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Boeing 787 > Electrical System > Flashcards

Electrical System Flashcards

0
Q

What are the 2 distinct power distribution methods?

A

Primary or Remote.

Direct distribution from the respective AC/DC buses or distribution via the Remote Power Distribution System.

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1
Q

What is an RPDU? How many are there?

A

Remote Power Distribution Unit. 17

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2
Q

What amperage loads do the RPDU’s distribute?

A

10 amps or less

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3
Q

How many main 235Vac power system buses are there?

How are they designated?

A

4

L1, L2, R1, R2

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4
Q

How do the generators power the main AC buses with both engines online?

A

Each VFSG is connected to a main AC bus

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5
Q

How do the generators power the main AC buses with one engine running and the APU online?

A

VFSG’s power the on side main AC buses, ASG’s power the P150 Auxiliary power panel which provides power to the other side main AC buses through the tie bus.

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6
Q

How are the main AC buses powered with external power online?

A

External power connected directly to 115Vac buses. Main AC buses connected by the bus tie and powered by power converters from the 115Vac buses.

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7
Q

On the ground with only forward external power selected, what powers the 115Vac buses?

A

115Vac buses powered by external power directly.

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8
Q

What is the BPCU and what does it provide?

A

Bus Power Control Unit

  • Overall load management.
  • Electrical power transfers.
  • Flight deck control and indications.
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9
Q

What power sources can the aircraft use for engine starts?

A

VFSG’s, ASG’s or external power.

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10
Q

Aft external power can only be used to assist a start for which engine?

A

The right engine

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11
Q

How many starters are needed to start the APU?

A

One

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12
Q

How many starters are needed to start an engine?

A

One

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13
Q

Are both ASG’s required to maintain the electrical load in flight?

A

Yes, but there will be load shedding.

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14
Q

What are the primary and backup power sources for the airplane brakes?

A

Primary: 28Vdc system
Backup: Main battery

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15
Q

On which side of the aircraft are the external power receptacles located?

A

Left side of the fuselage

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16
Q

How many external ground sources are required to energize the “Ground Handling Mode”?

A

One

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17
Q

In flight, when will the RAT automatically deploy?

A
  • Both engines have failed
  • All three hydraulic system pressures are low
  • Loss of all electrical power to the captains flight instruments
  • Loss of all four EMP’s and faults in the flight control system occur on approach
  • Loss of all four EMP’s and an engine fails on takeoff or landing
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18
Q

Which cockpit displays are powered during RAT operations?

A
  • Captain inboard DU
  • Captain outboard DU
  • Lower DU
  • ISFD
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19
Q

What major systems are not available on “In-air RAT only mode, Standby Power)?

A

Flaps, Slats, Stabilizer trim, Packs, Thrust reversers, Auto speedbrakes, HUD, WIPS, (window heats, autothrottle, TAT, TAP, HF radios, SATCOM, TCAS, GPWS, XPDR, WX radar, external lighting, LNAV/VNAV, FMC predictions)

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20
Q

How is load shedding determined by the bus power control unit?

A

Loads are shed in order of priority to stay within the capacity of the available power sources.

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21
Q

What equipment is energized in the “In-air Battery only” mode (Standby Power)?

A

Captains flight instruments and other essential equipment for flight controls, navigation and communication.

  • CPT and Lower DU’s
  • ISFD, ECL, FMC (Limited)
  • MCP, Autoflight & Autopilot (Limited)
  • DSP L, MFK L, CCD L
  • CPT/FO ACP & Interphone
  • VHF L, TCP L, CCR L
  • IRU, AHRU, INR, PFC
  • ENG/APU fire detection
  • Misc lighting
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22
Q

How can load shedding be monitored in the aircraft?

A

Electrical synoptic shows a list of systems affected by load shedding. Affected system synoptic (AIR, FUEL, HYD) also indicate equipment that is inhibited or shed.

23
Q

What does the main battery power directly?

A

Hot battery bus

24
Q

What are the primary and backup power sources for the flight control computers?

A

Primary: 3 engine driven Permanent Magnet Generators (2 left eng, 1 right eng)
Backup: Airplane 28Vdc system, airplane battery and dedicated batteries.

25
Q

What does the APU battery power on the ground?

A

APU start and Navigation lights (during battery only towing)

26
Q

How can the circuit breakers be accessed in the aircraft?

