CH6 ELECTRICAL Flashcards
What does the BATTERY switch do when turned ON?
Initiates L CCR start-up sequence and energizes the ‘On-Ground Battery Only’ mode
What happens when the BATTERY switch is turned OFF?
De-energizes the ‘On-Ground Battery Only’ mode after a delay, and de-energizes the L CCR
The delay can be up to 2 minutes
What indicates that the BATTERY switch is OFF?
Illuminated (amber) BATTERY OFF Light
What systems are energized when the IFE/PASS SEATS Power Switch is ON?
- In-flight entertainment system
- Passenger seat systems
- Video surveillance cameras
- Flight deck personal electronic device power outlets
What does the IFE/PASS SEATS OFF Light indicate?
Illuminated (amber) - the IFE/PASS SEATS power switch is OFF
What action does pushing the Forward External Power (FWD EXT PWR) Switch perform if the AVAIL light is illuminated?
Closes forward external power contactor
What happens when the Forward External Power (FWD EXT PWR) Switch is pushed if the ON light is illuminated?
Opens forward external power contactor
What does the illuminated Forward External Power ON light indicate?
Forward external power is selected ON.
When do the Forward External Power AVAIL lights illuminate?
When forward external power is plugged in and power quality is acceptable.
What happens to the Forward External Power AVAIL lights when the ON light illuminates?
They extinguish.
What does the ON position of the Generator Control (GEN CTRL) Switches do?
Arms generator control breaker and closes generator field.
What is indicated when the Generator OFF light is illuminated?
The generator control breaker is open.
What is the function of the Generator Drive Disconnect (DRIVE DISC) Switches?
Disconnects generator drive from engine.
What is required to reconnect the generator drive after using the DRIVE DISC switch?
Maintenance action on the ground.
Fill in the blank: The Forward External Power AVAIL lights extinguish when the ON light _______.
[illuminates]
True or False: The Generator Control (GEN CTRL) Switches in the OFF position open the generator control breaker.
True
List the two main functions of the Generator Control (GEN CTRL) Switches when set to OFF.
- Opens generator control breaker
- Resets fault protection systems
What does the amber light indicate when illuminated with the engine running?
A generator drive malfunction has occurred
What happens when the CABIN/UTILITY Power Switch is set to ON?
Energizes galleys, most cabin lights, and other non-essential cabin utility loads
What does the CABIN/UTILITY Power OFF Light indicate when illuminated?
CABIN/UTILITY power switch is selected OFF
What does the APU Generator (APU GEN) Switch do when set to ON?
Arms generator control breaker and closes generator field
This prepares the generator to operate when power becomes available
What are the effects of setting the APU Generator (APU GEN) Switch to OFF?
Opens generator control breaker, opens generator field, resets fault protection systems
This action disconnects the generator from the system and resets any fault conditions.
What does it mean if the APU Generator OFF Light is illuminated?
The APU generator control breaker is open or the APU GEN switch is selected OFF
What occurs when the AFT External Power (AFT EXT PWR) Switch is pushed if the AVAIL light is illuminated?
Closes aft external power contactor.
What happens when the AFT External Power (AFT EXT PWR) Switch is pushed if the ON light is illuminated?
Opens aft external power contactor.
This disconnects the external power source from the aircraft’s systems.
What does an illuminated AFT External Power ON Light indicate?
Aft external power is powering the large motor power system for right engine start.
The light is white.
What does an illuminated AFT External Power AVAIL Light signify?
Aft external power is plugged in and power quality is acceptable.
The light extinguishes when the ON light illuminates.
What are the battery status indicators on the Towing Power Panel?
HIGH, MEDIUM, LOW.
These indicators show the current state of the battery charge.
What is the function of the Towing Power Panel?
To control and indicate the status of the towing power system.
It includes battery status and a power ON indicator.
What does the Towing Battery Test Switch indicate when pushed?
The current state of charge of the batteries (HIGH, MEDIUM, LOW)
The applicable towing battery charge light illuminates to show the charge state.
What happens when the TOWING POWER switch is set to ON?
Selects the main and APU batteries for energizing the ‘Towing Power’ mode
The applicable towing battery charge light illuminates.
