Bleed Air

Question 1

what are the sources of bleed air

Answer 1

• engines
• APU
• external air

Question 2

what systems rely on the bleed air system

Answer 2

• airconditioning and pressurization
• wing and engine thermal anti-ice
• engine starting
• hydraulic reservoir pressurization
• water tank pressurization
• (841 and beyond) nitrogen generation system (NGS)

Question 3

where is the engine bleed air sourced from (LP/HP)

Answer 3

• LP = 5th compressor stage
• HP = 9th compressor stage

Question 4

engine bleed air valve:
- type
- activated/operated?

Answer 4

• pressure regulating and shutoff valve
• DC controlled and pressure operated

Question 5

what does the “DUAL BLEED” indication mean

Answer 5

APU bleed air valve open; AND
- ENG 1 BLEED AIR sw = ON; OR
- ENG 2 BLEED AIR sw AND isolation valve are open

Question 6

isolation valve switch

Answer 6

• close = closed
• open = open
• auto:
  
  • closed:
    
    • BOTH ENG BLEED AIR sw = ON; AND
    • BOTH AC PACK sw = AUTO/HIGH
  • opened:
    
    • either ENG BLEED AIR OR AC PACK sw = OFF

Question 7

what does the “WING-BODY OVERHEAT” indication mean (left/right)

Answer 7

overheat detected by the sensors located:
- engine strut
- inboard wing leading edge
- air conditioning bay
- keel beam (left only)
- APU bleed duct (left only)

Question 8

what does the “BLEED TRIP OFF” light indicate

Answer 8

excessive engine bleed air pressure/temperature
- related engine bleed air valve closes automatically
- requires a reset

Question 9

what does the “TRIP RESET” switch do to the system

Answer 9

if the fault condition is corrected:
- resets “BLEED TRIP OFF, PACK, DUCK OVERHEAT/ ZONE TEMP” LIGHTS
- related engine bleed air valve, pack valve, trim air modulating valve open

Question 10

what limitations apply when the “DUAL BLEED” light is illuminated

Answer 10

limit engine thrust to idle