HYDRAULICS

Question 1

How many HYD reservoirs are there in the system and what color code do they have in the maintenance manual?

Answer 1

3
Left (red)
Centre (blue)
Right (green)

Question 2

Which HYD system supplies the FLT controls?

Answer 2

All 3 systems. L, R and Center

Question 3

Are the HYD reservoirs pressurized?

Answer 3

Yes, by the bleed air system

Question 4

Which HYD system Powers the Normal brake system?

Answer 4

The Right HYD system

Question 5

List the primary pumps for the L R C hydraulic systems

Answer 5

Left: ENG
Right: ENG
Center: Electric C1 and C2 pumps

Question 6

List the demand pumps for the L R C systems

Answer 6

Left: Electric
Right: Electric
Center: C1 and C2 Air driven pumps

Question 7

In AUTO, when will the L and R Hydraulic demand pumps operate?

Answer 7

When there is a high demand for HYD fluid and for T/O and Landing

Question 8

Which HYD system Powers the ALTN/RSV brakes?

Answer 8

Center HYD system

Question 9

What systems are supplied by the C HYD system?

Answer 9

1. FLT controls
2. Flaps
3. Main gear steering
4. Alt/RSV brakes
5. Nose gear steering
6. Landing gear actuation

Question 10

What is the purpose of the RAT?

Answer 10

Used to power only the FLT controls getting fluid from the C HYD system when all power sources fails

Question 11

Will both C1 and C2 primary pumps run on the ground with one Engine running?

Answer 11

No, only C1 will run with one Power source

Question 12

Will both C1 and C2 demand pumps for C HYD system run if both are selected to ON?

Answer 12

No both pumps can’t operate at the same time. If both are selected on only C1 will operate.

Question 13

What systems are isolated if C HYD system quantity is low and airspeed is above 60 kts?

Answer 13

Alt brakes, nose gear actuation and steering, LE slats

Question 14

Will the RAT deploy automatically if the C HYD system is low?

Answer 14

No, all 3 HYD systems has to be low

Question 15

What buses must be powered to be able to manually deploy the RAT?

Answer 15

HOT BAT BUS or
APU BAT BUS

Question 16

Can the RAT be stowed once it is deployed, in flight?

Answer 16

No only by engineers on the ground

Question 17

What is the pressure in the hydraulic system?

Answer 17

3’000 psi

Question 18

What is the max, normal and standpipe level of fluid in the right and left systems?

Answer 18

Max: 47,8 liter
Normal: 28,0 liter
Standpipe level: 7,6 liter

Question 19

What is the max, normal and standpipe level of fluid in the center system?

Answer 19

Max: 97,0 liter
Normal: 41,7 liter
Standpipe level: 4,5 liter

Question 20

What does it mean, fluid level wise, if a hydraulic system shows 0,0 volume indication?

Answer 20

That the level is at the standpipe level.

Question 21

What is the CHIS and when does it become active?

Answer 21

Center Hydraulic isolation System
Becomes active when volume in center system is less than 0,40 and speed is above 60 kts.

Question 22

Describe what happens in the center system when Center Hydraulic Isolation System(CHIS) becomes active?

Answer 22

When CHIS is active, two isolation valves divides the center hydraulic system into different parts. The NLG actuation and steering and the leading edge slat hydraulic lines are isolated from center system pressure. The output of ACMP C1 goes only to the alternate brake system.
The output of the other center hydraulic system pumps goes to the trailing edge flaps, the MLG actuation and steering, and the flight controls(PFCS). If there is a leak in the NLG actuation and steering or LE slat lines, there is no further loss of hydraulic fluid. The alternate brakes, the trailing edge flaps, the MLG actuation and steering, and the PFCS continue to operate normally.
If there is a leak in the trailing edge flaps, the MLG actuation and steering, or the flight control lines, the reservoir loses fluid down to the standpipe level (0.00 indication). This causes a loss of these systems but the alternate brake system continues to get hydraulic power from ACMP C1. If there is a leak in the lines between ACMP C1 and the alternate brake system, all center hydraulic system fluid is lost.

Question 23

When does the CHIS stop its operation?

Answer 23

Both valves, nose gear and reserve, open again automatically when the center system quantity is more than 0.70 or airspeed is less than 60 knots for 5 seconds. Both valves also reset when the center system quantity is more than 0.70 and both engines and both engine-driven pumps operate normally for 30 seconds.

Question 24

When would the nose gear isolation valve in the CHIS system open up again?

Answer 24

When speed is below 60 kts

Question 25

Under what conditions will the RAT deploy automatically?

Answer 25

The RAT deploys automatically if: - Both engines are failed and C HYD SYS pressure is low, or - Both AC transfer busses are unpowered, or - All 3 HYD SYS pressures are low

Question 26

What does the EICAS “HYD RSVR PRESS” mean?

Answer 26

EICAS “HYD RSVR PRESS” shows when hydraulic reservoir bleed air pressure is less than 21 psi. Normal pressure is above 25 psi.

Question 27

When does the OF (overfill) indications come up on the status page?

Answer 27

If the HYD reservoir is more than 1.20 than an “OF” (overfill) message comes up on the status page.

Question 28

When does the RF (refill) indications come up on the status page?

Answer 28

If quantity is less than 0.75 then an “RF” comes up on the status page. The RF indication only comes on when the aircraft is on the ground.

Question 29

At what pressure or temp will a FAULT light come on for the L/R EDP in the hydraulic system?

Answer 29

1800 psi or 105 deg C

Question 30

At what pressure or temp will a FAULT light come on for the L/R ACMP in the hydraulic system?

Answer 30

1200 psi or 105 deg C