A

Through the Circuit Breaker Indication and Control (CBIC)

27
Q

What is the maximum number of load shed items that can be displayed on the electrical synoptic?

A

Maximum 8

28
Q

Does “Ground Handling Mode” have priority over “On-ground Battery only mode”?

A

Yes, initialized regardless of battery switch position

29
Q

Does “Ground Handling Mode” need an external power supply connected and selected “ON”?

A

No, only connected

30
Q

Can Thermal Circuit Breakers (TCB) be reset from the flight deck?

A

No, only ECB

31
Q

What is the difference between load shed and load inhibit?

A

Load inhibit are loads inhibited at predefined operational phases. This is because the affected system is not necessary.

32
Q

What does the EICAS message “MAIN BATTERY DISCH” indicate?

A
  • Main battery discharging
  • Main battery failure
  • Hot Bus not energized
33
Q

What is the VFSG and ASG power output?

A

VFSG - 250 kVA

ASG - 225 kVA

34
Q

The P100 and P200 panels receive power from the VFSG’s, the P150 from the ASG’s. Where are the panels located?

A

Aft E/E bay

35
Q

P300 and P400 are the 115Vac and 28Vdc power distribution panels. Where are they located?

A

Forward E/E bay

36
Q

What are the different voltages used throughout the system?

A

235Vac, 115Vac, 270Vdc, 28Vdc, 130Vdc

37
Q

What is a EBPSU? How many are there and where are they located?

A

Electrical Brake Power Supply Unit

4 in total, located in the forward E/E bay on the P500 & P600 panels

38
Q

How many Common Motor Start Controllers are there?

A

8 in total.

39
Q

Which system uses the large rated DC motors powered by 270Vdc and controlled by the CMSC’s?

A
  • Hydraulic EMP’s
  • NGS
  • Center tank fuel pumps
  • Power for engine start
  • CAC’s
  • Ram Air Fans
40
Q

Why is part of the Large Motor Power System energized by the APU?

A

APU energizes only the motor controller required to perform an APU battery start.

41
Q

Which part of the electrical system is cooled by the PECS?

A
  • The high voltage motor controllers on P700 and P800 panels.
  • ATRUs on P700 and P800 panels.
42
Q

Why is part of the Large Motor Power System energized by the aft external power?

A

Aft external power energizes only the motor controller required to perform a right engine start using only external power.

43
Q

How many external power connections are required to perform and engine start using only external power?

A

2

44
Q

When is the PECS energized?

A
  • With one/both engines running, or
  • APU running, or
  • FWD external power connected and selected on
45
Q

What are the electrical power sources?

A
  • 1 main battery
  • 1 APU battery
  • 2 forward external power receptacles
  • 1 aft external power receptacle
  • 4 Variable Frequency Starter/Generators
  • 2 Variable Frequency APU Starter/Generators
  • 1 RAT
  • 3 Flight control Permanent Magnet Generators
  • 2 EEC Permanent Magnet Alternators
45
Q

How are the CMSCs powered?

A

Energized by 270Vdc through power conversion from 235Vac buses.

46
Q

Where are the CMSCs located?

A

P700 and P800 panels in the aft E/E bay.

47
Q

Where are the ATUs, TRUs and ATRUs located?

A

ATUs and TRUs on the P500/P600 power conversion panels in the fwd E/E.
ATRUs on the P700/P800 panels in the aft E/E.

48
Q

How are the VFSGs cooled?

A

By a Fuel/Oil Heat Exhanger and

Air/Oil Heat Exchanger

49
Q

Which condition will require a manual drive disconnect of the VFSG?

A

Low VFSG oil pressure.

50
Q

What is the purpose of the ATUs?

A

Autotransformer Units

  • Converts 235vac power from the main buses to 115vac power.
  • Converts 115vac power from external power to 235vac for the main buses.
51
Q

What is the purpose of the 4 TRUs?

A

Converts 235vac from the main buses to 28vdc.
Supplies 28vdc to:
-28vdc buses
-CPT & FO instrument buses
-EBPSUs
-Battery chargers through the instrument buses

52
Q

What is the purpose of the EBPSU’s?

A

Regulates power for exclusive use of the electrical braking system.

53
Q

What is the power input for the 4 EBPSUs?

A

Two separate 28Vdc inputs to each unit.

  • 28Vdc bus system (primary)
  • Main battery (backup)

Boeing 787 (18 decks)

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