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B788-9 > ELECT > Flashcards

ELECT Flashcards

1
Q

Electrical power sources are?

A
  • four (4) variable frequency engine starter/generators
  • two (2) variable frequency APU starter/generators
  • three (3) external AC power receptacles
  • one (1) Ram Air Turbine (RAT)
  • one (1) main battery
  • one (1) APU battery
  • three (3) flight control Permanent Magnet Generators
  • two (2) EEC Permanent Magnet Alternators
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2
Q

When will the Generator Drive be disconnected?

A

Depending on the fault condition, the

generator drive is either automatically disconnected, or requires crew action to be disconnected.

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3
Q

How is the APU started powered?

A

Electrical power for APU start can be provided by forward external power, APU
battery, or engine generated power. The electrical system automatically selects a
single starter/generator to provide sufficient torque for APU start.

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4
Q

Which APU starter is used with External/Generator power?

A

Either the left or right starter/generator is used for APU start if an engine is running or forward external power is selected ON.

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5
Q

Which APU starter is used with Battery only?

A

For APU starts with the APU battery as the power source (no engine running and forward external power not ON), the right starter/generator is always used.

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6
Q

How many APU Generators are used Inflight or On the Ground?

A

On the ground, both APU generators are available to energize the airplane’s 235 Vac electrical buses; L1, L2, R1, and R2. In flight, one or both APU generators
provide power depending on the electrical load requirements of the airplane.

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7
Q

What is the output of the Engine Generators?

A

Each engine has two 235 Vac variable frequency starter/generators.

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8
Q

When is “Ground Handling” mode energized?

A

Connecting one or both power sources to the receptacles illuminates the AVAIL
light(s) in the power switch(es), and energizes “Ground Handling” mode. Only one connection is required to power this mode. If two sources are connected, the
first source connected is the one that is used.

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9
Q

How many power sources are needed for “Ground Handling” mode?

A

Only one connection is required to power this mode. If two sources are connected, the first source connected is the one that is used.

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10
Q

When is “External Power On” mode energized?

A

Selecting the external power switch(es) to ON energizes the “External Power On”
mode and extinguishes the AVAIL light(s).

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11
Q

What requirements must be met for External Power engine start? (No APU)

A

Connecting the two forward and one aft receptacles results in optimal start
performance. At a minimum, two 90 kVA rated forward external power sources
are required.

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12
Q

How is Aft External Power used?

A

The aft external power system can assist the forward system when starting the right engine first. To receive the benefit of the aft power source, both forward power
sources must also be connected,

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13
Q

The RAT deploys automatically if any of the following occur:

A
  • Both engines have failed
  • All 3 hydraulic systems are low
  • Loss of all electrical power to Captain and First Officer flight instruments
  • Loss of all 4 EMP’s and faults occur in the flight control system on approach
  • Loss of all 4 EMP’s and an engine fails on takeoff or landing
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14
Q

The main battery provides power for:

A
  • airplane power-up
  • APU start (assists APU battery)
  • refueling operations
  • towing operations
  • electric braking (as backup power source)
  • captain’s flight instruments (energizes essential instruments until RAT deployment)
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15
Q

The APU battery provides power on the ground for:

A
  • APU start

* navigation lights (during battery-only towing operations)

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16
Q

What is the primary source of power for the flight control electronics? Secondary?

A

Three engine driven Permanent Magnet Generators (PMGs - L2/R1 ) are the primary source of power. These power sources are independent from the main airplane electrical system, and are also independent from each other. A secondary source for flight control power is provided by the airplane’s 28 Vdc
bus distribution system, and the main battery. In addition, a backup system is
provided by dedicated batteries to assure positive flight control operation during
temporary power interruptions.

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17
Q

What is the the primary source of power for the EECs? Secondary?

A

Two engine driven Permanent Magnet Alternators (PMA) (one per engine). A secondary source for EEC power is provided by the airplane’s 115v AC bus
distribution system. During engine start, initial EEC power is provided by the
airplane.

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18
Q

How is AC power distributed Forward EE and Aft EE?

A

A limited number of high voltage 235 Vac electrical loads are energized from the aft E/E bay. The majority of airplane electrical loads are 115 Vac and 28 Vdc, energized by the forward E/E bay power panels and a decentralized network of 17 Remote Power Distribution Units (RPDUs) located throughout the airplane.

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19
Q

Where are the Batteries?

A

The forward and aft E/E bays also contain the main and APU batteries, respectively.

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20
Q

On the ground, with only forward external power selected ON, how are the 235 Vac buses powered? After APU start?

A

the 235 Vac buses are energized by the 115 Vac distribution system through power conversion devices. If the APU or an engine(s) is subsequently started, it energizes the four main 235 Vac buses, and external power transitions from ON to AVAIL.

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21
Q

How is power changed AC-DC or DC-AC?

A

Power conversion devices which change

power from one voltage or current type (AC/DC)

22
Q

On the ground, with only the APU power available (no external power or engine
generator power), each APU generator energizes?

A

two of the four main 235 Vac buses.

23
Q

With one engine and the APU running, how are the Main buses powered?

A

that engine’s two related 235 Vac buses are energized directly. The other two 235 Vac buses are energized by the APU
generators.

24
Q

Which loads are distributed by the RPDUs

A

The higher amperage (greater than 10 amps) loads are distributed directly by the bus system. The lower amperage (10 amps or less) loads are distributed by the RPDUs.

25
Q

With an engine(s) and/or APU running (external power OFF), how is the 115 Vac system energized? If External power is selected?

A

the main 235 Vac buses energize the 115 Vac system through power conversion devices. If forward external power is then selected ON, it energizes the 115 Vac system directly.

26
Q

How is power provided to the 28 Vdc system?

