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B747 > Electrical > Flashcards

Electrical Flashcards

1
Q

What does the AVAIL light indicate on the external and APU PWR switches?

A

The related power source is plugged in and the power quality is acceptable
FCOM 2 ELEC 6.10.5

The APU generator power quality is acceptable
FCOM 2 ELEC 6.10.4

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2
Q

What bus is powered on the ground when APU GEN 1 or EXT PWR 1 is available?

A

The ground handling bus is automatically powered on the ground when APU GEN 1 or EXT PWR 1 is available (not power hungry).

The ground service bus must be manually connected with the p/b whenever AC bus 1 is not powered***

FCOM 2 ELEC 6.20.5

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3
Q

When is the main deck cargo handling bus powered?

A

The main deck cargo handling bus is powered on the ground when external power 2 or APU generator 2 is available.

An interlock prevents either source from powering main electrical busses and the main deck cargo handling bus simultaneously.

Engaging the relevant avail source to ON will de-energise the main deck cargo handling bus.

If both EXT PWR 2 & APU GEN 2 are available, putting EXT PWR 2 to ON will transfer main deck cargo bus power to APU GEN 2.

FCOM 2 ELEC 6.20.8

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4
Q

What electrical power source would you select if cargo handling is required?

A

A number two source must be available so use external power 1 or APU gen 1
FCOM 2 ELEC 6.20.8

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5
Q

When is the ground service bus powered?

A

Whenever AC bus 1 is powered on the ground or in flight. If AC BUS 1 is not powered the ground service bus can be connected to the same source powering the ground handling bus by pushing the ground service switch on the 1L door.

FCOM 2 ELEC 6.20.5

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6
Q

What is the function of the standby power switch in the auto position?

A

It allows the main and APU standby busses to be powered from available sources

FCOM 2 ELEC 6.10.2

Batt position is for maintenance purposes**

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7
Q

Where would you find the electrical power up procedure?

A

FCOM 1 NP 6.1 ELEC POWER UP

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8
Q

What does a BUS isolation ISLN light illuminated indicate?

A

That the bus tie breaker (BTB) is open.

FCOM 2 ELEC 6.30.1

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9
Q

What happens when you push a generator drive disconnect (DRIVE DISC) switch?

A

It will disconnect the IDG from the engine when above idle speed; and
It will open the generator control breaker (GCB)

FCOM 2 ELEC 6.10.6

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10
Q

What condition would automatically disconnect the IDG if not manually disconnected by the flight crew?

A

Excessively high drive oil temperature. The relevant GCB opens.

An ELEC GEN OFF EICAS message will appear.

Manually pushing the drive disconnect switch after an auto disconnect will replace the ELEC DRIVE with DRIVE DISC EICAS message.***

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11
Q

How do you reconnect an IDG that has been disconnected?

A

An IDG cannot be reconnected by flight crew action

FCOM 2 ELEC 6.20.3

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12
Q

What does a generator DRIVE light indicate?

A

IDG oil pressure low
IDG oil temperature high
GCB open due to an uncorrectable generator frequency fault

FCOM 2 ELEC 610.7

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13
Q

What are some equipment items powered by the utility busses?

A

Forward main fuel pumps 2 & 3
Forward override/jettison pumps 2 & 3
Center override/jettison pump
Recirculating fans

**galley busses 1-4 are powered directly from the relevant AC bus.

FCOM 2 ELEC 6.20.6

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14
Q

Describe the electrical load shedding process

A

If load > capacity the Electrical Load Control Units (ELCU) will load shed in priority order.

If capacity later > demand the loads are restored in reverse order.

FCOM 2 ELEC 6.20.1

The following EICAS messages may appear:

  • FUEL PUMP 3 FWD
  • FUEL OVRD 2 FWD
  • FUEL OVRD 3 FWD
  • FUEL PRESS CTR L
  • FUEL PUMP 2 FWD
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15
Q

What is the purpose of the electrical system overload protection?

A

To ensure power is available to critical and essential equipment first

FCOM 2 ELEC 6.20.1

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16
Q

During load shedding, would you expect to see and EICAS. Advisory message ELEC UTIL BUS L, R?

A

No because while auto shedding the EICAS message ELEC UTIL BUS L, R is inhibited.

FCOM 2 ELEC 6.20.1

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17
Q

What are the main AC electrical power sources?

A

4 IDG’s
2 APU GEN’s
2 EXT PWR sources

FCOM 2 ELEC 6.20.2

18
Q

Describe the function of the split system breaker SSB

A

The SSB divides the synchronous bus allowing each side of the AC electrical system to be powered by a separate aux or external source.

FCOM 2 ELEC 6.20.2

19
Q

Describe the electrical system sequence of events during engine start with the SSB open

A

When an engine is started that IDG powers it’s side of the SSB and will trip off an APU or external source on its side.

When another engine is started, its IDG synchronises and causes the opposite side external or APU source to trip off, the SSB then closes to power all AC busses.

CPAT AC Power distribution 36/41

20
Q

Describe the electrical system sequence of events with a single power source power in the synchronous bus, when an engine is starting, SSB closed…

A

With a single APU or external source an engine start causes that IDG to trip off the external or APU source, the SSB remains closed and all AC busses are powered by one IDG until more engines are started.

