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