Section V - Electrical - Communications

Question 1

When does the Cockpit Voice Recorder system (CVR) automatically operate?

Answer 1

Anytime AC power is applied to the airplane.

Question 2

How many VHF radios are installed?

Answer 2

3 independent VHF radios are installed, designated:
VHF L , VHF C and VHF R.

Question 3

With respect to the Audio Control Panel, how could one switch the microphone source from the boom microphone to the oxygen mask?

Answer 3

By selecting the BOOM/OXY switch to the OXY setting

Question 4

What are sources of AC electrical power that can be utilized?

Answer 4

1. Left and Right IDGs
2. APU generator
3. External Power
4. Hydraulic Driven Generator (-300ER)

Question 5

What is the primary purpose of the Bus Tie System?

Answer 5

1. Prevents paralleling of systems
2. Isolates faults
3. Operates automatically to maintain power to both buses.

Question 6

What is the source order for powering the left and right main buses?

Answer 6

a. Respective IDG
b. APU generator
c. Opposite IDG

Question 7

What is the power source for the Ground Service Bus?

Answer 7

1. The right main AC bus.

Alternate sources of power are:
APU generator and external power.

Question 8

-What items are powered by the Ground Service Bus?

Answer 8

1. The main battery charger
2. APU battery charger
3. Miscellaneous cabin and system loads.

Question 9

When is the Ground Handling Bus powered?
Can it be powered in the air?

Answer 9

1. Powered from an APU GEN or
2. External power source (only needs to be plugged in).
3. It can only be powered on the ground

Cargo compartment systems
lights,maintenance access light and fueling systems

Question 10

With respect to external power, what does the AVAIL light on the switch indicate when illuminated?

Answer 10

It means that the voltage and frequency are within limits to select external power.

Question 11

During Autoland operations, what is the power source for the center autopilot?

Answer 11

The BATTERY powers the CENTER autopilot.

*During Autoland, the buses isolate to allow three independent sources to power the autopilots.

Question 12

When a generator is lost above 200 feet RA during Autoland operations, what actions occur?

Answer 12

Both bus tie breakers close and the operating generator powers both left and right AC BUSES.

The left main AC system powers the autopilot.

NO LAND 3 appears on the Autoland Status Annunciator.

Question 13

What is the power source for the Captain’s flight instrument transfer bus in the event of a Left + Right AC bus failure?

Answer 13

Hydraulic Driven Generator

Question 14

What buses are powered when the battery switch is selected ON prior to establishing APU or external electrical power (STBY power selector off)?

Answer 14

The BATTERY bus and HOT BATTERY bus

Question 15

What would cause the BUS OFF light to illuminate on the AC panel?

Answer 15

If an AC bus is unpowered.

Question 16

What are examples of automatic load shedding during normal / non normal operations?

Answer 16

a. Normal:
1. An Electric HYD Pump during engine start
2. Center tank fuel pumps prior to engine start

b. Non-Normal:
1. Utility buses after a generator failure
2. Center tank fuel pump after an engine failure
3. Thrust lever(s) advanced on the ground with engine(s) shutdown may cause inadvertent load shedding of the utility buses

Question 17

What items are powered by the hot battery bus?

Answer 17

1. Fire Protection (extinguisher bottles)
2. Captain’s clock
3. APU fuel valve
4. Spar fuel valves
5. Parking brake valve
6. IRS EMER Power
7. ALternate Gear Extension

Question 18

What busses are part of the Battery / Standby Power System?

Answer 18

a. Hot Battery Bus
b. Battery Bus
c. Standby AC bus
d. Standby DC bus

Question 19

What is the power source for the hot battery bus prior and after a AC power source has been established?

Answer 19

Prior to establishing electrical power:
The Main BATTERY.
After establishing electrical power:
The main battery CHARGER.

Question 20

What buses are powered by the Hydraulic Driven Generator when both the left and right main AC buses are unpowered?

Answer 20

Battery BUS
Hot battery BUS

2 Standby’s:
Standby DC
Standby AC

3 Transfers:
LEFT AC transfer
RIGHT AC transfer
Captains flight instrument transfer bus

Question 21

Why would the battery DISCH light stay illuminated when the HDG is powering the electrical system?

Answer 21

The amount of DC power produced by the HDG is less than the DC power produced by a fully charged battery. When the HDG first begins to operate, the battery DISCH light may illuminate, until the battery power decreases to the power level produced by the HDG.

Question 22

What would cause the DRIVE light to illuminate on a GEN DRIVE disc switch?

Answer 22

HOT LOP

The generator drive oil temperature is HIGH or the generator drive oil pressure
Is LOW

Question 23

What items are on the hot battery bus ?

Answer 23

1. Alternate LDG GEAR EXT
2. APU Fuel Shutoff Valve
3. Clock Time Base
4. Equipment Cooling GND Warning and AUTO test
5. Fire EXT Bottles
6. Fueling Systems
7. Parking Brake Valve
8. RAT Manual Deployment
9. Wing Spar Fuel Shutoff Valves

Question 24

If you have engines running and you select BAT on the STBY POWER switch what would happen in the system ?

Answer 24

The standby AC and standby DC would not longer be powered by the main AC Busses and only powered by the battery bus and inverter for the standby ac bus.

Note : The BAT switch position is only used on the ground to perform a standby power test.

Question 25

If all generators fail and the HDG is not operating what will power the plane and for how long ?

Answer 25

The main battery can provide 30 minutes of power for the standby power system

Question 26

What items are on the battery bus?

Answer 26

Fuel pump
Fuel valves
Fire detection

Question 27

What are some items you could lose if the Battery Bus is unpowered ?

Answer 27

Speedbrakes and AUTOBRAKES