Air System Flashcards
Bleed air can be supplied from:
Engines, APU or external cart or source.
The following systems rely on the bleed air system for operation:
- Air conditioning/pressurization
- Wing and engine thermal anti-icing
- Engine starting • Hydraulic reservoirs pressurization
- Water tank pressurization
- Aspirated TAT probe (as installed)
Engine bleed air is obtained from:
th and 9th stages of the compressor section.
The engine bleed air valve acts:
as a pressure regulator and shutoff valve
engine bleed air switch is
DC activated and pressure operated
BLEED TRIP OFF activates at …
490 F or 220 psi
Duct pressure indicator is…
AC Operated
Isolation valve is…
AC operated
Isolation valve position is not affected by…
the APU bleed air switch.
The APU Bleed valve is automatically closed when:
closes automatically when the APU is shut down
The APU bleed air valve is…
DC controlled and pressure operated.
thrust must be limited to … with the DUAL BLEED light illuminated.
Idle
A wing-body overheat condition is caused by a…
bleed air duct leak.
Excess air …, … , and … is combined in the mix manifold
from the left pack, air from the right pack, air from the recirculation system
Ram air system provides ….. for the heat exchangers.
Cooling air
On the ground, or during slow flight with the flaps not fully retracted, the ram air inlet doors move to …… for …. .
Full open / maximum cooling
In normal cruise, the doors …
modulate between open and closed.
The RAM DOOR FULL OPEN light illuminates whenever …
the ram door is fully open.
A turbofan is located in …
each ram air exit duct.
Turbofan augments the ram airflow …
on the ground or during slow flight (flaps not retracted)
The fan operates …
pneumatically using bleed air
It is activated … , when …, by the … .
electrically, the pack is on, air-ground safety sensor or flap limit switch
The deflector doors extends when activated … by … .
electrically / the air–ground safety sensor
An overheat condition causes the pack valve to … and … light to illuminate.
close / the PACK TRIP OFF
Air Conditioning Distribution
An overheat condition causes the appropriate mix valves to … and … light to illuminate
drive full cold / the DUCT OVERHEAT
The recirculation fan system reduces … and … .
the air conditioning system pack load / the engine bleed air demand
The recirculation fan is driven by … .
an AC motor
The fan operates with the recirculation fan switch in… except with … .
AUTO / both packs on and one or both in HIGH
Equipment cooling
Selecting the alternate fan should restore airflow and extinguish the OFF light within … .
Selecting the alternate fan should restore airflow and extinguish the OFF light within approximately 5 seconds.
… pressure relief valves provide safety pressure relief by limiting the differential pressure to a maximum of …
Two / 8.65 psi
DCPCS Airplanes
AUTO
Automatic pressurization control; normal mode of operation. Uses brushless DC motor
DCPCS Airplanes
ALTN
Automatic pressurization control; alternate mode of operation. Uses brushless DC motor
DCPCS Airplanes
MAN
Manual control of the system using DC motor.
DCPCS Airplanes
In the automatic and alternate modes of operation, airplane altitude is provided by …
by the air data computers (ADCs)
DCPCS Airplanes
The ADCs receive barometric corrections from ….
the Captain’s and First Officer’s altimeters.
DCPCS Airplanes
The controller receives additional information from … , … , and ….
the air/ground sensor, the cabin pressure altitude sensing ports, and the stall management computer
Cabin air outflow is controlled by …, … and …
the main outflow valve, the forward outflow valve , the flow control valve.
When the flow control valve closes …
air is directed around the forward cargo compartment liner for inflight heating.
DCPCS Airplanes
The main outflow valve is actuated by …
DC motors in any operating mode.
DCPCS Airplanes
The cabin begins to pressurize on the ground when
N1 is …
N2 is …
after a time delay of …
greater than 60%,
greater than 89% and
1.5 seconds
An amber OFF SCHED DESCENT light illuminates if
the airplane begins to descend without having reached the preset cruise altitude; for example, a flight aborted in climb and returning to the takeoff airport.
The controller programs the cabin to land at the takeoff field elevation without further pilot inputs
If the FLT ALT indicator is changed …
the automatic abort capability to the original takeoff field elevation is lost.
The cruise mode is activated when the …
airplane climbs to within 0.25 psi of the selected FLT ALT
Selected FLT ALT :
At or below 28,000 feet
Differential pressure limit : 7.45 psid
Selected FLT ALT:
Above 28,000 feet
7.80 psid
The descent mode is activated when the airplane descends to …
0.25 psi below the selected FLT ALT
DCPCS Airplanes An amber AUTO FAIL Light illuminates if any of the following conditions occurs:
- Loss of DC power
- Controller fault
- Outflow valve control fault
- Excessive differential pressure ( > 8.30 psi)*
- Excessive rate of cabin pressure change (±2000 sea level feet/minute)* • High cabin altitude (above 15,800 feet)*.
DCPCS Airplanes
With illumination of the AUTO FAIL light …
, the pressure control automatically transfers to the other auto controller (ALTN mode)
Moving the pressurization mode selector to the ALTN position extinguishes the AUTO FAIL light, however the ALTN light remains illuminated to …
indicate single channel automatic operation.
DCPCS Airplanes
Manual control of the cabin altitude is available if …
the AUTO and ALTN modes are inoperative
The main outflow valve is driven by … at …
a DC motor / a slower rate than the automatic modes
Outflow valve full range of motion can take up to …
20 seconds.