Study Guide: Hydraulics

Question 1

757: The power transfer unit (PTU) is automatically activated:

Answer 1

If the left engine fails or the left engine-driven pump pressure is low

Question 2

757: The hydraulic motor generator (HMG) is automatically powered by the
___________ whenever both main AC busses become unpowered in flight.

Answer 2

The left engine hydraulic pump or the PTU, if operating

Question 3

767: The hydraulic motor generator (HMG) is automatically powered by the
___________ when electrical power is lost from both main AC busses.

Answer 3

The center hydraulic system

Question 4

757/767: When deployed, the RAT drives a hydraulic pump that supplies adequate
pressure for flight controls down to an airspeed of approximately ______.

Answer 4

130 knots

Question 5

757: The center hydraulic system reservoir contains a standpipe to reserve hydraulic
fluid for the ________ in the event of a center system hydraulic leak.

Answer 5

Ram air turbine (RAT)

Question 6

757: To prevent electrical overloads, the No. 2 electric pump is inhibited when only one generator (APU or engine) or only external power is available and:

Answer 6

Both center hydraulic electric pump switches are on

Question 7

757/767: According to the graphic, what is the status of the ram air turbine (RAT)?

Answer 7

The RAT is not stowed and locked, and is producing hydraulic pressure

Question 8

757: External power is the sole source of electrical power. The center No. 2 electric hydraulic primary pump PRESS light is illuminated because:

Answer 8

In order to prevent electrical overloads, the pump is inhibited

Question 9

757/767: The hydraulic quantity for each hydraulic system is displayed:

Answer 9

On the EICAS status display

Question 10

757: According to the graphic, the RSVR light is illuminated. This indicates that:

Answer 10

Reservoir quantity is low (below 50%) or reservoir air pressure is low

Question 11

757: According to the graphic, the EICAS POWER XFER UNIT status message is displayed. What is the status of the power transfer unit (PTU)?

Answer 11

The PTU is not operating properly

Question 12

757: Trailing edge flaps and leading edge slats are hydraulically operated by drive units normally powered by the _____ hydraulic system(s).

Answer 12

Left

Question 13

757/767: Yaw control is provided by a single rudder which receives hydraulic power from
the _________ hydraulic system(s).

Answer 13

Left, center, and right

Question 14

757: According to the graphic, when the RESERVE BRAKES switch is activated, fluid trapped below a standpipe is made available to the _________ system electric hydraulic pump.

Answer 14

Right

Question 15

757: When activated, the power transfer unit (PTU) supplements the left hydraulic system electric motor-driven pump to operate the following:

Answer 15

Flaps and slats, landing gear, nose wheel steering, HMG

Question 16

767: Across the entire aircraft, how many hydraulic reservoir standpipes are there?

Answer 16

One

Question 17

757: Across the entire aircraft, how many hydraulic reservoir standpipes are there?

Answer 17

Three

Question 18

767: The center system reservoir contains a standpipe to reserve a supply of fluid for the:

Answer 18

Reserve brakes and steering system

Question 19

767: To prevent electrical overload, the No. 2 electric primary pump is inhibited when
only one generator (APU or engine) or only external power is available and _________ is/are commanded to operate.

Answer 19

The other three electric hydraulic pumps

Question 20

757/767: The _________ is available to supply hydraulic pressure to the center system
flight controls in the event of a dual engine failure in flight.

Answer 20

Ram air turbine (RAT)

Question 21

767: When the RESERVE BKS & STRG switch is pressed, the ____________ is turned
on regardless of switch position.

Answer 21

Center system No. 1 electric primary pump

Question 22

757/767: The ram air turbine (RAT) is armed:

Answer 22

On the ground above 80 knots

Question 23

767: In the AUTO position, the air-driven demand pump (ADP) operates automatically whenever the landing gear, flaps, slats, or speed brakes/ground spoilers are selected for operation. The ADP will also operate when:

Answer 23

Center system hydraulic pressure drops to a preset value

Question 24

757: When the hydraulic motor generator (HMG) is operating, hydraulic flow to the flaps
and slats is _______, resulting in:

Answer 24

Reduced, increased operating time for these items

Question 25

757: Can the hydraulic motor generator (HMG) be driven by the power transfer unit (PTU)?

Answer 25

Yes, the HMG may be driven by the PTU, if operating

Question 26

767: When the air-driven pump (ADP) is inoperative:

Answer 26

Landing gear retraction and flap extension/retraction times increase