Air Systems Flashcards
What sources supply air to the bleed air system?
-Engines
-APU
-ground external pneumatic air cart/source
What causes the engine bleed valve to automatically close? Which lights indicate this has occurred?
-Excessively high bleed air temp (254*C) or pressure (220 psi)
-BLEED TRIP OFF, AIR COND annunciator, and MASTER CAUTION
Which conditions will the TRIP RESET switch reset?
When pressed, will reset the bleed trip condition (BLEED TRIP OFF [amber]) if the exceedance no longer exists. With the engine bleed air switch ON, the valve will auto open with successful reset.
-TRIP RESET switch also used to reset ZONE TEMP and PACK lights
What will cause the automatic closure of the APU bleed valve?
-The valve closes automatically when the APU is shut down, regardless of switch position.
Normally, what is the position of the isolation valve with the isolation switch in AUTO?
-In AUTO, the isolation valve is closed when
—both engine bleed air switches are ON, and
—both pack switches are ON (auto/high)
-placing one switch to off (any bleed/pack) will auto open the ISOL valve.
-ISOL valve position not affected by APU BLEED air switch.
What does the DUAL BLEED (amber) light indicate?
-illuminates when the APU bleed air valve is open, and
—Engine 1 bleed switch is on and/or
—Engine 2 bleed switch is on with isolation valve open
What is the primary source of conditioned air in the flight deck?
-A portion of the conditioned air from the left pack flows directly to the flight deck.
-Excess air from the left pack, the right pack, and the air recirculating system is combined in the mix manifold, then distributed through the left/right sidewall risers in the pax cabin.
—if left pack not operating, mix manifold will provide air to flight deck.
A single pack on high flow mode can maintain pressurization up to what altitude?
-A single pack can maintain pressurization/acceptable temp up to max certified ceiling
What conditions would cause a pack to change to high air flow with both PACK switches in AUTO?
-When plane is airborne, flaps up, pack switches AUTO, ENG bleeds on, if one pack/engine fails or PACK switch selected off, the remaining pack switches to high air flow
—auto pack switching inhibited on ground or in flight with flaps extended (for single engine perf)
-auto switching to “high flow” occurs if both engine bleed switches OFF and APU bleed switch ON, regardless of flap position, air/ground status, or number of packs operating.
-High airflow mode=pack switch in “high”
-“APU high air flow” avail:
—aircraft on ground
—ENG Bleed switches OFF
—APU operating
—APU Bleed air Switch on, and
—either/both PACK switches to High
What is indicated by the PACK (amber) light on the bleed air panel?
-Indicates failure of both primary and standby pack controls for the same pack. The pack will continue to operate without control unless excessive temps cause the pack to trip off.
-or, indicates overheat condition. Pack valve closes. Terminates operation of associated pack
-during master caution recall, indicates a primary or standby pack control failure exists. Extinguishes with Master caution system reset.
What will cause the Isolation valve to open automatically with the Isolation Valve switch in auto?
-In AUTO, the Isolation Valve will be CLOSED when: (corner switches)
—both Engine BLEED Air switches on, and
—both Pack switches in AUTO or HIGH
*placing any one of these switches to OFF will automatically open the Isolation Valve
- not affected by the APU BLEED switch
What provides cooling air for the heat exchangers in the PACK system?
The ram air system.
-Automatically controlled by the packs
-full open
—on ground
—slow flight with flaps extended
What is indicated by the bright blue RAM DOOR FULL OPEN light?
-RAM DOOR FULL OPEN (blue light) illuminates when fully open
-doors modulate between open/closed in normal cruise
-deflector doors prevent FOD prior to liftoff/after touchdown. Connected mechanically to ram air inlet door
What is the purpose of the recirculation fans?
-Increase airflow to passenger cabin through main distribution system
-2 fans (left, right) either side of mix manifold
-pull air from electronics bay and and cabin floor grilles towards lining of forward cargo compartment, then into the mix manifold
-only recirc air passes through HEPA filters
What does the illumination of the ZONE TEMP (amber) lights indicate?
ANY ZONE TEMP
-supply duct overheat and associated Trim Air Modulating Valve closes
—may be reopened with TRIP RESET switch after duct cooled
CONT CAB ZONE TEMP (Amber)
-failure of both primary and standby temp controls
-during master caution recall, CONT CAB indicates failure of primary or standby flight deck temp control. Auto switch to backup control
FWD or AFT CAB ZONE TEMP (Amber)
-during master caution recall, FWD or AFT indicates failure of forward or aft temp control, and associated trim valve closes
—Temp Selectors operate normally but average the two passenger cabin zones
Left electronic controller
-controls aft cabin zone
-provides backup control to flight deck
Right electronic controller
-controls forward cabin zone
-provides primary control to flight deck
