Engine bleed air

Question 1

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

Answer 1

low power settings - e.g descent


Question 2

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


Answer 2

high power settings

Question 3

Which valves does the Engine Bleed Air Switches control by system logic when bleed air pressure is available?

Answer 3

HP Bleed, PRV, Enginge bleed valve


Question 4

Describe the general function of the Pressure Regulating Valve (PRV).

Answer 4

limits/ relieves bleed air pressure - prevents damage

Question 5

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

Answer 5

pressure actuated
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 - PRV will be closed

Question 7

What does an Engine Bleed Air System (SYS) FAULT light indicate?


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

PRV closes whenever start valve open - prevents reverse air flow into engine compressor sections

Question 10

What happens if the engine start valve fails to close?

Answer 10

bleed air isolated from engine starter because both PRV and engine bleed air valve remain closed
(No NAI available)

Question 11

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

Answer 11

PRV and HP Bleed 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

• PRV failed closed

• PRV closed due to overheat

• start valve not closed

Question 13

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

Answer 13

close respective isolation and 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

loss of trim air system (on center duct) - FD, UD, CR, MD trim air not available
-
backup modes in cabin:

if FD temp selector setting available to PTC, pack outled temp of all packs regulated to achieve 18-29

- if unavailable, outlet temp regulated to achieve last FD temp set

- if unavailable - regulated to achieve 24
temp to CR,UD,MD not regulated

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

electrically in secondary mode
‘FLAPS PRIMARY’?

respective demand pump turned off to avoid EICAS HYD PRESS DEM during aproach

Question 17

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

Answer 17

Hyd systems reservoir pressures on that side would isolated
Demand pump (1/4) on that side would be unavailable
LE flap asymmetry issues on landing due reverse thrust