 feet.

53
Q

to what cabin alt are you pressurized to upon landing?

A

300 feet below landing field elevation.

54
Q

Which valve or valves are being controlled when you go to manual pressurization?

A

Pneumatic Outflow (needle) valve (you are now the “chain” on the stopper).

55
Q

What is the procedure when going to manual pressurization?

A

1) Select manual pressure button
2) Take manual controller to 12 O’Clock
3) Make small adjustments to maintain cabin alt schedule in QRH.

56
Q

How is cabin overpressure prevented in the event the automatic controller fails?

A

Each outflow valve has an independent static port that measures outside and inside pressure and valves are designed to automatically fail in the open position when they sense a high delta P.

57
Q

Is the FWD avionics compartment pressurized?

A

No

58
Q

How is the fwd avionics compartment cooled?

A
  • NACA ducts with water separators
  • a pair of recirc fans that run as soon as the aircraft has DC power
  • a pair of individually thermostatically controlled exhaust fans.
59
Q

What the pressurized footprint area (pressure vessel)

A

Just aft of the fwd electronics to the aft electronics compartment.

Initial Ground School - E145 (15 decks)

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