Hydraulics

Question 1

(ALL) Recall the number of independent hydraulic systems and

how they are designated.

Answer 1

Three independent systems

• Left
• Center
• Right

Question 2

(756, 400) Recall the purpose of the (ADP) Air Demand Pump and
when it activates.

Answer 2

AUTO –
- The ADP operates when heavy load items are selected.
- The ADP operates when both center electric pump
output pressures are low (The Center system pressure is low)
 ON – The ADP operates continuously

Question 3

(756, 400) Recall the purpose of the HDG (Hydraulic Driven

Generator)

Answer 3

The HDG operates automatically as a backup source of electrical power in the event that both main AC busses become inoperative.

Question 4

(756, 400) Recall which hydraulic system powers the HDG.

Answer 4

 (757 as installed) The Left hydraulic system powers the
HDG using the Left engine driven pump or the PTU.

 (767 as installed) The Center hydraulic system powers the
HDG using the ADP

Question 5

(NG, 777, 756, 400) Identify where the reservoir hydraulic quantity
is displayed, and the associated indication of the reservoir requiring refilling.

Answer 5

 The EICAS STATUS page –
- The reservoir quantity is displayed in white
- A magenta RF (Refill).is displayed when the reservoir
requires refilling (Maintenance action)

Question 6

(756, 400, 777) Describe the purpose of the RAT (Ram Air Turbine).

Answer 6

 The RAT, when deployed, provides hydraulic power to the flight controls portion of the center hydraulic system.
Note: The RAT deploys automatically when both engines fail.

Question 7

(756, 400) Identify which hydraulic system powers the high load items (Memory Aid “Flaps, Slats, Gear, and Steer”)

Answer 7

 757 – Left System

 767 – Center System

Question 8

(756, 400, 777) Recall how the RAT can be deployed.

Answer 8

 In flight, the RAT deploys automatically when both engines fail.

Note: The RAT is inhibited from Auto deployment on the ground.

 Manually by pushing the RAM AIR TURB switch.

CAUTION: The RAT can be Manually deployed on the ground.

Question 9

(756, 400) Recall the minimum airspeed to ensure proper RAT

operation.

Answer 9

130 Knots.

Question 10

(756, NG) Describe the purpose of the PTU (Power Transfer Unit) and how it can be activated.

Answer 10

 The PTU is a hydraulic motor pump which transfers
hydraulic power from the right system to the left system.
 The PTU is automatically activated:
- If the left engine fails and the right engine is operating
- If the left engine-driven pump pressure is low and the right engine is operating.

Question 11

(756, 400) Explain the meaning of a SYS PRESS (system pressure) light

Answer 11

Illuminated (amber) – the hydraulic system pressure is low.

Question 12

(756, 400) Recall the meaning of a RSVR (reservoir) light

Answer 12

 B757 Illuminated (amber) –
 - Reservoir quantity is low
 - Reservoir pressure is low. (Air pressure in the reservoir)
 B767 Illuminated (amber) –
 - Reservoir quantity is low.

Question 13

(757/767) Recall the meaning of the RAT green PRESS light.

Answer 13

Illuminated (green) –
 The RAT is deployed.
 The RAT is producing hydraulic pressure.

Question 14

(757/767) Recall the meaning of the RAT UNLKD light.

Answer 14

Illuminated (amber) – the RAT is not stowed and

locked.

Question 15

(757/767) Recall the meaning of any HYD PUMPS press light.

Answer 15

Illuminated (amber) – the pump output pressure is low.

Question 16

(757/767) Recall the meaning of any OVHT HYD PUMPS light.

Answer 16

Illuminated (amber) – the pump temperature is high.

Question 17

(757/767) Recall the operation of the hydraulic demand pump selectors.

Answer 17

Left / Right Electric and Center Air (L/R ELEC and C AIR)
Demand Pump selectors
 OFF – The pump off.
 ON – The pump will operate continuously.
 AUTO –
- The left / right electric pumps operate when the engine
pump pressure is low
- The center air demand pump operates when both
center electric pump pressures are low or heavy load
items are selected