Electrical

Question 0

What happens if a power generating source fails?

Answer 0

Bus ties automatically connect to provide no system degradation.

Question 1

How many networks make up the electrical system on the airplane? Why?

Answer 1

I. 2 independent networks

II. Redundancy and fault isolation

Question 2

What components power the AC system?

Answer 2

2 Integrated Drive Generators (IDG)
Auxiliary Power Unit (APU)
Inverter
Ram Air Turbine (RAT)
AC GPU receptacle

Question 3

What components power in DC system?

Answer 3

2 NiCad batteries
3 Transformer Rectifier Units (TRU)
DC GPU Receptacle

Question 4

How does the IDG maintain a stable power output?

Answer 4

A Constant Speed Drive (CSD) attaches the IDG to the AGB (Accessory Gear Box)

Question 5

What monitors and controls the IDG’s?

Answer 5

Each has a Generator Control Unit (GCU)

Question 6

Can one IDG supply the entire electrical system?

Answer 6

Yes

Question 7

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

Answer 7

Hi oil temperature

Low oil pressure

Question 8

If an IDG manually disconnected, can it be reconnected by the flightcrew?

Answer 8

No. This is a maintenance function

Question 9

What is the primary purpose of the AC generators?

Answer 9

To power the AC BUSES and AC ESS BUS which…

Power the three Transformer Rectifier Unit (TRU) One, Two, and ESS

Question 10

What is the purpose of the Transformer Rectifier Units?

Answer 10

To convert 115V 400Hz AC to 28V 300 Amp DC

Question 11

Can the APU replace the failed IDG?

Answer 11

Yes (below 33,000ft)

Question 12

What is normal AC electrical priority?

Answer 12

Onside (IDG)
Inside (APU)
Outside (GPU)
Cross-side (other IDG)

Note: The airplane uses an onboard AC power source before an external AC source.

Question 13

How is it known that AC GPU is hooked up to the airplane and ready to provide electrical power?

Answer 13

GPU button displays AVAIL and the GPU icon is presented on the electrical synopsis page.

Once the GPU button is pushed in, the button will display IN USE provided another AC power source is not available.

Question 14

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

Answer 14

Ground service button is “IN USE”.

Cockpit GPU button will display “AVAIL” even though the ground service bus “IN USE”.

Question 15

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

Answer 15

Deselect the GPU button before the next GPU connection.

Question 16

What will charge the batteries?

Answer 16

Any AC Power Source.

Question 17

How long will the aircraft’s batteries last with no recharging?

Answer 17

10 minutes

Question 18

What is the purpose of the DC GPU receptacle?

Answer 18

For APU start when batteries < 22.5 VDC, or

If battery temp is < -20°C

Question 19

What is the minimum battery temp for APU start?

Answer 19

-20°C

Question 20

What is the minimum battery voltage to close the battery bus-ties?

Answer 20

18 volts

Question 21

What battery is used for the APU start?

Answer 21

BATT 2 powers the APU Start Bus

BATT 1 powers the FADEC & EICAS for monitoring

Question 22

What is the purpose of the inverter?

Answer 22

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

Question 23

What is on the AC STANDBY BUS?

Answer 23

Engine ignitors 1A & 2A

Question 24

What powers the Ram Air Turbine (RAT)?

Answer 24

Airflow turns the RAT propeller which spins the turbine inside

Question 25

When will the RAT deploy?

Answer 25

Automatically deploys if AC BUSES are not powered Manually by pilot

Question 26

How long after deployment before the RAT will supply power?

Answer 26

8 seconds

Question 27

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

Answer 27

No. Batteries supply power to the DC ESS BUSES and AC STANDBY BUS

Question 28

What does the RAT power?

Answer 28

ESS BUSES

Question 29

What is minimum airspeed for the RAT?

Answer 29

130 KIAS. (150 KIAS during deployment) | Load shedding occurs below this speed.

Question 30

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

Answer 30

When the RAT is deployed

Question 31

What manages the electrical system?

Answer 31

4 Integrated Control Centers (ICC) | 2 Secondary Power Distribution Assembly (SPDA)

Question 32

What is an ICC?

Answer 32

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

Question 33

What is an SPDA?

Answer 33

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

Question 34

Can the flight crew reset the ICC and SPDA remote electronic circuit breakers?

Answer 34

ICC circuit breakers can only be reset by maintenance. SPDA circuit breakers can be reset via the MCDU

Question 35

What is the purpose of the LICC?

Answer 35

The left integrated control center provides power distribution and protection for AC bus 1 and DC bus 1 and the AC and DC ground service buses. Line replaceable modules in the LICC are TRU 1, GCU 1, the external power module and several thermal circuit breakers.

Question 36

What is the purpose of the EICC?

Answer 36

The emergency integrated control center, located in the forward eBay, provides power distribution and protection for AC essential bus and DC essential bus 1 and 3. The standby AC bus and the hot battery bus are also integrated into the control center. Line replaceable modules in the EICC are the essential TRU and several thermal circuit breakers.

Question 37

What items are on the DC Hot Bus 1

Answer 37

* Engine 1A/2A fire extinguisher * Engine Fuel Shutoff Valve 1 * Hydraulic Shutoff Valve 1 * Engine 1 Oil Level Indication * Courtesy/Service Lights * DC Ceiling Lights

Question 38

What items are on the DC Hot Bus 2

Answer 38

* Engine 1B/2B Fire Extinguisher * Engine Fuel Shutoff Valves 2 * Hydraulic Shutoff Valve 2 * Engine 2 Oil Level Indication * CMC * Refuel Panel * Water and Waste System