Hydraulic CBT's

Question 1

How many hydraulic systems?

Answer 1

4 independent systems. 1 for each engine.

Question 2

What pressurizes the hydraulic fluid reservoirs?

Answer 2

Bleed air

Question 3

What is the nominal pressure of the hydraulic system?

Answer 3

3,000 PSI

Question 4

How many pumps does each system have? What types?

Answer 4

Each system has 1 EDP (engine driven pump) and 1 demand pump (used as a backup or for high demand).

System 4 also has an AUX pump

Question 5

The demand pumps are backup pumps for all 4 systems. What powers the demand pumps?

Answer 5

Demand systems 1 and 4: Powered by bleed air

Demand systems 2 and 3: Powered electrically

Question 6

How is the AUX pump powered? What is it used for?

Answer 6

It is an electric pump powered by the GROUND HANDLING BUS. Used for ground handling prior to engine start. (pressurizes parking brake accumulator)

Question 7

When would a SYS FAULT light illuminate on a hydraulic system?

Answer 7

• Low hydraulic system pressure
• Low hydraulic reservoir quantity
• Excessive hydraulic fluid temperature

Question 8

When would the demand pump pressure light (PRESS) illuminate?

Answer 8

• The Selector is in the OFF or AUX position
• The Demand Pump is operating but output pressure is low, or
• The Demand Pump has failed.

Question 9

When in AUTO, when would a demand pump kick on?

Answer 9

-engine pump output pressure is low
-when related fuel control switch is in CUTOFF.
-Demand Pump 1 & 4 also operates when trailing edge flaps are in transit, or flaps are extended beyond the 1 position (IN FLIGHT).

Question 10

The demand pump selector has an additional AUX position for system 4. When selecting AUX, does the demand pump still run?

Answer 10

No, it shuts down and the AUX pump starts.

Question 11

For system 4, when in AUX, when would the AUX pump shut down automatically?

Answer 11

Only after the number 4 engine is powering the EDP. At that point, you’d return the selector back to AUTO.

Question 12

When would the EDP be running?

Answer 12

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

Question 13

On the engine pump switches, what does an amber PRESS mean?

Answer 13

Pump Output Pressure is Low

NOTE: Its normal to see this prior to start and after shutdown.

Question 14

In regards to the hydraulic system, what happens when you pull a fire switch?

Answer 14

-Shuts off hydraulic fluid to engine driven pump
-Depressurizes engine driven pump

Question 15

If you pull a fire switch, do you lose all hydraulic pressure from that system?

Answer 15

No. You only shut down and depressurize the EDP.

Question 16

On the hydraulic fluid quantity on the status page, what is RF? When would it be displayed?

Answer 16

Refill required. Only would see this on the ground.

Question 17

What would a message RSVR PRESS next to the hydraulic reservoir indication on EICAS mean?

Answer 17

The bleed air that is pressurizing the reservoir is low pressure. (Not the hydraulic pressure itself.)

NOTE: This will not cause a SYS FAULT light

Question 18

What is the HYQUIM?

Answer 18

Hydraulic Quantity Interface Module

It is a single module that measures hydraulic fluid quantity. If it fails, you may get erroneous fault messages