HYDRAULICS

Question 1

When will the demand pumps be commanded to operate if the hydraulic demand pump selector is in the AUTO position?

Answer 1

• Demand pump operate when related engine pump output pressure is low,
or when related fuel control switch is in CUTOFF
• Demand pumps 1 & 4 also operate when flaps are extended past Flaps 1. On the
ground the pumps shut down when flaps reach the commanded position.
In flight the pumps continue to run.

  FCOM, VOL 2; 13.10.2

Question 2

What does the hydraulic system (SYS FAULT) fault light indicate?

Answer 2

• Low hydraulic system pressure
• Low hydraulic reservoir quantity
• Excessive hydraulic fluid temperature
FCOM, VOL 2; 13.10.2

Question 3

What does a hydraulic demand pump low PRESS light indicate?

Answer 3

• Demand pump selector positioned to OFF or AUX
• Demand pump operates and output pressure is low?
FCOM, VOL 2; 13.10.2

Question 4

What does a hydraulic reservoir quantity indication of .80 mean, as displayed on the Secondary EICAS display?

Answer 4

• 80% of normal service level.

FCOM, VOL 2; 13.10.3

Question 5

What does a magenta “RF” displayed next to a hydraulic quantity indicator on the Secondary EICAS mean?

Answer 5

• Displays on the ground When the reservoir requires refill.

FCOM, VOL 2; 13.10.3

Question 6

When is the engine driven hydraulic pump pressurized?

Answer 6

• When the engine is running and the engine pump switch is ON.

FCOM, VOL 2; 13.20.1

Question 7

Which demand pumps are air driven, and which ones are electric motor driven?

Answer 7

• Systems 1 and 4 are air driven pumps, through the bleed air manifold.
• Systems 2 and 3 are electric driven pumps.
FCOM, VOL 2; 13.20.1

Question 8

What is the purpose of the auxiliary pump?

Answer 8

• Used for ground handling operations.

FCOM, VOL 2; 13.20.1

Question 9

Why are the hydraulic reservoirs pressurized by the bleed air system?

Answer 9

• To prevent pump cavitation
• To ensure positive flow during high demand conditions
FCOM, VOL 2; 13.20.2

Question 10

How does pulling a fire switch affect the hydraulic system?

Answer 10

• Related hydraulic fluid shutoff valve closes
• The EDP depressurizes.
• The related demand pump operates.
FCOM, VOL 2; 13.20.2

Question 11

What are some examples of major system components powered by each hydraulic system?

Answer 11

• Systems 1 and 4 power the trailing edge flaps, body gear, nose gear,normal brakes
(SYS 4), alternate brakes (SYS 1), and steering. Systems 1 and 4 also provide
redundant power to the primary flight controls.

• Systems 2 and 3 power the primary flight controls, stabilizer trim, and
elevator feel. System 2 also powers the alternate brakes and lower
yaw damper. System 3 powers the upper yaw damper.

• Systems 1, 2, and 3 power the related center, right, and left autopilot servos
(L,C,R are powered by systems 3,1,2 respectively)

• Systems 2, 3, and 4 power the spoilers.

FCOM, VOL 2; 13.20.3