skyblue CBT air con and pressurisation Flashcards
where are the 2 packs located?
in the gear bays
where is the external air plug located?
right hand side of aircraft
what does the left duct supply?
flight deck and pax cabin
what does the right duct aupply?
pax cabin
can one pack supply both compartments?
yes, through the mixing chamber
what conditions bleed air after the pack valve?
air cycle machine (one on each side of the aircraft
where does conditioned air go after the air cycle machine?
the mixing chamber under the flor of the aircraft to be mixed with ambient air
how is air evacuated from the cabin and where does it go?
guides along left floor of the cabin
recircualted to the cabin or exhausted through outflow valves under the aft fuselage
how is the toilet ventilated?
a vent line regulated by cabin differential pressure
how is pressurisation regulated?
by constricting the amount of air vented overboard by opening and closing outflow valves under the aft fuselage
how are the pack valves controlled and operated?
electrically controlled and pneumatically operated
what is the purpose of the pack valves?
shut down the pack and maintain a constant air supply pressure to the pack
what powers both pack valves?
DC ESS BUS
what pressure will the pack valves deliver to the packs with the flow button out?
22psi
what pressure will the pack valves deliver to the packs with the button pressed in? (hi flow)
30psi
where is the primary heat exchanger located?
landing gear fairing
where does air flow after the pack valve?
heat exchanger
what does the ground cooling fan do?
blows air over the heat exchanger if ram air is insuffcient
how is the ground cooling fan powered?
pneumatic air through an impeller controlled by the turbofan shutoff valve
when does the turbofan shutoff valve open?
airspeed less than 150knots
gear extended or retracted for less than 10 mins
when is the turbofan shutoff valve closed?
anytime the airspeed is greater than 150 knots
what will the turbofan shutoff valve do if opposite low oil pressure is sensed?
open as long as speed is 150 or less
what will the pack valve do if the turbo fan shutoff valve is not in the commanded position?
close to prevent pack damage
where does air flow after the heat exchanger?
compressor, secondary heat exchanger
where does air for the heat exchangers come from?
ram air flow
where is air from the secondary heat exchanger sent?
used to power the turbine
what does air do once it reaches the turbine section?
undergoes rapid expansion which decreases temp
what controls airflow into the turbine?
turbine inlet control valve
where does air flow to from the turbine?
a condenser and then a mixing chamber
how does the condensor dry the air?
uses air from the primary heat exchanger to send air to the water extractor, then back through the turbine and to the mixing chamber
how is temperature control acheived?
mixing bleed air tapped downstream of the pack valve and air produced by expansion turbine
what controls how much bleed air is used wih regard to temperature control?
temperature controller set by electronic controller or the rotary knob in the flight deck
what information does the electronic temperature controller use to determine temperature whe set to auto?
- compartment ambient temperature
- aircraft skin temperature
- pack supply duct temperature
what is temperature limited to by the pack duct in manual mode?
88C
what temperature will trigger the AIR DUCT OVHT?
92C
at what temperature will the pack valve close if the overheat is downstream of the compressor?
204C
what does the mixing chamber mix?
air produced by air from pack and ambient cabin air
how is cabin air evacuated?
2 recirculation fans which send air back to the mixing chamber
what powers the recirculation fans?
DC UTIL BUS
when will the recirculation fans automatically run at full speed?
when cabin floor temp is less than 18C
what will cause a AIR RECIRC FAN caution?
fan speed too low
associated electric motor overheats
what parts of the plane are ventilated by ambient air?
flight deck
forward cargo compartment
electronic racks
where is ambient air from the flight deck, electric racks and forward cargo compartment sent?
pressurised compartment or overboard
what does the ventilation extract fan do?
draws air into the forward compartment to cool flight deck, electric racks and flight instruments
what speed will the extract fan operate at if flight deck temp is below 20 degrees?
low
what speed will the flight deck fan operate at if flight deck temperature is above 52 degrees?
high
why would we use the extract air flow lever?
to stop air from flowing forward if smoke is detected in forward cargo compartment
how long will the extract fan stop for during start to avoid pressure shocKS?
120 seconds
what does the overboard valve do?
allows air from the extract valve to be sent overboard
on the ground with engine 1 or has low oil pressure what will the overboard valve do?
it will be open. extract fan will run normally. underfloor will be closed
what will the extract fan do in flight or with engine 1 running on the ground?
underfloor valve open
overboard valve closed
what controls air outflow for pressurisation?
1 pneumatic outflow
1 electro pneumatic outflow
what happens with the pressurisation system in auto mode?
pneumatic outflow valve is slaved to the electro pneumatic outflow valve which allows them to operate simultaneously
when will the outflow valve protection activate through the manometric capsules?
positive differential pressure greater than 6.35psi
negative 0.5psi
what powers the pressurisation digital controller?
DC BUS 1
how does the digital controller position the outflow valves?
a torque motor
what 4 parameters does the digital controller use to calculate required cabin pressure?
- departure field elevation
- destination field elevation
- existing cabin altitude
- aircraft altitude (baro if ADC 1 STD if ADC 2)
which valve is used in manual pressurisaton mode?
pneumatic only
what ROC/ROD can be set in manual mode?
-1500 to +2500rpm
what does setting the pressure knob to 9-10 o clock ensure when switching to manual mode from automatic?
ensures no pressure bump at the switch over
what signal does the landing gear microswitch give to the pressurisation digital controller?
determines how much pressure is given to the outflow valve after takeoff to maintain field elevation after 3500ft
what is the maximum cabin rate of climb?
550fpm
what is max cabin pressure differential?
6 psi
at 25000ft, what will the cabin altitude be?
6740ft
what is max descent rate of cabin altitude?
400fpm
what pressure will the controller set for landing?
landing elevation -300ft
what will the digital controller do at touchdown?
open the outflow valves to reach field elevation
when is the automatic return feature available?
up to 3500ft
what does the FAST button do?
uses a descent rate of 500fpm
what is duct temperature limited to in automatic mode?
88c
when should we not open the overboard valve?
when differential pressure is more than 1psi
what will be triggered if we deselect the exhaust mode push button on the ground?
ground mechanic call
what does the ditch push button do?
closes both outflow valves with 2 electric motors powered by the DC EMER BUS
what will open if we press the dump button?
both outflow valves
what are the indications of a succesful pressurisation test?
18800
-8800 on the digital controller
when is the pressurisation test inhibited?
in flight
