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Southern 777 > Electrical System > Flashcards

Electrical System Flashcards

1
Q

How many batteries are there and what are they for?

A

2 batteries, main battery and APU battery

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2
Q

What does the Main battery power?

A 
Hot Battery Bus
Battery Bus
Captains flight instrument bus
Left and Center Flight control PSAs
Standby Inverter
Captains displays and CDU
Left Airplane Management System (AIMS)
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3
Q

What is connected to the Hot Battery Bus?

A

Engine fire bottles, APU fire bottles, and ADIRU (If switch is on)

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4
Q

With only battery power available, what is powered?

A

Standby power system, captain’s display, left aims, and everything connected to hot battery bus

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5
Q

Which bus is not powered in flight?

A

Ground Handling Bus

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6
Q

What does the ground handling bus power?

A

Cargo Doors, Main deck cargo handling system, cargo compartment lights, and maintenance access lights

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7
Q

What does the Ground Service Bus power?

A

Cabin lighting and outlets, Main and APU battery chargers, left forward fuel pump. Powered both on ground and in the air

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8
Q

When does the left fwd fuel pump engage?

A

To supply APU fuel

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9
Q

What does the APU battery power?

A

The APU starter motor and control circuits.

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10
Q

What does the DC power system power?

A
  1. PFDs
  2. Nav Displays
  3. GPS
  4. ADIRU
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11
Q

What is the primary source of DC power?

A

4 Transformer Rectifier units (TRU).

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12
Q

How do the TRU’s work?

A

The Transformer Rectifier Units convert AC into DC power and are powered by 2 transfer buses. They are fully automatic.

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13
Q

What buses do the TRU’s supply?

A 
4 DC buses:
Left main
Right main
Captains flight instrument bus
FO's instrument bus
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14
Q

What happens is a TRU fails?

A

DC tie relays connect the left and right main DC Bus and Capt/FO instrument bus

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15
Q

When does the Backup AC electrical system engage?

A
  1. Only one main AC generator (includes APU) is available
  2. Power to one or both of the main AC buses is lost
  3. Approach (APP) mode is selected for autoland
  4. Automatically tested after engine starts
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16
Q

Backup AC auto activates when:

A
  1. Automatically tested after engine starts
  2. On 1 generator
  3. 1 or both Main A/C buses fail
  4. APP mode selected for Autoland
17
Q

How many backup generators does the 777 have?

A

2 backup generators

18
Q

Explain the transfer busses

A

Normally powered by the Main A/C buses

Power the essential loads

19
Q

What are the essential loads?

A
  1. instrument Lighting
  2. Left and Right radios
  3. Center pitot heat
  4. Engine prob heat
20
Q

Explain the backup DC system.

A

2 Permanent Magnet Generators(PMG) housed within each backup generator
Provide dedicated power to Left, Center, and Right Power supply Assemblies and their respective flight control DC Buses

21
Q

What happens during a PMG failure?

A

If 1 or more Permanent Magnet Gen fails - Main DC buses or Captains flight Instrument Bus powers the Flight Control DC Bus

22
Q

What happens during Main DC Bus becomes unpowered

A

Hot Battery Bus Powers Left and Center Power supply Assembilies

23
Q

What are 1 minute battieries

A

Provide each power supply assembly to ensure no interruption of during transfer

24
Q

Does the RAT have any limits?

A

No, it works at all airspeeds and altitudes.

25
Q

What does the RAT provide?

A

Standby power to C1 and C2 Transformer Rectify Unit(TRUs)
Supplies electrical and hydraulic power simultaneously but if it cannot maintain RPM, the electrical load is shed uptil RPM is satisfactory.

26
Q

What consists of the Standby Electrical System?

A
  1. The Main Battery
  2. The Standby Inverter
    3 The RAT generator and it’s associated generator control unit
  3. C1 and C2 TRUs.
27
Q

Explain load shedding

A

Galleys first, then utility buses
The individual equipment items powered by the main AC busses

When power is restored, it’s restored in reverse order

28
Q

What TR powers the Capt Flight Instrument bus?

A

TR C1

29
Q

Describe the back up generators

A

It is variable speed, variable frequence generator mounted on each engine. A frequency convert converts the gen frequency to a constant 400Hz. Only 1 backup generator can power the converter at a time.

30
Q

How do you test the Backup Electrical System?

A

System is automatically tested after engine starts.

31
Q

What is the primary power for the flight control DC electrical system?

A

Permanent magnet generators(PMGs) housed within each backup generator.

32
Q

What does the EICAS message ELEC GEN DRIVE L,R mean?

A

Generator drive oil pressure is low.

Southern 777 (12 decks)

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