What is the function of the TOWING POWER switch when set to OFF?
De-energizes the ‘Towing Power’ mode.
What does an illuminated ON BAT Light (white) indicate?
The battery TOWING POWER switch is ON.
What do the Towing Battery Charge Lights indicate when illuminated (white)?
The state of charge indicators for the towing battery:
* HIGH - minimum of 60 minutes remaining
* MEDIUM - minimum of 30 minutes remaining
* LOW - minimum of 15 minutes remaining
Minimum times assume steady state towing (no braking).
Fill in the blank: The electrical synoptic is shown by pushing the systems (SYS) display switch, then selecting the _______ synoptic key.
[ELEC]
True or False: If heavy braking occurs, the actual time remaining before battery charge is depleted may exceed the minimum times listed.
False.
What does a green symbol indicate for the engine generator?
Engine generator on
Indicates that the engine generator is operational and powering the buses.
What does a white symbol indicate for the engine generator?
Engine generator off
Indicates that the engine generator is not operational.
What condition is indicated by the white box with a green arrow?
Engine starter on
This indicates that the engine starter is active during the starting process.
What does it mean if the engine is running and the GEN CTRL switch is ON?
Engine generator is powering buses
What advisory message is shown if the GEN CTRL switch is OFF while the engine is running?
ELEC GEN OFF LI, L2, RI, R2
What condition is indicated by an amber symbol for the engine generator?
Engine generator failed
Indicates that the engine generator is not functioning, though the engine is still running.
What happens when an engine generator fails?
• OFF light on GEN CTRL switch illuminates
• EICAS advisory message ELEC GEN OFF LI, L2, RI, R2 shows
What does a low intensity white symbol indicate?
Engine generator data invalid
Fill in the blank: An engine start is in progress when the _______ shows a green arrow.
Large Motor Power System symbol
True or False: An engine generator can be off while the engine is running.
True
The engine can run without the generator contributing to the electrical system if the GEN CTRL switch is OFF.
What does the amber symbol indicate for the starters?
Both (L1, L2 or R1, R2) starters inoperative
What message appears if both starters on respective engines fail?
STARTERS message appears across both starter symbols
Accompanied by an EICAS advisory message.
What does the green symbol indicate for the engine generator drive?
Engine is running and drive is connected
Indicates normal operational status.
What does the white symbol indicate for the engine generator drive?
Engine is not running
What does the amber symbol indicate for the engine generator drive?
Engine is running and drive is disconnected
What does the white, low intensity symbol indicate for the engine generator drive?
Engine generator drive condition unknown
What does the DRIVE (amber) indication signify?
Engine generator drive malfunction
It appears next to (L1, L2, R1, or R2) engine generator drive symbol.
What action is required when the DRIVE light appears?
Disconnect the respective engine generator drive
The DRIVE light on the generator drive disconnect switch illuminates.
What EICAS advisory message shows during a DRIVE fault?
ELEC GEN DRIVE L, R
What symbols appear together when a drive is disconnected?
DRIVE fault symbol and engine generator drive disconnected symbol
What does a green APU generator on symbol indicate?
APU generator is available and powering buses
APU is running, and APU GEN switch is ON.
What does the white APU generator off symbol signify?
APU is not running or APU GEN switch is OFF
If the APU GEN switch is OFF while the APU is running, it will show EICAS advisory message ELEC GEN OFF APU L,R.
What does the APU starter on symbol indicate?
APU start is in progress
It is represented by a white box with a green arrow.
If the APU is running and the APU GEN switch is ON but not powering buses, what does this indicate?
APU generator is available for power
The APU generator is operational but not currently supplying power.
What EICAS message is displayed if the APU GEN switch is OFF while the APU is running?
ELEC GEN OFF APU L,R
This indicates that the APU generator is not supplying power.
Fill in the blank: APU generator on symbol is indicated by _______.
green
This shows that the APU generator is available and in operation.
What does the APU generator available symbol indicate?
APU generator is running and not powering buses
It is represented by a green symbol.
What does a white box with a green arrow represent in APU indications?
APU starter on
This indicates that the APU is in the process of starting.
