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7 > Electrical - Power distribution > Flashcards

Electrical - Power distribution Flashcards

1
Q

How many busses provide power for airplane servicing? Which busses?

A

2 busses.

The ground handling bus & the ground service bus

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2
Q

Where are the controls located for the ground handling bus?

A

There are no controls for the ground handling bus.

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3
Q

How is the Ground Handling bus powered?

A

Automatically when external power is plugged in or, via the APU (automatically if it’s running).

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4
Q

Which power source has priority (for the Ground Handling Bus)?

A

External power has priority over the APU

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5
Q

The Ground Handling Bus powers ?

A
  1. Cargo Doors
  2. Cargo Compartment lights
  3. Maintenance access lights
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6
Q

Is the Ground Handling Bus powered in flight?

A

No

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7
Q

Who needs the Ground Service Bus?

A

Cabin Service Personnel

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8
Q

What does the Ground Service Bus power?

A
  1. Cabin lighting & outlets
  2. Main & APU battery chargers
  3. The Left fwd fuel pump (which supplies fuel to the APU)
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9
Q

When is the Ground Service Bus available?

A

It powers loads needed both on the ground & in the air.

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10
Q

When external power is the only source of power, & the main busses are not powered, how can you power the Ground Service Bus?

A

Selecting the GROUND SERVICE switch at the attendant panel at door 1L

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11
Q

Whenever the right Main AC bus is powered, the Ground Service Bus is ?

A

Powered

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12
Q

Ground Service Bus Power Sources

A
  1. External Power
  2. Right Main bus
  3. APU generator
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13
Q

If the right Main AC is not powered, the APU is running, the Ground Service bus is powered by ?

A

The APU generator through the GROUND SERVICE switch

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14
Q

With the CABIN/UTILITY power switch ON what is powered normally?

A
  1. GND SERVICE BUS
  2. Utility Bus
  3. Galleys (via Main DC Bus)
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15
Q

If you select the CABIN UTILITY power switch OFF what do you lose?

A

Cabin lighting & outlets

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16
Q

When the CABIN/UTILITY switch is selected OFF, the following cabin lights are turned on:

A

Night lights
Supplemental night lights
Reading lights
Attendant work lights

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17
Q

DC electrical power operates which important items?

A
  1. PFD’s & ND’s
  2. GPS
  3. ADIRU (Air Data Inertial Reference Unit)
18
Q

How many batteries does the 777 have?

A

2

19
Q

What are the 2 batteries on the 777

A
  1. APU battery
  2. Main battery
20
Q

What does the APU battery power?

A

APU starter motor & APU control circuits

21
Q

What does the Main a/c battery power?

A

Critical airplane systems when no other power sources are available

22
Q

What monitors the battery functions?

A

ELMS (Electrical Load Management system)
Displayed on ELEC synoptic

23
Q

What is the primary source of DC power?

A

4 Transformer rectifier units (TRUs)

24
Q

What do the TRUs do & what powers them?

A

Convert AC into DC

Powered from the 2 XFER busses

25
Q

The TRUs supply 4 DC busses, they are ?

A
  1. Left Main DC bus
  2. Right Main DC bus
  3. Captain’s flight instrument bus
  4. First Officer’s flight instrument bus
26
Q

If a TRU fails……

A

DC Tie relays connect the L & R Main DC busses & the Captain’s & First Officer’s flight instrument busses

27
Q

Are there any controls for the DC system?

A

No, it’s fully automatic

28
Q

The 777 is a Fly-by-Wire airplane, what does this mean?

A

Flight controls are actuated hydraulically, but controlled electrically

29
Q

How many backup generators are there?

A

2, 1 on each engine

30
Q

2 Permanent Magnet Generators (PMGs), are housed within each backup generator. What are their purpose?

A

They are the power source for the flight controls

31
Q

The PMGs provide dedicated power to ?

A

L, C & R power supply assemblies & their respective flight control DC busses
(L FCDC BUS, C FCDC BUS, R FCDC - Flight Control DC Busses)

32
Q

What happens if 1 or more PMGs fail in flight?

A

The Main DC busses or the Captain’s flight instrument bus power the flight control DC busses

33
Q

If the Main DC busses become unpowered, what provides power to the L & C power supply assemblies?

A

The Hot Battery Bus

34
Q

Should a transfer of power occur from one source to another (in the Flight Controls DC System), what insures no interruption of power during the transfer?

A

The 1 minute batteries provided on each power supply assembly

35
Q

To allow automatic landings with the lowest possible minimums, the electrical system configured to that ?

A

Each of the 3 autopilots is powered by a seperate power source

36
Q

Autoland Electrical Config - During approach, power to the R XFER bus switches from the R Main AC bus to ?

A

The backup generators (same for the L etc).

This transfer provides indeed EBT sources to each of the 3 autopilots

Elec system returns to normal when a GA is performed or APs are disengaged.

37
Q

Which bus operates only on the ground?

A

The Ground Handling Bus

38
Q

What provides DC power on this airplane?

A

TRUs

39
Q

What is the electrical configuration during Autoland approaches?

A

The right transfer bus isolates from the right main bus

40
Q

What is the secondary source of power for fly-by-wire if one or more PMGs are unpowered?

A

DC Busses

7 (21 decks)

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