Hydraulics

Question 1

How many hydraulic systems are on the aircraft?

Answer 1

• 3

Question 2

What systems use hydraulic power?

Answer 2

• Flight controls
• Spoilers
• Landing gear
• Nose wheel steering
• Wheel brakes
• Thrust reversers

Question 3

Can hydraulic fluid be transferred between systems?

Answer 3

No

Question 4

How many HYD pumps are there?

Answer 4

6, two engine-driven pumps (EDP) and four AC motor pumps (ACMP)

Question 5

What are the basic components of the HYD systems?

Answer 5

• reservoir
• pumps
• accumulators

Question 6

What is normal HYD pressure?

Answer 6

3000 PSI

Question 7

How would you be alerted to a HYD low quantity or overtemp?

Answer 7

The HYD synoptic and EICAS

Question 8

Where would I find a visual representation of the HYD system operation and parameters?

Answer 8

On the HYD synoptic page

Question 9

Why wait after power-up prior to turning on any hydraulic pumps

Answer 9

To allow the flight controls to complete their built-in tests

Question 10

How long after power-up before any HYD pumps should be turned on and why?

Answer 10

3 mins, to allow flight controls to complete built-in checks

Question 11

What is the normal and alternate pump for each system?

Answer 11

• Systems 1 and 2: Engine driven pump, electric is backup
• System 3: 2 AC pumps, A is primary B is secondary. System operates completely automatically when the switches are in AUTO

Question 12

What is the primary power source for HYD systems 1 and 2?

Answer 12

The respective engine driven pump (EDP)

Question 13

What is used as a backup for the EDP?

Answer 13

The AC electric HYD pump

Question 14

When is the electric HYD pump activated?

Answer 14

With the electric HYD pump selector knob in AUTO, whenever an EDP fails or for takeoff when the flaps are not set to the 0 position and the thrust lever are set to takeoff thrust or ground speed > 50 knots and for landing when flaps > 0

Question 15

Why does electric HYD pump 2 automatically come on after engine 1 is started and the parking brake is released?

Answer 15

To provide nosewheel steering and inboard brakes during a single-engine taxi

Question 16

What is the purpose of the accumulator?

Answer 16

• Helps maintain constant pressure by covering transient demands
• Helps to avoid pump cavitation

Question 17

How would you be alerted to a HYD low quantity or overtemp?

Answer 17

On the EICAS and confirmed on the HYD synoptic

Question 18

Can we disable the engine driven hydraulic pump?

Answer 18

No, but you can close the HYD SOV using the ENG PUMP SHUTOFF button which will isolate the pump.

Question 19

What happens when you push the SYS 1 and SYS 2 ENGINE PUMP SHUTOFF guarded buttons?

Answer 19

Closes the HYD SOV, isolating the respective engine driven pump (EDP) from the associated system

Question 20

Where in the flow is the HYD SOV, before or after the engine? Could the engine get hot if you close it? How else could you close it besides the HYD ENG PUMP SHUTOFF?

Answer 20

• Before the engine
• Yes the engine could get hot
• Pulling the associated fire handle

Question 21

What is the PTU, how does it work and why?

Answer 21

• Power transfer unit
• Mechanical pump that uses SYS 1 HYD press and SYS 2 HYD fluid to assist in gear retraction and extension in the event of an engine 2 or EDP 2 failure
• No fluid transfer occurs

Question 22

How can you turn on the PTU?

Answer 22

Rotate the PTU control knob from AUTO to ON

Question 23

When will the PTU automatically activate if the PTU control knob is in the AUTO position?

Answer 23

Flaps >0, if:

• Engine 2 fails, or
• EDP 2 fails (HYD pump)

Question 24

Why do we need a PTU when the #2 electric pump is backup to the #2 engine pump?

Answer 24

The flow rate on the #2 electric pump is insufficient to operate the landing gear

Question 25

What would you expect the FADEC to do with the HYD system 1 or 2 in the event of an engine flameout?

