Electrical

Question 1

How many inverters and what are there voltages?

How does the inverter system work?

Answer 1

2X 250V 450HZ inverters that provide 115v AC and 26v AC
inverter 1 runs all 4 busses (normal and emerg)
only when turned off inverter 2 takes over.

2x 115v failure auto transfer
2x 26v failure req manual transfer

Question 2

How many batteries and Amps?

Answer 2

36 amp hour (load 60amps normal ops so = 30min run time.

Backup battery is a 5 amp hour used for standby AH and also smooths out power spikes.

Question 3

How do you conduct the battery test

Answer 3

Hold battery test until 70C then let go

2 heating elements actually heat up the testing unit.

Question 4

Starter generator max amp output for start sequence using which bus.

Answer 4

600amp
so before you start an engine check 150amp or less as the start sequence can use about 400amp
400+150 = 550 leaving a 50AMP buffer

Engine start is from the central bus but requires battery connection as well (generator assisted start only)

Question 5

Engine stable self sustaining NH

Answer 5

50%

Question 6

APU start volt req

Engine start volt reg

Answer 6

22volt apu

24volt engine start

Question 7

Electrical input priority ?

Answer 7

1. main generators
2. external power
3. APU

Question 8

Central bus volt protection

Answer 8

32V

Question 9

How is the backup battery charged ?

where does the standby AH get its power from?

Answer 9

Bat charged from Emerg DC bus 2
STBY AH on Emerg DC bus 1
if voltage is bellow 19v the automatic transfer occurs AH now runs from backup battery.

Question 10

What systems are lost in Emergency mode?

Answer 10

F- Fuel quantity 
A- Autopilot 
C- Coms (except com 1)
E- Engine inst. (except T6 and TQ)
F- Flap
L- Lights (expt. Left LDG light and Emerg lights)
P- Pressurization

Question 11

Before starting of an engine what must you check?

Answer 11

max 150 AMP limit before start. of Engine and/or APU.

Question 12

In electrical emergency mode what should your initial actions be?

Answer 12

Start descent as your slowly depressurizing
(about 2000ft /min cabin climb rate)

8000ft cabin alt = 60sec before you get your first “Cabin” pressure announcement(10,000ft).
14,000ft and masks will drop.

Elec emergency is normally due to dual generator failure / dual engine failure.

Question 13

How can you tell if you have had a double gen failure vs a short circuit?

Answer 13

Double gen or engine failure will have all 6 lights light up.
BUS1 , Gen1, Central, Batt, BUS2, Gen2.

Short circuit will cut off the effected side and you would expect 4 lights on.
Eg BUS1, Gen1, Central bus, Batt.

In some cases if DC Tie1 catches the short circuit before DC Tie2 in that example then Central bus might not light up however it is still not usable.
(it appears as though DC bus2 is still powering Central bus)

Also engine start is not possible because Battery and Central Bus are not useable.
(both are required for start)

Question 14

If you want to turn off the battery select switch what should you check first?

Answer 14

Always check that the backup battery and emergency lights are off first.