skyblue CBT pnemuatics Flashcards
what is the purpose on the pneumatic system?
to provide high pressure air to\;
- air con
- pressurisation
- de icing
where is air tapped from?
high and low pressure stages of the compressor
what provides air to the air con packs?
the respective side
where does air for the de icing system come from?
high pressure stage
how does low pressure air enter the bleed air system?
through a one way check valve
what supplements bleed air when power is not high enough from the low pressure pneumatics?
high pressure bleed
what does the HP valve require to open?
electrical power and pneumatic pressure
what powers the HP valves?
the respective DC bus
what will happen to the HP valve if electrical power is lost?
it will close
when will the high pressure bleed air temperature sensor close the HP valve?
more than 270C
when will the HP valve reopen after closing due to an overheat?
after a cooling period
what ultimately determines the position of the high pressure valve?
pressure output at the low pressure stage
at what LP pressure output will the HP valve open?
22psi
what prevents backflow into the LP part when HP valve is open
LP check valve
how is the bleed valve controlled and operated?
electriclly controlled and pneumaticaly operated
what closes the bleed valve if power is lost?
solenoid
what powers the bleed valves?
DC ESS BUS
when will the bleed valve automatically close?
if power or airflow is lost
where are the temperature sensors located?
downstream of the bleed valve
at what duct temperature will the bleed valve and HP valve automatically close?
274C
when will a bleed automatically close?
- leak
- over temp
- engine failure on opposite side
- fire handle pulled
when will the left bleed valve only automatically closed?
prop brake engagement
what is the purpose of the crossfeed?
to feed both packs with one engine on the ground only
when is the crossfeed open on the ground?
when right engine is running and supplying air
when should a pack be turned off in flight?
when a bleed valve fails
what is max altitude with only one bleed operating?
20000ft
what powers the crossfeed valve?
DC BUS 1
where does the leak detection system look for bleed leaks?
- wing leading edges
- wing to fuselage fairings
- upper/lower fuselage floor
- air conditioning pack area
what is the leak detection tube made of?
control lead surounded by an insulating material and surrounded by an inconel tube
how is a leak detected?
increasing temperature reduces the resistance in the leak detection loop until it is grounded at 124C. this triggers an AIR LEAK caution
what happens 1 second after an air leak is sensed?
pack, bleed and HP valves close. System is inop for rest of the flight
if the leak was in the left system, the crossfeed will also close
what controls the HP and bleed valves from the flight deck?
BLEED button
what psi does a bleed valve require to open?
10psi
when do we get an AIR BLEED caution?
when switch position disagrees with bleed valve position, overpressure, overheat or leak
when does the OVHT illuminate?
the temp sensor downstream of the bleed valve exceeds 274C
