Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
105 Cards in this Set
- Front
- Back
|
How many main AC busses are in the electrical system?
|
Four main AC busses.
|
|
|
What is the purpose of the synchronous bus?
|
AC busses are interconnected through the synchronous bus. This arrangement distributes electrical loads and allows the individual AC busses to be powered through the synchronous bus when their generators are NOT operating.
|
|
|
When does the External Power Available (AVAIL) light illuminate?
|
When external power is plugged and the voltage and frequency of the externalpower source are within acceptable limits.
|
|
|
Where is external power connected to the synchronous bus?
|
Through the left and/or right side of the synchronous bus.
|
|
|
What is the purpose of the split system breaker (SSB)?
|
To divide the synchronous bus into left (busses 1 and 2) and right (busses 3 and 4) sides. Allows separate powering of each side of the AC system by one external source or one APU generator, or one source to power the entire synchronous bus. External/APU power sources can’t be paralleled.
|
|
|
What are the sources of AC power on the aircraft?
|
Four IDG’s, two APU generators, and two external power receptacles.
|
|
|
What is an IDG?
|
An IDG, integrated drive generator, is each engine's generator and constant speed drive contained within a common housing. The IDG is lubricated by a self-contained oil system.
|
|
|
What does an illuminated generator DRIVE light indicate?
|
- low oil pressure- high oil temperature- the generator control breaker is open due to uncorrectable generator frequency fault (on the newest IDGs).
|
|
|
Can the IDG automatically decouple?
|
Yes, for high oil temperature in the newest IDGs, which may be on any aircraft.
|
|
|
What is the indication that an IDG has been manually disconnected?
|
After pushing the Generator Drive Disconnect switch the EICAS Advisory message changes from ELEC DRIVE to >DRIVE DISC. The DRIVE light is illuminated for both Advisory messages. The ELECT GEN OFF EICAS Advisory message is displayed and GEN CONT OFF light is illuminated. The electric synoptic also indicates the disconnected condition.
|
|
|
What is the indication that an IDG has been automatically disconnected?
|
ELEC DRIVE EICAS Advisory message with a DRIVE light overhead. ELEC GEN OFF EICAS Advisory message with a GEN CONT OFF light overhead.
|
|
|
Once an IDG has been disconnected, can it be reconnected in flight?
|
No, the IDG can only be reconnected on the ground by maintenance.
|
|
|
How are the IDG’s connected to the main aircraft busses?
|
Through the generator control breakers (GCBs).
|
|
|
What does pushing a Generator Control switch ON accomplish?
|
Closes the generator field and arms the generator control breaker to close when acceptable IDG power is available.
|
|
|
What is indicated when a Generator Control switch OFF light is illuminated?
|
Generator control breaker is open.
|
|
|
How can generator control logic be reset?
|
By pushing the Generator Control switch OFF and then ON.
|
|
|
With all engines running and the Generator Control switches selected ON what is the power source for the AC busses?
|
Their respective IDGs.
|
|
|
How does the generator control breaker operate?
|
With the Generator Control switch ON, system logic will close the generator control breaker and provide power to the respective AC busses when the IDG power quality (frequency and volts) is acceptable.
|
|
|
What is indicated if the generator control breaker remains open with the IDG up to acceptable limits?
|
EICAS Advisory message ELEC GEN OFF will be displayed if a generator control breaker is open with its respective engine running and the OFF light will be illuminated in the switch.
|
|
|
How is each AC bus connected to the synchronous bus?
|
Through its respective bus tie breaker (BTB).
|
|
|
What is the proper position of the GEN CONT and BUS TIE switches prior to engine start?
|
BUS TIE switches in AUTO and GEN CONT switches ON.
|
|
|
How do the bus tie breakers operate?
|
The AUTO position arms automatic operation of the BTB and closes the DC isolation relay (DCIR).
|
|
|
What will the BTB do when it's respective AC bus receives unsynchronized power?
|
The respective BTB opens automatically NOT allowing connection to the synchronous bus and the isolated bus will continue to operate from it's own IDG.
