Electrical Flashcards
How many electrical networks are on the aircraft? Why?
- 2 independent networks
- Redundancy
What happens if a power generating source fails?
Bus ties automatically connect to provide no system degradation
What components power the AC system?
- 2 IDG’s
- APU
- Inverter
- RAT
- AC GPU receptacle
What components power the D.C. System?
- 2 nicad batteries
- 3 TRUs
- DC GPU receptacle
How does the IDG maintain a stable power output?
A constant speed drive attached to the accessory gear box
What monitors and controls the IDGs
Each has a generator control unit (GCU)
Can one IDG power 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, it’s a maintenance function
What is the primary purpose of the AC generators?
What buses and components are powered?
- Powers AC BUS 1, 2 and AC ESS BUS which…
- Power TRU 1, 2, and ESS
What do the TRUs do?
Convert 115V AC to 28V DC
Can the APU replace a failed IDG?
Yes
What is the AC system’s source priority?
- Onside
- Inside
- Outside
- Cross-side
How do you know if an AC GPU is connected and ready to provide electricity?
- GPU button displays AVAIL and the GPU icon is presented on the electrical synoptic page
- once GPU button is depressed it will display IN USE unless another AC Power source is 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 use
If the airplane is using the AC GPU and the APU is started what should the pilot be sure to do?
Deselect the GPU pushbutton before the next GPU connection
What will charge BATT 1 and 2
Any AC power source
How long will the batteries last with no recharging?
10 mins
What is the purpose of the D.C. GPU receptacle?
If the battery temp is < -20C
What is the min battery temp for APU start?
-20 C on BATT 2
What is the min voltage to close the battery bus ties?
18 V
How are the batteries used for APU start?
- BATT 2 powers the APU start bus
- BATT 1 powers the APU FADEC and 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 an AC source is not available
What is on the AC STANDBY BUS?
Engine exciters 1A and 2A
What powers the 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
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 D.C. ESS BUSSES and AC STANDBY BUS (via the inverter)
What does the RAT POWER ?
The ESS BUSSES
What is the minimum airspeed for the RAT?
130 kts
- load shedding occurs below this speed
When is the RAT icon displayed on the electrical synoptic page?
When the RAT is deployed
What manages the electrical system?
- 4 ICC’s (Integrated Control Centers)
- 2 SPDA’s (secondary power distribution assemblies)
What is an ICC?
An electronic 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 aircraft systems according to distribution logic
Can the flight crew reset the ICC and SPDA remote electronic CBs?
- ICC CBs can only be reset by maintenance on the ground
- SPDA CBs can be reset via the MCDU
