Engine Bleed Air

Question 1

Schematic

Answer 1

Image

Question 2

When is HP air used?

Answer 2

• Descent ( Lo Thrust )

Question 3

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

Answer 3

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

Question 4

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

Answer 4

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

Question 5

Function of PRV for?

Answer 5

Prevents damage to ducting and equip downstream by limiting bleed air pressure.

Question 6

Engine bleed air SYS FAULT Light for?

Answer 6

• Overheat - Overpressure - HP valve OPEN w/commanded CLOSE - PRV open w/commanded CLOSE

Question 7

What does bleed duct isolation (ISLN) VALVE light indicate?

Answer 7

Isolation valve position disagree w/switch position

Question 8

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

Answer 8

PRV close

Question 9

What happens if engine start valve fails to close?

Answer 9

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

Question 10

What two valves close in engine for bleed air overheat?

Answer 10

• PRV - HP Valve

Question 11

What would prevent NAI operation when respective bleed air switch is ON?

Answer 11

• PRV failed closed - PRV closed due to overheat - Start valve not closed

Question 12

How would you isolate bleed air duct section for bleed duct leak?

Answer 12

• Close the respective isolation valve - Close the engine bleed air valves

Question 13

With L or R duct isolated, how would leading edge flaps extend?

Answer 13

Electrically in secondary mode for isolated side. Opposite side normally (20-45 sec). There will be momentary asymmetry.

Question 14

How does an isolated L or R duct affect hydraulic systems?

Answer 14

Respective hydraulic demand pump 1 or 4 is turned OFF.

Question 15

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 15

Turn ON the NAI * Won’t override if valves have failed or closed for overheat however