Term
| What are the main AC electrical power sources? |
|
Definition
Four IDGs
Two auxiliary power sources (APU generators) (except LCF)
Two external power sources |
|
|
Term
| How is DC power provided by the electrical system? |
|
Definition
Four transformer-rectifier units (TRUs)
APU and Main batteries |
|
|
Term
| If you lose an AC Bus, is the associated DC Bus still powered? |
|
Definition
| Yes, the DCIR remains closed and the DC Tie Bus powers the DC Bus |
|
|
Term
| What does the “AVAIL” light indicate on the EXT and APU PWR switches? |
|
Definition
APU or EXT power is plugged in and available
The power quality is acceptable |
|
|
Term
| Which bus is powered on the ground when APU 1 or EXT 1 is available? |
|
Definition
|
|
Term
| What are some of the equipment items powered by the Ground Handling Bus? |
|
Definition
Lower cargo handling equipment and compartment lights
Fueling system
Auxiliary hydraulic pump 4 |
|
|
Term
| When is the Main Deck Cargo Handling Bus powered? |
|
Definition
| When the “AVAIL” light is displayed on the APU 2 or EXT 2 switches. |
|
|
Term
| What electrical power source would you select if cargo handling is required? |
|
Definition
|
|
Term
| When is the Ground Service Bus powered? |
|
Definition
| When A/C bus 1 is powered, either on the ground or in flight |
|
|
Term
| How can the Ground Service Bus be powered when AC bus 1 is not powered, while on the ground? |
|
Definition
| By pushing the ground service switch at door L1, ground service is then connected to the same power source as the Ground Handling Bus |
|
|
Term
| What is the source of power to the battery chargers? |
|
Definition
|
|
Term
| What are some of the equipment items powered by the Ground Service Bus? |
|
Definition
Main and APU battery chargers
Fuel pumps for APU start
Flight deck flood, navigation, and service lights
Miscellaneous service outlets and equipment |
|
|
Term
| Which busses are powered with the Battery switch OFF? |
|
Definition
Main and APU Battery
Main and APU Hot Battery |
|
|
Term
| Which busses are powered with the Battery switch ON? |
|
Definition
Main and APU Battery
Main and APU Hot Battery
Main and APU Standby |
|
|
Term
| What is the function of the Standby Power Switch in the AUTO position? |
|
Definition
| Allows the Main and APU Stby busses to be powered from available sources |
|
|
Term
| How do you know if the Standby bus is powered? |
|
Definition
Captain's PFD, ND, FMS-CDU
Primary EICAS |
|
|
Term
| Describe the function of the Split System Breaker (SSB). |
|
Definition
| Divides the synchronous bus, allowing each side of the AC electrical system to be powered by separate auxiliary or external power sources |
|
|
Term
| Describe the electrical system sequence of events for starting engines 4 and 1 with two sources powering the sync bus. |
|
Definition
SSB is open
The IDG for engine 4 powers its side of the sync bus and disconnects previous power source
SSB remains open
When engine 1 is started, the previous power source is removed and the SSB closes |
|
|
Term
| Describe the electrical system sequence of events for starting engines 4 and 1 with a single power source powering the sync bus. |
|
Definition
SSB is closed
The IDG for engine 4 powers the sync bus and disconnects previous power source
When engine 1 is started, SSB remains closed |
|
|
Term
| Describe the electrical load shedding process. |
|
Definition
Utility busses are shed one at a time through ECLUs
They are restored in reverse order |
|
|
Term
| What are the indications that load shedding has occurred? |
|
Definition
EICAS messages for fuel pumps only
ELEC UTIL BUS and utility off lights are inhibited |
|
|
Term
| What are some of the equipment items powered by the Utility busses? |
|
Definition
Forward main pumps 2 and 3
Forward override/jettison pumps 2 and 3
Center override/jettison pump
Galley equipment (freighter) |
|
|
Term
