Bleed Air Flashcards
Bleed air sources
Engines APU and ground pneumatic
Supplied through
Bleed air ducts
Following systems use bleed air
Air driven hydraulic pumps Wing anti ice Cargo heating Engine and APU starting Air con packs Hydraulic reservoir pressurisation Trim air
APU bleed air
Air con and engine starting
Max alt in flight of APU bleed air fl220
APU switch to auto
Opens APU bleed air valve
All three isolation valves allowing air into the bleed air ducting
Engine bleed air
Comes from the LP and HP section
Air from HP section is used to supplement low pressure air during low thrust settings such as during descents
Engine bleed air system is controlled by
The air supply and cabin pressure controller or ASCPC
ASCPC
Opens and closes the high pressure valve and adjusts the fan air modulating valve to provide cool air for the pre cooler, which controls the bleed air temperature in the ducts
Pressure regulating and shutoff valve or PRSOV
Controls the flow and pressure of air to the ducts
If fan air pre cooler cannot provide enough coolingfor the bleed air
The PRSOV reduces the quantity of bleed air to keep the temp within limits
When an engine is supplying bleed air
The APU bleed air valve closes
Isolation valves
Open when ground cart supplying bleed air
APU supplying bleed air with the engines off
Left engine start-Right isolation valve closed all others open
Right engine start-Left closes others open
Crossbleed start all open
Cross bleed start
Other engine supplying bleed air for other engine start
Engine out
All isolation valves open
Bleed air leak detection
Leak detected then the bleed air isolation valve close(applicable) to isolate the leak
Bleed loss msg on EICAS
