Electrical

Question 1

What two conditions cause the BUS TIE ISLN light to illuminate?

Answer 1

Bus tie breaker is open because BUS TIE switch is OFF, or switch is in AUTO and fault has occurred

Question 2

In the Generator Control (GEN CTRL) switch, what does the amber OFF light indicate?

Answer 2

The generator breaker is open

Question 3

What condition illuminates the generator DRIVE light?

Answer 3

Low IDG oil pressure

Question 4

Which system provides load management and protection to ensure critical systems are powered?

Answer 4

Electrical Load Management System (ELMS)

Question 5

What condition might shed the galleys/utility buses in flight or on the ground?

Answer 5

When electrical loads exceed the power available

Question 6

List the main AC electrical sources

Answer 6

1. Left and Right IDGs
2. APU generator
3. Primary and Secondary external power

Question 7

If an IDG fails in flight, is there sufficient power available to prevent load shedding?

Answer 7

No, two main AC power sources are required to supply the entire AC electrical load

Question 8

Other than the IDGs, what other aircraft power source for the main AC buses is available in flight?

Answer 8

The APU generator

Question 9

In the external power switches what does the AVAIL light indicate?

Answer 9

Power supply is plugged in and the voltage and frequency are within limits

Question 10

In the external power switches what does the ON light indicate?

Answer 10

External power is supplying the bus(es)

Question 11

After landing if an external power AVAIL light is in, will it take over from a main generator when the power is selected on?

Answer 11

Yes

Question 12

When the APU is started, how is power transferred from external to the APU generator?

Answer 12

Automatically (replaces SEC EXT PWR on the left AC bus)

Question 13

After landing with the APU generator switch ON will the APU generator take over automatically from the main generators when the engines are shut down?

Answer 13

Yes

Question 14

With the Bus Tie switches latched in AUTO what is the position of the bus tie breakers with ground power removed, the APU operating normally and the first engine (right) just started?

Answer 14

Right BTB open, left BTB closed

Question 15

With the Bus Tie switches latched in AUTO what is the position of the bus tie breakers When both engines are running?

Answer 15

Both BTBs open

Question 16

Which main bus normally powers the Ground Service Bus?

Answer 16

The right main AC bus

Question 17

Is the Ground Service Bus normally live during flight?

Answer 17

Yes

Question 18

If the right generator fails, and the right Bus Tie ISLN light is illuminated, will the right AC bus be powered?

Answer 18

No, the Bus Tue Breaker is locked open

Question 19

If the right generator fails, and the right Bus Tie ISLN light is illuminated, will the batteries continue to charge?

Answer 19

No, the Ground Service Bus will also fail

Question 20

When will the Backup Electrical System automatically power one or both Transfer Busses?

Answer 20

1. Only one main AC generator (includes APU) is available
2. Power to one or both of the main AC busses is lost
3. Approach (APP) mode is selected for autoland
4. The system is automatically tested after engine starts

Question 21

What is the power source for the Backup AC Electrical system?

Answer 21

One Backup Generator mounted on each engine

Question 22

How many Backup Generators can connect to the electrical system at one time?

Answer 22

One

Question 23

What normally powers the captain’s flight instruments?

Answer 23

C1 TRU

Question 24

What powers the captain’s flight instruments if the C1 TRU fails?

Answer 24

C2 TRU through FO FLT INST bus

Question 25

What powers the captain’s flight instruments if both C1 and C2 TRUs fail?

Answer 25

Battery Bus

Question 26

Which units normally power the left and right main DC buses?

Answer 26

The L TRU and R TRU

Question 27

Which buses power the L and R TRUs?

Answer 27

The L and R Transfer buses respectively

Question 28

During normal conditions what powers the Hot Battery Bus?

Answer 28

The main battery charger

Question 29

During normal conditions what powers the Battery Bus?

Answer 29

Captain’s Flt Inst Bus (C1 TRU)

Question 30

During normal conditions what powers the Standby AC Bus?

Answer 30

L Transfer Bus

Question 31

If the left TRU fails what powers the left main DC bus?

Answer 31

The right Main DC bus

Question 32

Where are the battery chargers powered from?

Answer 32

The ground service bus

Question 33

What are the primary electrical sources for the flight control DC electrical systems?

Answer 33

Engine driven Permanent Magnetic Generators (PMGs)

Question 34

If PMG AC power is not available, what secondary source of power supplies which DC Flight Control Buses?

Answer 34

Main DC busses supply L and R Flight Control DC busses; Captain’s Flight Instrument bus supplies the C Flight Control DC bus

Question 35

When operating on the Standby Electrical System, which DC Flight Control Buses will be powered from the Hot Battery Bus?

Answer 35

L and C Flight Control DC busses only

Question 36

If primary power is lost, what does the Standby Electrical System supply power to?

Answer 36

AC and DC power to selected flight instruments, communications and navigation systems, and the flight control system

Question 37

The Main battery can provide standby power to which busses?

Answer 37

1. Hot Battery bus 2. Battery Bus 3. Captain’s Flight Instrument bus 4. L and C flight control PSAs 5. Standby Inverter

Question 38

For how long can the Main battery provide standby power?

Answer 38

Minimum 10 minutes

Question 39

In flight, when would the RAT deploy automatically?

Answer 39

When both AC transfer busses lose power

Question 40

The RAT generator provides standby power to what?

Answer 40

To the C1 and C2 TRUs

Question 41

What supplies power until RAT deployment?

Answer 41

The Main battery