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747-400F Oral > Electrics > Flashcards

Electrics Flashcards

1
Q

What does “AVAIL” light indicate on the External and APU PWR switches?

A

Power quality is acceptable

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2
Q

What Bus is powered on the ground when APU1 or EXT1 is available?

A

Ground handling bus

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3
Q

When is the Main Deck Cargo Handling Bus powered?

A

Ext/APU 2 AVAIL
If both Ext and APU 2 available, can select either ON and other will power main deck cargo handling bus

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4
Q

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

A

Ext/APU 2 AVAIL
If both Ext and APU 2 available, can select either ON and other will power main deck cargo handling bus

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5
Q

When is Ground Service Bus Powered?

A

AC BUS 1 powered or Ext/APU 1 ON/AVAIL with Ground service switch ON

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6
Q

What is the function of the Standby Power Switch in the auto position?

A

Allows main+APU standby busses to be powered from available sources

(with BATT switch ON) Allows Standby buses to be powered (through standby inverters) from Hot Batt buses. If AC 1 powered this comes through Main and APU batt chargers. If AC 1 not powered comes from batteries themselves. (In BAT) inverters powered (through Hot Batt buses) by Batteries themselves.

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7
Q

Where would you find the Electrical Power-up procedure?

A

Supp procedures (Section 6)

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8
Q

What does a Bus Isolation (ISLN) light illuminated indicate?

A

BTB open
AC bus isolated from sync bus

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9
Q

What happens when you push a Generator Drive Disconnect (DRIVE DISC) switch?

A

*disconnects IDG (mechanically) from engine when above idle speed
*opens Generator Control Breaker (GCB)

Can only be reopened on ground

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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 temp

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11
Q

How do you reconnect an IDG that has been disconnected?

A

ground maintenance required

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12
Q

What does a Generator DRIVE light indicate?

A
  • IDG oil pressure low, or
  • IDG oil temperature high, or
  • GCB open due to uncorrectable generator frequency fault
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13
Q

What are some of the equipment items powered by the Utility busses?

A
  • Foward Main Fuel Pumps 2 & 3
  • Forward Override/ Jettison Pumps 2 & 3
  • Center Override/ Jettison Pump
  • Galley Equipment
  • APU T/R (utility bus 4)
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14
Q

Describe the electrical load shedding process.

A

Sheds AC loads by priority
utility bus loads shed one at a time through ELCUs in programmed sequence until overload condition relieved
restored in reverse order when additional AC power source available
ELEC UTIL BUS L/R messages and utility off lights inhibited
may get the following EICAS:
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

ensures power available to critical and essential equipment

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16
Q

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

A

no - inhibited

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17
Q

What are the main AC electrical power sources?

A

4 IDGs (engines)
2 APU (from 1 APU system)
2 Ext (separate sources)

18
Q

Describe the function of the Split System Breaker (SSB)?

A

Opens and closes automatically to allow one AC source to operate all AC buses (closed) or multiple sources to operate their own side of AC buses (open)

19
Q

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

A

IDG powers its side of the sync bus when voltage and frequency are acceptable.
Previous power source disconnected.
When an engine on opposite side of airplane started, the IDG powers its side of the sync bus.
Previous power source disconnected and SSB closes

20
Q

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

A

External/APU power available and powering entire electrical system through sync bus).
When engine started IDG powers entire sync bus when voltage and frequency acceptable.
SSB remains closed throughout and original power source disconnected

(Output from external source and IDG briefly synced to ensure smooth power transfer before external source disconnected)

21
Q

Which bus powers the Captain’s transfer bus and the main standby bus?

A
  1. AC BUS 3
  2. AC BUS 1
22
Q

Which bus powers the First Officer’s transfer bus?

A
  1. AC BUS 2
  2. AC BUS 1
23
Q

Which bus provides backup power for both (Captain and FO) transfer buses?

A

AC BUS 1

24
Q

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

A
  • Main & APU Battery Chargers
  • Fuel Pumps for APU Start
  • Flight Deck Flood, Navigation & Service Lights
  • Misc Service Outlets & Equipment
25
Q

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

A

EXT/APU 1 available/ON
ground service switch ON (L1 door)

26
Q

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

A

Lower Cargo Doors
* Lower Cargo Handling Equipment
* Lower Cargo Lights
* Fueling System
* Aux Hyd Pump 4

27
Q

What bus powers the APU standby bus?

A
  1. Capt Xfer bus - powered by AC BUS 3 (1 backup)
  2. APU STBY INVR - powered by APU HOT Batt bus
28
Q

How is the electrical system configured during an automatic ILS approach (auto-land)?

A

BTBs for AC BUSes 1, 2, 3 open
AC 1-3 power independent sources for 3 APs
AC Bus 4 powers sync bus

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

30
Q

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

A

AC BUS 3

31
Q

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

A

MAIN STBY INVR powered by Main Hot Batt bus

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

MAIN STBY INVR powered by Main Hot Batt bus powered by Main Bat
- minimum 30 mins

33
Q

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

A
  • LEFT EIU, CDU, ILS, VOR, ADC, Xponder, EFIS Control
  • STBY Ignition for all Engines
  • Primary EICAS, RMI, STBY Instrument Lights
  • Various Flight Control components
34
Q

What are the equipment items on the APU standby bus?

A
  • L PFD
  • L ND
  • L FMC
35
Q

How is DC power provided by the electrical system?

A
  • TRs from each AC bus power respective DC buses, connected by DCIRs to a DC Tie Bus
  • one DC Bus can power all other DC Buses through DC Tie Bus
36
Q

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

A

DC Bus 3

37
Q

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

A

Respective Hot Batt bus

38
Q

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

A

APU Controller (alternate), Fuel Valves (all Engines), All Crossfeed Valves
* Dome, Storm, & selected Interior Lights
* IDG Disconnect, Manual Pressurization Controller, Trailing Edge Flap Control
* CA’s Interphone, Left Radio Tuning Panel, Left VHF

39
Q

How is each hot battery bus normally powered?

A

Respective chargers - acting as TRUs for AC power from Ground Service bus
- If chargers unpowered, powered from respective BATs - min 30 mins

40
Q

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

A
  • APU Fuel SOV, Spar Valves (All Engs)
  • APU & Lwr Cargo Fire Extinguishers
  • Engine Fire Extinguishers (All Engs), Fire Sw Unlock (All Engs)
41
Q

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

A
  • IRU L, C, R DC Power
    • L & R Outflow Valves
    • APU Inlet Door, APU Controller (primary)

747-400F Oral (22 decks)

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