A320 Hydraulics

Question 1

What are the three hydraulic systems?

Answer 1

Green, blue, and yellow

Question 2

What major components are operated via hydraulic power?

Answer 2

Flight controls, flaps and slats, landing gear, cargo doors, and the emergency generator

Question 3

What is the normal hydraulic pressure provided by the engine driven hydraulic pumps?

Answer 3

3000 psi

Question 4

What components can provide backup hydraulic pressure?

Answer 4

-Electrically driven hydraulic pumps (on the blue and yellow systems)
-A power transfer unit (PTU)
-A ram air turbine (RAT)
-A hand pump

Question 5

What prevents hydraulic fluid from returning to the engine driven pump during an engine fire?

Answer 5

A hydraulic fire shutoff valve upstream from each engine driven pump

Question 6

Which hydraulic systems have an associated acccumulator?

Answer 6

All 3, green, blue, and yellow.

Question 7

What do the accumulators in each system do?

Answer 7

Help maintain a constant pressure during transient demands

Question 8

What are some items powered by the green hydraulic system?

Answer 8

Landing gear*
Normal brakes*
Engine 1 reverser*
Slats/flaps
Other flight control components

• ONLY powered by the green system

Question 9

How is the nose wheel steering different for older vs newer A320’s?

Answer 9

It was originally on the green hydraulic system, but newer aircraft have it on the yellow system.

*I need to refer back to our operating manuals to know which aircraft of ours are configured in which way

Question 10

How is the green system pressurized?

Answer 10

Normal pressure comes from a single engine driven pump powered by engine number 1. Backup pressure can be provided by the PTU.

Question 11

What are some items powered by the yellow hydraulic system?

Answer 11

Nosewheel steering* 1
Alternate brakes*
Parking brake*
Engine #2 reverser*
Cargo doors*
Flaps
Other flight control components

*ONLY powered by the yellow system
1 On older aircraft the nosewheel steering may be powered by the green system

Question 12

How can the yellow hydraulic system be pressurized?

Answer 12

-Via a single engine driven pump on engine #2
-Via an electric pump
-Via the PTU
-Via a hand pump, in order to open the cargo doors when the aircraft is unpowered on the ground

Question 13

What are some items powered by the blue hydraulic system?

Answer 13

-The emergency generator*
-Slats
-Other flight control components

*only powered by the blue system

Question 14

How can the blue system be pressurized?

Answer 14

-An electric pump
-A ram air turbine

Question 15

Which systems have a fire shutoff valve?

Answer 15

Green and yellow

Question 16

How can the fire shutoff valves be closed?

Answer 16

By pressing the ENG 1 FIRE and ENG 2 FIRE push buttons

Question 17

What does it mean if the 1 or 2 indications on the hydraulic page turn from white to amber?

Answer 17

That the 1 or 2 engines respectively have shut down

Question 18

If the green or yellow fire shutoff valves are closed, can the systems still be pressurized?

Answer 18

They can by the PTU. The hydraulic fire shutoff valve only keeps hydraulic fluid from flowing to the engine driven pump but not from flowing to the PTU.

Question 19

What happens when the ENG 1 PUMP or ENG 2 PUMP push buttons on the overhead panel are pressed?

Answer 19

The respective engine driven pump is depressurized, OFF appears in white on the pushbutton, and the pump symbol changes to an amber dash on the hydraulics page.

Question 20

What does the fault light on the ENG 1 PUMP or ENG 2 PUMP push buttons mean?

Answer 20

It means any of the following:
-Low pump output pressure
-Low reservoir quantity
-Reservoir fluid overheat
-Reservoir low air pressure

Question 21

Which systems have electric pumps?

Answer 21

Blue and yellow

Question 22

Will the yellow electric pump come on automatically if yellow system pressure is low?

Answer 22

No

Question 23

When will the yellow electric pump operate automatically? What is powered when it’s operated automatically?

Answer 23

Prior to engine start, when the cargo door selector is placed in either the open or closed position. When this occurs only the following are powered
-The cargo doors
-The alternate brake system
-The engine two thrust reverser

*the ON light in the yellow ELEC PUMP pushbutton will NOT illuminate when the pump is operated automatically

Question 24

When does the blue electric pump operate automatically?

