Electrical Flashcards
During takeoff, if the right engine generator fails, what happens to the utility and galley power?
Both utility and galley buses will be shed
Where is the ground service switch used to power the ground service bus located?
Forward cabin flight attendant panel
In flight, the left engine is shut down. What electrically powered items are lost?
Both utility buses, the left center fuel boost pump, both recirc fans, and the C2 hydraulic pump
The AVAIL light on the external power switch is an indication of what?
The external power cart is plugged in and the volts and frequency are within limits
What is accomplished by pushing the AC Bus Tie Switch to AUTO?
Arms the automatic operation of the Bus Tie Breaker
What causes the Standby Power Bus OFF light to illuminate?
Loss of the Standby AC or DC bus or STBY power switch is in the OFF position
What normally powers the Battery Bus during cruise?
Left DC bus
Inflight the left generator trips off. What electrical buses are lost?
The two UTILITY buses and the galley buses.
Which bus is powered automatically when external power is plugged in?
The ground handling bus
What automatically has the highest priority on the left main AC bus?
Left engine driven generator
With external power available and the APU supplying both electrical and pneumatic power, what happens as the first engine is started?
Both utility buses trip off
What electrical bus powers the discharge squibs for the fire extinguisher bottles?
The hot battery bus
What bus powers most of the fire detection systems?
Battery bus
What is an integrated drive generator (IDG)?
Generator and CSD (Constant Speed Drive) in one casing using the same oil
Which has priority in supplying the ground handling bus?
External power
What is required to enable the Captain’s flight instrument transfer bus to transfer with the loss of the left main AC?
Both the left and right Bus Tie Switches must be in AUTO
When can the ground handling bus be powered?
Only on the ground
When will the utility buses be shed during an engine start?
Only when the APU is supplying electrical and pneumatic power
With the APU supplying both electrical and pneumatic power, what happens as the second engine is started?
Only the utility bus for the engine being started trips off
During triple channel approach, the left generator is lost at 140’ RA. As a result, the left main AC bus is lost. True/False?
True
What action would cause the engine generators to trip off?
Pushing the External Power switch ON
With the APU supplying electrical power, what happens when the first engine starts (reaches idle RPM)?
The engine driven generator powers its respective main AC bus only
With the Generator Control switch ON, what automatically closes when the engine starts?
Generator breaker only
Which has priority in supplying the ground handling bus: the APU or External Power?
External power
When will the APU Generator Control OFF light illuminate?
When the APU generator breaker opens due to a fault
The left main DC bus can power the battery bus with the battery switch off. True/False?
True
What normally powers the battery bus during cruise?
The left main DC bus
What is powering the standby buses?
Left main AC and left main DC
The APU can be used to power the left main AC bus while the right engine generator is powering the right main AC bus. True/False?
True
To what bus is the utility bus connected, when the Utility Bus switch is ON?
Respective main AC bus
What is accomplished by pushing the AC Bus Tie switches to AUTO?
Arms the automatic operation of the AC and DC bus tie system
With the Bus Tie switch in AUTO, what causes the AC Bus ISLN light to illuminate?
Bus fault has occurred
Pushing a Generator Control switch off opens both the field and generator breakers. True/False?
True
Pushing the Generator Control switch off and then on resets the fault trip circuitry. True/False?
True
What does the run light on the APU panel indicate?
That the APU is at operating speed
Will the Generator Control Breaker close automatically when the voltage and frequency of the respective IDG are within limits?
Yes
What has occurred if during flight, an OFF light illuminates and the “on” indicator is visible in the generator control switch?
A fault has occurred and the generator control circuit breaker has automatically opened
What can cause the DRIVE light of the GEN DRIVE DISC switch to illuminate?
The generator drive disconnect switch is pressed, High oil temp, Low oil pressure
How many electrical buses are there in the Standby Power System?
4
How is the hot battery bus normally powered?
Right main AC bus through the ground service bus and the main battery
The battery bus is normally powered by the…?
Left DC bus
What is the backup source of power for the battery bus if the normal source is not available?
The main battery
The left main DC bus can charge the battery bus with the battery switch in the OFF position. True/False?
True
The standby AC bus is normally powered by the…?
Left main AC bus
The standby DC is normally powered by the…?
Left main DC bus
With a loss of main AC and DC power, what provides electrical power to the standby AC and DC buses?
The main battery
An amber standby bus off light illuminates and the EICAS message Standby Bus Off displays when?
Either standby AC or DC bus is unpowered
What is the priority of power supply to the main AC buses?
Respective engine-driven generator, APU generator, opposite engine-driven generator
What does an ISLN light mean in the bus tie switch?
The switch is off or a fault has occurred
The AC bus tie switch must be on for the DC bus tie breaker to operate. True/False?
True
The ground handling bus can only be powered on the ground by?
APU or external power
Both batteries (main and APU) receive power directly from which source?
Ground service bus
What is the alternate source of power for STBY AC?
Battery bus (through and inverter)
When the utility bus switch is “on”, the utility bus is connected to the…?
Respective main AC bus
The HDG is supplied from which hydraulic system?
Center
Which condition is not an example of load shedding?
Left or right AC bus load shedding
When will the utility bus shed during an engine start?
Only when the APU is supplying electrical and pneumatic power
With the Standby Power Selector in the BAT (Battery) position…
The main battery and standby inverter powers the standby AC bus
Which electrical power sources can provide for the Lower Cargo Doors, Main Cargo Door, and Fueling Panel?
External power (AVAIL or ON) or APU generator
What happens when you push a Generator Drive Disconnect (DRIVE DISC) switch?
Disconnects IDG from engine when above idle speed and opens related Generator Control Breaker
