Chapter 6 - Electrical Flashcards
What do the APU GEN and GEN CONT switches do ?
They ARM to close the breaker when power is available.
When do the APU GEN and GEN CONT OFF light illuminate ?
Whenever the breaker is open (because power is not available).
What does the BUS TIE switch do ?
It arms:
- The AC bus tie
- The DC bus tie
- The respective flight instrument transfer bus
When does the bus tie ISLN light illuminate ?
When the AC bus tie breaker is open.
Not in case of the DC bus tie.
How can the load shed circuitry be reset ?
By recycling the UTILITY BUS switch.
When does the generator DRIVE light illuminate ?
When the oil pressure is low OR oil temperature is high.
Can a generator disconnect be reset in-flight ?
No.
When does the standby power OFF light illuminates ?
When the AC or DC standby bus or the battery bus is not powered.
When does the battery OFF light illuminate ?
When the battery switch is off.
Can one AC source power the whole electrical load ?
No. Two sources are required for the full load.
If APU is running and external power is connected, is the APU powering the main busses ?
No.
What is priority of AC power sources ?
- Ground power
- IDG
- APU
- Opposite IDG
Are there any indications or EICAS messages for a galley bus which is not powered.
No. Only when the utility bus is not powered as well.
Which bus powers the GND SVC bus ?
R MAIN AC BUS.
How is the GND HANDLING bus powered ?
From the APU GEN or from external power.
What happens above 200 ft in case of loss of a generator during an autoland ?
> 200ft, the bus ties close again. The L main AC system powers the center autopilot. NO LAND 3 is shown.
During autoland, how is the center autopilot powered ?
By the standby power system.
What happens with the AC bus ties during autoland ?
They open.
How are the flight instruments powered in case of loss of both generators ?
By the HDG.
Are the transfer busses powered in case of loss of both generators ?
Yes, by the HDG.
What is the order of AC load shedding ?
- Galley bus
- Utility bus
- Main AC items
Is load shedding automatically reverted ?
Yes.
Before engine start, two load sheddings may occur:
- one electric hydraulic pump
- center tank fuel pumps
During engine start, one load shedding may occur:
Utility busses
What happens on the ground, when the engines are shut down, and the thrust levers are advanced ?
It may cause inadvertent load shedding of the utility busses. Solution: return the thrust levers to idle, and recyle the UTILITY BUS switches.
Is the DC bus tie armed when only one BUS TIE switch is in auto ?
No.
The standby power system consists of:
battery bus
hot battery bus
AC standby bus
DC standby bus
How is the battery bus powered ?
By the L DC bus or the main battery.
How is the DC standby bus powered ?
By the L DC bus or by a combination of:
- the main battery AND APU battery.
How is the AC standby bus powered ?
By the L AC TRANSFER BUS or by a combination of:
- the main battery AND APU battery + inverter
When is the HDG activated ?
When the L AND the R MAIN AC bus are not powered.
Is the amount of power of the HDG more than that of full batteries ? What is the consequence ?
No. Consequence is that initially BAT DISCH for both batteries may occur.
What busses are lost in case of a failure of L AC main bus ?
L AC transfer bus
L utility bus
L galley bus
