Boeing 747 > Electrical > Flashcards

Electrical Flashcards

(45 cards)

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1
Q

What does AVAIL light mean on APU GEN or EXT PWR switches

A

APU - generator power acceptable

EXT PWR - external power plugged in and power is acceptable

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2
Q

When would a generator DRIVE light illuminate?

A
  • IDG oil pressure low
  • IDG oil temperature high
  • Generator Control Breaker (GCB) open due to uncorrectable generator frequency fault
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3
Q

Main AC electrical power sources

A
  • 4 Integrated Drive Generators (IDGs) (one mounted to each engines accessory gear box)
  • 2 APU generators
  • 2 external power sources
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4
Q

What happens if electrical load exceeds power available (airplane or external)?

A

Electrical Load Control Units (ELCUs) shed AC loads in a programmed sequence until overload is relieved

  • Galley busses are shed first, followed by utility busses (galley busses only on passenger)
  • Utility Buses 1 and 2 and Galley Buses 1 and 2 (pax) are powered by ELCU logic (Utly Pwr Sw L)
  • Utility Buses 3 and 4 and Galley Buses 3 and 4 (pax) are powered by ELCU logic (Utly Pwr Sw R)
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5
Q

When will an IDG be automatically disconnected?

A

Excessively high IDG oil temperature without prior disconnection by flight crew

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6
Q

When can APU generators be used?

A

APU auxiliary power can only be used on the ground

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7
Q

Purpose of Split System Breaker (SSB)

A
  • divides the synchronous bus allowing each side of the AC electrical system to be powered by separate auxiliary or external power sources
  • Auxiliary and external power sources cannot be connected to the same side of the synchronous bus simultaneously.
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8
Q

What is the meaning of ELEC BUS ISLN on the EICAS display?

A

The related Bus Tie Breaker (BTB) is open

  • can be reset by pushing the Bus Tie Switch Off, and then AUTO, if fault is cleared
  • Bus is disconnected from the sync bus
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9
Q

How is AC power distributed?

A
  • four main buses (AC BUS 1, AC BUS 2, AC BUS3, AC BUS 4)
  • two transfer buses (CA and FO)
  • ground service bus and ground handling bus
  • four utility buses
  • four galley buses (pax)
  • two standby buses (pax)
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10
Q

Purpose of transfer buses and how are they powered?

A
  • provide AC power to critical flight related equipment
  • CA transfer bus normally powered by AC Bus 3 (AC Bus 1 as back up)
  • FO transfer bus normally powered by AC Bus 2 (AC Bus 1 as back up)
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11
Q

When is the Main Deck Cargo Handling Bus powered?

A
  • powered on the ground when EXT PWR 2 or APU GEN 2 are AVAIL
  • pushing the AVAIL source deenergizes the main deck cargo handling bus
  • EXT PWR 2 is prioritized over APU GEN 2 if both AVAIL
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12
Q

Components of AC Standby Power System?

A
  • Main standby bus
  • APU Standby bus
  • Main Battery
  • APU Battery (24V)
  • Main standby inverter
  • APU standby inverter
  • Standby Power selector
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13
Q

How long can main battery provide power to the main standby bus with the battery charger unpowered?

A

30 mins

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14
Q

Power source priority for Main Standby Bus

A

1) AC Bus 3
2) main standby inverter via main hot battery bus (with batt charger powered via AC 1)
3) mani standby inverter via main hot battery bus (without batt charger powered) - 30 mins

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15
Q

Power source priority of APU standby bus

A

1) CA transfer bus via AC Bus 3
2) CA transfer bus via AC Bus 1
3) APU standby inverter via APU Hot Batt Bus (charger not powered) - 30 mins

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16
Q

Components of DC electrical System

A
  • 4 Transformer Rectifier Units (TRUs) powered by respective AC bus and providing DC power to respective DC Bus
  • 4 DC Isolation Relays (DCIRs) connecting DC Buses to DC Tie Bus
  • Main Battery
  • APU Battery
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17
Q

Voltage of APU Battery

A

24V

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18
Q

Main Power Source of APU DC electric starter?

A

APU start transformer rectifier (TR) via:

Primary:

  • utility bus 4 (freight) via external or internal AC source
  • galley bus 2 (pax) vis external or internal AC source

Secondary:
- 24V APU Battery (disconnects battery charger during start)

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19
Q

Back up power for IRS

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A
  • APU Hot Battery Bus
  • Center IRU operates for 5 mins and shutsdown
  • ON BATT Light on Maintenance Panel
20
Q

ELEC DRIVE EICAS Advisory message

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A
  • IDG oil pressure low
  • IDG oil temp is high
  • Generator control open due to uncorrectable freq fault
21
Q

What does AVAIL light indicate?