| What happens when you push a Generator Drive Disconnect (DRIVE DISC) switch? |
|
Definition
Disconnects IDG from engine when above idle speed
Opens related Generator Control Breaker (GCB) |
|
|
Term
| What condition would automatically disconnect the IDG if not manually disconnected by the flight crew? |
|
Definition
| Excessively high drive oil temperature |
|
|
Term
| How do you know when an IDG has been disconnected? |
|
Definition
|
|
Term
| What does a Generator DRIVE light indicate? |
|
Definition
IDG oil pressure low, or
IDG oil temperature high, or
GCB open due to uncorrectable generator frequency fault |
|
|
Term
| What does a Bus Isolation (ISLN) light indicate? |
|
Definition
BTB open
AC bus isolated from sync bus |
|
|
Term
| What is the difference between a BTB opening automatically and pushing the BTB switch to off? |
|
Definition
Auto: disconnects AC bus from sync bus
Manual: disconnects AC bus from sync bus and opens DCIR |
|
|
Term
| What are the indications that an AC Bus is not powered? |
|
Definition
ELEC AC BUS
ISLN light in bus tie switch
OFF light in GCB |
|
|
Term
| What are the indications when there are OFF and ON lights in a GCB switch? |
|
Definition
| The GCB opened due to a fault |
|
|
Term
| What are the normal and backup power sources for the Captain and First Officer Xfer busses? |
|
Definition
Captain - AC Bus 3
First Officer - AC Bus 2
Backup - AC Bus 1 |
|
|
Term
| What is the normal power source for the Main and APU Batt busses? |
|
Definition
|
|
Term
| If either DC or AC Bus 3 is unpowered, how is each battery bus powered? |
|
Definition
|
|
Term
| How is each Hot Batt Bus normally powered? |
|
Definition
| Through its related battery charger which is powered by the Ground Service Bus |
|
|
Term
| What are the normal power sources for the Main and APU Stby busses? |
|
Definition
Main - AC Bus 3
APU - Captain Xfer Bus |
|
|
Term
| What items are powered by the APU Standby bus? |
|
Definition
|
|
Term
| How does the Main Stby Bus get power if AC Bus 3 becomes unpowered in flight? |
|
Definition
Through AC Bus 1
Route is AC Bus 1 - Ground Service Bus - Battery Charger - Hot Batt Bus - stby inverter - Stby Bus |
|
|
Term
| How does the APU Standby Bus get power if AC Bus 3 becomes unpowered in flight? |
|
Definition
| Bus is still powered through the Captain Xfer Bus, but the source is now AC Bus 1 |
|
|
Term
| If both AC bus 3 and AC bus 1 are not powered, how is the Main Standby Bus powered and for how long? |
|
Definition
30 minutes through the battery
Route is battery - Hot Batt Bus - stby inverter - Stby Bus |
|
|
Term
| If both AC bus 3 and AC bus 1 are not powered, how is the APU Standby Bus powered and for how long? |
|
Definition
30 minutes through the battery
Route is battery - Hot Batt Bus - stby inverter - Stby Bus |
|
|
Term
| How is the electrical system configured during an automatic ILS approach (autoland)? |
|
Definition
Below 1500' RA:
AC and DC Bus 1,2, and 3 are isolated from the sync bus
AC Bus 4 continues to power the synchronous bus |
|
|
Term
| Where are the P6 and P7 circuit breakers located? |
|
Definition
P6 - on right sidewall
P7 - aft of the overhead panel |
|
|
Term
| What items are powered in flight with a loss of all normal AC power (loss of all generators)? |
|
Definition
Left PFD, ND, FMC
Upper EICAS
Left VHF Comm
Left and right interphone panels
Captain's pitot heat
Dome light |
|
|
Term
| How is the trim system affected with a loss of all generators? |
|
Definition
Control wheel trim switches are inoperative
Alternate trim is available |
|
|
Term
| Can an ILS be flown with a loss of all generators? |
|
Definition
| Yes, but no flight director or autopilot |
|
|
Term
| Which flight control and landing gear systems are not available with a loss of all generators? |
|
Definition
Leading edge flaps cannot be extended (FLAP DRIVE msg)
Left trailing edge flap indication
Anti-skid
Auto-speedbrakes (manual okay)
Thrust reversers |
|
|
