Electrics Flashcards
What does the electrical system of an airplane generate and distribute?
AC and DC power to other airplane systems
What are the main components of the electrical system?
- main AC power
- backup power
- DC power
- standby power
- flight controls power
How does the system operation function in terms of electrical faults?
Electrical faults are automatically detected and isolated
What is the primary source of electrical power in the airplane?
The AC electrical system
What is the function of the Electrical Load Management System (ELMS)?
Provides load management and protection to ensure power availability
What happens when electrical loads exceed available power?
ELMS automatically sheds AC loads by priority
List the order of load shedding by the ELMS.
- galleys first
- utility busses
- individual equipment items powered by the main AC busses
What message displays on the electrical synoptic when load shed conditions exist?
LOAD SHED
What are the main AC electrical power sources?
- left engine integrated drive generator (IDG)
- right engine IDG
- APU generator
- primary external power
- secondary external power
How do the main AC power sources normally operate?
Isolated from one another
What occurs during power source transfers on the ground?
Operating sources are momentarily paralleled to prevent power interruption
What happens when an engine starts with the GENERATOR CONTROL switch ON?
The IDG automatically powers the respective main bus
How can the IDG be electrically disconnected from the busses?
By pushing the GENERATOR CONTROL switch to OFF
What indicates low oil pressure in an IDG?
The DRIVE light illuminates and the EICAS message ELEC DRIVE FAULT L or R displays
What is the function of the APU generator?
Can power either or both main busses and may be used in flight as a replacement to an IDG source
What happens when the APU generator becomes available?
It automatically connects to both main AC busses if no other power source is available
What does the PRIMARY EXT PWR switch do?
Connects primary external power to both main busses
What is the purpose of the secondary external power source?
Can power the left and right main busses
When is the ground service bus powered?
Normally powered by the right main bus
What does the ground handling bus provide power for?
- cargo handling
- fueling/defueling operations
- engine turning system
- other equipment during ground operations
What is the function of the backup electrical system?
Automatically provides power to selected airplane systems
What are backup generators used for?
Provide backup power and supply power to the flight control DC electrical system
What is the role of transformer-rectifier units (TRUs) in the DC electrical system?
Produce DC power from AC transfer busses
What does the main battery provide?
Standby power to other busses
What happens if the main battery charge is below the level required for dispatch?
What does the hot battery bus provide power to?
Standby power to other busses
See Standby Electrical System
What maintains the main battery fully charged?
The main battery charger
What message is displayed if the main battery charge is below the required level for dispatch?
MAIN BATTERY LOW
How long can battery charging take with one or both engines running or with external power?
5-10 minutes
What happens to battery charging time when the APU is running?
It goes to a slower charging mode and can take up to 18 minutes
What does the APU battery power?
The APU electric starter
What is the purpose of the TOWING POWER switch in BAT position?
Permits towing operations without AC power
What does the standby electrical system provide power to?
Selected flight instruments, communications and navigation systems, and the flight control system
What components make up the standby electrical system?
- The main battery
- The standby inverter
- The RAT generator and its associated generator control unit
- The C1 and C2 TRUs
What does the standby inverter do?
Converts DC power to AC power
What does the RAT generator provide standby power to?
The C1 and C2 TRUs
Does the RAT generator have operating time limits?
No
When is the RAT deployed automatically?
If both AC transfer busses lose power in flight
What systems can electrical power to some cabin and utility systems be controlled from?
The flight deck
What does the IFE/PASS SEATS switch control?
- In-Flight Entertainment (IFE) system
- Passenger seat systems
- Video surveillance cameras
- Flight deck personal electronic device (PED) power outlets
What happens when the IFE/PASS SEATS Power switch is selected to OFF?
Power is removed from all IFE components and passenger seats
What does the CABIN/UTILITY Power switch control?
Power to cabin and utility systems
When the CABIN/UTILITY Power switch is OFF, what systems still receive power?
- Night lights
- Reading lights
- Attendant work lights
- Some galley and crew rest lights
What does the Passenger Wi-Fi switch allow?
On-board Wi-Fi functionality to be available to the flight crew and passengers when ON
Fill in the blank: The standby inverter powers the AC standby bus if the _______ is not powered.
left transfer bus
