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ELECTRICAL SYSTEM Flashcards

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1
Q

what are the four ways to power the a/c with DC power

A

2 starter generators, a/c main battery, GPU

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2
Q

where are the starter/generators? what do they supply?

A

one on each engine accessories drive gearbox. provide 28 VCD power

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3
Q

what do the starter / generators require to provide the rated generated output

A

58% n2

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4
Q

the generators power the main bus and then the load bus. what does it also power?

A

supplies power to the battery (charging it) thru the battery charge bus

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5
Q

each generator has a ________________________ that ____________________________________________

A

generator control unit. it controls starting and generating modes of operation

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6
Q

what functions does the GCU allow?

A

equalization circuit to share system load, reverse current protection, fault protection, overvoltage protection, ground fault protection

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7
Q

what happens when the generator feed line detects a ground fault

A

GCU disconnects the generator from the main bus, dropping it’s voltage to 0

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8
Q

what is the main a/c battery? where is it?

A

24 volt, 40 amp hour lead acid battery located in the aft fuselage

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9
Q

what does the main a/c battery do?

A

supplies secondary electrical power for ground ops, engine starting, and emergency requirements

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10
Q

what is the battery protected by

A

the battery feeder protection unit

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11
Q

what does the battery start bus do

A

provides DC power distribution for battery or external DC power

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12
Q

what is energizes when the battery switch is in ON

A

battery relay, battery tie in relay, and emergency bus relay

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13
Q

what powers the emer bus when battery is ON

A

the generator thru the emergency bus power relay

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14
Q

what does placing the battery switch in EMER do

A

disengages the battery relay and battery tie in relay, ISOLATING the battery from the start bus

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15
Q

what is happening when battery is in EMER

A

battery supplies DC power to emer bus BATT CUT OFF comes on

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16
Q

when does BAT CUT OFF come on

A

battery in EMER battery start bus loses power

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17
Q

external DC power is used for

A

ground engine starts, battery charging, and maintenance requiring electrical power

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18
Q

how do we test BATT FDR FAIL

A

pressing BATT FEED TEST

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19
Q

what causes illumination of BATT FDR FAIL BATT CUT OFF, and EMER BUS FDR FAIL

A

ground fault occurs on the feeder line

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20
Q

while on external ground power, do not operate these two things at the same time. why?

A

defog blower and/or windshield heat at the same time as electric heat. could cause excessive amperage pull (overheats the ground plug/receptacle)

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21
Q

electrical ground power can power the a/c start bus when the __________________. this allows

A

battery is ON this allows the GPU to power the battery

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22
Q

charging a low state battery (less than ___________) using external power will ____________________________. this should be done by ______________________

A

22 volts reduce battery life maintenance

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23
Q

what does the DC stby power system consist of

A

standby battery, aux battery, and emergency supply system

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24
Q

what type of battery is the standby battery? how long does it last? where is it?

