How does the bleed system maintain adequate and safe bleed supply pressure
It selects between low pressure and high pressure engine bleed sources.
It opens and closes the Low Pressure Check Valve and the High Stage Bleed Valve
What is bleed air used for
- Environmental Control System (ECS)
- Engine start
- Engine and wing anti-ice
- Water pressure
What does the Engine Bleed Valve do
Regulates bleed pressure provided by the engine bleed system
What is used to cool the bleed air provided by the engines
A precooler that uses engine fan air
What conditions required to command the Engine Bleed Valve open
- Respective bleed switch is set to AUTO
- Respective engine bleed is available
- No fire is detected in respective engine
- no bleed duct leak is detected
When will the system automatically shut down the effected bleed system
When a leak, overpressure, or fail condition is identified
What prevents engine bleed air from flowing to the APU when engines are bleed source
The APU Bleed Check Valve
What controls APU bleed airflow to the system
The APU Bleed Valve
When is the APU Bleed Valve commanded open
- APU switch is set to AUTO
- APU bleed is available
- no APU and left bleed duct leak
- left engine bleed is unavailable
- anti-ice system not requested (or anti-ice system selected ON and anti-ice system is failed)
What conditions must exist for the cross bleed to be commanded open
XBLEED button is pressed to AUTO and any of the following:
- One side provides manifold pressure and there is not a bleed air source on the opposite side
- APU bleed button pushed OUT for main engine start
- Engine #2 start in the air
- APU bleed OFF and engine #1 start in the air
- no bleed leak, unless starting an engine
- neither engine fire extinguishing handle has been pulled
When will engine bleed #1 be commanded closed
If cross bleed fails OPEN and the other bleed source is the #2 engine
What type of overheat detection is provided
Dual loop system. Overheat is only indicated when both loops detect the condition
On the ground, when will the AMS give the bleed priority to the APU
When all conditions are met:
- APU bleed and cross bleed push buttons are set to AUTO
- APU bleed valve and the cross bleed valve are operating normally
- ground speed less than 50 kts
- either (REF ECS is OFF and REF A/I is not ALL on the MCDU T/O DATA SET MENU page) or single engine taxiing
What will provide bleed air if taxiing above 50 kts using only left engine? Right engine?
Left only: left engine supplies bleed air to both packs
Right only: APU provides to left pack, right engine provides to right pack
Which recirculating fan supplies the gasper system
Right
At what temp does the gasper shutoff valve open
35C / 95F
What is the ratio of fresh/recirculated air entering the cockpit and pax cabin
52% fresh / 48% recirculated
When are the recirculation fans commanded off
- both packs are commanded OFF
- during on-ground, cabin warm-up mode with APU as bleed source
- cargo bay fire signal activates
- the DUMP button is pressed
- smoke is detected in recirculation bay
During airborne engine start without anti-ice, which bleed source will start the left engine
The right engine’s bleed air, provided the right bleed pressure is greater than min required for engine start
During airborne engine start, which bleed source will start the right engine
Left Engine or APU
When does the AMS give priority to engine bleeds when APU and both engine bleeds are available
- Engine bleed is available
- the XBLEED valve is operating normally
- ENG REF ECS is selected ON
During engine start with anti-ice, what bleed source gets priority
Cross bleed
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Lighting13
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Doors10
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Waste10
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Environmental Control System14
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Pneumatic22
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Automatic Flight51
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Cabin Pressure Control System (CPCS)8
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Electrical31
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Fuel13
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Ice and Rain Protection14
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Oxygen17
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APU15
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Hydraulics16
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Fire Protection27
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Communication0
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Memory Items10
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Flight Controls55
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Landing Gear and Brakes28
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Navigation7
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Warning System6
