ENGINE BLEED AIR SYSTEM

Question 1

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

Answer 1

• Descent
• Other low power setting operations

Note:FCOM, VOL 2. 2.40.1

Question 2

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

Answer 2

• High power setting operations.

Note:FCOM, VOL 2; 2.40.1

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

Note:FCOM, VOL 2; 2.10.25 and 2.40.1

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.

Note:FCOM, VOL 2; 2.40.1 and 2.40.2

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.

Note:FCOM, VOL 2; 2.40.1

Question 6

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

Answer 6

• No

Note:FCOM, VOL 2; 2.40.2

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

Note:FCOM, VOL 2; 2.10.25

Question 8

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

Answer 8

• Isolation valve position disagrees with switch position

Note:FCOM, VOL 2; 2.10.24

Question 9

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

Answer 9

• The PRV is positively closed

Note:FCOM, VOL 2; 2.40.2

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.

Note:FCOM, VOL 2; 2.40.2 (thrust reverse) bottom of page

Question 11

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

Answer 11

• PRV
• HP valve

Note:FCOM, VOL 2; 2.40.2

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

Note:FCOM, VOL 2; 2.40.2

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.

Note:FCOM, VOL 2; 2.40.3

Question 14

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

Answer 14

• Open

Note:FCOM, VOL 2; 2.40.3

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.

Note:FCOM, VOL 2; 2.40.4

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)

Note:FCOM, VOL 2; 2.40.4; 9.30.1

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.

Note:FCOM, VOL 2; 2.40.4

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

Note:FCOM, VOL 2; 2.40.6 (diagram)