|
|
|
What occurs if the IDG is NOT able to maintain acceptable power quality for the AC bus?
|
The respective generator control breaker (GCB) will open, and the bus tie breaker (BTB) will close to power the bus from the synchronous bus.
|
|
|
What does the AC Bus Tie Isolation (ISLN) light mean when illuminated?
|
Bus tie is locked open due to a fault on the bus, or the bus tie switch is selected OFF.
|
|
|
What does the AC Bus Tie Isolation (ISLN) light mean when illuminated?
|
Bus tie is locked open due to a fault on the bus, or the bus tie switch is selected OFF.
|
|
|
If an AC BUS TIE switch is turned OFF, what will occur?
|
Opens the AC bus tie breaker; opens DC isolation relay; resets fault circuitry.
|
|
|
How is an open bus tie breaker indicated?
|
By the EICAS Advisory message ELEC BUS ISLN and illumination of the AC Bus Isolation (ISLN) light on the BTB switch.
|
|
|
What resets the bus tie breaker logic and allows the BTB to close if the fault is corrected?
|
Pushing the Bus Tie switch to OFF, then AUTO.
|
|
|
What normally powers the Captain’s Transfer bus?
|
AC bus number 3.
|
|
|
What normally powers the First Officer’s Transfer bus?
|
AC bus number 2.
|
|
|
What will provide backup power for the Transfer busses in the event of AC bus 3 failure for the Captain or AC bus 2 failure for the First Officer?
|
AC bus 1 serves as a backup for both Transfer busses.
|
|
|
Can both Transfer busses be powered simultaneously from AC bus 1 in the event that both AC busses 2 and 3 fail?
|
Yes.
|
|
|
What are the flight deck indications that the transfer has occurred?
|
No indications of transfer but you would see indications that AC bus 3 and/or AC bus 2 have failed.
|
|
|
What is the normal power source for the Standby bus?
|
This bus is normally powered from AC bus 3.
|
|
|
What will provide power to the Standby bus if AC bus 3 becomes unpowered?
|
With the Standby Power selector in AUTO and the Battery switch ON, the Standby bus would be powered by AC bus 1 through the standby inverter.
|
|
|
If AC bus 1 is also unpowered, what would provide power to the Standby bus?
|
Main battery through the main standby inverter for a minimum of 30 minutes.
|
|
|
TRUE or FALSE. Aircraft 6315 have an additional APU Standby bus which is normally powered from AC bus 3 through the Captain's Transfer bus?
|
True.
|
|
|
What will provide power to the APU Standby bus (aircraft 6315 and 6316) if AC bus 3 becomes unpowered?
|
With the Standby Power selector in AUTO and the Battery switch ON, the APU Standby bus is powered by AC bus 1 through the Captain’s Transfer bus.
|
|
|
If AC bus 3 and bus 1 are unpowered what is the power source for the APU Standby bus (aircraft 6315 and 6316)?
|
APU battery through the APU Standby inverter for a minimum of 30 minutes.
|
|
|
Must the BATTERY switch be in the ON position to allow the main/APU batteries to be a backup power source for the Standby bus/busses?
|
Yes.
|
|
|
With the Standby Power selector in the BAT position, what provides power to the Standby bus/busses?
|
The Standby busses are powered by the Main and APU batteries through the Main and APU Hot Battery busses and standby inverters (provided the Battery switch is ON). BAT position is NOT used for flight operations.
|
|
|
Will the Main or APU battery chargers remain connected with the Standby Power selector in BAT?
|
The battery chargers are disconnected from the batteries with the Standby Power selector in the BAT position. EICAS Advisory message >BAT DISCH MAIN/APU will be displayed.
|
|
|
Will the Standby bus last indefinitely with BAT selected?
|
No, the Standby bus can be powered by it’s battery for a minimum of 30 minutes and will last until it’s charge depletes.
|
|
|
If all four engines flame out inflight what is the power source for ignition?
|
The standby inverter via the Main Hot Battery bus.
