Electrical Non-normals

Question 1

How is electrical power ensured for essential loads?

Answer 1

The backup power system (consisting of 2 backup generators)

Question 2

Essential loads are powered by ?

Answer 2

The L & R transfer busses

Question 3

Essential loads include ?

Answer 3

1. Instrument & panel lighting
2. Captain & FOs nav & communication radios
3. L & C pitot & engine probe heat

Question 4

Transfer busses are normally powered by ?

Answer 4

The L & R Main AC busses

Question 5

What do the XFER busses connect to when their respective AC busses are unpowered ?

Answer 5

One of the back up generators

Question 6

Backup Power System Provides for:

Answer 6

1. Loss of 1 Main AC bus
2. Loss of both Main AC busses
3. Only 1 Main generator available
4. Autoland

Question 7

In the event of a loss of ALL main & backup generators ?

Answer 7

A standby system powers critical AC & DC equipment

Question 8

Critical AC equipment?

Answer 8

1. C ILS
2. Radio Alt
3. Marker beacon L
4. ATC transponder L
5. VOR L
6. Engine igniters

Question 9

Critical DC loads?

Answer 9

Captain & FOs flight instruments & displays

Question 10

The standby system consists of ?

Answer 10

1. The battery busses
2. Captain’s & FOs instrument busses
3. An AC standby bus

Question 11

The busses in the standby power system are normally powered from ?

Answer 11

The L & R AC XFER busses directly or, through the TRUs

Question 12

If the transfer busses become unpowered, (in the standby power system) how do you get power?

Answer 12

A RAT (ram air turbine) provides DC power through the TRUs

The standby AC bus is powered from the battery bus through a standby inverter

Question 13

Why would you deploy the RAT in flight?

Answer 13

To provide electrical & hydraulic power simultaneously (in a standby power situation)

Question 14

What is the primary source of standby electrical power if all normal sources are lost?

Answer 14

The RAT - Ram Air Turbine

Question 15

3 things about the RAT:

Answer 15

1. Located in aft R fairing
2. Non-time-limited source of power
3. < 1/10 power of IDG

Question 16

The RAT is deployed automatically if:

Answer 16

1. Both XFER busses are unpowered
2. All 3 hydraulic system pressures are low
3. Dual EF & C hydraulic pressure low

Question 17

If the RAT doesn’t deploy automatically ?

Answer 17

It can be deployed manually

Question 18

The ‘PRESS’ light on the RAT illuminates when?

Answer 18

The RAT is producing a minimum of 1,500 psi for the flight controls

Question 19

If the RAT is unable to maintain hydraulic pressure what is sacrificed?

Answer 19

Electrical load is shed until hydraulic pressure is satisfactory

Question 20

When RAT electrical loads are shed, or prior to RAT deployment, what powers the standby power system?

Answer 20

The Main Battery

Question 21

When the RAT provides electrical power which busses are powered?

Answer 21

Both Captain’s & FOs flight instrument busses

Question 22

When the battery provides standby power which busses are powered?

Answer 22

Only the Captain’s flight instrument bus

Question 23

What is the primary source for the transfer busses?

Answer 23

Main AC busses

Question 24

If all main & backup generators fail, what is the primary source of power for the standby electrical system?

Answer 24

RAT