Electrical

Question 1

How many inverters and what are their voltages?

Answer 1

2X 250V 450HZ inverters that provide 115V 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

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

Back up battery is a 5amp 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 heat up the testing unit.

Question 4

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

Answer 4

600amp
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 req

Answer 6

22V APU

24V engine start

Question 7

Electrical input priority?

Answer 7

1. Main generatos
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 gets its power?

Answer 9

Battery charged from emergency DC bus2
STBY AH on emergency 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 com1)
E- Engine instruments (except T6 and TQ)
F- Flap
L- Lights (except left LDG light and emergency lights)
P- Pressurization

Question 11

Before starting of an engine what must you check?

Answer 11

Max 150amp limit start of engine and/or APU.

Question 12

In electrical emergency mode what should your initial actions be?

Answer 12

Begin descent as you’re slowly depressurizing (about 2000ft / min cabin climb rate)

8000ft cabin alt = 60sec before you get your first “Cabin” pressure announcement (10,000ft).
14,000ft 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 short circuit?

Answer 13

Double gen or engine failure will have 6 lights up.
Bus1, Gen1, Central, Batt, Bus2, Gen2.

Short circuit will cut off the effected side and you would expect 4 lights on.
Bus1, Gen1, Central bus, Batt.

In some cases if DC Tie1 catchs 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 engine start)

Question 14

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

Answer 14

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