Systems: Electrical & Lighting

Question 1

What are the main DC power sources?

Answer 1

Four independent engine-driven generators
1 APU starter-generator
2 NiCad batteries
1 lead-acid back up battery
external power receptacle

Question 2

What is the main AC power source?

Answer 2

single-phase AC inverter, which converts 28 volt DC power into 115 AC.

Question 3

What happens when the battery switches are turned to AUTO in a cold, dark airplane?

Answer 3

Battery contactors 1 and 2 close, and the Electrical Distribution Logic configures the system so that all busses except the shed busses are energized.

Question 4

Between the APU and GPU, which power source has priority?

Answer 4

Whenever the GPU is selected, it has priority. The GPU does not charge the batteries.

Question 5

In flight, when there are 4 or more generators online, how many electrical networks are operating?

Answer 5

2

Question 6

In flight, when there are 3 or less generators online, how many electrical networks are operating?

Answer 6

1

Shed buseses are de-energized

Question 7

In flight, whenever no generators are online, what electrical busses are available and what is their power source?

Answer 7

Batteries supply power to the essential and hot busses for for 30 minutes (including 3 APU start attempts).

Question 8

On the ground, all DC busses are are energized if at least one of the following conditions occurs (3)?

Answer 8

1. At least 3 generators are online
2. The GPU is powering the aircraft
3. At least 1 generator is on-line and the shed bus is set the OVRD

Question 9

What are the limits for each generator?

Answer 9

400 amps

Question 10

Which networks can the APU power in flight?

Answer 10

APU can power the entire electrical system in flight EXCEPT for the shed busses

Question 11

On the ground, what electrical networks can the APU power?

Answer 11

APU can power the entire electrical system on the ground if shed bus switch is in OVRD

Question 12

Can the batteries be charged by the GPU? APU?

Answer 12

GPU does not charge the batteries

APU does charge the batteries

Question 13

Which battery starts the APU?

Answer 13

Battery 2

Note: battery 1 contact opens

Question 14

How long can the aircraft batteries provide back up power for the electrical system IN FLIGHT?

Answer 14

40 minutes

ISIS has 240 minutes

Question 15

How long can the aircraft batteries provide back up power for the electrical system ON THE GROUND?

Answer 15

10-15 minutes

It is absolutely essential to connect a GPU or start the APU

Question 16

When do the engine-driven generators come online?

Answer 16

Roughly 56.4% N2 (with generator push-buttons selected)

Question 17

Where can all generator info be found?

Answer 17

MFD electrical panel

Question 18

What items are in the hot bus?

Answer 18

Engine Fire handle (shuts 4)
Fueling panel
APU FADEC
ISIS
ELT
Courtesy lights

Question 19

What is the purpose of the OVRD function of the Shed bus switch?

Answer 19

To allow the shed busses to be energized when less than 3 generators are online (on the ground).

Question 20

If a bus fault occurs, what will happen?

Answer 20

If a bus failure produces an over current, the GCU isolates the system networks by opening the bus tie contractors.

Question 21

How does the APU provide power for the electrical system?

Answer 21

On the ground. APU can provide for entire electrical system in OVRD. In flight, APU can replace one generator.

Question 22

What do inverters do?

Answer 22

Convert DC to AC

Question 23

What systems do the inverters power?

Answer 23

TCAS
GPWS
Windshear