What does an amber indication for the APU generator signify?
APU generator failed
This means the APU is running, but the generator is not powering buses and the OFF light on the APU GEN switch illuminates.
What does the EICAS advisory message ELEC GEN OFF APU L.R indicate?
APU generator failure has occurred
This message appears when the APU generator is not supplying power to the buses.
What is indicated by the condition ‘APU generator condition unknown’?
APU generator data invalid
This is represented by a white, low-intensity light.
What does the green indication for forward external power signify?
Forward external power is on
This means the forward external power switch has been selected and is successfully powering the buses.
What does a green indication for forward external power signify?
Forward external power is available
This means it is plugged in, power quality is acceptable, and the switch has not been selected.
What does a white indication for forward external power mean?
Forward external power is off
What does the AVAIL light indicate in the power switch for forward external power?
Forward external power is available
The AVAIL light illuminates when the power is plugged in and the switch has not been selected.
What does a white, low-intensity indication for forward external power indicate?
Forward external power data invalid
What does a green indication for aft external power signify?
Aft external power is on
This indicates that aft external power is available and the switch has been selected.
What does the ON light in the power switch for aft external power indicate?
Aft external power is powering the motor controllers
This is specifically for right engine start.
What does a green indication for aft external power available mean?
Aft external power is plugged in and power quality is acceptable
The switch has not been selected, and the AVAIL light illuminates.
What does the indication ‘Aft external power data invalid’ signify?
Aft external power condition unknown
This is represented by a white, low-intensity light.
What does a green symbol indicate in the Main Bus Synoptic Indications?
LI, L2, R1, R2 bus is powered
This indicates that the respective bus is receiving power.
What does an amber symbol represent in Main Bus Synoptic Indications?
L1 MAIN Bus off
This indicates that the bus is not powered.
What does a white, low-intensity symbol indicate regarding bus data?
L1, L2, R1, R2 bus data invalid
This signifies that the bus CONDITION UNKNOWN
What caution message appears if the bus is unpowered due to a fault?
EICAS caution message ELEC AC BUS L1, L2, R1, R2
What does the symbol for the Large Motor Power System represent?
All of the high power electrical motors.
The symbol indicates the electrical components related to high power motors.
What do the green straight arrows in the Large Motor Power System symbolize?
Power flow from aft external and main AC buses to the system when applicable.
These arrows indicate the direction of power flow in normal operation.
What do the 90-degree green arrows represent in the context of the Large Motor Power System?
Power flow from the system during APU and engine start.
What does the Start Power Indication show for the right engine during start?
Indicates right engine start in progress with a green arrow.
Both right engine starter symbols are displayed during this process.
What does the Start Power Indication show for the left engine during start?
Indicates left engine start in progress with a green arrow.
Both left engine starter symbols are displayed during this process.
What does the Start Power Indication show during APU start?
Indicates APU start in progress with a green arrow.
Either the left or right APU starter symbols are displayed during this process.
What does the LOAD SHED symbol indicate?
Reduction or shedding of electrical loads in a system
LOAD SHED indicates that power to certain systems has been reduced to maintain overall functionality.
What is displayed on the AIR synoptic when load shedding occurs?
AIR - LOAD SHED
This indicates that the air system is affected by load shedding.
Which systems could be impacted under CABIN LOADS during load shedding?
- Galley
- Galley floor heaters
- Chiller
- Cabin lighting
- In-flight entertainment (IFE)
- Door area heaters
These cabin systems may experience reduced power due to load shedding.
What types of loads are shed under COMM/NAV?
- VHF
- TCP
- HF
- SATCOM
- DME
- Flight interphone
These communication and navigation systems may be impacted by load shedding.
Which exterior lights can be affected by load shedding?
- Beacon
- Strobe
- Wing landing
- Nose landing gear
- Taxi
- Navigation (position)
- Logo
- Runway turnoff
These lights may be reduced or turned off during load shedding.
What does the LOAD SHED message display on the FUEL synoptic indicate?
Reduction of fuel system loads
This shows that power to one or more fuel systems has been shed.
What does the LOAD SHED message on the HYD synoptic signify?
