Boeing 777: Bleed Air

777 Bleed Air by jerome meriweather
	Maintenance OverHead Glareshield Forward Pedestal
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777 Photo and/or Graphic Element
The Engine Bleed Air system is controlled by two air supply and cabin pressure controllers (ASCPCs) which open and close appropriate valves. Engine Bleed Air comes from the high stage or low stage engine compressor section. Low stage air is used during high power setting operation and high stage air is used during descent and other low power setting operations.

Left/Center/Right Isolation Switches

Auto - Isolation valve closes automatically if either of the following occur:
- A duct leak is detected
- Bleed Air pressure is lost
CLOSED - Valve is closed due to one of the following conditions:
- Duct leak
- Loss of Bleed Air source
- Switch selected CLOSED
- Valve failed CLOSED

APU Bleed Switch

Auto - APU bleed valve is armed to open when Bleed Air is available.
OFF - APU bleed valve is closed due to one of the following conditions:
- Duct leak
- APU not supplying Bleed Air
- Switch selected OFF
- Valve failed closed
- APU fire handle pulled

Left/Right Engine Bleed Switches

ON - Engine bleed valve is armed to open when Bleed Air is available.
OFF - Bleed valve is closed due to one of the following conditions:
- System fault
- Respective Engine not supplying Bleed Air
- Switch selected OFF
- Valve failed closed
- Engine fire handle pulled

FWD/AFT Outflow Valve Switches

AUTO - Outflow valve position is controlled automatically.
MAN - Allows Manual positioning of the Outflow Valve using the OUTFLOW VALVE MANUAL switch.

Manual Switch
Outflow Valve Manual Switches Moves the Outflow Valve toward full open or close when MAN is selected on the respective OUTFLOW VALVE switch.

Landing Altitude Knob

Pull out - Removes the FMC Landing Altitude. Pushing back in, restores it.
Rotate - Manually sets Landing Altitude. Altitude display (on EICAS) changes in 100 foot increments at first detent, 1000 foot increments at the second detent.