Electrical Flashcards
What is the secondary power source for the Main Standby bus?
Main standby inverter
During autoland below 1500’, automatic isolation of which buses occurs?
AC and DC buses 1, 2, 3
What is the secondary power source for the FO transfer bus?
AC Bus 1
What does the main deck cargo handling bus power?
Nose and side cargo doors
When is the main deck cargo handling bus powered?
APU Gen 2 or Ext PWR 2 is AVAIL
What does the ground service bus powers?
- Flight deck flood,
- Nav and service lights,
and - Battery chargers
If AC bus 1 is unpowered on the ground how can the Ground Service Bus be powered?
GND SERVICE switch at Door 1L
How is the Ground Service Bus normally powered?
AC bus 1
What does the Ground Handling Bus power?
- Lower lobe cargo handling equipment and lights;
and - AUX hydraulic pump 4 (and 1 if installed).
When is the Ground Handling Bus powered?
When APU GEN 1 or EXT PWR 1 is avail or ON
How is the Main Standby Bus normally powered?
AC Bus 3
What is the secondary power source for the Captain Transfer Bus?
AC Bus 1
How is the FO transfer bus normally powered
AC Bus 2
What does the Main Standby Bus power?
Left:
1) EIU,
2) CDU,
3) ILS,
4) VOR,
5) ADC,
6) Transponder,
7) EFIS panel.
The Split System Breaker opens and divides the synchronous bus allowing what to happen?
Separate APU or EXT sources to power each side
Which bus powers fire detection for the APU and engines?
APU Battery Bus
What buses isolate when a BTB is manually selected to ISLN?
The associated AC and DC buses
The synchronous bus allows how many IDGs to be connected at the same time?
4
What is the purpose of the sync bus?
To prevent an AC bus from becoming unpowered, if its respective generator fails.
How does each AC bus connect to the synchronous bus?
BTB
Which sources of power may be connected to the synchronous bus at the same time
All four IDGs
When will the generator DRIVE light illuminate? and when would an IDG automatically disconnect?
IDG oil temp high
What are the main sources of AC power?
- 4 IDGs,
- 2 APU genrt,
- 2 Ext Pwr srcs.
How is the Captain Transfer bus normally powered?
AC bus 3
The FO Transfer bus is normally powered by which AC bus?
AC bus 2
What conditions would cause the generator DRIVE light to illuminate in the Generator Drive Disconnect (DRIVE DISC) switch (accompanied by the EICAS message ELEC DRIVE) provide the engine is operating?
- GCB open due to uncontrollable generator frequency fault;
and - IDG oil temperature high.
Which bus provides power for all fire extinguishing
Main hot battery bus
The main and APU battery busses are normally powered by which DC bus?
DC bus 3
If an AC bus is unpowered or TRU fails, what powers the respective DC bus?
DC tie bus
The APU standby bus powers which equipment items?
Left FMC, ND, PFD
With the battery switch ON, Standby power selector OFF and no other electrical sources are connected or available, which buses are powered?
Main and APU battery and hot battery buses
With the Battery switch ON, standby power selector in AUTO and the Captain Transfer Bus not powered, what is the power source for the APU standby bus?
APU Standby inverter
What is the normal power source for the APU standby bus?
Captain Transfer bus
The main standby bus is normally powered by which AC bus?
AC bus 3
Assume the aircraft dispatches with AC gen 2 inoperative. During automatic ILS approach once below 1500’ AGL and LAND 3 is displayed on the AFDS which AC bus would power the sync bus?
AC bus 4
The main deck cargo handling bus is powered on the ground only when what conditions are met?
When APU GEN 2 or EXT PWR 2 is AVAIL
How is the APU Standby bus normally powered?
Captain transfer bus
If both AC bus 1 and 3 are unpowered what is the power source for the Captain Transfer bus?
The bus will be unpowered
If AC bus 3 is unpowered, which AC bus would then power the Captain transfer bus?
AC bus 1
The Captain tranfer bus is normally powered by which AC bus?
AC bus 3
On the ground, with only External PWR 1 AVAIL light illuminated (AC Bus 1 unpowered), how can the ground service bus be powered?
Through the ground service switch (cabin panel door 1L)
The ground service bus is powered on the ground and in flight whenever which AC bus is powered?
AC bus 1
With external power connected to each side of the electrical system (SSB open), when engine 4 and 3 are started, what is the configuration of the SSB?
OPEN
What condition would disconnect the IDG automatically if not manually disconnected by the flight crew?
Excessive oil temperature
How is each DC bus normally powered?
Its respective AC bus through its TRU
The APU and Main batteries will provide Standby power for how long?
Minimum of 30 minutes
Which bus powers fire protection for the APU and all engines?
Main hot battery bus
What is the secondary power source for the APU standby bus?
APU standby inverter
During automatic ILS approach, once below 1500’ AGL and LAND 3 is displayed on the AFDS which AC bus powers the sync bus
AC bus 4
What are the main sources of DC electrical power?
Four TRU’s, main battery and APU battery