Reduction of hydraulic system loads
Indicates that hydraulic power to one or more systems has been shed.
What does the VOLTS indication show in the electrical system?
Battery charge in volts
A low voltage level triggers the MAIN BATTERY LOW EICAS advisory message.
What do the AMPS values indicate in the electrical system?
Battery rate of charge or discharge in amps
A DISCH indication triggers the MAIN BATTERY DISCH EICAS advisory message.
What do green flow lines with an arrow end represent?
Power is flowing
What do white solid flow lines indicate?
Power is not flowing
What does CBIC stand for?
Circuit Breaker Indication and Control
What does CBIC provide for Electronic Circuit Breakers (ECB)?
Indication and control
What does CBIC provide for Thermal Circuit Breakers (TCB)?
Indication only
How can CBIC be accessed on the multifunction display?
By pushing the systems (SYS) display switch and selecting the CB key
What does a green symbol indicate on the CBIC display?
ECB or TCB closed
This indicates that the circuit is powered.
What does a white symbol signify for an ECB on the CBIC display?
ECB open
The circuit is not powered.
What does the amber symbol indicate for an ECB?
ECB tripped
The circuit is open and not powered due to a fault.
True or False: TCBs can be controlled by CBIC.
False
TCBs state can be monitored but not controlled by CBIC.
What does a white tag with a cyan lock collar on an ECB signify?
INOP
The ECB is open and collared for dispatch. Circuit is not powered.
What does a red tag with a cyan lock collar on an ECB signify?
DO NOT CLOSE
The ECB is open and collared for maintenance purposes. Circuit is not powered.
What does an amber symbol indicate when the ECB or TCB condition is unknown?
UNKNOWN
The circuit status cannot be determined.
Fill in the blank: TCBs state can be _______ but not controlled by CBIC.
monitored
This indicates the limitations of TCB control.
What is the main function of the 787 airplane electrical system?
Generates, distributes, and manages airplane electrical power
What types of power does the 787 electrical system primarily use?
115 Vac and 28 Vdc
A limited number of systems are optimized with 235 Vac.
List the electrical power sources for the 787 electrical system.
- Four variable frequency engine starter/generators (VFSG)
- Two variable frequency APU starter/generators
- Three external AC power receptacles
- One Ram Air Turbine (RAT)
- One main battery
- One APU battery
- Three flight control Permanent Magnet Generators
- Two EEC Permanent Magnet Alternators
The power sources remain isolated from each other throughout the system.
True or False: The engine starter/generators are only used for engine start.
False
They function as both starter motors for engine start and as generators once the engines are running.
How are the engine starter/generators connected to the engines?
Directly connected to the engine gearboxes
They produce variable frequency power proportional to engine rotor speed.
What happens to the engine starter/generators after engine start?
They function as generators to energize their respective main AC buses
The buses are designated L1, L2, R1, and R2.
Fill in the blank: The electrical power for engine start can be provided by _______.
[external power, APU generated power, or the opposite engine’s generated power]
The system automatically selects both starter/generators for optimal torque.
What indicates the generator status in the 787 electrical system?
Generator switch indications, MFD electrical synoptic, and the EICAS message system
What is the purpose of the Ram Air Turbine (RAT) in the electrical power sources?
Provides emergency electrical power
What is the role of the APU battery in the electrical system?
Provides electrical power when the APU is not running
What mechanism allows the generator to be mechanically disconnected from the engine?
Drive disconnect mechanism
This mechanism can either automatically disconnect or require crew action.
What indicators show when a condition requires the flight crew to disconnect the generator drive?
Generator DRIVE light, generator DRIVE synoptic indication, EICAS advisory message ELEC GEN DRIVE
What functions do APU starter/generators serve?
Starter motors for APU start and generators once the APU is running
They also provide electrical power for ground operations and supplemental power during flight.
How many APU starter/generators are there and what are they designated?
Two, designated left (L) and right (R)
Each produces variable frequency power proportional to APU speed.
What sources can provide electrical power for APU start?
- Forward external power
- APU battery
- Engine generated power
The system automatically selects a single starter/generator to provide sufficient torque for APU start.
