Study Guide: Electrical

Question 1

757/767: According to the graphic, the right utility bus OFF light is illuminated. What is
the cause for its illumination?

Answer 1

The right utility bus is unpowered

Question 2

757/767: According to the graphic, the L GEN DRIVE DISC DRIVE light is illuminated.
What is the cause for its illumination?

Answer 2

The associated generator drive oil temperature is high or oil pressure is low

Question 3

757/767: According to the graphic, the standby power bus OFF light is illuminated.
Which bus(ses) is/are not powered?

Answer 3

Standby AC, standby DC, or battery bus(ses) not powered

Question 4

757/767: According to the graphic, what is providing power to the standby busses?

Answer 4

Left main AC and DC

Question 5

757/767: When external or APU electrical power is available on the ground, which bus is
automatically powered?

Answer 5

Ground handling bus

Question 6

757/767: When the associated AC bus tie breaker is armed for automatic operation, the
AC busses are powered according to the following system priorities:

Answer 6

Respective IDG, APU generator, opposite IDG

Question 7

757/767: As the first engine is started with APU supplying electrical and pneumatic
power, what load shed occurs?

Answer 7

Both utility and all galley busses load shed

Question 8

757/767: During flight, the hydraulic motor generator (HMG) automatically starts and
supplies AC and DC power:

Answer 8

When primary AC power is lost on both main AC busses during flight

Question 9

757/767: The center busses transfer from the left main busses directly to the static
inverter and the hot battery bus when:

Answer 9

At least two generators are operating and three autopilots are armed for an
autoland approach

Question 10

757/763: On a three autopilot approach with a LAND 3 indication, what will the ASA
indicate if an engine-driven generator is lost below 200 feet AGL without the APU
running?

Answer 10

LAND 3

Question 11

757/767: Once commanded to operate, are there limitations associated with how long
the hydraulic motor generator (HMG) can run?

Answer 11

No, there is no time limit for HMG operation

Question 12

757/767: According to the graphic, what is providing power to the Ground Handling bus?

Answer 12

External electrical power

Question 13

757/767: The main aircraft battery and the APU battery are connected to their own
respective battery chargers. Both battery chargers are powered by the:

Answer 13

Ground service bus

Question 14

757/767: The integrated drive generator (IDG) oil is cooled by:

Answer 14

A fuel/oil heat exchanger

Question 15

757/767: The main DC electrical system is powered:

Answer 15

By the transformer-rectifier units (TRU’s) powered by the main AC busses

Question 16

753/764: During hydraulic motor generator (HMG) operations, what is the status of the
IRUs?

Answer 16

All three IRU’s remain powered

Question 17

752/763: Hydraulic motor generator (HMG) operation automatically switches the Captain’s RDMI to:

Answer 17

The center IRU

Question 18

757/767: In the case of a generator overload, which busses automatically load shed?

Answer 18

Associated utility and galley busses

Question 19

757/767: The ground service bus is normally powered by the:

Answer 19

Right main AC bus

Question 20

767: The left recirculation fan is powered by the:

Answer 20

Left utility bus

Question 21

757/767: The associated utility and galley busses have shed due to a generator overload. What is required to restore power to the bus?

Answer 21

The utility busses (and therefore galley busses) must be reset manually

Question 22

757/763: If primary AC power is lost on both main AC busses during flight, the hydraulic
motor generator (HMG) automatically starts and supplies AC power to the:

Answer 22

Left and right AC transfer busses, standby AC bus via the left AC transfer bus,
and Captain’s flight instrument transfer bus

Question 23

752/763: According to the graphic, which electrical busses are still being powered? (HMG not operating)

Answer 23

Hot battery bus, battery bus, standby DC bus, standby AC bus

Question 24

757/767: According to the graphic, the DISCH light is illuminated. The main aircraft battery:

Answer 24

Is discharging

Question 25

757/767: According to the graphic, the BUS TIE ISLN light is illuminated. This occurs when:

Answer 25

The AC bus tie breaker is locked open from a fault trip