Flashcards in Electrical Deck (107):
How many independent electrical systems are on the airplane? Why?
-2 independent networks
What components power the AC system?
• 2 Integrated Drive Generators (IDG) (40 KVA)
• Auxiliary Power Unit (APU)
• Ram Air Turbine (RAT) (15 KVA)
• AC GPU receptacle
What components power the DC system?
-2 NiCad batteries
-3 transformer rectifier units (TRU)
-DC GPU receptacle
List all the DC buses
-GND service bus
-APU start bus
-2 HOT BAT buses
-2 DC buses
-3 DC ESS buses
What is the source priority order for powering the AC main buses?
- Inside (APU GEN)
- Outside (GPU if connected)
- Cross-side (Opposite IDG)
How does the IDG maintain a stable power output?
A constant speed drive (CSD) attaches the IDG to the AGB (accessory gear box)
What monitors and controls the IDGs?
Each has a generator control unit (GCU)
If only 1 IDG is on, what powers the other side? What if you start the APU? What would power it?
- IDG will power both sides through BTC 1
- APU will power the right side (system 2) through BTC 2
Are the IDG icons on the MFD always in view even when the IDGs are not powered?
Almost always. They become 3 dashes if invalid or out of range. Otherwise they are always in view.
Can one IDG power the entire electrical system?
Does the IDG have its own oil supply? If yes, can you see it's quantity?
On the electric control panel, the amber lights near the IDG control knob indicates what?
Which IDG must be disconnected and its associated EICAS message
What are three reasons for the IDG disconnect light to illuminate?
- High oil temperature
- Low oil pressure
- Annunciator test button
If an IDG is mechanically disconnected can it be reconnected on the ground or in flight by the flight crew?
No, this is a maintenance function.
What indication would you get with an IDG low oil pressure or high oil temperature?
An amber LED next to the associated IDG switch and an associated EICAS IDG 1(2) oil illumination
During "normal operation" will a failed IDG de-power the respective AC bus?
What happens when the IDG selector knob is in AUTO, OFF or DISC?
AUTO: Allows the automatic operation of the electrical system. It closes the IDG contractor, connecting the IDG to its respective AC bus.
OFF: The generator is de-engergized and the IDG contractor is opened isolating the IDG from the respective AC bus
DISC: must be held in this position for one second to mechanically disconnect the IDG
What is the primary purpose of the AC generators?
To power the AC BUSs and the AC ESS BUS which...
Power the 3 transformer rectifier units TRU 1, 2 and ESS
What is primary and alternate sources of power for the AC ESS BUS?
Primary is the AC BUS 2. ALT is AC BUS 1 (and the RAT when both AC BUSs 1 and 2 are not powered)
What is the normal and alternate source of power for the AC standby bus?
Normal is the AC ESS BUS and the alternate is the AC inverter
State the source priairoty for powering the AC main buses
Which AC source has priority, the APU or GPU
APUhas priority and will automatically switch when the API is ip and running
Will the AC APU icon always be in view on the MFD>
No, only when the APU is available (3 seconds after 95%)
What is the purpose of the transformer rectifier units?
To convert 115 VAX to 28 VDC
What happens when the TRU 1 (2) and TRU ESS switches are in AUTO?
AUTO allows automatic operation of the electrical system. TRU 1 and 2 connect to its respective DC BUS, TRU ESS connects to the ESS BUS 3
What does the OFF position of TRU 1 and 2 do?
Isolates the TRU from its respective DC BUS
What does the OFF position of TRU ESS do?
Isolates the TRU from ESS BUS 3
During normal operations, TRU 1 supplies power to what?
DC BUS 1, DC ESS BUS 1, DC ground service bus, HOT BATT 1, and BATT 1 charging
During normal operations TRU 2 supplies power to what?
DC BUS 2, DC ESS BUS 2, HOT BATT BUS 2, and BATT 2 charging
During normal operations TRU ESS supplies power to what?
DC ESS BUS 3
When are batteries being charged?
Whenever the TRUs are powered from any source
TRU transforms AC to DC, is there a way to change DC to AC?
Yes, the inverter
BATT 1 or 2 normally charges through which TRU?
the associated side
Cant eh APU fully replace a failed IDG?
The APU GEN button, when depressed, does what?
- Connects the APU GEN to the AC bus tie according to source priority and provided the power is within limits
- Allows automatic operation of the electrical system
What happens when he APU GEN pushbutton is out?