A

24 VDC lead acid battery, about 30 mins. in the nose

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25
what does the standby bus have on it
standby instrument module UHF radio RTU 1 EFC for starting
26
what does STBY PWR switch in ARM mean
stby battery is connected to the stby bus, meaning if you lose electrical power it will turn ON
27
if STBY PWR is not armed during preflight, the stby bus
will not be auto powered with the loss of electrical power
28
what type of battery is the AUX battery? where is it>
24 VDC lead aid battery, located in avionics rack
29
what does the aux bs contain
copilot audio control panel audio hub MFD oil pressure
30
how long does the aux battery last
6 amp load will give 1 hour of emer power
31
what does pressing AUX BAT TEST do
indicates the battery is charged, don't press it more than once
32
when is aux stby bus powered
battery is ON or airborne (WOW switch)
33
how does power get from the main buses to the load buses?
three feeder lines (2 active, 1 stby)
34
what does L or R BUS FDR FAIL mean
the third feeder line is active, indicating one or more of the other feeder lines have tripped
35
how are the left and right load buses connected
LOAD BUS TIE
36
where does secondary power being
the load buses
37
what are on the load buses
non essential buses overhead buses radio master buses stby bus aux stby bus
38
DC standby power distribution
stby battery to stby bus aux batt to aux bus emer bus supplies a charge current to the stby battery
39
how does the emergency bus normally receive power
from the a/c generator
40
during an engine start, the emer bus receives power from
the left load bus
41
with the battery in EMER, the emergency bus is powered by the
battery
42
what does the emergency bus power?
gear indicator lights ignition and control (left) VHF (nav 1, adf) emergency pitch trim stby bus audio control panel fire extinguisher/bell
43
generator master switches in NORM meaning
generators and battery are allowed to be connected to the main buses and emer buses respectively.
44
master gens in EMER and battery in ON
isolates generators and the battery from the main buses and emergency bus
45
how to connect the battery to the emer bus when master gen in EMER
battery to EMER
46
in the event of electrical system failure excluding the a/c battery, placing the battery in EMER causes the battery to power
the emer bus, stby bus, and stby battery
47
GEN RESET in OFF
generators are isolated from main buses
48
DC voltafe switch tells you
the voltage display for L gen, Batt, and R Gen
49
the DC ammeters show you
current supplied by the right and left generator
50
what does the AC power system do?
converts DC power to AC power
51
what powers the no.1 inverter
left load bus
52
what powers the no.2 inverter
emergency bus or right load bus (primarily RLB)
53
what is on inv 1
25/115 primary bus 26/116 primary shed bus
54
what is on inv 2
26/115 secondary bus
55
inverter selector witch in AUTO
inv 1 powers primary buses, inv 2 powers secondary buses with fault protection. if inv 1 fails, inv 2 powers primary buses (depowers secondary)
56
inverter selector switch in no. 1
forces inv 1 to power primary buses with no fault protection. no 2 inverter powers secondary buses with fault protection
57
inverter selector switch in no. 2
inv 1 powers secondary buses, inv 2 powers primary buses. NO fault protection
58
what causes AC BUS SHED
no 2 inverter is powering primary buses and the no 2 inverter is getting power from the emer bus
59
what causes a tripped circuit breaker
overcurrent
60
blue circuit breaker
left load bus
61
green circuit breaker
stby power bus
62
red circuit breaker
emer power bus
63
white black circuit breaker
non essential power buses
64
yellow circuit breaker
right load bus
65
what can be operated while on external power
high draw systems like the VCCS
66
GEN RESET switches in NORM
enables the GCUs to control and provide normal generator operation
67
GEN RESET in RESET
resets the generators and GCU functions
68
what is the primary source of electrical DC power
starter/generators
69
GCUs monitor starter speed and remove power from the starter when the engine reaches
35-40% n2
70
what do start relays do
connects external or battery power to the starter generators for engine start
71
what does the battery charge bus do
acts as a connection bus for all DC power
72
what is the emer bus normally powered by
the generators
73
battery in OFF
disconnects battery. if gens are online, nothing is lost but the battery is NOT charging
74
what powers the emer bus when the battery is OFF and gens are online
the left load bus
75
what causes BATT CUT OFF
when battery is in EMER or the start bus loses power
76
EMER BUS FDR FAIL
the generator or battery power is not being fed thru the emergency bus feeder line
77
battery min voltage for start. what to turn on during battery start?
22 volts. the gens should be in norm
78
generator assisted start op limit
do not attempt to start the second engine until the gen load on the first engine is below 150 amps
79
with no normal power or a/c battery power, what powers the stby bus?
stby battery
80
BATTERY EMER - what powers stby battery
emergency bus
81
what powers the stby bus normally
the left load bus
82
diodes into the stby power from powering
prevents stby bus from powering left load bus prevents stby batt from powering the emer bus
83
what normally powers the emergency bus?
generators
84
battery feeder test fail
only stby aux buses. check for FDR fail, stby pwr ON, stby instruments, MFD, and RTU
85
battery feeder test, battery in EMER
depowers the aux bus. only emer and stby remains.
86
what to confirm on batt feeder test with batt in EMER
instrument flood flight, AC BUS SHED, BATT CUT OFF, RTU 1, INV 1 FAIL, landing gear lights, co pilot clock, stby instrument module on. MFD depowered
87
when does the stby pwr indicate ON
the stby battery is the only source powering the stby bus
88
single gen failure indicators
failed gen amps read 0. operating gen may read higher than normal. failed gen volts read 0, operating gen reads 28 volts
89
what do you lose with single gen failure
nothing, one gen can supply whole load
90
min power setting with a single generator
58% n2
91
amp allowance based on altitude
above 32.5 = 280 amps below 32.5 = 400 amps ground = 280 amps lower altitudes creates greater cooling airflow
92
amp and volts reading for dual gen failure
amps 0 for both gens. volts read 22-24 b/c a/c battery is powering the electrical system
93
what do you lose with dual gen failure
normal pitch trim, EFCs, fuel transfer. anti ice valves open and must use 70% n2
94
what is inoperative with dual gen failure
normal landing gear extension, flaps, speed brakes, anti skid. consider increased landing roll
95
with battery in EMER or OFF, what do you lose on touchdown.
everything on aux stby bus
96
BATTERY FDR FAIL (solo)
battery feeder protection circuit has lost power. check FDR PROT cb. not tripped/wont reset = land as soon as practical using generator power.
97
BATTERY FDR FAIL and EMER BUS FDR FAIL
left load bus is powering emer bus. losing the left load bus will result in the loss of the emergency bus.
98
BATTERY FDR FAIL and EMER BUS FDR FAIL and BATT CUT OFF
batt cut off means the battery relay is open. battery is not sharing and generators are supplying power. land as soon as practical.
99
BATTERY FDR FAIL and EMER BUS FDR FAIL and BATT CUT OFF. procedures
if battery is needed for flight; turn the battery OFF then ON. if the issues is not corrected, turn battery OFF and land as soon as practical
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