Hydraulic System

Question 1

Each demand pump has a switch titled “OFF, AUTO, ON.” Describe this switch and its positions.

Answer 1

OFF: Demand pump off
AUTO: Turns on when related engine pump pressure low or when related fuel control is in CUTOFF.
(For demand pumps 1 and 4, also turns on when TE flaps in transit, or flaps extend past 1 in flight.)
ON: Turns on demand pump

Question 2

Each engine hydraulic pump has a switch. Describe this switch.

Answer 2

Pushed in= ON: Engine pump pressurizes when engine rotates
Pushed out=OFF: Engine pump off
Amber PRESS light: Engine hydraulic pump pressure low

Question 3

Above each demand pump switch, there is a light. What does it mean if this light is on with the amber PRESS?

Answer 3

-Demand pump pressure low
-Demand pump OFF or AUX
-or, demand pump has failed

Question 4

Each hydraulic system has an amber SYS FAULT light. What does seeing this light mean?

Answer 4

-Low pressure
-Low quantity
-High temp

Question 5

What would a full hydraulic reservoir indicate on the hydraulic synoptic?

Answer 5

1.00 is full

Question 6

What is the nominal pressure of the hydraulic system?

Answer 6

3,000 PSI

Question 7

On the synoptic, you see a magenta RF. What does this mean?

Answer 7

Displays only on ground-refill needed.

Question 8

On the synoptic, you see a magenta LO. What does this mean?

Answer 8

Low hydraulic reservoir quantity

Question 9

How many hydraulic systems?

Answer 9

4 independent systems

Question 10

What are all of the items that are hydraulically powered?

Answer 10

• primary flight controls
• autopilot servos
• spoilers
• stabilizer trim
• elevator feel
• landing gear
• flaps
• brakes
• nosewheel steering/body gear steering

Question 11

Each system is powered by how many pumps? What types? How are they powered

Answer 11

-Each system has at 1 demand pump and 1 engine driven pump
-System 1 and 4 demand pumps powered by bleed air
-System 2 and 3 demand pumps electric
-System 4 also has an electric AUX pump for ground handling

Question 12

How is each hydraulic reservoir pressurized? Why?

Answer 12

-Bleed air.
-To prevent pump cavitation, and to ensure positive pressure in high demand conditions.

Question 13

Which system powers the flight controls? Is there manual reversion?

Answer 13

ALL hydraulic systems redundantly power the flight controls.
No manual reversion.

Question 14

There are 3 autopilot servos, all hydraulically powered. Left, center and right. Which hydraulic system powers each?

Answer 14

Left: System 3
Center: System 1
Right: System 2

Question 15

What systems power the spoilers?

Answer 15

2, 3 and 4

Question 16

How many hydraulic reservoirs?

Answer 16

1 per system.

Question 17

Normally, which pump provides pressure to the hydraulic system? What is its backup?

Answer 17

-Normal: EDP (Engine driven pump)
-Backup: Demand pump. Automatically operates during periods of high demand, such as flap in transit and gear retraction, or if the EDP fails.

Question 18

When do demand pumps automatically turn on?

Answer 18

ALL: -When EDP pressure low
-When related fuel selector is
in CUTOFF

Demand pump 1 and 4 only:
-When trailing edge flaps in
transit
-When flaps extended greater
than flaps 1 in flight

Question 19

When hydraulic system 4 AUX pump is selected, does the demand pump run?

Answer 19

No. The demand pump is OFF. Only the electric AUX pump would run.

Question 20

An EDP operates if______

Answer 20

The pump switch is ON, the engine is running, the fire switch is not pulled.

Question 21

You see a RSVR PRESS white indication on the hydraulic synoptic page. But the SYS FAULT light is not illuminated overhead.. what does this mean?

Answer 21

It means the bleed air pressure to a reservoir is low.

Question 22

What measures hydraulic quantity?

Answer 22

HYQUIM (Hydraulic Quantity Interface Module.)

Note: Can give erroneous indications if it faults due to overvoltage

Question 23

Where is the hydraulic reservoir located?

Answer 23

In each respective engine pilon

Question 24

Big ticket Items on System 1

Answer 24

-Nose and body gear (operation and steering)
-INBOARD Trailing edge flaps

Question 25

Big ticket items on system 4

Answer 25

-Wing gear
-OUTBOARD Trailing edge flaps

Question 26

Big ticket Items on system 2 and 3

Answer 26

-Upper and lower rudder
-upper and lower yaw damper
-Stab trim