Pneumatics 747-400

Question 1

What are the required thrust power settings for anti-ice operation with the bleed air switch in off ?

Answer 1

Works only at high power settings.

Question 2

What does BLEED 4 on the primary EICAS mean?

Answer 2

Either:

1) HP bleed valve failed open
2) PRV failed open
3) Engine bleed over pressure

• Combination can be critical

Question 3

If BLEED 4 appears on primary EICAS, will Nacelle anti ice and Thrust reverser work, one of them or none of them?

Answer 3

Only thrust reverser would work.

Question 4

What does BLD 4 PRV on the primary EICAS mean?

Answer 4

Bleed overheat or PRV failed closed, or both.

Question 5

What is a typical reason for a Bleed air overheat?

Answer 5

Faulty fan air modulating valve leading to insufficient bleed air pre cooling.

Question 6

What does BLEED HP ENG 4 on primary EICAS mean?

Answer 6

HP bleed valve failed closed.

• For Anti-ice add more power
• Reverser will deploy slower during touchdown.

Question 7

With the BLEED HP ENG 4 on primary EICAS, and thrust is at idle power, what is the position of the PRSOV?

Answer 7

Closed.

With intermediate pressure only, the engine produces only little pressure when idle. PRSOV closes due to reverse flow protection.

Question 8

What does the BLD DUCT LEAK L on the primary EICAS mean?

Answer 8

A bleed leak has occurred.

Question 9

What could cause a BLD DUCT LEAK C on the primary EICAS while on the ground?

Answer 9

If air conditioning bay doors are closed while in hot weather.

Question 10

What does BLEED ISLN R on primary EICAS mean?

Answer 10

The isolation valve is not in commanded position.

Question 11

If all packs are turned off for takeoff, will you still have TR and NAI, and what is the reason you will either loose or have them?

Answer 11

Have both as the NAI and TR valves are before the PRSOV.

Question 12

If APU is off, does the APU bleed valve switch need to be OFF?

Answer 12

No. When the APU bleed valve switch in the ON position, the bleed valve operates automatically.

Question 13

What pressure stage supplies the engine pressure duct at low thrust settings?

Answer 13

The 14th Stage (HP)

Question 14

What do you loose when the BLD 4 OVHT / PRV message is displayed?

Answer 14

No NAI, or TR.

Question 15

If the right main duct is isolated, what do you expect to loose?

Answer 15

Wing Anti-ice for right wing, and right leading edge flaps will work in secondary mode.

Question 16

When does NAI not work?

Answer 16

1) When PRV is failed closed, or overheat is detected.
BLD OVHT / PRV.
2) When HP bleed valve failed open and engine bleed air switch in OFF.