Hydraulics

Question 1

What are the conditions required for the demand pump AUTO operation?

Answer 1

During periods of high system demand. (Gear retraction, Flap extension)

When engine pump output pressure is low.

FCOM 1 29.10.1

Question 2

What are the conditions required for the Auxiliary pump operation?

Answer 2

On the ground when the respective engine driven pump is unpressurised.

Respective demand pump off.

FCOM 1 29.10.1

Question 3

Does demand pump PRESS light extinguish during AUX pump operation?

Answer 3

No
Pressure light illuminates when:
-demand pump selector positioned to OFF or AUX.
-Demand pump commanded to operate and output pressure is low.

FCOM 1 29.10.2

Question 4

What are the reasons for hydraulic “SYS FAULT” light illumination?

Answer 4

• Low hydraulic system pressure
• Low hydraulic reservoir quantity
• Excess hydraulic fluid temperature

FCOM 1 29.10.2

Question 5

What does the green “PRESS” on the RAT switch indicate?

Answer 5

• The RAT is operating
• System 3 primary flight control hydraulic pressure is greater than approximately 1500 PSI

FCOM 1 29.10.2

Question 6

How can hydraulic information be presented in the MDF?

Answer 6

STAT (Status)
HYD (Hydraulic synoptic)

FCOM 1 29.10.3

Question 7

How is unpressurised system presented in the HYD synoptic page?

Answer 7

System pressure is displayed

• Shows as a list: shows which subsystems that aren’t pressurised.
• Absence of hydraulic power flow (green) in synoptic page.

FCOM 1 29.10.6

Question 8

How is each hydraulic system powered and what pumps are being used?

Answer 8

Each system is powered by an Engine driven pump and a demand pump installed in parallel.

Systems 1 and 4 have AUX pumps.
System 3 contains RAT

Question 9

What does the RAT power?

Answer 9

Provides emergency hydraulic power to system 3 and pressure for both left elevators via the elevator transfer valve.

Question 10

When does the RAT deploy automatically and what are the indications?

Answer 10

UNLKD amber light and PRESS green light.

Deploys automatically when any 3 engines drop below 50% N2 and manually when RAT switch pushed.

Question 11

What pressurises the hydraulic reservoirs?

Answer 11

Bleed Air system.

Question 12

When is the RF hydraulic indication inhibited?

Answer 12

RF inhibited in Flight and replaces with LO for low quantity.

Question 13

What are the indications when the HYQUIM has failed and how many systems are affected?

Answer 13

Blank hydraulic quantity indications on the EICAS status page and HYD synoptic page.

Question 14

When does the hydraulic shutoff valve to the EDP close?

Answer 14

When an engine fire switch is pulled.

Question 15

Landing gear systems and trailing edge flaps are powered by which hydraulic systems?

Answer 15

Systems 1 and 4.

Question 16

Which hydraulic systems supply stabiliser trim?

Answer 16

Systems 2 and 3.

Question 17

What hydraulic systems are used for the L, C and R AUTOPILOT servos?

Answer 17

Systems 3, 1 and 2

Question 18

What does “HYD COLD SYS X” EICAS message mean and what is the required action?

Answer 18

Hydraulic system too cold for takeoff.

Slowly move flight controls full deflection to warm up fluid to more than 18 degrees.

QHR NNC.13.2

Question 19

Where can hydraulic systems be indicated and what are the indications?

Answer 19

EICAS status page and hydraulic synoptic page.

-fluid pressure, temperature and reservoir quantity.

FCOM 1 29.10.3