Air Conditioning, Pressurization and Pneumatics Flashcards Preview

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Flashcards in Air Conditioning, Pressurization and Pneumatics Deck (39):

What is the purpose of the ECU?

Regulates bleed air flow rate and pres for air conditioning, pressurization and deicing.


What is normal max dif?

When will the safety valve open?

When is neg relief provided?

What is max cabin altitude?

When does the "Cabin Pres" warning light come on?

5.46 psi

5.8 +/-0.15 psi

-.5 psi

8000 ft

9800 ft


What is takeoff memorization mode?

Pressurization controller stays in takeoff mode for 10 minutes after takeoff or 5000 above field altitude, whichever occurs first.

This facilitates a return to the departure airport.


What does the cabin pressurize to if bleeds are on, when still on the ground?


What rate?

400 ft below aircraft altitude.

PLA > 60°

400 ft/min


How are outflow valves operated?

Opened pneumatically and closed by spring.


What happens when you make a temp selection?

TSOV and bypass valve are modulated at the same time


What happens when a temp selection is made towards cool?

The ECU modulates the pack bypass valves to add warm air to the cold air coming off the turbines.

*It closes restricting warm air from mixing.


What happens if a pack overheats?

-Computer takes it offline.

-Flow will go to norm or hi automatically.

Remaining pack handles 70%


What does the environmental system provide?

Pressurization, heating, cooling and ventilation.


What are the two air conditioning modes?

What is the difference?

What happens if both digital and analogue channels fail on one side?

Analogue and automatic

There is no protection on analogue

You will not get a “Bleed Hot” caution light as one channel has to be functioning. So you get no indication of over temp or over pressure.


When does the "Bleed Hot" caution light come on?

What is the result?

When there is an over temp, an over pressure or a leak at 180°C in bleed ducts in between the duct and shroud.

The bleed air system automatically shuts down. (HPSOV, P2.2 cooling valve and PRSOV shuts off)


Which valves will be open at low power and bleeds on?

If bleeds are on and engine power setting is low, where is bleed air coming from?

If bleeds are on and engine power is high, where is bleed air coming from?

What happens to these valves in the event of loss of electrical power?

HPSOV and Nacelle FCSOV

HP compressor. (P3.0 or HPSOV)

LP compressor. (P2.7)

They will failsafe close.


What speed does the recirc fan run at when only one bleed pack is selected?

What will be the flow rate compared to two pack operation if only one pack is working?


70% of two pack operation.


What is the temperature range the ECU keeps in the supply ducts?

2.8°C to 71 °C


When in AUTO control what temperature does the ECU regulate the cabin to? How

What does MAN selection do? What is the temp range? When is it used.

Coldest: 15°C - full counter clockwise
Warmest: 27°C - full clockwise.

It determines what the duct temperature should be in order to achieve the desired temperature. Therefore, disregard temperatures of duct when in AUTO.

MAN selection controls duct temperature between 3 °C to 71°C. Duct temperatures need to be monitored more closely in MAN mode. It's used only when AUTO mode fails.


How are cabin and flight deck temperatures related?

They are not fully independent. A temp increase in the flight deck can raise the temp in the cabin because a percentage of the flight compartment air goes to the cabin.


Apart from air conditioning for the flight compartment, where else is air conditioning supplied to?

Fwd FA gasper, Lav, and rear baggage compartment.


How does the ECU distribute the air in the cabin zone for heating/cooling?

70/30. i.e. Heating: 70% for lower dado panels and 30% for PSU gaspers. Cooling is the opposite.


When would the inlet/outlet ventilation valve for the baggage compartment close? How would you know?

When smoke is detected in the baggage compartment or electrical power is lost. Two white lights on the FPP turn on when the valves close.


Where is avionics cooling provided to?

5 LCDs
Avionics rack
Wardrobe rack


How many fans cool the avionics?
How many are used on battery power and what's the limitation?
How many have to fail in order to get a message?

1. You get reduced brightness on screens


What are the five modes of pressurization?

-Smoke removal
-Pressure dump


What is the difference between the fwd outflow knob and the fwd outflow valve on the FO side?

Is electrical power required for either?

Fwd outflow valve opens the fwd safety valve more gradually whereas the knob on the FO side opens the fwd safety valve more rapidly.



How is the fwd outflow valve used to remove smoke?

When you turn the fwd outflow valve, the aft outflow valve closes while the cabin pressure is still being maintained by the fwd safety valve opening. This removes the smoke.


What is the aft safety valve used for?

Negative pressure relief and over pressure relief.


How is the forward outflow valve powered?

Pneumatically (suction)


How is the air supplied from the Flt Compt pack divided between the cabin and flight deck (percentage)?

How is Air from cabin comp pack divided between flight deck and cabin?


100% for the cabin. Therefore cabin gets 3/4 of total airflow.


What does P2.2 bleed air supply.

Deicing systems and oil pre cooler.


What are the two takeoff sequences of the pressurization system?

When do the sequences start?

Pre pressurization: if the bleeds are selected on for takeoff, the cabin starts pressurizing to 400 ft below the takeoff altitude at a rate of -300ft/min. This is to avoid a pressure bump that you would get if you takeoff with the bleeds off and then turn them on after takeoff.

Flight abort after takeoff: For ten minutes after lift off, if you have to return back to the departure airport, you don't have to reselect the landing altitude at the departure airport.

PLA set to more than 60 degrees.


What is the cabin descent rate for descent rate <2300 fpm?

...>3000 fpm

300 fpm and 1000fpm respectively.


How is the forward safety valve operated?

Operation is through suction only, created by aircraft slipstream.


What happens when you turn the Auto/Man/Dump switch to Dump?

Opens the outflow valve fully.


What happens when you turn on bleed air with bleed switches?

What happens when you shut off bleed?

Opens NCSOV.

Closes NCSOV and HPSOV.


What happens if there is a malfunction with the FCSOV?

What if both digital channels of ECU fail?

What if one digital channel of ECU fails?

It defaults pneumatically to the open position to permit ECS operation.

FCSOV closes and both packs stop working.

Remaining digital Chanel controls pack FCSOV.


What is required for the recirculating valve to operate at high speed?

Both packs must be on either MAN or Auto.


What happens if you switch both packs to off?

What happens if both packs are off and you turn one of the packs to MA or AUTO?

The PFCSOV and both TSOVs close.

The PFCSOV opens and the related TSOV opens and related bypass valves opens.

Ref: FS 1-7


What does the rotary bleed control switch do?

Controls NSOV.


What does the High Stage Pre cooler do? How does it work?

Cools HP air as it is too hot for use. It uses P2.2 air to cool P3.0 air and then vents it overboard.


What does the Deice Pre coo,er do?

Cools air for deicing by reducing pressure of the P2.7 and P3.0 air.