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B747 > Electrical > Flashcards

Electrical Flashcards

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1
Q

Standby Power Selector, what are the 3 options and what do they do?

A

OFF;
standby power not available
main and apu standby busses disconnected from all power sources

AUTO: allows main and apu standby busses to be powered from available sources

BAT:
powers main battery bus from main battery through the main hot battery bus with battery switch ON
powers APU battery bus from APU battery through the APU hot battery bus with battery switch ON
disables main and APU battery chargers
powers main and APU standby busses from their related batteries through their hot battery busses and standby inverters with battery switch ON

BAT position for ground mx only

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2
Q

Battery Switch

A

ON:
main battery available as backup power source for main battery bus and main standby bus
APU battery available as backup power source for APU battery bus and APU standby bus

OFF: disconnects main and apu batteries from related battery busses

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3
Q

Battery switch off light

A

amber - battery switch off

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3
Q

Utility Power Switches

A

On - each switch powers two uktitiy electyrical control units

OFF
-removes power from related ELCUs
-resets fault logic circuitry

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3
Q

Utility Power OFF lights Illuminated (amber)

A

power removed from related ELCU by fault protection logic or
related utility power switch off
not illuminated during load shedding

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4
Q

APU Generator (APU GEN) Control Switches

A

push -

AVAIL light illuminated; connects related APU generator to AC electrical system

ON Light illuminated; disconnects related Apu generator from AC electrical system

NOTE; when the main deck cargo handling bus is powered by any generator 2, push it causes main deck cargo handling bus to lose power

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5
Q

APU generator power available (AVAIL) Lights

A

Illuminated white :
APU generator power quality acceptable
main deck cargo handling bus powered when APU generator 2 avail light illuminated
extinguishes when ON light illuminates

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6
Q

APU Generator Power ON Lights

A

illuminated white:
related apu generator connected to AC electrical system
extinguishes when avail light illuminates

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7
Q

External Power (EXT PWR) Control Switches

A

Push:
AVAIL light illuminated connects related external power to AC electrical system
when the main deck cargo handling bus is powered by external power 3 pushing it control switches causes main deck cargo handling bus to lose power

ON light illuminated: disconnects related external power from AC electrical system

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8
Q

BUS TIE Switches

A

AUTO
arms automatic AC bus tie circuitry
closes related DC isolation relay

OFF
opens BTB and related DCIR
resets fault logic circuitry

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8
Q

generator drive disconnect (DRIVE DISC) switches

A

Push:
disconnects IDG from engine when above idle speed
opens related generator control breaker (GCB)

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8
Q

Bus isolation (ISLN) Lights

A

amber-
BTB open
ac bus isolated from synchronous bus

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9
Q

generator DRIVE lights

A

amber
IDG oil pressure low or
IDG oil temp high or
GCB open due to uncorrectable generator frequency fault

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10
Q

generator control (GEN CONT) Switches

A

ON - arms GCB to close when generator power quality acceptable
OFF
opens generator field and GCB
resets fault control logic circuitry
isolates generator from its related AC bus

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11
Q

Generator OFF lights

A

GCB Open

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12
Q

What electrical system is the main source of airplane electrical power?

A

AC

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13
Q

Where do the main sources of AC power come from?

A

4 IDGs,2 APU generators, 2 external power sources

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14
Q

What are the main components of an IDG?

A

AC gen, self contained lube system, auto control and protection components

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15
Q

What causes the IDG to automatically disconnect?

A

Excessive high drive oil temperature

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15
Q

When an IDG is disconnected can it be restored by the flight crew?

A

no

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16
Q

how is AC power distributed?

A

4 main busses, 2 transfer busses, ground service/handling bus

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17
Q

is APU power available in the air?

A

no

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18
Q

where are the external power receptacles located?

A

two power receptacles on the lower right forward fuseulage

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19
Q

if only 1 external power source is connected is the SSB open or closed?

A

Closed. but will open if another external source is connected to the other side.

