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B777 CATHAY STUDY GUIDE > ELECTRICAL > Flashcards

ELECTRICAL Flashcards

1
Q

What is the purpose of ELMS?

A

To provide load management and protection to ensure power is available to critical and essential equipment

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2
Q

What loads does ELMS shed first?

A

Galleys first and then utilities

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3
Q

What indication is there of ELMS load shedding?

A

LOAD SHED on EICAS

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4
Q

List the main electrical sources?

A

L GEN
R GEN
APU GEN
Primary and secondary EXT power

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5
Q

What will cause the EICAS message ELEC GEN DRIVE and what are your actions?
What will happen technically when the action is executed?

A

Low oil pressure being detected in an IDG
You should then immediately disconnect the IDG by pushing the respective DRIVE DISCONNECT switch. When you press that switch with the fuel control switches in the RUN position, the two-piece IDG input shaft moves apart.

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6
Q

What causes automatic disconnection of an IDG?

A

The melting of a thermal plug at high drive temperature that causes a disconnect to happen

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7
Q

When will the APU start automatically?

A

If both transfer busses are unpowered

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8
Q

When does the EXT PWR AVAIL light illuminate?

A

When the external power source voltage and frequency are within limits

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9
Q

What is the generator priority for main AC Busses?

A

In flight:

  1. The respective IDG
  2. APU
  3. Opposite IDG
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10
Q

What is normally the source for the ground service bus?

A

The right AC main bus

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11
Q

How is the ground service bus powered without supply from the main bus?

A

With the APU or external power.

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12
Q

What Equipment is powered by the Ground Service Bus?

A

Main battery charger
APU battery charger
Miscellaneous cabin systems and loads

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13
Q

How can the Ground Handling Bus be powered?

A

From APU or EXT PWR source

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14
Q

What Equipment is powered by the Ground Handling Bus?

A

Cargo handling
Fueling/de-fueling
The powered door opening system for the engine cowls.

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15
Q

Which busses can be supplied by the Back up GENs?

A

R AC transfer Bus

L AC transfer Bus

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16
Q

What unit converts the Back up GENs frequency?

A

A frequency converter

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17
Q

How many back up generators can be used at a time?

A

Only one, as they both connect to the same frequency converter

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18
Q

How many PMG are in each back up generator?

A

2

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19
Q

What are the two PMGs in each back up generator used for?

A

Supplying DC Power to the flight control DC electrical system

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20
Q

How are the TRUs supplied?

A

By the AC transfer busses

21
Q

What normally powers the HOT BAT BUS?

A

The main battery charger

22
Q

What is the purpose of the APU battery?

A

To provide dedicated Power to the APU Electric starter and APU control unit in case there is insufficient bleed air duct pressure for the APU air turbine starter (ATS)

23
Q

What is the secondary power source for the C FCDC PSA?

A

The captains flight instrument bus

24
Q

Which FCDC PSAs can be powered by the hot battery bus?

A

The left and Centre PSAs

25
Q

How long can the dedicated PSA battery provide Power for?

A

Max 10 minutes

26
Q

What is the purpose of the dedicated PSA battery?

A

To prevent interruptions to the related flight control DC bus

27
Q

What items does the standby electrical system supply power to?

A

Selected flight instruments, Communications and navigation systems and the flight control system
AC: Center ILS, Radio alt, ENG igniters, VOR left
DC: Captains and F/O s flight instument displays

28
Q

When does the static inverter supply the AC stanby bus?

A

If the left transfer bus is not powered

29
Q

What are the two sources of Power for the AC standby bus?

A

BAT BUS via an inverter and LEFT XFER BUS

30
Q

What does the RAT generator supply power to?

A

Stand-by power to the C1 and C2 TRUs

31
Q

What are the altitude and airspeed limitaitons on the RAT?

A

There are none, the RAT operates at all airspeeds and altitudes

32
Q

What supplies power until the RAT RPM is sufficient?

A

The main battery

33
Q

What will cause automatic deployment of the RAT?

A

Both AC transfer busses losing power in flight

All HYD systems are low

34
Q

What is DC Power used for?

A

Flight displays (PFD and ND)
GPS
ADIRU
Flight control system

35
Q 
What are the power ratings for:
IDG
APU
EXT PWR
RAT
A

IDG 120 kva
APU 120 kva
EXT PWR 90 kva
RAT 7,5 kva

36
Q

What two components are the IDGs a combination of?

A

IDGs are a combination of a constant speed drive (CSD) and an AC generator.

37
Q

What drives the IDGs

A

The engine

38
Q

Can a disconnected IDG be re-connected in flight?

A

No, can only be done on the ground

39
Q

What kind of power and rating is provided to the Main AC BUS?

A

The IDGs and APU supplies 115 VAC, 400 Hz power to the left and right main AC buses.

40
Q

What is the power source order for the Main AC BUS?

A

The source order for powering the left and right main busses in flight are:

  • Respective IDG
  • APU generator
  • Opposite IDG
41
Q

What equipment does the utility buses power?

A

The utility busses powers galley heater, chiller boost fan, gasper fan, cockpit foot and shoulder heaters, door area heaters, lavatory water heaters and shavers

42
Q

If both transfer buses needs power, which back-up generator will supply the power?

A

The right back-up generator supplies power if it is available.

43
Q

List the power sources for the three PSAs?

A
  • The R PSA gets power from the R PMG, R MAIN DC BUS and a short term battery supply
  • The C PSA gets power from the R PMG, HOT BAT BUS, CPT FLT INSTR BUS and a battery
  • The L PSA gets power from the L PMG, L MAIN DC BUS, HOT BAT BUS and a battery
44
Q

What is the purpose of the BAT and APU chargers?

A
  • Change the AC power to DC power for the related DC buses, functions like a TRU.
  • Charge the batteries
45
Q

For how long can the Main battery supply power for?

A

It can supply standby system power for a minimum of 5 min

46
Q

What power sources are used for the stand-by power system

A

Hot BAT BUS
RAT
Left X-transfer bus

47
Q

Does the RAT supply AC or DC power?

A

AC that is converted to DC through the C1 and C2 TRUs

48
Q

What are the three power sources used for autoland?

A

The three power sources for an Autoland are:

  • Left IDG
  • Right Back-up generator
  • Right IDG
49
Q

Describe how the three autopilots gets power during an AUTOLAND.

What feeds them and what are the respective power sources for the different feeds?

A
  • The left set gets fed from the L X-TRANSFER BUS (AC) and L DC BUS (DC) with the L IDG as the power source
  • The center set gets fed from the STANDBY AC BUS (AC) and BAT BUS (DC) with the R IDG as the power source.
  • The right set get fed from the R X-TRANFER BUS (AC) and R DC BUS (DC) with the R BACK-UP generator as the power source.

B777 CATHAY STUDY GUIDE (24 decks)

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