What happens if both APU generators are connected on the ground?
They are available to energize the airplane’s 235 Vac electrical buses
This includes buses L1, L2, R1, and R2.
What does the generator status indicate?
Generator switch indications, MFD electrical synoptic, EICAS message system
These systems provide real-time feedback on generator performance.
How many Common Motor Start Controllers (CMSC) are available for the APU starter generators?
Three
Two prioritize main engine start, while the third prioritizes the hydraulic electric motor pump.
What may cause an APU start to be aborted?
- Demand pumps turned on during APU start
- Engine shut down during APU start
Both scenarios may lead to a power interrupt affecting the CMSC.
What does the 115 Vac external power system consist of?
Forward and aft systems with corresponding receptacles, controls, and indications
The forward system is primarily for general ground operations.
What happens when one or both power sources are connected to the forward system?
Illuminates the AVAIL light(s) and energizes ‘Ground Handling’ mode
Only one connection is required to power this mode.
What is the minimum requirement for external power to start an engine?
Two 90 kVA rated forward external power sources
This enables either engine to be started first.
Fill in the blank: The APU has ________ 235 Vac variable frequency starter/generators.
two
These are designated left (L) and right (R).
True or False: The drive cannot be reconnected by the flight crew once it has been disconnected.
True
The system is designed to prevent reconnection by the crew.
What is the minimum requirement for external power to start an engine when the APU is unavailable?
Two 90 kVA rated forward external power sources are required
How does the use of external power affect engine start times compared to an APU start?
Results in longer engine start times
What occurs during engine start when using external power?
Load shedding occurs
What is the function of the aft external power system during engine start?
Assists the forward system when starting the right engine first
Where is the aft external power receptacle located?
On the airplane fuselage aft of the left wing
What conditions require the Ram Air Turbine (RAT) to deploy automatically?
Any of the following:
* Both engines have failed
* All three hydraulic system pressures are low
* Loss of all electrical power to captain’s and first officer’s flight instruments
* Loss of all four EMPs and faults in the flight control system occur on approach
* Loss of all four EMPs and an engine fails on takeoff or landing
Can the RAT be deployed manually, and if so, how?
Yes, by pushing the RAM AIR TURBINE switch on the hydraulic panel
What are the two types of batteries on the airplane?
One main battery and one APU battery
Where is the main battery power switch located?
On the overhead electrical panel
Does the APU battery have a flight deck power switch?
No, it functions automatically
What provides operating indications for the main and APU batteries?
The electrical synoptic
Fill in the blank: The RAT serves as an emergency source of _______ power.
[electrical and hydraulic]
What are the main functions of the main battery in the B787?
The main battery provides power for:
* airplane power-up
* APU start (assists APU battery)
* refueling operations
* towing operations
* electric braking (as a backup power source)
* captain’s flight instruments (after a power failure, energizes essential instruments until RAT deployment)
What does the APU battery provide power for on the ground?
The APU battery provides power for:
* APU start
* navigation lights (when Towing Power mode is active)
What happens if a fault is detected in either battery?
The protection system stops battery charging and, if necessary, isolates the battery electrically.
This is part of the safety measures to prevent battery overcharging.
What safety feature is in place if a battery overheats?
A sealed enclosure ensures that the resulting heat and gases are contained. If the heat and gases reach a level normally associated with a cell failure, a burst disk activates, venting gases directly overboard through a vent tube opening in the fuselage.
Where is the main battery vent opening located?
The main battery vent opening is located aft of the forward E/E door, near the airplane centerline.
What may be present in the flight deck prior to the main battery burst disk activation?
A brief odor may be present in the flight deck.
Where is the APU battery vent opening located?
The APU battery vent opening is located aft of the access door to the aft E/E compartment, near the airplane centerline.
What is the primary source of power for the flight control electronics in the B787?
Three engine driven Permanent Magnet Generators (PMG) are the primary source of power for the flight control electronics.
Are the Permanent Magnet Generators (PMG) independent from each other?
Yes, the PMGs are independent from each other.
What secondary source is provided for flight control power?
The airplane’s 28 Vde bus distribution system and the main battery provide a secondary source for flight control power.
