Electrical Questions Flashcards
How man networks make up the electrical system on the airplane? Why?
- 2 independent networks
- Redundancy and fault isolation
What happens if a power generating source fails?
- BUS ties automatically connect to provide no system degradation
What components power the AC system?
- 2 integrated drive generators (IDG)
- Auxiliary power unit (APU)
- Inverter
- Ram Air Turbine (RAT)
- AC GPU receptacle
What components power the DC system?
- 2 NiCad batteries
- 3 transformer rectifier unit (TRU)
- DC GPU receptacle
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 IDG’s?
- Each has a Generator control unit (GCU)
Can one IDG supply the entire electrical system?
Yes
What will cause the amber IDG light on the overhead panel to illuminate?
- High oil temperature
- Low oil pressure
If an IDG is manually disconnected can it be reconnected by the flight crew?
- No. This is a maintenance function
What is the primary purpose of the AC Generators?
- To power the AC BUSSES and AC ESS BUS
- Power the 3 transformer rectifier units (TRU) 1,2 and ESS
What is the purpose of the transformer rectifier unit?
- To convert 115 VAC to 28 VDC
Can the APU replace a failed IDG?
- Yes
What is the AC electrical system priority?
- Onside (IDG)
- Inside (APU)
- Outside (GPU)
- Cross-side (other IDG)
How is it known that an AC GPU is hooked up to the airplane and ready to provide electricity?
- GPU button displays 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 provided another AC power source is not available
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 the use
If the airplane is using the AC GPU and the APU is started what should the pilot be use to do?
- Deselect the GPU button before the next GPU connection
What will charge the batteries?
- Any AC power source
How long will the aircraft’s batteries last with no recharging?
- 10 min
What is the purpose of the DC GPU receptacle?
- For APU start when batteries < 22.5 VDC or
- If battery temp os < -20 C
What is the minimum battery temp for APU start?
-20 C
What is the minimum battery voltage to close the battery’s-ties?
18 Volts
What battery is used for the inverter?
- BATT 2 powers the APU start BUS
- BATT 1 powers the FADEC & EICAS for monitoring
What is the purpose of the inverter?
- Converts 28 VDC from the batteries to 115 VAC to power the AC STANDBY BUS when and AC source is not available
What is the AC STANDY 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 BUSSES are not powered
- Manually by pilot
How long after deployment before the RAT will supply power?
- 8 Seconds
Is there a total loss of power during the 8 second RAT deployment?
- No. Batteries supply power to the DC BUSSES and AC STANDBY BUS
What does the RAT power?
- ESS BUSSES
What is minimum airspeed for the RAT?
- 130 Kias
- Load shedding occurs below 130 Kias
When is the RAT icon displayed on the electrical synoptic page?
- When the RAT is deployed
What manages the electrical system?
- 4 Integrated Control Centers (ICC)
- 2 Secondary power distribution assembles (SPDA)
What is an ICC?
- An electrical control device, which provides power distribution and protection for electrical loads.
What is an SPDA?
- An electrical load-management unit (powered by the ICC’s) that distributes electrical loads to the aircraft systems according to distribution logic.
Can the flight crew reset the ICC and SPDA remote electronic CB’s?
- ICC CB’s can only be reset by maintenance
- SPDA CB’s can be reset via the MCDU