A

The 235 Vac system provides power to the 28 Vdc system through power
conversion devices.

27
Q

Where is Large Motor Power Distribution System?

A

A dedicated large motor power distribution system in the aft E/E bay power panels energizes the motor controllers..

28
Q

Which Large Motor Controllers are powered by APU Battery only? Aft External Only?

A

The APU battery energizes only the motor controller required to perform an APU battery start. The aft external power system energizes only the motor controller required to perform a right engine start using external power as
the sole power source.

29
Q

What is the Power Electronics Cooling System and when is it powered?

A

The Power Electronics Cooling System (PECS) dissipates heat created by these
high voltage motor controllers. PECS is energized if one or both engines or the
APU is running, or if forward external power is connected and selected ON.

30
Q

What are the Electrical System modes?

A 
Towing Power mode
On-Ground Battery Only mode
Ground Handling mode
Ground Service mode
External Power On mode
In-Air Rat Only mode (Standby Power)
31
Q

What is the high priority equipment for the Towing Power mode when the TOWING POWER switch is selected to ON (with the main BATTERY switch OFF).?

A

• captain’s ACP
• captain’s flight interphone
• brakes
Note: Radio communication systems are not energized in the towing power mode.

32
Q

What is the high priority equipment for the On-Ground Battery Only mode when the BATTERY switch is selected
to ON while the airplane is on the ground,?

A
  • captain’s inboard DU
  • lower DU
  • MCP
  • APU start capability
  • wing fueling panel
  • captain’s / first officer’s ACP
  • CCR L
  • ground crew call horn
  • engine/APU fire detection
  • brakes
33
Q

What is the high priority equipment for the Ground Handling mode when the first forward external power receptacle is connected (not selected ON)?

A 
• lower DU
• APU start capability
• MFK L
• CCD L
• CCR L, R
• equipment cooling fans
• engine/APU fire detection
• cargo lighting, door actuation, loading 
• wing fueling panel
• battery chargers
Note: Ground Handling mode has priority over On-Ground Battery Only mode, and initializes regardless of BATTERY switch position.
34
Q

What is the high priority equipment for the Ground Service mode when the GROUND SERVICE switch on the master attendant switch panel is selected ON while in Ground Handling Mode.

A
  • cabin systems (limited operation)
  • cabin lighting (limited operation)
  • flight deck dome lighting
35
Q

What is the high priority equipment for the External Power On mode when at least one forward external power receptacle is connected and selected ON with the APU and engine generators off.

A 
• flight deck equipment, controls, and indications
• cabin systems (limited operation)
• cabin lighting (limited operation)
• PECS (single loop only)
Additional loads energized by this mode with two forward external power sources
• NGS (limited operation)
• hydraulics (limited operation)
• PECS (both loops)
36
Q

Are Packs and cargo heat are operative in External Power On mode.

A

Note: Packs and cargo heat are inoperative in External Power On mode.

37
Q

In-Air Rat Only mode is active if loss of all electrical power to captain’s and first officer’s flight instruments occurs in flight. What significant items are inoperative?

A

Note: Inoperative items on standby power include: TAT, autothrottle, LNAV/VNAV, FMC predictions, FMC thrust limits, TAP, flaps, slats, stabilizer trim, thrust reversers, auto speedbrakes, packs, Head-Up displays, HF radios, SATCOM system, TCAS, GPWS, transponder,
weather radar, external lighting, WIPS, and window heat.

38
Q

What is the difference between Load Inhibit and Load Shedding

A

• Load inhibit – loads are inhibited at predefined operational phases. This is because the affected system is not required, or additional power is
temporarily needed by another system.
• Load shed – loads are shed in the order of priority to stay within the capacity of the available power sources.

39
Q

BATTERY Switch

ON –

A
  • initiates L CCR start-up sequence

* (after L CCR start-up complete) energizes the “On-Ground Battery Only” mode

40
Q

BATTERY Switch

OFF –

A
  • (after delay of up to 2 minutes) de-energizes the “On-Ground Battery Only” mode
  • de-energizes the L CCR
41
Q 
Generator Control (GEN CTRL) Switches
OFF –
A
  • opens generator control breaker
  • opens generator field
  • resets fault protection systems
42
Q

TOWING POWER Switch

ON –

A

selects the main and APU batteries for energizing the “Towing Power” mode.

43
Q

Towing Battery Charge Lights
• HIGH –
• MEDIUM –
• LOW –

A

• HIGH – a minimum of 60 minutes remains
• MEDIUM – a minimum of 30 minutes remains
• LOW – a minimum of 15 minutes remains
If heavy braking occurs, actual time remaining may fall

44
Q

Engine Generator Synoptic Indications

white, low intensity

A

condition unknown.

45
Q

What order is the Load Shed Message List displayed?

A

The most recent system impacted by load shed is

listed at the top.

46
Q

What does ECB collared and tagged DO NOT

CLOSE (red tag, cyan lock collar) mean?

A

ECB is open and collared for maintenance purposes. Circuit is not powered.

47
Q

What does ECB collared and tagged INOP (white tag, cyan lock collar) mean?

A

ECB is open and collared for dispatch.

Circuit is not powered.

48
Q

What does ECB tripped (amber) mean?

A

ECB is tripped due to a fault. Circuit is open and not powered.

49
Q

What does ECB ECB open (white) mean?

A

Circuit is not powered.

50
Q

Circuit Breaker Indication and Control (CBIC) provides _____ for Electronic Circuit Breakers (ECB), and _____ for Thermal Circuit Breakers (TCB).

A

indication and control for Electronic Circuit Breakers (ECB), and
indication-only for Thermal Circuit Breakers (TCB).

B788-9 (15 decks)

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