What is the purpose of the airplane’s 28 Vde bus distribution system?
Provides a secondary source for flight control power
It ensures positive flight control operation during temporary power interruptions.
What are the primary sources of power for the Engine Electronic Control (EEC)?
Two engine driven Permanent Magnet Alternators (PMA)
One PMA is installed per engine.
How does the airplane serve as a backup EEC power source?
If a PMA is inoperative
The airplane can provide initial EEC power during engine start until the PMA is operational.
What are the two distinct power distribution methods used in the electrical system?
- Primary
- Remote
Primary method energizes higher amperage loads; remote method energizes lower amperage loads.
What loads are energized by the primary power distribution method?
Higher amperage loads directly from bus power panels
These panels are located in the forward and aft E/E bays.
What is the role of the 17 Remote Power Distribution Units (RPDUs)?
Energizes lower amperage loads throughout the airplane
Each RPDU handles loads of 10 amps or less.
What types of electrical loads are primarily found in the airplane’s electrical system?
- 235 Vac high voltage loads
- 115 Vac loads
- 28 Vdc loads
Majority of loads are 115 Vac and 28 Vdc.
What types of devices are located in the forward and aft E/E bays?
- Main and APU batteries
- Power conversion devices
- System controllers
They manage the distribution and conversion of electrical power.
List some primary 115 Vac loads in the airplane.
- Cabin & Exterior Lighting
- Cabin Systems & IFE
- Galley Power
- GPWS
- WXR
These loads are powered directly from the forward E/E bay.
What are some primary 28 Vdc loads in the airplane?
- Ground Operations
- Common Core System
- Audio & VHF Comm
- Autopilot / Autothrottle
- Engine Igniters
- DC Fuel Pump
- Fit Deck Instr & Displays
- Bus Power Control Units
- Brake Power
These loads are powered through RPDUs.
True or False: The Permanent Magnet Alternators (PMA) are dependent on the main airplane electrical system.
False
PMAs are independent from the main airplane electrical system.
Fill in the blank: The electrical system uses _______ power distribution methods.
[two distinct]
How many RPDUs are mentioned?
17 RPDUs total
What is the maximum load for RPDUs?
10 amps or less
What does E/E Bay refer to?
Electrical/Electronic Bay
What are the four main 235 Vac buses designated as?
L1, L2, R1, R2
Where are the primary power system buses located?
Aft E/E bay power panels
What systems do the 235 Vac buses distribute power to?
High voltage AC airplane systems and other airplane bus systems
How are the 235 Vac buses energized on the ground with only forward external power selected ON?
By the 115 Vac distribution system through power conversion devices
What happens when an APU or engine is started on the ground?
It energizes the four main 235 Vac buses, and external power transitions from ON to AVAIL
With only APU power available, how many of the 235 Vac buses does each APU generator energize?
Two of the four main 235 Vac buses
What energizes the 235 Vac buses when one engine is running and no APU or external power is available?
That engine’s two related 235 Vac buses are energized directly; the other two are energized by the two powered buses
When both engines are running, how are the main 235 Vac buses energized?
Each main 235 Vac bus is energized directly from its related engine generator
What indicates when a main 235 Vac bus is inoperative?
EICAS caution message ELEC AC BUS (LI, L2, R1, R2)
What is the structure of the 115 Vac Bus Distribution System?
Multiple 115 Vac buses using primary power system buses and RPDUs
How does the 115 Vac system energize the 235 Vac bus system on the ground with forward external power ON?
It energizes directly, then energizes the 235 Vac bus system through power conversion devices
What is the role of the RPDUs in the 115 Vac system?
Distributing lower amperage loads (10 amps or less)
How does the 28 Vde Bus Distribution System distribute power?
Using primary power system buses and RPDUs
What loads does the 28 Vdc system distribute directly?
Higher amperage loads (greater than 10 amps)
How does the 235 Vac system provide power to the 28 Vde system?
Through power conversion devices
How many electrical brake power supply units are used in the airplane’s electric brake system?
Four
What are the two sources of input for each electrical brake power supply unit?
28 Vdc bus system and main battery
Which power source is considered the primary for the electric brake system?