- Opens the APU GEN cofactor and isolates the APU from the AC BUS TIE. The APU GEN is tripped off line and de-excited
- White stripe illuminates
During ground operations with the APU operating, the failure of an IDG will cause its respective AC BUS to get power from where?
You receive the aircraft at the gate and it is powered by the AC GPU. You start the APU. Once it's up and running how can you tell the APU GEN has automatically taken over the electrical load?
AVAIL light on the AC GPU button and the MFD electrical page shows green APU icon
In flight, with the APU operating, an intentionally disconnected IDG will cause the respective AC BUS to seek power from?
What happens when the GPU pushbutton is out?
Isolates the AC GPU from the AC BUS TIE
At the gate, ground power is connected. What do you have to have to get an AVAIL light outside and in the cockpit?
Volts/Amps/Freqs are within limits
How is it known that an AC GPU is plugged in and the outside GPU panel button displays IN USE?
- GPU buttons display AVAIL and the GPU icon is presented on the electrical synoptic page
- Once the GPU button is pushed in, the button will display IN USE. Connects the AC GPU to the AC BUS TIE according to source priority
What does it mean if the AC GPU is plugged in and the outside GPU panel button displays IN USE?
-Ground service bus is in use
- Cockpit GPU button will display AVAIL even though the ground service bus is in use
Will the AC GPU icon always be in view on the MFD?
No. It comes into when when connected and the power is good
If the airplane is using the AC GPU and the APU is started what should the pilot be sure to do?
Deselect the AC GPU button so the power can be connected the next time it is used. Going from out to in closes the generator relay
Will the AC GPU provide power to start the APU?
No, the AC GPU will only charge the batteries
What will charge the batteries?
Any AC power source
The battery icon is always displayed on the MFD. How can you tell if the voltage is good?
- The parameters are indicated (voltage and temp). All the battery icon is green above 18 volts and white below 18 volts
- RJET limits: 22.5V for start and -20C
What does it mean when the battery associated digits turn RED on the MFD?
The battery temp reached 70C for 2 seconds. The BATT 1(2) OVERTEMP EICAS massage is also displayed.
Why is there an AUTO position on BATT 2?
BATT 2 supplies the APU START BUS during APU starting
Name a six items on the HOT BATT BUSES
- Engine Fire Extinguishers
- Fuel shutoff valves
- Hydraulic shutoff valves
- Engine oil level systems
- Refueling panel
- Water and waste system
What happens when BATT 2 switch is in AUTO or OFF?
AUTO: Allows automatic operation of the electrical system. BATT 2 connects to DC ESS BUS 2
OFF: The battery supplies power to the HOT BATT BUS 2
What happens with the BATT 1 selector ON or OFF?
ON: The battery is connected to the DC ESS BUS 1
OFF: The battery supplies power to the HOT BATT BUS
During an electrical emergency, the batteries supply essential loads for how long?
How long will the aircraft batteries last without recharging?
During an electrical emergency what equipment is available?
DU 2 (Locked into a PFD), DU 3, Clock, IESS, MCDU 2, CCD 1
Does turning the battery selector knobs to "ON/AUTO" cause the battery to power its respective HOT BATT BUS?
What is the min battery voltage for the SAFETY and POWER ON checklist?
22.5 VDC (needed for APU start)
What if the batteries are not at 22.5 VDC during the SAFETY and POWER ON checklist?
GPU can provide power to the aircraft. Reference SOP chapter 6 to determine how long is necessary to recharge the batteries
What is the min battery voltage to close the battery bus ties?
What battery is used for APU start?
BATT 2 powers the APU START BUS
BATT 1 powers the APU FADEC (logic for the start)
Why is there an AUTO position for BATT 2?
- BATT 2 supplies the APU start bus to be powered exclusively during the APU start
- The disconnect of DC BUS 2
What is the min battery temp for APU start?
What would you do if the BATT 2 was colder than -20C
Connect the DC GPU which powers the APU start bus and isolates BATT 2
What is the purpose of the DC GPU receptacle
- For APU start when the batteries
What is the purpose of the inverter?
Converts 28 VDC from the batteries to 115 VAC to power the AC STANDBY BUS when an AC source isn't available
What happens when the AC BUS TIE switch is in AUTO?
Auto allows automatic operation of the electrical system. Controls the operation of the bus tie contractors IAW system logic
What does the OPEN 1 position of the AC BUS TIES knob do?
Opens the BTC 1 which segregates AC BUS 1 from 2
What does the OPEN 2 position of the AC BUS TIES knob do?
Opens the BTC 2 which segregates AC BUS 2 from 1
What happens if a power generating source fails?
