6 - Electrical Flashcards
What happens when you push the BUS TIE Switches to AUTO? (2)
- ‘ARMS’ automatic AC bus tie circuitry
* ‘CLOSES’ related DC isolation relay (DCIR)
What happens when the Bus Isolation (ISLN) Light illuminates? (2)
- BTB open
* AC bus isolated from synchronous bus
Generator Drive Disconnect (DRIVE DISC) Switches - Push (2)
- disconnects IDG from engine (when above idle speed)
- opens related Generator Control Breaker (GCB)
Note: Ground maintenance action required to reconnect IDG
What does a Generator DRIVE Light indicate? (3)
- IDG oil pressure low, or
- IDG oil temperature high
- GCB open due to uncorrectable generator frequency fault
(EICAS - ELEC DRIVE)
Generator Control (GEN CONT) Switches
ON - (1)
OFF - (3)
arms GCB to close when generator power quality acceptable
- opens generator field and GCB
- resets fault control logic circuitry
- isolates generator from its related AC bus
Split System Breaker OPEN Light
Illuminated (white) -
split system breaker open
The Electrical synoptic displays the configuration of the AC power system in a _____ schematic format. DC power flow is ___ represented. The depiction is generated by the status of various system breakers and conductors and ______ represent actual power flow. Therefore, the display ______ an accurate representation of system operation
simplified
not
does not
does not
The electrical system is ______
Electrical faults are ______ detected and isolated
automatic
automatically
Electrical system overload protection is provided by a _____ system configured to ensure power is available to ______ equipment
load management
critical and essential
The load management system sheds _____ by priority until the loads are _____ of airplane or ground power generators
AC loads
within the capacity
Utility bus loads are shed one at a time through _____ in a programmed sequence until the overload condition is relieved. When an additional AC power source is available, loads are restored in ______
During load shedding, the ELEC UTIL BUS L and R messages and utility off lights are _____
ELCUs
reverse order
inhibited
The main AC electrical power sources are: (3)
- four IDGs
- two auxiliary power sources (APU generators)
- two external power sources
Each IDG incorporates: _________ with _______ lubricating system and _____ control and protection components
AC generator drive unit
self-contained
automatic
Each IDG can be mechanically disconnected from its engine accessory gearbox by pushing the ______
When an IDG is disconnected, generator power output is lost and cannot be _____ by flight crew action
Generator Drive Disconnect switch
restored
The EICAS message ELEC DRIVE displays for: (3)
- low IDG oil pressure
- high IDG oil temperature
- GCB open due to uncontrollable frequency fault
(Generator DRIVE light illuminates)
Auxiliary power is available only ______ from ___ generator(s) mounted on the APU. External power is available from ground sources through two power receptacles located _______
on the ground
2
on the lower right forward fuselage
When cargo handling is required, selecting ______ or _____ ON ensures the main deck cargo handling bus remains powered
only the number ONE; auxiliary or external power source
AC power is distributed by the following busses: (6)
- four main busses
- four utility busses
- two standby busses
- two transfer busses
- ground service bus
- ground handling bus
Each IDG normally powers its related AC bus through a ______
Each AC bus is connected to the synchronous bus by a ______
GCB (Generator Control Breaker)
BTB (Bus Tie Breaker)
If power on an AC bus is unacceptable, the related ____ opens and the bus disconnects from the ______
If the IDG is not able to maintain acceptable power quality, the ____ opens and the ____ closes to provide power from the synchronous bus
BTB
synchronous bus. (However, the AC bus remains powered by its IDG)
GCB
BTB
The EICAS message ______ displays if the BTB is open.
Pushing the Bus Tie switch OFF, then AUTO, _______ and allows the BTB to close if the fault is corrected. The AC bus is reconnected to the synchronous bus
ELEC BUS ISLN
resets logic circuitry
What powers the ground service bus and provides back-up power for both transfer busses?
AC bus 1
What powers the first officer transfer bus?
AC bus 2
What powers the captain transfer bus and the main standby bus?