28 Vdc bus system
MAIN BATTERY AS BACKUP
Which power source provides backup for the electric brake system?
Main battery
What type of power do large motor loads require for operation in the airplane?
Variable frequency power
Where are the motor controllers for large motor loads energized?
Dedicated large motor power distribution system in the aft E/E bay power panels
What voltage does the main distribution system use to energize the large motor power system?
235 Vac
What energizes the motor controller required for APU battery start?
APU battery
What energizes the motor controller required for right engine start using external power?
Aft external power system
What system dissipates heat created by high voltage motor controllers?
Power Electronics Cooling System (PECS)
When is the Power Electronics Cooling System (PECS) energized?
If one or both engines or the APU is running, or if forward external power is connected and selected ON
What does the Bus Power Control Unit (BPCU) manage?
Flight deck control/indication, power transfer functions, overall load management and protection
What happens in the event of a BPCU failure?
A second BPCU assumes all functions
What does the electrical system of the 787 dynamically manage?
Electrical loads
How does the 787 electrical system efficiently use available airplane power?
By automatically cycling on or off loads using electronic controllers
What is the purpose of the modes of operation in the electrical system?
To selectively energize individual loads on different buses
Fill in the blank: The _______ provides backup power to the electric brake system.
main battery
List significant loads energized by Towing Power mode.
- captain’s ACP
- captain’s flight interphone
- flight deck dome lights
- aisle stand flood lights
- navigation lights
- brakes
Radio communication systems are not energized in this mode.
What is On-Ground Battery Only mode?
On-Ground Battery Only mode is active when the BATTERY switch is selected to ON while the airplane is on the ground, and there are no other power sources connected.
This mode supports the airplane power-up sequence.
List significant loads energized by On-Ground Battery Only mode.
- captain’s inboard DU
- lower DU
- МСР
- APU start capability
- wing fueling panel
- captain’s / first officer’s ACP
- captain’s / first officer’s flight interphone
- VHF L
- TCP L
- DSP L
- MFK L
- CCD L
- AHRU L, R
- FMC
- CCR L
- ground crew call horn
- engine/APU fire detection
- miscellaneous lighting
- brakes
What mode is active when the first forward external power receptacle is connected and no other power sources are present?
Ground Handling mode
Ground Handling mode has priority over On-Ground Battery Only mode and initializes regardless of BATTERY switch position.
List significant loads energized by Ground Handling mode.
- lower DU
- APU start capability
- cargo compartment lighting
- MFK L
- cargo door actuation systems
- CCD L
- cargo handling systems
- cargo loading lights
- CCR L, R
- service compartment lights
- equipment cooling fans
- wing fueling panel
- engine/APU fire detection
- battery chargers
What additional loads does Ground Service mode energize compared to Ground Handling mode?
- cabin systems (limited operation)
- flight deck dome lighting
- cabin lighting (limited operation)
What must be selected ON for Ground Service mode to be active?
GROUND SERVICE switch on the master attendant switch panel
What is the condition for External Power On mode to be active?
At least one forward external power receptacle is connected and selected ON with the APU and engine generators off
True or False: Ground Handling mode has a higher priority than External Power On mode.
False
Ground Handling mode has priority over On-Ground Battery Only mode but not over External Power On mode.
Fill in the blank: Some overhead panel indicator lights are inoperative in _______ mode.
On-Ground Battery Only mode
What happens to significant loads in Ground Handling mode when the GROUND SERVICE switch is activated?
Additional loads are energized by Ground Service mode
What mode is active when at least one forward external power receptacle is connected and selected ON with the APU and engine generators off?
External Power On mode
This mode allows for limited operation of cabin systems and controls.
What significant loads are energized in External Power On mode with one forward external power source connected?
- flight deck equipment, controls, and indications
- cabin systems (limited operation)
- cabin lighting (limited operation)
- PECS (single loop only)
PECS refers to the Power and Electrical Control System.
What additional loads are energized in External Power On mode with two forward external power sources connected?
- NGS (limited operation)
- hydraulics (limited operation)
- IFE (limited operation)
- cabin systems (basic operation)
- cabin lighting (basic operation)
- PECS (both loops)
What systems are inoperative in External Power On mode?
