Electrical System

Question 1

Where does the AC power normally come from?

Answer 1

Two AC IDG

Plus Ext AC APU

Question 2

Where does the DC power normally come from?

Answer 2

4x TRU

two batteries and Ext DC

Question 3

What buses does the AC normally supply?

Answer 3

AC Bus 1
AC Bus 2
Ess AC Bus

(plus indirectly to galley bus 1 2, Emerg AC Bus, AC GND SER Bus)

Question 4

What buses does DC normally supply?

Answer 4

DC Bus 1, DC Bus 2, DC Ess Bus, Emerg DC Bus, DC GN HDLG Bus, DC GND SER BUS
(plus indirect Dual DC Bus)

Question 5

If a AC generator power is lost, what power is still available?

Answer 5

If running on one, all buses will be powered, except galley bus de-energizes.

Question 6

What alert is presented i a AC Generator power is lost? Where will the alert be shown?

Answer 6

A level 2 Alert (2 chimes, caution light, GEN1/2 on MDFU and local fault light)

Question 7

How long would you expect the batteries to last if you lose all generators?

Answer 7

30mins

Question 8

On the ground, how can you expect the ground handling and ground service buses to be powered?

Answer 8

Via APU or via AC ext power. BAttery

Question 9

When external AC is plugged in, but not switched on, what is powered and what indications would you get?

Answer 9

You will get a AVAIL light on Ext Panel and AC GND SER Bus, GND Service TRU and DC GND HDLG Bus will be powered.

Question 10

On engine start, when does engine generators normally come online?

Answer 10

when voltage and frequency are within predetermined limits, the GCU connects the generator to the line.

Question 11

What is an IDG?

Answer 11

Integrated drive generator.

Question 12

What is a GCU and what does it do?

Answer 12

Generator Control unit, connects the generator when ready to the line and disconnects Generators from the line when a failure is detected.

Question 13

If an IDG overheats, what happens and what indication do you get?

Answer 13

Alert 1, IDG TEMP light on MDFU. GCU isolates the Generator.

Question 14

Is the APU generator equipped with a constant speed drive?

Answer 14

No

Question 15

If external AC power is online and parameters go out of limits, what will happen?

Answer 15

The Ground Power Control Unit (GPCU) automatically disconnects the external power.

Question 16

From which generators do AC buses 1 and 2 normally receive power?

Answer 16

Gen 1 and Gen 2.

Question 17

When is the automatic AC cross-tie inhibited?

Answer 17

by the AUTO AC XTIE p/b.

Question 18

What buses remain powered after the ESS+EMERG PWR ONLY push button us pressed?

Answer 18

only ESS and EMER buses are powered.

Question 19

What are the power source priorities for the ESS AC Bus?

Answer 19

Gen 1, Gen 2 and then APU.

Question 20

From where can the EMER AC bus obtain power?

Answer 20

from the ESS AC Bus, if fails, then from Batteries via a inverter

Question 21

When is the galley power shed automatically>

Answer 21

during single Gen operations

Question 22

You are airborne and generator 1 goes offline. The APU gen is no available. What happens? and if the APU generator is available?

Answer 22

If GEN 1 goes offline, Gen 2 via bus ties will power entire system.

If APU is available, it will power AC Bus 1.

Question 23

What happens if a TRU fault occurs? What might the fault be?

Answer 23

TRU automatically disconnect in case of overheat or reverse current. Alert 2 will appear. Have to manually tie DC bus tie.

Question 24

What does the dual DC bus supply and for what purpose?

Answer 24

uninterrupted power source for the light dumpers, anti skid and speed brakes.

Question 25

What can be powered by the batteries alone?

Answer 25

EMERG DC and AC only.

Question 26

How can the DC buses be tied together?

Answer 26

Via DC Xtie p/b.

Question 27

If the ESS TRU becomes inoperative, where does the ESS DC get its power from?

Answer 27

TRU 1 via DC Bus 1.

Question 28

Where does the EMER DC Bus get its power from?

Answer 28

ESS AC Bus via ESS TRU.

Question 29

What does the DC ground handling bus supply?

Answer 29

pax door, Fueling panel, towing hydraulic service and engine starter valve.

Question 30

What can be powered from the external DC and what indications do you get?

Answer 30

The DC GND SER bus, no indications.