Electrical 175

Question 1

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

Answer 1

2 independent networks
redundancy and fault isolation

Question 2

what happens if a power generating source fails?

Answer 2

bus ties automatically connect to provide no systems

Question 3

what components power the AC system?

Answer 3

2 integrated drive generators (IDGs) (40kVa, 115 VAC, 400 Hz)
Auxiliary power unit (APU)
Inverter (250VA - 28V DC to 115 VAC)
Ram Air Turbine (RAT 15kVA, 115 VAC, 400 Hz)
AC GPU receptacle

Question 4

What powers the IDG?

Answer 4

respective AC BUS

Question 5

What is Batt 2’s primary purpose?

Answer 5

Start APU

Question 6

What is the minimum battery temperature for APU start?

Answer 6

-20 degrees C

Question 7

What happens when you hit the GPU AVALi button?

Answer 7

it turns from Aval to In Use.
The AC GPU has priority over the batteries to power the electrical system
Correct frequency, amperage, voltage

Question 8

When does GPU available button turn on?

Answer 8

External GPU cart is properly plugged in
Proper amperage, voltage, frequency

Question 9

What’s the AC priority

Answer 9

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

Question 10

How does ground service and maintenance get power for mx and flight preparation?

Answer 10

Pushing the respective button located on the front ramp panel or on the flight attendant panel at forward right galley

Question 11

what is the purpose of the inverter? What bus is it connected to ?

Answer 11

converts 28VDC from batteries to 115 VAC to supply the standby AC bus when an AC power source is not available

Question 12

When does the RAT automatically come online?

Answer 12

Whenever AC power sources are not powering AC buses.

Question 13

What are the batteries powering during the 8 seconds of RAT deployment?

Answer 13

DC Ess Buses and Standby AC bus

Question 14

Which pump for RAT drive and what does it do?

Answer 14

AC motor driven pump 3A for primary flight control tasks. high lift system actuation and power for essential avionics, communication and battery recharging.

Question 15

What is the min speed for RAT? What does the RAT power?

Answer 15

130 kts
DC essential bus 1, 2, 3
AC essential bus
AC standby bus
Hot bat bus 1
Hot bat bus 2

Question 16

What components power the DC system?

Answer 16

2 NiCad batteries (24 volt, 22 to start)
3 Transformer Rectifier Units (TRU) (rated at 300A, convert 115 AC to 28VDC)
DC GPU receptacle

Question 17

What is the purpose of the DC GPU?

Answer 17

to start the APU if batteries are below 22 V and temperature is below 20 degrees C.

Question 18

How many TRUs? Do they rely on each other or isolated?

Answer 18

3 and in isolation. Buses will automatically be powered by the remaining TRUs as long as the DC BUS TIES toggle switch is selected to AUTO

Question 19

What does TRU 1 power?

Answer 19

provides DC power to DC BUS 1, DC Ess Bus 1, DC GND SVC Bus, HOT bat bus 1 and battery 1 charging

Question 20

What does TRU 2 power?

Answer 20

provides DC power to DC BUS 2, DC ESS BUS 2, HOT BATT BUS 2 and battery #2 charging

Question 21

What does TRU Ess power?

Answer 21

DC power to DC ESS BUS 3

Question 22

what charges the batteries?

Answer 22

any AC source thru the TRUs, including the RAT and AC GPU.

Question 23

How long do batteries last in an emergency?

Answer 23

10 min

Question 24

How does IDG maintain a stable power output

Answer 24

a constant speed drive (CDS) attaches the IDG to the AGB (Accessory gear box)

Question 25

what monitors and controls IDGs

Answer 25

each has a generator control unit (GCU)

Question 26

What causes the amber IDG light on the overhead panel to illuminate?

Answer 26

High oil temperature Low oil pressure

Question 27

What is the primary purpose of the AC generators?

Answer 27

power the AC buses, AC essential bus which powers the 3 TRU (1,2, essential)

Question 28

whats the minimum battery voltage to close the battery bus ties?

Answer 28

18 volts

Question 29

what battery is used for APU start?

Answer 29

battery 2

Question 30

what is the purpose of the inverter?

Answer 30

converts 28 VDC from the 115 VAC to power the AC standby bus when AC source is not available

Question 31

What is on the AC standby bus?

Answer 31

engine exciters 1A and 2A

Question 32

When is the RAT icon displayed on the electrical synoptic page

Answer 32

when the RAT is deployed

Question 33

What manages the electrical system?

Answer 33

4 integrated control centers (ICC) Left ICC Right ICC Emergency ICC Auxiliary ICC

Question 34

What is an ICC?

Answer 34

an electrical control device which provides power distribution and protection for electrical loads.

Question 35

what is SPDA?

Answer 35

secondary power distribution assembly. an electrical load-management unit, powered by ICC, that distributes electrical loads to aircraft systems according to distribution logic and performs BITs (built in tests) on many components

Question 36

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

Answer 36

ICC CB's can only be reset by maintenance. SPDAs can be reset by crew in MCDU

Question 37

What are LRU's and LRMs

Answer 37

LRUs and LRMs allow quick access and easy replacement of electrical components. plug and play. take a module out and put a new one in with new system logic.

Question 38

What's on the AC essential bus?

Answer 38

flaps/slats hydraulic pump 3A Ac fuel pump 2A

Question 39

Whats on DC hot bat bus 1?

Answer 39

Courtesy/service lights ceiling lights engine 1 oil level indication engine 1A/2A fire extinguishing engine fuel SOV 1 Hyd SOV 1

Question 40

What's on DC hot bat bus 2?

Answer 40

CMC Engine 1B/2B fire extinguisher engine fuel sov 2 hyd system sov 2 panel refuel 3 water and waste system

Question 41

What turns on when you put Batt 1 on, Batt 2 AUTO?

Question 42

what's on AC standby Bus?

Answer 42

engine 1 exciter 1A engine 2 exciter 2A

Question 43

What is shed first when we load shed?

Answer 43

galleys and right windshield heating