Packs and cargo heat
What mode is active if there is a loss of all electrical power to the captain’s and first officer’s flight instruments during flight?
In-Air RAT Only mode (Standby Power)
What does the main battery provide until RAT deployment?
Standby power
This ensures that essential systems remain operational until the RAT can function.
What significant loads are energized by the RAT during In-Air RAT Only mode?
- captain’s inboard DU
- captain’s outboard DU
- lower DU
- DSPL
- ISFD
- ECL
- autoflight system (limited operation)
- autopilot (limited operation)
- FMC (limited operation)
- IRUL, R
- AHRU L, R
DU refers to Display Units, DSPL is Display, ISFD is Integrated Standby Flight Display, ECL is Engine Command Limiter, FMC is Flight Management Computer, IRUL and AHRU refer to Inertial Reference Unit and Airborne Head-Up Reference Unit respectively.
What are some inoperative items during In-Air RAT Only mode?
- autothrottle
- LNAV/VNAV
- FMC predictions
- FMC thrust limits
- TAP
- flaps
- slats
- stabilizer trim
- thrust reversers
- auto speedbrakes
- packs
- Head-Up displays
- HF radios
- SATCOM system
- TCAS
- GPWS
- transponder
- weather radar
- external lighting
- WIPS
- window heat
What may happen after operation in In-Air RAT Only mode when normal electrical power is restored?
Some critical systems may not restore
In particular, air conditioning system CACs may fail to restore, affecting cabin pressurization.
What could be required if none of the CACs restore after In-Air RAT Only mode?
Descent to a lower altitude
This is necessary to maintain cabin pressurization during the flight.
What are the EICAS messages that can occur after operation in In-Air RAT Only mode?
• FUEL PUMP CENTER R
• AUTOTHROTTLE DISC
• AUTOPILOT
• PACK L+R OR PACK L or PACK R
What does In-Air Battery Only mode energize?
The same equipment as the ‘In-Air RAT Only’ mode, except for center pitot heat
This mode is also referred to as Standby Power.
What are the two types of automatic load reduction to maintain power for essential systems?
• Load inhibit
• Load shed
Load inhibit occurs at predefined operational phases, while load shed prioritizes loads to stay within power capacity.
What is the purpose of the electrical synoptic in relation to load shedding?
It shows a list of airplane systems affected by load shedding and indicates equipment that is inhibited or shed
Affected loads are marked with ‘LOAD SHED’ text next to their symbols.
What does the IFE/PASS SEATS switch control?
In-Flight Entertainment (IFE) system, passenger seat systems, video surveillance cameras, and flight deck personal electronic device power outlets
This switch is located on the flight deck overhead electrical panel.
What systems does the CABIN/UTILITY switch control?
Galleys, most cabin lights, and other non-essential cabin utility loads
This switch is also found on the flight deck overhead electrical panel.
Can circuit breakers be opened or closed using CBIC during flight?
Yes
However, the flight crew should not reset tripped circuit breakers in flight unless directed by maintenance or a non-normal checklist.
Is cycling (pulling and resetting) of circuit breakers recommended to clear a non-normal condition?
No, unless directed by maintenance or a non-normal checklist
What is not recommended for flight crew regarding tripped circuit breakers in flight?
Resetting a tripped circuit breaker
What appears after selecting the OPEN soft key in flight?
Confirmation window
This window prompts the user to confirm the action.
DOESNT OCCUR ON GND
What is the status of the circuit breaker after performing the OPEN command?
It is opened
The control menu is then closed.
What is the first step to perform on the ground for circuit breaker control?
Select CTRL soft key (displays control menu)
What happens when the CLOSE soft key is selected on the ground?
Closes circuit breaker and closes control menu
What is the sequence of steps to close a circuit breaker in flight?
- Select CTRL soft key (displays control menu) * Select CLOSE soft key (displays confirmation window) * Select ENTER key on multifunction keypad (closes circuit breaker and closes confirmation window)
Fill in the blank: On the ground, after selecting the CTRL soft key, the next step is to select the _______.
CLOSE soft key