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20
what happens if power on an AC bus is unacceptable?
The related BTB opens and the bus disconnects from the synchronous bus. The AC bus will remain powered by its IDG. If the IDG cant maintain acceptable power the GCB opens and and BTB closes from the Synchronus
21
The EICAS message ELEC DRIVE displays for what?
low IDG oil pressure or high IDG oil temp or GCB is open due to an uncontrollable generator frequency fault
22
What causes the IDG to disconnect automatically?
excessive high drive oil temp, this opens the GCB and displays EICAS ELEC GEN OFF
23
When is AUX power available? where does it come from?
APU, only on the ground
24
How does an IDG power its related AC Bus?
Through the GCB
25
How is an AC bus connected to the synchronous bus?
A BTB
26
What does the EICAS message ELEC BUS ISLN mean?
a BTB is open
27
What happens if you push the bus tie switch from auto - off - auto?
resets logic circuitry and allows the BTB to close if the fault is corrected
28
What other busses do the main AC busses power
AC bus 1 powers the ground service bus and provides back up power for both transfer busses. AC bus 2 powers the first officers transfer bus AC bus 3 powers the captain transfer bus and main standby bus each ac bus powers a utlitity bus
28
The Main AC busses power individual equipment such as?
TRUs, nav radios and flight control computers, flight deck lighting, pitot and window heat
29
When is the ground service bus powered?
on the ground and in flight whenever AC bus 1 is powered
30
What does the ground service bus power?
Main and APU battery chargers, fuel pumps for apu start, flight deck flood, nav, service light, misc service outlets and equipment
31
When is the ground handling bus powered?
on the ground when APU GEN 1 or EXT power 1 is available
32
What does the ground handling bus power?
Lower cargo handling equipment and compartment lights, fueling system, aux hydraulic pump 4
33
how many transfer busses are there?
2, CA and FO transfer busses, powers critical flight related equipment
34
how is the captains transfer bus powered?
Normally AC bus 3, if ac bus 3 is unavailable then AC bus 1
35
What other bus does the CA transfer bus power?
APU standby bus
36
What individual equipment does the CA transfer bus power?
Center EfIS/EICAS interface unit (EIU), Left HF, Center ADC (if installed)
37
How is the first officer transfer bus normally powered
AC Bus 2, if not then AC Bus 1
38
What individual equipment does FO transfer bus power?
Autothrottle servo, lower eicas display, right ADC / EFIS / EIU/ FMC, Right CDU / HF / ND / PFD
39
Each Ac bus powers how many utility busses?
1 for 1
40
How is a utility bus controlled?
ELCU that protects from electrical system from utility bus faults, and provides load management thru auto shedding
41
What do the utility busses power
Forward main fuel pump 2,3 forward override jettison pump 2,3 center override/jettison pump galley equipment
41
Left / right utility switch power which utlitlity busses?
left 1/2 right 3/4
42
what does the ELEC UTIL BUS EICAS message mean?
one or both utility busses are unpowered due to a fault or the related utility power switch is off
43
When is the Main deck cargo handling bus powered?
When external power 2 or APU gen 2 is available,
44
Do you have to select APU or EXT 2 to power the main deck cargo handling bus?
no, as long as they have power it is powered
45
What happens to the AC and DC busses during an autoland approach
AC and DC busses 1,2,3 are isolated from the synchronous bus to provide independent power sources for the three autopilots. AC bus 4 continues to power the synchronous bus
46
What happens if an AC or DC bus fails when busses are isolated for Autoland?
the system reconfigures automatically to maintain independent power sources for the three autopilots
47
What happens to the electrical system during autoland?
AC bus isolation lights 1,2,3 remain extinguished, EICAS message ELEC BUS ISLN not displayed, Message ELECTRICAL SYNOPTIC INHIBITED FOR, and AUTOLAND is displayed
48
What are the major components of the AC standby system?
main/apu standby busses, main/apu batteries, main/apu standby inverters, standby power selector
48
When is the electrical system no longer configured for Autoland?
All autopilots disengaged, TOGA mode is annunciated and the airplane is higher than 100ft, approach mode is disarmed or deselected, electrical system is unable to maintain a configuration for Autoland bus isolation
49
The main standby bus is powered by?
AC bus 3
50
with the battery switch ON, standby power selector in AUTO, and AC bus 3 not powered, how is the main standby bus powered?
main standby inverter
51
the main standby inverter (normally unpowered) is activated and receives power from?
Main battery charger through the main hot battery bus
52
How is the main battery charger normally powered
AC bus 1 through the ground service bus
53
with the battery switch ON, standby power selector in AUTO, and AC bus 3 and AC bus 1 not powered, how is the main standby bus powered?
main standby inverter through main battery through main hot battery bus, with main battery bus unpowered (normally powered via AC bus 1 through ground service bus), the main battery can provide power to main stand by bus for 30 minutes min
54
The main standby bus powers what individual equipment
Left EIU / CDU / ILS / VOR, various flight control components, standby ignition for all engines primary EICAS display, standby instrument lights, Left ADC / transponder / EFIS control panel
55
APU standby bus is normally powered by?
Captain transfer bus
56
with the battery switch ON, standby power selector in AUTO, and the captain transfer bus not powered (loss ac bus 1,3) how is the APU stand by bus powered
APU standby inverter
57
Where does the APU standby inverter receive power from?
APU battery through the APU hot battery bus, with the apu battery charger unpowered the apu battery can provide power for a minimum of 30 minutes
58
With the battery switch ON and standby power selector in BAT and main and apu battery chargers disabled, how is each stand by bus powered?
related battery and inverter minimum power of 30 mins
59
how does the main DC system produce DC power?
4 TRUs
60
How is each TRU powered?
By its related AC bus
61
IF a DC Busses respective AC bus or TRU fails, is it still powered?
yes via the DC isolation relays (DCIR) to the DC tie bus
62
Main DC busses power what individual equipment?
cabin pressure, fuel jettison, and pack temperature controllers wing anti-ice control engine driven and hydraulic demand pump control fuel transfer and jettison valve control individual nacelle anti ice control
63
Besides TRU's what also provides DC power?
battery busses - main, apu, main hot, apu hot
64
main and Apu battery bus are normally powered by?
DC bus 3, if either DC bus 3 or ac bus 3 is unpowered then by their respective hot battery bus
65
the main battery bus provides power to what equipment
APU controller (alternate), fuel valves (all engines), all crossfeed valves, dome,storm,selected indicator lights IDG disconnect, manual pressurization control, trailing edge flap control ISFD (installed)
66
the apu battery bus powers what equipment
-apu dc fuel pump, engine start air control -cargo,first officer and service interphones, pa system -apu and engine fire/overheat detection loops A and B -APU fire warning horn
67
how is each hot battery bus normally powered?
ground service bus through its related battery charger.
68
the main hot battery bus powers what?
apu fuel shutoff valve, spar valves apu and lower cargo fire extinguishers engine fire extinguishers (all engines), fire switch unlock (all engines)
69
the apu hot battery bus powers what?
IRU left, center, right DC power left and right outflow valves APU inlet door, APU controller (primary)

B747 (7 decks)

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