|
|
|
What items does the Ground Handling bus power?
|
The Ground Handling bus powers the fueling system, cargo handling equipment, cargo doors, cargo compartment lights, number 4 hydraulic system auxiliary pump, and Flight Deck Access lights.
|
|
|
What is the power source for the Ground Handling bus?
|
Number one priority is external power one, second source is APU generator one.
|
|
|
When can the Ground Handling bus be powered?
|
Only on the ground and less than 3 engines operating at 75 percent N2 RPM. (The bus is inhibited if 3 engines are operating above 75 percent N2 RPM.)
|
|
|
Does EXT 1 or APU GEN 1 have to be selected as the aircraft power source to be able to power the Ground Handling bus?
|
No. EXT 1 or APU GEN 1 only have to be available to power the Ground Handling bus.
|
|
|
If neither external power nor APU power is available, what will power the Ground Handling bus?
|
Nothing, the Ground Handling bus will no longer be powered.
|
|
|
After all engines are started and the APU is shut down, you are asked to return to the gate to take on more cargo. What must be accomplished to open the cargo doors?
|
Either external power 1 AVAIL or APU 1 AVAIL must be available to power the Ground Handling bus. Ground personnel can also mechanically crank open the door if external power or APU is NOT available.
|
|
|
What items does the Ground Service bus power?
|
Main and APU battery chargers, fuel pumps for APU start, upper deck doors, flight deck floodlights, navigation lights, cabin and service lights, miscellaneous service outlets/equipment.
|
|
|
When is the Ground Service bus powered?
|
On the ground and in flight, normally by AC bus 1.
|
|
|
Is there another way that the Ground Service bus can be powered if AC bus 1 is NOT powered?
|
Yes, on the ground only the Ground Service bus can be connected to the same source powering the Ground Handling bus by means of the Ground Service switch on the flight attendant’s panel at door 2L.
|
|
|
If AC bus 1 is powered can the Ground Service bus be connected to the APU or external power using the Ground Service switch on the flight attendant’s panel at door 2L?
|
No. AC bus 1 is the normal/preferred power source for the Ground Service bus.
|
|
|
The normal power source for the battery chargers (Main and APU) is:
|
The Ground Service bus.
|
|
|
What does a UTILITY OFF light and ELEC UTIL BUS EICAS Advisory message indicate?
|
Utility switch is OFF, galley or utility bus has tripped off due to a fault, or the galley emergency power switch is OFF.
|
|
|
How many utility and galley busses are provided?
|
Four galley and four utility busses.
|
|
|
How are the utility busses and the galley busses connected to their associated AC bus?
|
Each through it's own electrical load control unit known as an ELCU.
|
|
|
What is the purpose of an ELCU?
|
Each ELCU protects the electrical system from utility and galley bus faults and provides automatic load shedding functions.
|
|
|
There are only two utility bus switches. How do they control 4 utility busses and 4 galley busses?
|
The left switch controls ELCUs for utility and galley busses 1 and 2, and the right switch controls ELCUs for utility and galley busses 3 and 4.
|
|
|
How do the ELCUs operate in general terms?
|
ELCUs provide fault protection and are powered by the utility power switches. They continuously compare available generator power to electrical system demand. If available power is reduced because of generator or engine failure, the ELCU’s shed their respective galley and utility busses according to priority logic until the electrical power demand is within the remaining generator capacity. Logic order: galleys 1, 4, 2, 3, then utilities 1, 4, 2, 3.
|
|
|
What EICAS indication is there that load shedding is occurring?
|
Normally there is none. EICAS electrical messages and the utility bus OFF lights are inhibited during load shed. But, if load shedding is excessive, it is possible EICAS alert messages will be displayed for specific unpowered fuel pumps.
|
|
|
If generator capacity is regained or increased, will the ELCUs automatically restore their utility and galley busses?
|
Yes, if the available generator capacity is increased the ELCUs restore the utility and galley busses in reverse order of shedding.
|
|
|
How is the DC power system configured?
