Electrical

Question 1

How is AC power normally produced?

Answer 1

By engine driven Integrated Drive Generators (IDG) and/or APU generator.

Question 2

How many TRUs convert AC to DC power?

Answer 2

Five (5)

Question 3

What’s the purpose of emergency batteries?

Answer 3

They power emergency avionics and emergency egress lighting.

Question 4

What’s the difference between red and black circuit breakers?

Answer 4

Red CBs are related to essential circuits and black CBs are considered non-essential.

Question 5

What’s the purpose of GCUs?

Answer 5

They work with electrical system to provide quality power.

Question 6

How can GCU be reset?

Answer 6

By cycling associated generator control switch (L GEN, R GEN or APU GEN) to OFF and then ON>

Question 7

True/False: All non-failure AC power transfers are NBPTs, except between external AC power and APU power sources.

Answer 7

True

Question 8

How is electrical power normally controlled?

Answer 8

By two (2) BPCUs, three (3) GCUs and two (2) ESCs
Electrical System Controllers BPCU are brains of system and control most contractors.

Question 9

Describe emergency batteries.

Answer 9

Two(2) lead acid emergency batteries: one located up forward in LEER and one located back aft on left side of baggage compartment in Forward BEER.

Question 10

What are the three modes of emergency batteries?

Answer 10

Like main batteries, they have three (3) modes of operation: charge, discharge, and TR mode.

Question 11

How are emergency batteries activated?

Answer 11

ON switch is depressed or they’re ARMED and left or right essential DC bus drops below 20 VDC (even momentarily).

Question 12

What items are powered down to emergency batteries?

Answer 12

Both SFDs without air data TSCs 2 & 3 Back up Eng/Rad Emergency lighting.

Question 13

When would MAIN BATTERY switches indicate amber ON?

Answer 13

When starting APU (left battery discharge only), operating aux pump, or powering ESS DC buses if MAIN BATTERY switches are selected ON and ESS DC buses have no other source of power.

Question 14

What additional function does right battery have on ground?

Answer 14

It’s used to power ground service bus when not powered by right main DC bus or external DC power.

Question 15

What are main battery charging requirements?

Answer 15

AC power applied.

Question 16

When is TR mode intitiated?

Answer 16

If battery switches are selected ON, main AC buses are powered, and the following occur - APU start switch is selected ON, aux pump is turned on, or essential DC buses require power from batteries.

Question 17

What mode of battery/charges is lost with loss of Main AC buses?

Answer 17

TR and charge mode.

Question 18

The batteries have split bus configuration. What does that mean?

Answer 18

Left battery is involved in APU start; both batteries power aux pump.

Question 19

When should you remove batteries?

Answer 19

Cold soak conditions (-20 degrees Celsius).

Question 20

On dark airplane, what occurs when EXTERNAL BATTERY switch is selected ON?

Answer 20

Power is provided from both main batteries and anti-collision beacon illuminates.

Question 21

What’s the purpose of ground service bus (GSB)?

Answer 21

To provide DC power to equipment required for minimal servicing while on ground.

Question 22

What are the sources of power for ground service bus?

Answer 22

Right main DC bus, external DC, or right battery.

Question 23

Name the locations of four (4) GSB control switches.

Answer 23

One behind cockpit on REER System/Monitor Test panel, one in Security/Gnd Svc panel, one on ground service panel in tail compartment, and one in refuel panel.

Question 24

What happens on dark airplane when GND SVC BUS switch is selected to ON?

Answer 24

Right battery powers ground service bus and anti-collision beacon illuminates.

Question 25

There are four (4) GND SVC Bus annunciator lights: one in cockpit, one in Security/GND SVC panel, one in refuel panel, and one on ground service panel in tail compartment. When do they illuminate?

Answer 25

When GND SVC BUS is powered by right battery or by external DC power (i.e., other than normal source of power).

Question 26

When is ground service bus automatically deactivated?

Answer 26

When all doors are closed: tail compartment door, main door, Security/Gnd Sc panel door, and refuel door.

Question 27

What’s the function of EBHA battery?

Answer 27

It’s dedicated source of power of Electric Backup Hydraulic Actuators (EBHAs).

Question 28

What’s the purpose of UPS battery?

Answer 28

It’s dedicated source of power to flight control computers.

Question 29

If both AC and DC external power is connected, which has priority?

Answer 29

AC

Question 30

Describe APU generator.

Answer 30

It’s mounted on APU, is usable on ground or in flight. It’s physically and distinctly different from IDGs but produces same type of power up to 35,000’.

Question 31

What’s the source of power for personal electronic devices, electric razors, hair dryers, blender, toaster, etc.?

Answer 31

60 Hz power system compromised of two converters. One converter is active while other is standby.

Question 32

True/False: CABIN/GALLEY and 60 Hz Master switches are wired in series (i.e., both must be selected ON for converters to produce power).

Answer 32

True. CABIN/GALLEY Master switch also controls 28 VDC to cabin. It’s single switch for load shedding all power to cabin.

Question 33

What’s the purpose of Secondary Power Distribution System (SPDS)?

Answer 33

It takes power from primary power system and distributes it to various aircraft loads.

Question 34

SPDS is composed of two Electrical System Controllers (ESCs) and 14 Modular Power Tiles (MPTs) (4 for AC and 10 for DC). What’s the difference between ESCs and MPTs?

Answer 34

ESCs perform system control functions and interface with other aircraft systems. MPTs perform power routing and circuit protection functions using AC and DC Solid State Power Controllers (SSPCs).

Question 35

What causes “AC” or “DC” legend of AC/DC RESET switchlight to activate?

Answer 35

Fault in AC or DC bus, logic fault within BPCU, or relay or component failure.

Question 36

What happens when you depress
RESET switch?

Answer 36

It resets lockout and allows tripped
contactors to close if fault no longer exists

Question 37

When would you select L/R Bus Tie
to ISLN?

Answer 37

When directed by checklist. It prevents associated contactors from closing and isolates respective main AC bus from
other power sources.

Question 38

Describe RAT deployment.

Answer 38

It’s totally manual and is accomplished by
pulling guarded RAT DEPLOY handle.

Question 39

What does RAT power once it reaches operating speed (usually 5-8 seconds)?

Answer 39

FCC UPS bus and EBHA bus through Emerg AC bus, and both Essential DC buses through Left and Right ESS TRUs

Question 40

How is RAT stowed?

Answer 40

On ground using installed hand-operated
piston pump mounted above RAT
assembly: it cannot be stowed in flight.

Question 41

What happens as airspeed falls below
limit of RAT operation (200 knots)?

Answer 41

RAT stops operating and Main, UPS and
EBHA batteries begin to power flight
critical systems for up to 10 minutes.

Question 42

When is AUX DC bus load shed or
not powered?

Answer 42

During single generator operation, RAT
generator operation, battery only
operation, or when Aux TRU is powering
another DC bus. Load shed feature is
inhibited on ground.

Question 43

Describe purpose of fifth or Aux
TRU.

Answer 43

It serves as backup to primary TRUs.
When not serving in backup role, Aux
TRU powers Aux DC bus which provides
28 VDC power to cabin loads.

Question 44

What’s Aux TRU priority?

Answer 44

Essential before main and left before right