Answer 25

It depressurized the respective engine driven pump so as to facilitate engine windmill rpm (reduces torque for a restart)

Question 26

How is single engine taxi possible if nose wheel steering is on HYD 2?

Answer 26

Releasing the parking brake activates ACMP 2 if the # 2 EDP is not operating

Question 27

What causes SYS 2 ELEC PUMP to operate during single engine taxi?

Answer 27

On the ground, after starting engine 1, releasing the parking brake will automatically activate electric pump 2 to allow single engine taxi

Question 28

What is the primary purpose of HYD 3 system?

Answer 28

Backup for the flight controls

Question 29

Why are HYD ACMP 3A and 3B pump switch positions ON and AUTO respectively?

Answer 29

- HYD ACMP 3A is primary and has no automation | - HYD ACMP 3B is a backup and automatically activates if 3A fails when the

Question 30

Why are the #3 electric pump B OFF-AUTO-ON and #3A is only ON-OFF?

Answer 30

Because #3B is a backup to #3A electric pump when the pump is in AUTO

Question 31

What is the purpose of ELEC PUMP 1 and 2?

Answer 31

Used as a backup to their respective engine driven pump (EDP)

Question 32

What does the ON position do on HYD systems 1 and 2 ELEC PUMP knob?

Answer 32

Override the system logic and turns the respective electric pump on

Question 33

What happens when the SYS 1 (2) ELEC PUMP selector knob is in AUTO?

Answer 33

Activates the electric pump whenever the EDP fails or when flaps are selected to any position other than zero. For takeoff and landing the pumps are automatically activated when: - Thrust levers set to takeoff thrust - Weight on wheels switch indicates in flight - Groundspeed > 50 knots

Question 34

What HYD ACMP will function if the RAT is the only power source?

Answer 34

HYD ACMP 3A only

Question 35

In an emergency and before the RAT comes online, what provides HYD pressure to flight controls?

Answer 35

- HYD 3 accumulator | - After 8 secs the RAT will power up ACMP 3A via the AC ESS BUS

Question 36

What provides HYD pressure from system 3 during an electrical emergency?

Answer 36

Initially, an accumulator provides the pressure until the RAT is deployed and AC ESS BUS is powered. System then returns to HYD system electric pump A (B is a backup)

Question 37

In an electrical emergency can HYD 3 system power requirements overload the RAT?

Answer 37

No. A flow limiter valve is used to reduce flow and limit pump electrical power draw to prevent a RAT stall

Question 38

Explain how the two dedicated valves in HYD system 3 work during an electrical emergency?

Answer 38

The pump unloader and flow limiter valves will reduce the amount of electricity used by HYD sys electric pump A so as not to stall the RAT

Question 39

What systems use HYD system 1?

Answer 39

``` G - ground spoilers panel 2 both sides E - elevator L outboard T - thrust reverser engine 1 M - multifunction spoiler panels 3 and 4 O - outboard brakes R - rudder upper actuator E - emergency parking brake ```

Question 40

What is the flow rate of HYD system 1 and 3 EDP?

Answer 40

11.5 GPM

Question 41

What is the flow rate of HYD system 3 electric HYD pumps>

Answer 41

3.0 GPM

Question 42

What systems use HYD system 2?

Answer 42

``` G - ground spoiler panels 1 I - inboard brakes M - multifunction spoiler panels 5 E - elevator L and R inboard T - thrust reverser engine 2 A - ailerons L and R inboard L - landing gear N - nosewheel steering E - emergency parking brake ```

Question 43

What are some important items controlled by HYD 2?

Answer 43

- Landing gear - Nosewheel steering - Inboard brakes

Question 44

The HYD PBIT will not run if the reservoir temp is below what?

Answer 44

10C

Question 45

What systems use HYD 3?

Answer 45

E - elevator R outboard A - ailerons outboard R - rudder lower actuator

Question 46

Using RAT power if HYD pump 3A fails will 3B operate?

Answer 46

No. HYD pump 3B is powered by AC BUS 2 which will be unpowered using RAT power