|
Each main AC bus powers a TR which in turn provides DC power to its associated DC bus.
|
|
|
What is the purpose of the DC Isolation relay?
|
Allows each individual DC bus to remain powered through the DC Tie bus if the respective AC bus or its associated TR fails.
|
|
|
What AC system configuration allows normal operation of the DC Isolation relays?
|
DC Isolation relays operate automatically provided the Bus Tie switches remain in AUTO.
|
|
|
If an AC Bus Tie switch were manually opened, what would be the position of the DC Isolation relay?
|
The respective DC Isolation relay would open and isolate the DC bus from the DC Tie bus.
|
|
|
If an AC bus is automatically isolated due to an AC bus fault, the respective AC bus tie breaker would open. Does this also open the DC Isolation relay?
|
No, automatic isolation of an AC bus due to a fault does NOT open the DC Isolation relay. Isolation of AC busses 1, 2, 3 during autoland does open DCIR 1, 2, 3.
|
|
|
How many battery busses are in the electrical system?
|
There are 4 battery busses in the DC electrical system, the Main Battery bus, the Main Hot Battery bus, the APU Battery bus, and the APU Hot Battery bus
|
|
|
When would the Hot Battery busses be unpowered?
|
Never, provided good batteries are installed in the airplane.
|
|
|
Are there any items powered with the Battery switch OFF in a cold, dark airplane?
|
Yes, all items on the Hot Battery bus/busses.
|
|
|
What is the normal power source for the Main Battery bus and APU Battery bus with AC power available?
|
DC bus 3.
|
|
|
What will power the Main Battery bus and APU Battery bus if DC bus 3 is NOT available?
|
Provided the Battery switch is ON, the Main and APU batteries automatically power their respective busses.
|
|
|
If one APU generator is powering the AC busses through the synchronous bus (SSB closed) and an engine on the same side as the APU generator is started, will there be an automatic power transfer and if so, how does it occur?
|
Yes, power is automatically transferred from the APU to the IDG. The respective engine IDG will automatically power the synchronous bus when voltage and frequency are within limits. The split system breaker remains closed.
|
|
|
If both APU generators are powering the aircraft, the split system breaker is open and engine four is now started, how will the electrical system reconfigure itself when the engine four IDG comes up to speed?
|
The engine four IDG will automatically power its side of the sync bus and automatically disconnect APU GEN 2. The split system breaker remains open and APU GEN 1 continues to power its side of the synchronous bus.
|
|
|
After engine four is started engine four IDG powers the right side of the synchronous bus and APU GEN 1 powers the left side. When does the split system breaker automatically close?
|
When an engine on the left side of the airplane is started it’s IDG will automatically take over that side of the synchronous bus in the same manner as the number four engine, and the split system breaker will close when the IDGs are synchronized.
|
|
|
What indicates acceptable voltage and frequency from the APU generators?
|
APU generator AVAIL light is illuminated.
|
|
|
When autoland is engaged (below 1500’ AGL, APP selected, LOC and GS engaged) how is the electrical system configured?
|
When autoland is engaged AC and DC busses 1, 2, and 3 are automatically isolated and all three autopilots are individually powered.
|
|
|
If AC busses 1, 2, and 3 are automatically isolated what is the configuration of AC bus 4 on a multiple autopilot ILS approach?
|
AC bus 4 will continue to power the synchronous bus and will automatically power any other AC bus in the event that its generator fails before descending below 200 feet AGL when bus tie lockout occurs.
|
|
|
During autoland bus isolation, are there ISLN lights on bus tie breakers 1, 2, 3?
|
No, the Bus Tie Breaker lights are inhibited during an autoland approach.
|
|
|
TRUE or FALSE. Below 200 feet on an automatic approach, engine generator 1, 2, or 3 loss will result in an AC bus failure.
|
True. One autopilot will be unpowered. The aircraft will continue the approach, landing, and rollout using the two remaining autopilots. No change to AFDS.
|
|
|
During preflight (prior to engine start), what occurs to the SSB when the first APU Generator or External Power switch is pushed ON?
