Electrical

Question 1

How many electrical networks are on the aircraft? Why?

Answer 1

• 2 independent networks

- Redundancy

Question 2

What happens if a power generating source fails?

Answer 2

Bus ties automatically connect to provide no system degradation

Question 3

What components power the AC system?

Answer 3

• 2 IDG’s
• APU
• Inverter
• RAT
• AC GPU receptacle

Question 4

What components power the D.C. System?

Answer 4

• 2 nicad batteries
• 3 TRUs
• DC GPU receptacle

Question 5

How does the IDG maintain a stable power output?

Answer 5

A constant speed drive attached to the accessory gear box

Question 6

What monitors and controls the IDGs

Answer 6

Each has a generator control unit (GCU)

Question 7

Can one IDG power the entire electrical system?

Answer 7

Yes

Question 8

What will cause the amber IDG light on the overhead panel to illuminate?

Answer 8

• High oil temperature

- Low oil pressure

Question 9

If an IDG is manually disconnected can it be reconnected by the flight crew?

Answer 9

No, it’s a maintenance function

Question 10

What is the primary purpose of the AC generators?

What buses and components are powered?

Answer 10

• Powers AC BUS 1, 2 and AC ESS BUS which…

- Power TRU 1, 2, and ESS

Question 11

What do the TRUs do?

Answer 11

Convert 115V AC to 28V DC

Question 12

Can the APU replace a failed IDG?

Answer 12

Yes

Question 13

What is the AC system’s source priority?

Answer 13

• Onside
• Inside
• Outside
• Cross-side

Question 14

How do you know if an AC GPU is connected and ready to provide electricity?

Answer 14

• GPU button displays AVAIL and the GPU icon is presented on the electrical synoptic page
• once GPU button is depressed it will display IN USE unless another AC Power source is available

Question 15

What does it mean if the AC GPU is plugged in and the outside GPU panel button displays IN USE?

Answer 15

• Ground service bus is in use

- Cockpit GPU button will display AVAIL even though the ground service bus is in use

Question 16

If the airplane is using the AC GPU and the APU is started what should the pilot be sure to do?

Answer 16

Deselect the GPU pushbutton before the next GPU connection

Question 17

What will charge BATT 1 and 2

Answer 17

Any AC power source

Question 18

How long will the batteries last with no recharging?

Answer 18

10 mins

Question 19

What is the purpose of the D.C. GPU receptacle?

Answer 19

If the battery temp is < -20C

Question 20

What is the min battery temp for APU start?

Answer 20

-20 C on BATT 2

Question 21

What is the min voltage to close the battery bus ties?

Answer 21

18 V

Question 22

How are the batteries used for APU start?

Answer 22

• BATT 2 powers the APU start bus

- BATT 1 powers the APU FADEC and EICAS for monitoring

Question 23

What is the purpose of the inverter?

Answer 23

Converts 28 VDC from the batteries to 115 VAC to power the AC STANDBY BUS when an AC source is not available

Question 24

What is on the AC STANDBY BUS?

Answer 24

Engine exciters 1A and 2A

Question 25

What powers the RAT?

Answer 25

Airflow turns the RAT propeller which spins the turbine inside

Question 26

When will the RAT deploy?

Answer 26

- Automatically deploys if AC BUS 1 and 2 are not powered | - Manually by pilot

Question 27

How long after deployment before the RAT will supply power?

Answer 27

8 seconds

Question 28

Is there a total loss of power during the 8 second RAT deployment?

Answer 28

No. Batteries supply power to the D.C. ESS BUSSES and AC STANDBY BUS (via the inverter)

Question 29

What does the RAT POWER ?

Answer 29

The ESS BUSSES

Question 30

What is the minimum airspeed for the RAT?

Answer 30

130 kts | - load shedding occurs below this speed

Question 31

When is the RAT icon displayed on the electrical synoptic page?

Answer 31

When the RAT is deployed

Question 32

What manages the electrical system?

Answer 32

- 4 ICC's (Integrated Control Centers) | - 2 SPDA's (secondary power distribution assemblies)

Question 33

What is an ICC?

Answer 33

An electronic control device which provides power distribution and protection for electrical loads

Question 34

What is an SPDA?

Answer 34

An electrical load-management unit, powered by the ICC's, that distributes electrical loads to aircraft systems according to distribution logic

Question 35

Can the flight crew reset the ICC and SPDA remote electronic CBs?

Answer 35

- ICC CBs can only be reset by maintenance on the ground | - SPDA CBs can be reset via the MCDU