1.6 Electrical System

Question 1

How many generators are there? What are their DC voltage?

Answer 1

• 2 generators

- 28V DC

Question 2

What operates as a combined starter-generator?

Answer 2

GEN 1

Question 3

Can each generator alone capable of supplying full electrical load?

Answer 3

Yes

Question 4

How many batteries are there in the aircraft and where do they supply power to?

Answer 4

• BATT 1 supplies power to BATT BUS and starter
• BATT 2 supplies power to BATT BUS and BATT DIRECT BUS
• Emergency Bus supplies power to EMERGENCY BUS

Question 5

Where are the two generators located? What is their voltage and amperage?

Answer 5

• Both are on the engine accessory gearbox

- 28V DC, 300A

Question 6

What bus does GEN 1 power?

Answer 6

GEN 1 BUS

Question 7

What bus does GEN 2 power?

Answer 7

GEN 2 BUS

Question 8

What do the generator control units do?

Answer 8

1) Maintain factory set voltage at 28.5 V DC
2) Protects from overvoltage/undervoltage
3) Overload
4) Reverse polarity and reverse current.

Question 9

If either generator fails, what supplies power to the rest of the aircraft?

Answer 9

The other generator.

Question 10

How are the batteries powered?

Answer 10

1) By aircraft generated power

2) When connected from ground power

Question 11

How long do the main batteries supply electrical power to services essential for flight? What does this assume?

Answer 11

30 minutes

• Fully charged
• Current load is less than 60A

Question 12

How long can emergency battery supply power to SFD?

Answer 12

30 minutes

Question 13

Where is BATT 1 installed?

Answer 13

Engine compartment.

Question 14

What is BATT 1 used for apart from supplying power to BATT BUS?

Answer 14

To power the starter on engine start

Question 15

Where is BATT 2 located and what does it power?

Answer 15

• Located in avionics bay

- Power BATT BUS and BATT DIRECT BUS

Question 16

Where is the emergency battery located?

Answer 16

In avionics bay

Question 17

What monitors the polarity and voltage of the supplied external power?

Answer 17

External Power Monitor

Question 18

What does the EPM monitor for?

Answer 18

• Incorrect polarity

- Voltage not between 24 V and 30 V

Question 19

In normal operation, what powers the BATT BUS and GEN 1 BUS?

Answer 19

GEN 1

Question 20

In normal operation, what powers the GEN 2 BUS?

Answer 20

GEN 2

Question 21

What supplies power to the MISSION BUS?

Answer 21

The BATT BUS

Question 22

What services are powered by the MISSION BUS?

Answer 22

• MC
• UFCP
• RMFD
• PMM CB

Question 23

What services does the Emergency Bus power through the emergency battery?

Answer 23

• SFD
• ADU
• MHS
• Inertial Separator System (Intake Bypass)

Question 24

What does the Reset button do on electrical control panel? How many times should this be attempted?

Answer 24

• Resets a GCU if it has been tripped

- Should only be attempted once

Question 25

What does the BTC switch do?

Answer 25

• It allows the pilot to isolate the BATT BUS, GEN 1 BUS and GEN 2 BUS from each other which allows the BATT BUS to be de-energized
• This allows services from GEN 1 and GEN 2 BUS to be retained.

Question 26

What do Red, Amber, Green, and Grey mean on the electrical system page?

Answer 26

Red (warning) = Equipment off line and some system function missing
Amber (caution)= Equipment off-line but no system function missing
Green (correct) = Equipment online
Grey = Electrical connection not active

Question 27

What are the current and voltage bands for the GPU?

Answer 27

0 –> 300 A

24 –> 30 V

Question 28

What electrical system information is shown on the bottom right of the EMD?

Answer 28

• BATT BUS voltage

- Sum of two battery currents