AC bus 3
When is the ground service bus powered?
any time AC bus 1 is powered (on the ground and in flight)
The ground service bus powers individual equipment items such as: (5)
- main and APU battery chargers
- fuel pumps for APU start
- upper deck emergency doors
- flight deck flood lights
- miscellaneous service outlets and equipment
The ground handling bus is powered on the ground when ______
If both are available, ______ is automatically used
APU generator 1 or External power 1 AVAIL
external power
The ground handling bus powers individual equipment items such as: (3)
- lower cargo handling equipment and compartment lights
- fueling system
- auxiliary hydraulic pump 4
Two transfer busses provide AC power to _______ equipment.
The transfer busses have a common back-up power source _______
critical flight-related
AC Bus 1 (transfer to the back-up power source is automatic)
The captain transfer bus is normally powered by ______. If unpowered, ______ powers the captain transfer bus.
The captain transfer bus powers the _____ bus
AC bus 3
AC bus 1
APU standby bus
The captain transfer bus powers individual equipment items such as: (2)
- center EIU (EFIS/EICAS Interface Unit)
* left HF
The first officer transfer bus is normally powered by _______. If unpowered, ______ powers the first officer transfer bus
AC bus 2
AC bus 1
The first officer transfer bus powers individual equipment items such as: (2/8)
- autothrottle servo
- lower EICAS display
• right - EFIS, EIU, ADC, PFD, ND
FMC, CDU, HF
Each main AC bus powers one utility bus. Each utility bus is controlled by ____ that protects the electrical system from utility bus faults and provides load management through automatic load shedding. With the Left Utility Power switch ON, utility bus(ses) _____ are powered according to ____ logic. With the Right Utility Power switch ON, utility bus(ses) _____ are powered according to _____ logic
ELCU
1 and 2
ELCU
3 and 4
ELCU
Utility busses power individual equipment items such as: (4)
- forward main fuel pumps 2/3
- forward override/jettison pumps 2/3
- center override/jettison pump L
- galley equipment
A main deck cargo handling bus interlock _____ external power 2 or APU generator 2 from powering main electrical busses and the main deck cargo handling bus simultaneously.
Pushing the available power source switch ON _____ the main deck cargo handling bus.
prevents
deengergizes
When both external power 2 and APU generator 2 are available, _____ is used
external power 2
The AC standby power system provides electrical power to ______
Major components of the system include: (4)
critical flight deck equipment
- main and APU standby busses
- main and APU batteries
- main and APU standby inverters
- Standby Power selector
The main deck cargo handling bus powers equipment items such as: (2)
• main deck cargo handling equipment
and lighting
• side cargo door
During automatic ILS approach, ____ and ____ busses _____ are isolated from the synchronous bus to provide independent power sources for the three autopilots.
_____ continues to power the synchronous bus.
AC and DC
1, 2, and 3
AC bus 4
(If any AC or DC source fails when busses are isolated for autoland, the system reconfigures automatically to maintain independent power sources for the three autopilots)
The main standby bus is normally powered by ______
With the Battery switch ON, Standby Power selector in AUTO, and ______ not powered, the main standby bus is powered by ______
Normally unpowered, it is activated and receives power from the _____ through the _____
AC bus 3
AC bus 3
main standby inverter
main battery charger
main hot battery bus
(with the main battery charger unpowered, the main battery can provide power to the main standby bus for a minimum of 30 minutes)
The main battery charger is normally powered by _______ through the ______
AC bus 1
ground service bus
The main standby bus powers individual equipment items such as: (3+)
- standby ignition
- left: EFIS, EIU, ADC, stby instrument lights, primary EICAS, CDU, ILS, VOR, transponder
- various flight control components
The APU standby bus is normally powered by _____
Battery switch ON, Standby Power selector in AUTO, and the captain transfer bus not powered (loss of AC busses 1 and 3), the APU standby bus is powered by ______
captain transfer bus
APU standby inverter
The APU standby inverter, normally unpowered, when activated receives power from the _____ through the _____
APU battery
APU hot battery bus
(With the APU battery charger unpowered, the APU battery can provide power to the APU standby bus for a minimum of 30 minutes)
The APU standby bus powers these equipment items: (3)
left - PFD, ND, FMC
The main DC electrical system uses _____ to produce DC power.
