Chapter 6.50 - Electrical

Question 1

What does each AC power system consist of?

Answer 1

• One transfer bus
• One main bus
• Two galley busses
• One ground service bus

Question 2

What does the DC power system consist of?

Answer 2

• TR 1
• TR 2
• TR 3
• DC bus 1
• DC bus 2
• DC standby bus
• Battery bus

Question 3

What normally powers DC bus 1, DC bus 2, and the DC standby bus?

The battery bus?

Answer 3

TR 1 and TR 2 thru the cross bus tie relay

TR 3

Question 4

What is the backup power source for TR 1 and TR 2?

The battery bus?

Answer 4

TR 3

The battery

Question 5

What is the power source for the battery charger?

Answer 5

Single Battery
- AC ground service bus 2

Dual Battery

• AC ground service bus 2
• Auxiliary battery charger through AC ground service bus 1

Question 6

When will the DC cross tie bus relay automatically open?

Answer 6

• At glideslope capture during a flight director or autopilot approach
• Bus transfer switch positioned to OFF

Question 7

What is the primary power source for the AC standby bus?

DC standby bus?

What is the backup power source for the AC standby bus?

DC standby bus?

Answer 7

AC transfer bus 1

TR 1 and TR 2 , backed up by TR 3

The battery thru the static inverter

The battery

Question 8

When will the automatic transfer of the standby busses occur?

Answer 8

If power from either AC transfer bus 1 or DC bus 1 is lost

Question 9

What does the amber TR UNIT light indicate on the ground?

In flight?

Answer 9

Any TR has failed

TR 1 failed, or TR 2 and TR 3 failed

Question 10

What does the amber ELEC light indicate?

Answer 10

A fault exists in the DC or standby power system, operates only on the ground

Question 11

What causes an amber generator DRIVE light to illuminate?

What four reasons may cause this?

Answer 11

Low oil pressure

• IDG failure
• Engine shutdown
• IDG automatic disconnect due to high oil temperature
• IDG disconnected by disconnect switch