CPAT AC power distribution 36/41

21
Q

Which bus powers the captains transfer bus and the main standby bus?

A

CAPT TXFR:
AC Bus 3 but will revert to AC Bus 1 if that is unpowered.

Main Standby:
AC3; or
With Batt ON, STBY PWR in AUTO & AC 3 not powered the Main standby bus gets power from the main standby inverter drawing power from main battery charger through the main hot battery bus.

FCOM 2 ELEC 6.20.9

22
Q

Which bus powers the first officers transfer bus?

A

AC bus 2 backed up by AC Bus 1

FCOM 2 ELEC 6.20.4

23
Q

Which bus provides backup power for both transfer busses?

A

AC Bus 1

FCOM 2 ELEC 6.20.4

24
Q

What are some of the equipment items powered by the ground service bus?

A

Main and APU battery chargers
Fuel pumps for APU start
Flight deck flood, navigation and service lights
Miscellaneous service outlets and equipment

FCOM 2 ELEC 6.20.5

25
Q

How can the ground service bus be powered when AC bus 1 is not powered, while on the ground?

A

It can be connected to the same source as the ground handling bus by pushing the ground service switch at door 1L

FCOM 2 ELEC 6.20.5

26
Q

What are some of the equipment items powered by the ground handling bus?

A

Lower cargo handling equipment and compartment lights
Fuelling system
Auxiliary hydraulic pumps 4 (&1 if installed)

FCOM 2 ELEC 6.20.5

27
Q

What bus powers the APU standby bus?

A

The captain transfer bus

FCOM 2 ELEC 6.20.6

28
Q

How is the electrical system configured during an automatic ILS approach (autoland)?

A

During an Autoland:
AC busses 1, 2 & 3 isolate from the synchronous bus
AC bus 4 powers the synchronous bus
The EICAS displays “ELECTRICAL SYNOPTIC INHIBITED FOR AUTOLAND”

FCOM 2 ELEC 6.20.8

29
Q

What are some of the major components of the AC standby power system?

A

Main and APU standby busses
Main and APU batteries
Main and APU standby inverters
Standby power selector

FCOM 2 ELEC 6.20.9

30
Q

What is the normal source of power for the main standby bus?

A

AC bus 3

FCOM 2 ELEC 6.20.9

31
Q

How does the main standby bus get power if AC Bus 3 becomes unpowered in flight, all other conditions normal?

A

The main standby inverter activates and draws power from the main battery through the main hot battery bus for at least 30 minutes

FCOM 2 ELEC 6.20.9

32
Q

If both AC bus 3 and AC bus 1 are not powered, all other conditions normal, how is the Main standby bus powered, and for how long can it be powered?

A

Through the main standby inverter which draws power from the main battery through the main hot battery bus for at least 30 minutes

FCOM 2 ELEC 6.20.9

33
Q

What are some of the equipment items on the main standby bus?

A 
Left EIU
Left CDU
Left ILS
Left VOR
Various flight control components
Standby ignition for all engines
Primary EICAS display
Standby instrument lights
RMI if installed
Left ADC
Left transponder
Left EFIS control panel

FCOM 2 ELEC 6.20.9

34
Q

What are the equipment items on the APU standby bus?

A

Left FMC
Left ND
Left PFD

FCOM 2 ELEC 6.20.10

35
Q

How is DC power provided by the electrical system?

A

By 4 Transfer Rectifier Units (TRU’s) each powered by its related AC bus

FCOM 2 ELEC 6.20.13

36
Q

What is the normal power source for the main and APU Battery busses?

A

DC bus 3 or if not available by its related hot battery bus

FCOM 2 ELEC 6.20.13

37
Q

If either AC Bus 3 or DC bus 3 is unpowered, how is each battery bus powered?

A

By its related hot battery bus

FCOM 2 ELEC 6.20.13

38
Q

What are some examples of individual equipment items on the main battery bus?

A 
APU controller
Fuel valves
Crossfeed valves
Dome lights
Storm lights
Selected indicator lights
IDG disconnect
Manual pressurisation control
Trailing edge flap control 
Captain interphone 
Left radio tuning panel
Left VHF
ISFD if installed (has its own 150 minute battery supply)

FCOM 2 ELEC 6.20.13

39
Q

How is each hot battery bus normally powered?

A

Via the Ground Service Bus through its related battery charger which acts as a TRU for the hot battery bus.

FCOM 2 ELEC 6.20.14

40
Q

What are some examples of equipment items on the main Hot battery bus?

A 
APU fuel shutoff valve
Spar valves
APU and lower cargo fire extinguishers
Engine fire extinguishers
Fire switch unlock

FCOM 2 ELEC 6.20.14

41
Q

What are some examples of equipment items on the APU hot battery bus?

A 
Left IRU DC power 
Center IRU DC power 
Right IRU DC power 
Left outflow valve
Right outflow valve
APU inlet door
APU controller

FCOM 2 ELEC 6.20.14

B747 (7 decks)

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