Each ______ is powered by ______ and provides DC power to a DC bus
four transformer-rectifier units (TRUs)
TRU
its related AC bus
The four DC busses are connected through _____ to the DC tie bus, which allows each DC bus to remain powered if its related AC bus is unpowered or _____ fails
Pushing the Bus Tie switch to AUTO closes the related _____ and _____
DC isolation relays (DCIRs)
TRU
BTB
DCIR
Pushing the Bus Tie switch OFF opens the _____ and ______
This isolates the DC bus from the DC tie bus, leaving it powered by its ______ and ____
Automatic isolation of an AC bus due to an electrical fault opens the ____ , but does not open the ______
BTB and DC Isolation Relay (DCIR)
AC bus and TRU
BTB
DC Isolation Relay (DCIR)
TRU DC electrical power is distributed to _____ main DC busses. Main DC busses power individual equipment items such as:
- cabin pressure, fuel jettison, and pack temperature controllers
- wing anti-ice control
- engine-driven and hydraulic demand pump control
- fuel transfer and jettison valve control
The main and APU battery busses are normally powered by ______
If either _______ or ______ is unpowered, each battery bus is powered by its related hot battery bus
DC bus 3
AC bus 3
DC bus 3
The main battery bus provides power to individual equipment such as:
- APU controller (alternate), fuel valves (all engines), all crossfeed valves
- dome, storm, and selected indicator lights
• IDG disconnect (all engines), manual pressurization control, trailing edge flap control
(N919CA)
• captain interphone, left radio tuning panel, left VHF
The APU battery bus powers individual equipment items such as:
- APU DC fuel pump, engine start air control
- cargo, first officer, service interphones, and PA system
- APU and engine fire/overheat detection loops A and B
• APU fire warning horn
(N952CA)
• captain interphone, left radio tuning panel, left VHF, nacelle anti-ice control (all engines)
Each hot battery bus is normally powered by the _______ through _______, which acts as a TRU for the hot battery bus while simultaneously maintaining its related battery fully charged
Each battery is directly connected to its related ________
ground service bus
its related battery charger
hot battery bus
With the Battery switch ON, the main and APU hot battery busses power their related battery busses if either ______ or ______ is unpowered
AC bus 3
DC bus 3
The main hot battery bus powers individual equipment items such as:
- APU fuel shutoff valve, spar valves (all engines)
- APU and lower cargo fire extinguishers
- engine fire extinguishers (all engines), fire switch unlock (all engines)
The APU hot battery bus powers individual equipment items such as:
- IRU left, center, right DC power
- left and right outflow valves
- APU inlet door, APU controller (primary)
What are the main items power by the Ground Handling Bus?
- lower cargo doors, lights and handling equipment
- fueling system
- aux hydraulic 4/(1)
How is the Ground Handling Bus powered?
Is it powered on the ground or in-flight?
EXT 1/APU 1 - AVAIL or ON
on the ground only
no controls or indicators
What are the main item powered by the Ground Service Bus? (3)
main/APU battery chargers
fuel pump for APU start
flight deck flood lights
How is the Ground Service Bus powered?
Is it powered on the ground or in-flight?
AC Bus 1 or Ground Handling Bus power source if Ground Service switch on cabin panel is ON
both
(no controls or indicators)
How is the Main Deck Cargo Handling Bus powered?
EXT/APU AVAIL only
EXT has priority
What is powered by the Main Stby Bus? (4)
Stby ignition
Primary EICAS
Left - EFIS, EIU, ADC, CDU, ILS, VOR, transponder
various flight control components
What is powered by the Standby Power System? (4)
CA’s:
PFD
ND
Upper EICAS
CDU
What is available with (only) BATT Switch ON?
L/R/Aisle Stand flood lights, Interphone, PA, L VHF/Radio Tuning Panel
What does Hot Battery Bus power with no electrical power to A/C?
- APU Fire Warning and shutdown controls
- Engine, APU and lower cargo fire extinguishers
- L/R outflow valves
- IRS DC power (if IRS selectors are on
STBY Power AUTO and BATT Switch ON; what is powered?
CA PFD/ND
Upper EICAS
L CDU
(using battery power/stby inverters)
What is the normal power source for the MAIN and APU Battery Buses?
DC Bus 3