Bus ties automatically connect to provide no system degradation
What happens when the DC BUS TIES switch is in AUTO or OFF?
AUTO: allows automatic operation of the electrical system
OFF: Opens all BUS TIE contactors
What is on the AC STANDBY BUS?
Engine exciters 1A and 2A
What powers the Ram Air Turbine (RAT)?
Airflow turns the RAT propeller which spins the turbine inside
When will the RAT deploy?
- Automatically deploys if AC BUS 1 and 2 are not powered
- Manually by pilot
Both IDGs and the APU generator are rated at 40KVA. What is the RAT rated at KVA and volts?
15 KVA and 115 VAC
Is there an altitude restriction for operation of the RAT?
How long after deployment before the RAT will supply power?
Is there a total loss of power during the 8 second RAT deployment?
No. HOT BATT BUS 1 and 2 supply power to DC ESS BUSS 1/2 and AC STANDBY BUS through the AC inverter
What BUSES does the RAT power?
AC ESS BUS, AC STBY BUS, TRU ESS, ESS BUS 3, DC ESS BUS 1, HOT BATT BUS 1, DC ESS BUS 2, HOT BATT BUS 2
With both IDGs and APU generator offline, and the AC BUS TIE set to AUTO, will the RAT power the AC BUSES via the AC ESS BUS?
What does the RAT power?
Powers the AC and DC ESS BUSES
What is the minimum airspeed for the RAT?
- 130 knots
- Below this speed power the to the DC ESS BUSES are initially powered by the battery, then load shedding occurs and eventually the AC ESS BUS is no longer powered
- 150 knots on the QRH checklist is to ensure that the ESS TRU contractor will close, Once it closes and the RAT is supplying the ESS BUSES it is possible to maintain the 130 knot minimum,
How would you deploy the RAT in the event of an automatic deployment failure?
Use the RAT manual deployment handle
If a TRU fails, will the respective DC BUS be unpowered?
Briefly describe the electrical power distribution and control system?
- 4 ICCs
- 2 secondary power distribution assemblies (SPDAs)
What is an ICC?
An electrical control device which provides power distribution and protection for electrical loads
Name the four ICCs.
LICC, RICC, EICC, AICC
The ICCs are located where?
In the E-bays
What do the ICCs contain?
Line replaceable units and modules, thermal circuit breakers and the AC/DC buses including the essential buses and HOT BATT buses
Which ICC houses the the HOT BATT 2 and the APU start bus?
What is an SPDA?
An electrical load-management unit powered by the ICC's that distributes electrical loads to aircraft systems IAW distribution logic
Each SPDA has specific slots that house what?
Electronic modules that provide associated functions such as COMM, data processing and power distribution. The MAU does the thinking, the ICC's provide the power and the SPDA's do the switching.
Four independent DC BUSES power each SPDA. Which buses power SPDA 1?
DC BUS 1, DC ESS BUS 1, DC ESS BUS 2, and DC GND SVC BUS
Four independent DC BUSES power each SPDA. Which buses power SPDA 2?
DC BUS 2, DC ESS BUS 1, DC ESS BUS 2, and DC GND SVC BUS
What type of CB protection is incorporated into the SPDAs?
Electronic CBs (solid state CBs)
Can the remote electronic CBs be monitored? (in the E-Bays?)
Yes via the MCDU
What items will the SPDA command to be load-shed IOT prevent the remaining electrical source from overloading?
- Right windshield
Can the flight crew reset the ICC and SPDA remote electronic CBs?
- ICC CB's can only be reset by maintenance on the ground
- SPDA CB's can be reset bia the MCDU
What powers the IESS in case of electrical emergency?
If the APU is available and one engine generator fails, the failed generator is replaced by:
If you start an engine at the gate with the GPU, is the electrical system split?
During dual engine failure checklist says min airspeed of 265 knots. Why?
Windmill speed for the start envelope. If you start the engine with insufficient airflow you risk core lock
You board a depowered airplane and proceed to establish electrical power. Which panel is of relevance to you and where is it?
- Galley electronic panel behind cockpit door
- Ground service buses must be disconnected prior to applying power through the AC GPU
What happens if only the ground personnel push their GPU button?
Their button shows IN USE and the cockpit shows AVAIL. Only the ground service buses are powered
How many display units (DUs) come to life when you bring the batteries online? Which ones are they?
2, DU 2 and 3
An electrical PBIT test during the power-up of the aircraft will not be interrupted if?
APU is started