Bleed Flashcards
High-pressure air has 3 sources:
EAH
- Engine bleed systems
- APU load compressor
- HP ground connection
The pneumatic system supplies high-pressure air for:
FEWFAAW
- Fuel Tank Inerting System
- Engine starting
- Water pressurization
- FWD cargo heating
- AFT cargo heating
- Air conditioning
- Wing anti-icing
or
SWITCH
- Starting
- Water
- Icing
- Tank
- Condition
- Heat
What interconnects the engine bleed systems and receives air from the APU and ground sources where appropriate?
A crossbleed duct.
A valve mounted on the crossbleed duct allows the leftaide (engine 1) and right side (engine 2) to be interconnected.
What controls and monitor the operation of the pneumatic system?
2 Bleed Monitoring Computers (BMC1 and BMC2)
What is the engine bleed air systems designed to do?
- Select the compressor stage to use as a source of air
- Regulate the bleed air temperature
- Regulate the bleed air pressure
What pressure does the HP stage maintain?
36±4 PSI
What is the normal bleed pressure?
45±5 PSI
Note: Bleed pressure may fluctuate between 38 and 56 PSI (with a maximum peak to peak prssure of 16 PSI) particularly at high engine power (takeoff or climb) up to FL100
When will the HP valve close automatically?
The HP valve closes automatically:
‐ Pneumatically:
* In case of low upstream pressure
* In case of excessive upstream pressure
‐ Electrically :
* When the bleed valve is closed electrically
* In case of overpressure upstream of the HP valve with wing anti-ice off, two packs ON and aircraft altitude above 15 000 ft.
When will the bleed valve fully closed?
The bleed valve is fully closed:
‐ Pneumatically:
* If upstream pressure goes below 8 PSI
* If there is return flow
‐ Electrically by means of:
* The BLEED pushbutton switch (switched OFF)
* The ENG FIRE pushbutton (pushed)
* The Bleed air Monitoring Computer (BMC) in the following cases:
‐ Overtemperature
‐ Overpressure
‐ Leak
‐ Open starter valve
‐ Engine shutdown
‐ APU bleed being ON.
What temperature does the precooler regulate?
200°C