|
SSB remains closed and the selected source powers both sides of the synchronous bus.
|
|
|
Prior to engine start with one APU Generator supplying power to the synchronous bus, what occurs when a second APU Generator switch is pushed ON?
|
The SSB automatically opens. APU GEN 1 and APU GEN 2 are powering each respective side of the synchronous bus.
|
|
|
Can an external power source and an APU generator power the same side of the synchronous bus simultaneously?
|
No.
|
|
|
When APU generator power, external power, and engine generator power are applied to the same side of the synchronous bus, what has priority?
|
Whichever source of power was selected last.
|
|
|
When transferring power from the IDGs to external or APU power:
|
EXT PWR or APU must be selected ON; the power sources momentarily synchronize ("make before break").
|
|
|
TRUE or FALSE. At the gate, if external power is plugged in and selected ON at the conclusion of a flight, the engine-driven generators are immediately replaced.
|
True. External power now has priority over the engine-driven generators.
|
|
|
Before engine start with each side of the synchronous bus powered by any of the possible APU generator or external power combinations, what happens if one side’s power source fails or is disconnected?
|
The SSB closes automatically maintaining AC power to the entire synchronous bus.
|
|
|
How is the bus tie breaker (BTB) logic reset?
|
By pushing the BTB switch OFF and then ON.
|
|
|
How is ELCU logic reset?
|
By pushing the respective Utility Power switch OFF and then ON.
|
|
|
If a DC Isolation relay is opened by placing its respective BTB switch OFF, is power on the associated DC bus lost?
|
Not necessarily. The affected DC bus may still be powered from its respective AC bus and T/R.
|
|
|
How is an open DCIR indicated?
|
There is no indication.
|
|
|
What is the normal power source for the Main Hot Battery bus with AC power available?
|
AC bus 1 through the Ground Service bus and the Main Battery charger.
|
|
|
What two busses can be powered from the APU battery?
|
The APU Hot Battery bus and the APU Battery bus.
|
|
|
What is the normal power source for the APU Hot Battery bus with AC power available?
|
AC Bus 1 through the Ground Service bus and the APU Battery charger.
|
|
|
What powers the Standby bus with the Standby Power selector in the OFF position?
|
Nothing, the Standby bus is left unpowered.
|
|
|
How can Standby Power be verified?
|
Primary EICAS is displayed on the upper CRT.
|
|
|
With APU GEN 1 and/or EXT PWR 1 indicating AVAIL, is the Ground Handling bus powered?
|
Yes, when the AVAIL light is illuminated the Ground Handling bus is powered.
|
|
|
What is the status of the Main and APU Battery chargers when the Standby Power selector is turned to BAT?
|
The Main and APU Battery chargers are NOT powered.
|
|
|
Does the Utility bus OFF light illuminate with associated load shedding?
|
No, only during faults.
|
|
|
EXT PWR 1 is powering the synchronous bus. You have been asked by maintenance to start engine #4 first. Which of the EXT PWR 1 is powering the synch bus. You start engine 4 first. Which of the following is true after the engine is started?-A) Engine #4 IDG powers the left side of the synchronous bus-B) Engine #4 IDG powers the right side of the synchronous bus; EXT PWR 1 powers the left side and the SSB is open-C) Engine #4 IDG powers the synchronous bus; EXT PWR 1 is automatically removed; SSB closes-D) SSB opens; AC buses 1 and 2 are unpowered.
|
Answer: B
Engine #4 IDG powers the right side of the synchronous bus; EXT PWR 1 powers the left side and the SSB is open |
|
|
What happens when the Battery switch is pushed ON and no other power sources are connected?
|
The Main and APU batteries are connected to their respective Battery busses.
|
|
|
TRUE or FALSE: When power is transferred from IDGs to an external source or APU generator, the IDGs will automatically synchronize with the new power source, allowing power transfers without interruptions.
|
True
|
|
|
Where can the battery charge indications be read?
|
The STATUS page.
|
