Engine Bleed Air System Flashcards
Under what conditions would High Pressure (HP) air be used?
- Descent
- Other low power settings
Under what conditions would Intermediate Pressure (IP) air be used?
High power operations
Which valve does the Engine Bleed Air Switches control by system logic when bleed air pressure is available?
- Engine Bleed Air Valve
- PRV
- HP Bleed Valve
Describe the general function of the Pressure Regulating Valve (PRV)
Prevents damage to the ducting downstream by limiting bleed air pressure
How are the engine bleed air valves actuated and when do they open for forward flow?
- the bleed air valves are electrically controlled and pressure actuated (remain closed until engine bleed air pressure causes forward flow)
- with Engine Bleed Air Switch ON system logic allows bleed air to open
+ HP bleed valve
+ PRV
+ Engine Bleed Air Valve
And flow into the bleed air duct
With the HP valve failed open and the respective bleed air switch OFF will Nacelle anti-ice be available?
No
Norm avail with bleed air switch closed except:
- PRV failed close
- PRV closed due to bleed overheat
- start valve not closed
- HP bleed valve failed open
What does an engine bleed air system (SYS FAULT) light indicate?
- bleed air overheat
- bleed air over pressure
- HP bleed valve open when commanded close
- PRV open when commanded close
What does a bleed duct isolation (ISLN VALVE) light indicate (amber)?
Isolation valve position disagrees with switch position
What prevents reverse flow into the engine compressor sections during engine start
The PRV is positively closed to prevent reverse air flow into the engine compressor sections
What happens if the engine start valve fails to close?
- EICAS message STARTER CUTOUT (1,2,3,4)
- Per QRH:
+ if condition does not correct with pushing engine START switch
+ engine bleed air switch OFF: no Nacelle anti-ice or reverse thrust for that engine
What two valves close in the engine if a bleed air over heart is detected?
- PRV and HP valves close
- pushing Engine Bleed Air switch from OFF to ON resets the engine bleed fault detection system
What conditions in the engine bleed air system would prevent nacelle anti-ice operation when the bleed air switch is ON
Is available unless:
- PRV has failed closed
- PRV has been closed due to a bleed air overheat
- the start valve is not closed
How would you isolate a bleed air duct section in the event a bleed duct leak is detected
Per QRH
- Close respective ISLN Valve
- Close affected side ENGINE BLEED air valves
Do we normally operate with the isolation valves open or closed
Open
If the center duct is isolated how is temperature controlled in all temperature zones
- backup temperature control mode without trim air
+ control cabin temperature based on Flight Deck temperature - Flight Deck Temperature available to Pack Temperature Controller (PTC) all pack outlets regulated by Flight Deck Temperature Selector 65f (18c) - 85f (29c)
- if the flight deck temperature selector is unavailable to the PTC pack outlet temperature is regulated to the last flight deck temperature set
- if the last flight deck temperature is unavailable pack outlet temp is regulated to average flight deck temp of 75f (24c)
With a left or right duck isolated, how would the leading edge flaps extend on the affected side, and what EICAS advisory message would display
- LE flaps on affected side operate electrically in secondary mode
- EICAS message FLAPS PRIMARY will display
How does an isolated left or right duct affect the hydraulic systems?
-lose affected side Air Demand Pump (affected side HYD 1 or 4 of pre QRH)
- lose hydraulic reservoir pressure on affected side (R duct: Hyd 1&2 res press, L duct: Hyd 3&4 res press)
What two systems use engine bleed air downstream in the engine prior to the engine bleed valve
- Thrust Reverser
- Nacelle Anti-Ice
