Electrical Flashcards
What provides normal AC power?
IDGs
What connects the Main AC buses ?
2 Synchronous buses
What are the auxiliry sources of AC power?
2 APU generators
2 EXT power connections
How is AC converted to DC?
Transformer Recifiers
When on the ground, auxiliary AC power can be provided by ________.
2 APU generators or
2 EXT power connections
T/F: Both AC and DC Power Flow are displayed on the Electrical Synoptic Display.
False
What is the normal position of the Split System Breaker?
Closed and the AC buses are interconnected
How is IDG oil cooled?
By Engine fuel flow and fan bypass air
What do the IDG DRICE DISC switch fo?
Disconnect the IDG from the engine, must be reset on the ground
When will the split system breaker be open?
When two aux sources on the ground are powering the system
A fault is detected
When is uninterrupted power transfer availible?
On the ground only
What does turning a IDG GEN CONT switch to OFF do?
Opens the associated Generator Control Breaker.
When can IDG disconnect be preformed?
With the engine running above idle speed
What does a IDG DRIVE light indicate?
IDG Oil Pressure
IDG Oil Temperature
When will an automatic IDG disconnect occur?
With engine running and excessive oil temperature detected.
What connects the auxiliary power to the main AC busses?
The synchronous bus
What power Main Deck Cargo Handling Bus?
Number 2 Auxiliary Power Source
There are ______ IDGs, _____ APU generator(s), and _____ external power source(s) that supply AC power to the B747-400.
4,2,2
T/F: Disconnecting an IDG is an irrevocable action that can only be reset on the ground.
True
External Power and an APU generator cannot both be connected to the same side of the synchronous bus simultaneously. What divides the synchronous bus and allows each side to be powered by two different auxiliary sources?
Split System Breaker (SSB)
How many IDGs are required to power the electrical system?
1
What is the purpose of the ground handling bus?
Power items without the need of flight deck activation.
How is the ground handling bus powered?
When any auxiliary power is available
How is the main deck cargo handling bus powered?
Any auxiliary power 2
APU 2 or EXT 2 only if they are NOT ON
What powers the ground service bus?
AC bus 1
If the ground handling bus is powered, how can the ground service bus be used?
By pressing the GND service switch by door L1
What are the Captain/FO transfer bus power?
Critical flight equipment
What is the ELCU?
Electrical Load Control Unit, protects electrical system from utility load faults and load management by auto load shedding.
Each IDG normally powers its related AC bus through a _________.
Generator Control Breaker (GCB)
T/F: The Ground Handling Bus is never available during flight.
True
The Captain’s Transfer Bus is normally powered by ________.
AC Bus 3
If the Left Utility Power switch is ON, which utility busses are powered?
Utility Bus 1 and Utility Bus 2
What is a DCIR?
DC Isolation Relay, provides an interconnection between all DC busses
What powers the MAIN BATT BUS and APU BATT BUS?
DC BUS 3 or the respective HOT Battery BUS
How can the battery busses receive power from the HOT battery busses?
Battery must be ON and AC Bus 3 unpowered
Where is battery information displayed?
Status page
What is on the MAIN Hot Battery Bus?
-APU Fuel SOV, Spar Valves all engines
-APU and Lower cargo fire extinguishers
-Engine fire extinguishers
-Fire Switch Unlock
What is on the APU Hot Battery Bus?
-IRU L, C, R DC Power
-Left and Right Outflow Valve
-APU Inlet Door, APU Controller
What powers the Battery Chargers?
AC Bus 1
How do the Battery Chargers function?
They act as TRU for the associated HOT Battery Bus and also charge the battery
What is another sources that can power the Battery Chargers?
GND Service Switch
When will the Standby Inverted be powered?
A loss of power on DC Bus 3
The four main DC busses are connected through ____ to the DC tie bus.
DC Isolation Relays (DCIR)
T/F: There are NO switches or relays to control power to the Hot Battery busses.
True
Why are the busses isolated during an autoland?
To prevent faults to crossover onto other busses
During an autoland, when are the busses isolated?
Descending below 1,500’ RA
During an autoland, what busses are isolated and why?
AC and DC 1,2, and 3 This separates the 3 autopilots
During an autoland, what powers the synchronous bus?
AC bus 4
What indication does the crew get when the busses are isolated for an autoland?
None
What is displayed on the Electrical Synoptic Display during an autoland?
“ELECTRICAL SYNOPTIC INHIBITED FOR AUTOLAND”
How is Autoland Isolation cancelled?
-Autoland is canceled
-TO/GA is activated
-Autopilot Disengaged
-Loss of autoland redundancy
Autoland Isolation occurs during what conditions?
Autoland approach, when descending below 1,500’ RA
T/F: The Electrical Synoptic is inhibited during autoland.
True
What normally powers the captains transfer bus?
AC Bus 3
What will power the captains transfer bus if AC Bus 3 fails?
AC Bus 1
As it relates to the captains transfer bus, what will happen if both AC Bus 1 and 3 fail?
The APU Standby Bus will be powered by the APU Standby Inverter.
When the APU battery charger is not powered, how long can the APU battery provide power and to what?
Minimum of 30 minutes to the APU standby inverter and the Standby Bus
If AC Bus 3 is not powered, the Standby Bus will be automatically powered by the _____________.
Standby Inverter
The Standby Power Selector is required to be in the _____ position for the automatic switching of the Standby Power System.
AUTO
