ENGINE bleed air System ***

Question 1

Under what conditions would High Pressure (HP) air be used?

Answer 1

• Descent

* Other low power setting operations

Question 2

Under what conditions would Intermediate Pressure (IP) air be used?

Answer 2

• High power setting operations.

Question 3

The Engine Bleed Air Switches control which valves by system logic, when bleed air pressure is available?

Answer 3

• Engine bleed air valve
• PRV
• HP bleed valve

Question 4

Describe the general function of pressure regulating valve (PRV).

Answer 4

• Prevents damage to ducting and equipment downstream, the PRV limits
bleed air pressure.

Question 5

How are the engine bleed air valves actuated, and when do they open for forward flow?

Answer 5

• The bleed air valves are pressure actuated.

* They remain closed until engine bleed air pressure causes forward flow.

Question 6

With the HP valve failed open and the respective bleed air switch OFF, will nacelle anti-ice be available?

Answer 6

• No

However if BAV is open and the pressure switch of nacelle anti-ice doesn’t detect over pressure will open NAI

Question 7

An Engine Bleed Air System (SYS) FAULT light indicates what?

Answer 7

• Bleed air overheat
• Bleed air overpressure
• HP bleed valve open when commanded closed
• PRV open when commanded closed

Question 8

What does a bleed duct Isolation (ISLN) VALVE light indicate (amber)?

Answer 8

• Isolation valve position disagrees with switch position

Question 9

What prevents reverse air flow into the engine compressor sections during engine start?

Answer 9

• The PRV is positively closed

Question 10

What happens if the engine start valve fails to close?

Answer 10

• Bleed air is isolated from the engine starter
• The PRV remains closed
• The engine bleed air valve remains closed.
• Nacelle anti-ice and thrust reverse are not available for the respective
engine.

Question 11

What two valves close in the engine if a bleed air overheat is detected?

Answer 11

• PRV

* HP valve

Question 12

What conditions in the engine bleed air system would prevent nacelle anti ice operation when the bleed air switch is ON?

Answer 12

• The PRV has failed closed, or
• The PRV has been closed due to a bleed air overheat, or
• The start valve is not closed

Question 13

How would you isolate a bleed air duct section in the event of a bleed duct leak
is detected?

Answer 13

• Close the respective isolation valve

* Close the engine bleed air valves.

Question 14

Do we normally operate with the Isolation Valves open or closed?

Answer 14

• Open

Question 15

If the center duct is isolated, how is temperature controlled in all temperature
zones?

Answer 15

• All temperature zones operate in backup temperature control mode
• Trim air is unavailable.

Question 16

With a left or right duct isolated, how would the leading edge flaps extend on the affected side, and what EICAS Advisory message would display?

Answer 16

• The respective LEF operate electrically in secondary mode.

* FLAPS PRIMARY (until LEF extended)

Question 17

How does an isolated left or right duct affect the hydraulic systems?

Answer 17

• The respective hydraulic demand pump 1 or 4 is turned off.

Question 18

What two systems use engine bleed air downstream in the engine prior to the engine bleed valve?

Answer 18

• Nacelle anti-ice

* Thrust reverse

Question 19

Schematic check Bleed valve off will close the HP valve ?

Answer 19

When the engine bleed is off and the NAI is on the only one who supply the NAI is the IP valve, because the HP valve will get close with the Bleed valve!!!,!!!

Question 20

When is HP air used?

Answer 20

• Descent ( Lo Thrust )

Question 21

When is IP air used? What does IP check valve do?

Answer 21

Takeoff, Climb, Cruise ( Hi Thrust )
* Prevents reverse flow air from HP section from entering IP section of compressor

Question 22

Engine Bleed Air switches via system logic, control which valves?

Answer 22

• ENG bleed air valve
• PRV
• HP bleed valve
• These 3 close when switch turned OFF

Question 23

What happens if engine start valve fails to close?

Answer 23

• PRV remains closed (No air out)
• Engine bleed air valve remains closed (No air in)
• NAI and TR no avail for engine

Question 24

What two valves close in engine for bleed air overheat?

Answer 24

• PRV
• HP Valve

Question 25

If you have the ENG BLEED switch OFF (thus the PRV is closed) what you could do to override system logic and OPEN PRV without turning ENG BLEED ON?

Answer 25

Turn ON the NAI

• Won’t override if valves have failed or closed for overheat however

Question 26

With the engine bleed air switch off is the air available for NAI?

Thrust Reversers?

Any exceptions?

Answer 26

Bleed air is available for NAI and Thrust Reverser operation with the switch off with the following exceptions:

The PRV has failed closed or closed due to a bleed overheat; or the start valve is not closed.

In addition the NAI is not available if the HP bleed valve has failed open.

Question 27

What are the 5 items on the Left Duct

Answer 27

Look at the overhead panel

Pack 1
L/E Flap
A/I
Demand Pump #1
Hyd Reservoir pressures #1/2

Question 28

What are the 5 items on the Right Duct

Answer 28

Look at the overhead panel

Pack 3
L/E Flap
A/I
Demand Pump #4
Hyd Reservoir pressures #3/4

Question 29

What are the 5 items on the Center Duct

Answer 29

Look at the overhead panel

Pack 2
Aft Cargo Heater
All Trim Air
Smoke Detector
Water

Question 30

What is lost if the start vale fails to close @ 50% N2

Answer 30

No NAI

No Thrust rev.

Question 31

What is lost if there is a bleed overheat

Answer 31

No NAI

No Thrust rev.

Question 32

What is lost if the PRV fails in the closed position

Answer 32

No NAI

No Thrust rev.

Question 33

What is lost if the HP fails open

Answer 33

No NAI

No Thrust rev.