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A
  • power source is available

- power is acceptable

21
Q

When is Ground Service Bus Powered

Study These Flashcards
A

1) AC Bus 1

2) EXT 1 or APU GEN 1 Avail via Ground Service Switch at Door L1

22
Q

Function of the Standby Power Switch in Auto or Batt

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A

AUTO - allows main and APU standby busses to be powered from available sources
BATT - MX function for testing
- disables man and APU battery chargers

23
Q

Where is the Electrical Power-Up procedure located?

Study These Flashcards
A

FCOM VOL 1; Supplemental Procedure 6.1

24
What happens when you push Generator Drive Disconnect switch
- disconnect IDG from engine - open related GCB * can only be reconnected on the ground by MX
25
Equipment powered by Utility Busses
- FWD Main Fuel Pumps 2 and 3 - FWD Override/Jettison Pumps 2 and 3 - Center Override/Jettison Pump (L) - Galley Equipment - APU TR
26
Describe the electrical load shedding process?
- 4 ELCUs (electrical load control units) - via logic sheds AC loads by priority until the loads are within the capacity of airplane or ground power generators - loads are restored when additional AC power becomes available
27
What is the purpose of the electrical system overload protection?
- provided by load management system | - configured to ensure power is available to critical and essential equipment
28
Describe the sequence of events during engine start with SSB open (two external sources)
- the IDG powers its side of the synchronous bus when voltage and frequency are acceptable - The previous power source is disconnected - When an engine on the opposite side of the airplane is started, the IDG powers its side of the synchronous bus - The previous power source is disconnected and the SSB closes
29
What are some of the equipment items powered by the ground service bus?
* main and APU battery chargers * fuel pumps for APU start * flight deck flood, navigation, and service lights * miscellaneous service outlets and equipment
30
Equipment items powered by the ground handling bus?
- lower cargo handling equipment - lower cargo compartment lights - lower cargo doors - fueling system - auxiliary hydraulic pump 4
31
Electrical Configuration during Autoland
- AC and DC buses 1, 2, and 3 are isolated from the sync bus * provides independent power sources for all 3 power autopilots - AC 4 powers the sync bus - BTB 1, 2, and 3 open - DCIR 1, 2, and 3 open
32
Equipment powered by Main Standby Bus?
- left EIU, left CDU, left ILS, left VOR - left ADC, left transponder, left EFIS control panel - various flight control components - standby ignition for all engines - primary EICAS display - standby instrument lights - RMI (if installed)
33
Equipment on the APU standby bus
- left FMC - left ND - left PFD
34
Power Source of Main and APU battery busses
Normal: DC Bus 3 (powered by AC Bus 3 via TR) Backup: respective Hot Battery Bus
35
Equipment on Main battery bus
- APU controller (alternate) - fuel valves (all engines) - all crossfeed valves - dome, storm, and selected indicator lights - IDG disconnect (all engines) - manual pressurization control - trailing edge flap control - CA interphone - left radio tuning panel - left VHF
36
Normal power source of each hot battery bus
- ground service bus via related battery charger (which acts as a TR) - AC Bus 1 powers ground service bus
37
Equipment powered by Main Hot Battery Bus
- APU fuel shutoff valve - spar valves (all engines) - APU and lower cargo fire extinguishers - engine fire extinguishers (all engines) - fire switch unlock (all engines)
38
Equipment on APU Hot Battery Bus
- IRU left, center, right DC power - left and right outflow valves - APU inlet door - APU controller (primary)
39
Battery Locatoins
Main Battery - E and E Compartment | APU Battery - Tail
40
MAIN DECK Handling Bus Priority Power Soure
Priority: EXT PWR 2 (AVAIL)
41
What EICAS messages may appear during load shedding?
``` FUEL PRESS CTR L FUEL PUMP 2 FWD FUEL PUMP 3 FWD FUEL OVRD 3 FWD FUEL OVRD 2 FWD ```
42
Which busses power AP L, C, and R?
AP L - AC Bus 3 AP C - AC Bus 1 AP R - AC Bus 2
43
What screens are powered with BATT on and STBY PWR switch Auto?
- Left PFD - Left ND - Primary EICAS - Left CDU
44
Main Power source of IRUs
3:1:2 Left IRU: AC Bus 3 Center IRU: AC Bus 1 Right IRU: AC Bus 2
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