6 Electrical

Question 1

🟧 TR UNIT
FLT
GND

Answer 1

FLT: TR 1 failed OR TR2 + TR3
GND: any TR fail

Question 2

🟧 ELEC

Answer 2

fault in DC power system OR standby power system, ONLY ON GROUND

Question 3

BATTERY SWITCH
OFF
ON (guard)

Answer 3

OFF
- removes power from batt bus and switches hot batt bus when operating with normal power source available
- removes power from batt bus, switched hot batt bus, dc standby bus, static inverter and AC standby bus when batt is only power source

ON
- provides power to switched hot batt bus
- energizes relays to provide automatic switching of standby electrical system to battery power with loss of normal power

Question 4

🟧 DRIVE
illuminate when:
IDG disconnects when

Answer 4

IDG low oil pressure caused by: IDG failure, ENG shutdown, IDG disconnect through GEN DRIVE DISCONNECT SWITCH. HIGH OIL TEMP

electrical power available + ENG start lever at IDLE. Can NOT be reconnected in AIR

Question 5

🟧 STANDBY PWR OFF

Answer 5

when one or more are unpowered: AC STBY BUS, DC STBY BUS, battery bus

Question 6

AC STDBY BUS powered by
DC STDBY BUS powered by

Answer 6

Normal: AC transfer bus 1, loss of all AC power: by batt through Inv
Normal: TR1,2,3, loss of all AC power: by batt

Question 7

🟦 GEN OFF BUS
🟧 SOURCE OFF
🟧 TRANSFER BUS OFF

Answer 7

IDG not supplying power to related transfer bus

no source selected to power transfer bus OR source bus has been disconnected

related transfer bus not powered

Question 8

Generator switches

Answer 8

(dis)connects IDG to transfer bus by opening/closing Generator Circuit Breaker

disconnecting previous power source when gen switches switched On

Question 9

BUS transfer switch OFF

Answer 9

isolates transfer bus 1 from transfer bus 2, if IDG is delivering power to both AC transfer busses: BTB both open and cross bus tie relay opens and TR3 is to the right

Question 10

APU generator switch

Answer 10

powers related L or R transfer bus, the non-selected side will remain powered by ENG IDG

Disconnects previous power when selected ON

Question 11

Aircraft Primary Power
- parallel
- selecting new source
- divisions

Answer 11

2 ENG IDG 3 phase 115V 400 Cycle AC
P - NO paralleling of AC source of power
S - Selecting new source automatically disconnects existing source
D - AC power, DC power, STBY power

Question 12

AC power system
- powered from
- BTB in flight when IDG stops
- AUTOMATIC GEN ON feature

Answer 12

P - either external power or APU, not both powering separate busses. If IDG is selected on Gen 1/2, other bus will still be powered from apu/ext power.
B - BTB automatically closes when IDG delivery power stops
A - IDG automatically connects to transfer busses when APU shuts down/fails

Question 13

AUTOMATIC LOAD SHEDDING, with ONE generator
- priority
- config change
-manual restore

Answer 13

P - galley + main bus on transfer bus 2 sheds first, than from transfer bus 1. When overload still exists: IFE busses are shed
C - when more power available, auto restore
M -attempted by CAB/UTIL switch OFF than On

Question 14

AUTOMATIC LOAD SHEDDING APU
- IN FLT
- GND
- Manual restore

Answer 14

I - with APU only source of electrical power, all galley busses and main busses automatically shed. Not sufficient, IFE busses are shed
G - APU attempts to carry full load, still overload, APU shuts down galley busses + main busses until load within limits
M - CAB/UTIL OFF than On

Question 15

IDG
- lubricated and cooled
AC voltage and frequency meter for:
AC ammeter for:
DC Voltage and amperage
DC voltage

Answer 15

L - by self-contained oil system
A - STBY power, ground power, generator APU, GEN 1and 2 and static inverter
A - generator IDG’s 1/2 and APU
D - (aux) batt and each of three TR
D - STBY power and batt bus

Question 16

DC power

Answer 16

28V power supplied by 3 TR’s

Question 17

TR
- purpose
- transfer bus switch auto
- how many TR to carry full load

Answer 17

• converts 115AC to 28V DC
• TR3 powered by Transfer bus 2 and back up from transfer bus 1
• 2 tr carry full load

Question 18

Cross Bus tie relay
Opens automatically when:

Answer 18

• at GS capture during FD or A/P ILS approach, this isolates DC busses during approach to prevent a single failure from affecting both NAV receivers and flight control computers
• bus switch in OFF position

Question 19

Battery power
- Power
- Operation
- 2 batteries
- loss of both Generators, the battery powers:
- hot batt bus

Answer 19

P - Dual 24V nickel-cadmium batteries, main and auxiliary located in electronics compartment.
O - Aux batt operates in parallel with main batt, when batt is powering STBY system
2 - sufficient to power stby power for at least 60 min
L - batt bus, dc stby bus, hot batt bus, switched hot batt bus,
H - ALWAYS connected to the battery

Question 20

Primary batt charger

Answer 20

charges hot batt bus and switched hot batt bus. Also powers batt bus when TR3 fails

Question 21

AUX BATT

Answer 21

normally isolated from batt, but works parallel with it when main batt is powering stby system

Question 22

STBY power switch to off

Answer 22

de-energizes both AC and DC STBY bus, and switched hot batt bus.

Question 23

static inverter

Answer 23

converts 24V DC from batt to 115V AC power

Question 24

STBY power system V

Answer 24

24V