Hydraulic System: General

Question 1

Main components of the system?

Answer 1

1. 1 Reservoir
2. 3 Pumps
3. Manifolds
4. Control and Shut-Off Valves
5. 2 Accumulators (Main system/Brake)

Question 2

What does the hydraulic system operate?

Answer 2

1. Landing Gear
2. Landing Gear Doors
3. Brakes
4. Flaps
5. Spoilers/Spoilerons
6. Thrust Reversers

Question 3

How many hydraulic pumps does the system have?

Answer 3

1. (2) Engine-Driven Pumps

2. (1) 28VDC Auxiliary pump

Question 4

What can the Auxiliary Pump operate in the event of the main system fail?

Answer 4

1. Landing Gear
2. Flaps
3. Backup Brake

Question 5

Type of hydraulic fluid and how much can it hold?

Answer 5

• MIL-H-5606

- 7.3 Quartz

Question 6

Is the reservoir pressurized?

Answer 6

Yes

Question 7

How is the reservoir pressurized and how much psi is that?

Answer 7

• Through engine bleed air

- Approx. 24 psi.

Question 8

Does the reservoir have excessive pressure protection and what psi?

Answer 8

• Overboard relief valve vents and vacuum relief vent
• Approx. 26.5 psi.
• > 340°F thermal shut-off valve closes

Question 9

What does “HYD XFLOW” provide?

Answer 9

• Auxiliary hydraulic power to:
  1. Landing Gear
  2. Flaps
  3. Brake Accumulator

Question 10

What is the normal pressure of the system?

Answer 10

• 3,000 psi.

Question 11

What is the maximum output of each engine driven pump?

Answer 11

• 4.6 Gal/min

Question 12

How much psi. does the engine drive pumps maintain?

Answer 12

• 2,210 to 3,600 psi.

Question 13

How much psi. does the aux. pumps maintain?

Answer 13

• 2,610 to 3,600 psi.

Question 14

What is the maximum output of each auxiliary pump?

Answer 14

• 1.0 Gal/min

Question 15

Why is the reservoir split into two sections?

Answer 15

• Redundancy
• One side for engine-driven pumps
• Another side for auxiliary pumps

Question 16

What happens when the auxiliary pump is used for more than 20 minutes?

Answer 16

• Volume reduced to .75 Gal/min

- Psi is reduced to 2,850 psi.

Question 17

What are the automatic auxiliary pump operations?

Answer 17

1. Pump comes off when aircraft is on
2. Pump comes off when gear handle is selected UP
3. Pump comes on when gear handle is selected DOWN
4. Pump comes off when aircraft is powered down

Question 18

At what psi. would you receive an EICAS indication?

Answer 18

• 1,900 psi. or less

Question 19

What provides hydraulic pressure status on the EICAS?

Answer 19

• Transducer located on the main filter manifold

Question 20

When will the EICAS indicate HYD PUMP LO?

Answer 20

• Pump output pressure is < 1,900 psi. for more than 5 seconds

Question 21

The main system status turns amber when?

Answer 21

• <1,500 psi. or >3,600 psi.

Question 22

The B-Accumulator status turns amber when?

Answer 22

• <1,200psi. or >3,600 psi.

Question 23

What do you lose when you have no main hydraulic pressure?

Answer 23

1. Spoilers/Spoilerons
2. Thrust Reversers
3. Main system (accumulator)

Question 24

Why is it recommended to alternate engine starts?

Answer 24

• Only way to check the engine driven pump output