Answer 24

If AC power is available:
-On the ground when at least one engine is running
-In flight, it operates continuously even if both engines are shut down

Question 25

When does the PTU become active?

Answer 25

Whenever the PTU pushbutton is in AUTO (lights out) and a differential pressure of at least 500 PSI is sensed between the yellow and green systems.

Question 26

What memo appears when the PTU is in operation?

Answer 26

HYD PTU is shown on the memo section of E/WD

Question 27

Does the PTU transfer fluid between the green and yellow systems?

Answer 27

No, just pressure

Question 28

Can the PTU output pressure meet all the demands of the respective systems operating requirements?

Answer 28

Yes!

Question 29

When does the PTU fault light come on?

Answer 29

For either the green or yellow systems: -Fluid overheat -Low air pressure -Low fluid quantity

Question 30

When is the PTU inhibited?

Answer 30

-When the yellow systems electric pump is running due to cargo door operation -During engine start, when the ENG MASTER switches are in opposing positions and either the nosewheel steering is disconnected, or the parking brake is on.

Question 31

When does the PTU perform a self test?

Answer 31

Momentarily during the second engine start

Question 32

When does the RAT deploy automatically in flight?

Answer 32

If both AC BUS 1 and 2 are unpowered, and airspeed is above 100 knots. The RAT does NOT automatically deploy for a loss of hydraulic pressure.

Question 33

Where is the RAT located?

Answer 33

Under the fuselage near the left wing root

Question 34

How does the RAT supply emergency power?

Answer 34

The RAT provides pressure to the blue hydraulic system. The blue hydraulic system then uses hydraulic pressure to run the emergency generator.

Question 35

What does the RAT MAN ON pushbutton on the hydraulics panel do?

Answer 35

It manually deploys the RAT to provide blue hydraulic pressure but does not cause the emergency generator to come on line.

Question 36

What does the EMER ELEC PWR MAN ON pushbutton on the EMER ELEC PWR panel do?

Answer 36

It manually deploys the RAT powering BOTH the blue hydraulic system, and the emergency generator.

Question 37

What message is displayed any time the RAT is extended?

Answer 37

RAT OUT is displayed in the memo section of the E/WD

Question 38

Once deployed, how can the RAT be stored?

Answer 38

Only by maintenance personnel

Question 39

Is the status of the hand pump displayed in the cockpit?

Answer 39

No

Question 40

When is the hand pump used?

Answer 40

Only when the aircraft is unpowered to provide yellow hydraulic pressure to open/close the cargo doors. If the aircraft had electrical power available, i.e. ground power was connected, then the yellow electric pump would come on automatically to open and close the cargo doors.

Question 41

Can the aircraft be flown with a loss of all hydraulic systems?

Answer 41

No, you must have at least one

Question 42

What is the normal system hydraulic pressure?

Answer 42

3000 PSI

Question 43

If the accumulator pressure is low and an external walk around is to be completed, what should you do?

Answer 43

Obtain ground clearance, then turn on the yellow electric pump to pressurize the accumulator

Question 44

When is the PTU inhibited (version 2)?

Answer 44

-First engine start -Parking brake is set and only one ENG MASTER switch is ON -NWS in towing position and parking brake released -Cargo door operation (PTU is also inhibited for 40 seconds after the end of cargo door operation) -PTU pushbutton off

Question 45

If the ECAM actions lead you to turn off the PTU for a reservoir overheat, will the fault light extinguish?

Answer 45

No, not until the overheat subsides

Question 46

If the FAULT light in the PTU pushbutton is ON, are there any other indications on the hydraulic panel?

Answer 46

Yes, the FAULT light will also be illuminated on the respective ENG PUMP pushbutton

Question 47

Can the yellow electric pump run the PTU?

Answer 47

Yes

Question 48

What is the function of the hydraulic priority valves?

Answer 48

It cuts hydraulic power to the slats, flaps, landing gear, and emergency generator if pressure drops below a predetermined value

Question 49

What normally provides air pressure to the hydraulic reservoirs?

Answer 49

ENG #1 HP bleed air pressures the reservoirs automatically. If the bleed air pressure is too low, the system takes bleed air pressure from the crossbleed duct.