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

• when engine pump output pressure low, or

• when fuel control switch CUTOFF
• demand pumps 1 and 4 (air) also operate when trailing edge flaps are in transit, or in flight when flaps extended past 1

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

Question 3

What does a hydraulic demand pump low PRESS light indicate?

Answer 3

-demand pump selector positioned to OFF or AUX

- demand pump commanded to operate and output pressure low

Question 4

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

Answer 4

80% full

Question 5

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

Answer 5

reservoir requires refill (displayed on ground)

Question 6

When is the engine driven hydraulic pump pressurized?

Answer 6

when engine rotates and engine hyd pump switch ON

Question 7

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

Answer 7

Air - 1 and 4
Elec motor - 2 and 3

Question 8

What is the purpose of the auxillary pump?

Answer 8

Ground handling operations

(operates on ground until engine pump pressurizes
- demand pump 4 set to AUX to ensure system 4 pressurized first
- prevents fluid transfer between systems through the brakes
- verify system fault light extinguished
- demand pump low PRESS remains illuminated
- brake source light extinguished
- brake accumulator pressure in green)

Question 9

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

Answer 9

• prevents cavitation
• ensures positive flow during high demand

Question 10

How does pulling a fire switch affect the hydraulic system?

Answer 10

• shuts off hydraulic fluid to EDP

• depressurizes EDP

Question 11

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

Answer 11

System 1
- Nose gear steering and actuation
- Body gear steering and actuation
- Inboard TE Flaps
System 2
- Lower yaw damper
- Spoilers 2,3, 10,11
System 3
- Upper yaw damper
- spoilers 1,4, 9,12
System 4
- Wing gear actuation
- Outboard TE flaps
- Spoilers 5,6, 7,8

See diagrams for joint systems