Electrical Flashcards
What happens if a power generating source fails?
Bus ties automatically connect to provide no system degradation.
How many networks make up the electrical system on the airplane? Why?
I. 2 independent networks
II. Redundancy and fault isolation
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 in DC system?
2 NiCad batteries
3 Transformer Rectifier Units (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?
Hi oil temperature
Low oil pressure
If an IDG manually disconnected, can it be reconnected by the flightcrew?
No. This is a maintenance function
What is the primary purpose of the AC generators?
To power the AC BUSES and AC ESS BUS which…
Power the three Transformer Rectifier Unit (TRU) One, Two, and ESS
What is the purpose of the Transformer Rectifier Units?
To convert 115V 400Hz AC to 28V 300 Amp DC
Can the APU replace the failed IDG?
Yes (below 33,000ft)
What is normal AC electrical priority?
Onside (IDG)
Inside (APU)
Outside (GPU)
Cross-side (other IDG)
Note: The airplane uses an onboard AC power source before an external AC source.
How is it known that AC GPU is hooked up to the airplane and ready to provide electrical power?
GPU button displays AVAIL and the GPU icon is presented on the electrical synopsis 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 button is “IN USE”.
Cockpit GPU button will display “AVAIL” even though the ground service bus “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 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 minutes
What is the purpose of the DC GPU receptacle?
For APU start when batteries < 22.5 VDC, or
If battery temp is < -20°C
What is the minimum battery temp for APU start?
-20°C
What is the minimum battery voltage to close the battery bus-ties?
18 volts
What battery is used for the APU start?
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 the AC source is not available
What is on the AC STANDBY BUS?
Engine ignitors 1A & 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 BUSES 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 that 8 second RAT deployment?
No. Batteries supply power to the DC ESS BUSES and AC STANDBY BUS
What does the RAT power?
ESS BUSES
What is minimum airspeed for the RAT?
130 KIAS. (150 KIAS during deployment)
Load shedding occurs below this speed.
When is the RAT icon displayed on the electrical synapses page?
When the RAT is deployed
What manages the electrical system?
4 Integrated Control Centers (ICC)
2 Secondary Power Distribution Assembly (SPDA)
What is an ICC?
An electrical control device which provides power distribution and protection for electrical loads
What is an SPDA?
And 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 circuit breakers?
ICC circuit breakers can only be reset by maintenance.
SPDA circuit breakers can be reset via the MCDU
What is the purpose of the LICC?
The left integrated control center provides power distribution and protection for AC bus 1 and DC bus 1 and the AC and DC ground service buses. Line replaceable modules in the LICC are TRU 1, GCU 1, the external power module and several thermal circuit breakers.
What is the purpose of the EICC?
The emergency integrated control center, located in the forward eBay, provides power distribution and protection for AC essential bus and DC essential bus 1 and 3. The standby AC bus and the hot battery bus are also integrated into the control center. Line replaceable modules in the EICC are the essential TRU and several thermal circuit breakers.
What items are on the DC Hot Bus 1
- Engine 1A/2A fire extinguisher
- Engine Fuel Shutoff Valve 1
- Hydraulic Shutoff Valve 1
- Engine 1 Oil Level Indication
- Courtesy/Service Lights
- DC Ceiling Lights
What items are on the DC Hot Bus 2
- Engine 1B/2B Fire Extinguisher
- Engine Fuel Shutoff Valves 2
- Hydraulic Shutoff Valve 2
- Engine 2 Oil Level Indication
- CMC
- Refuel Panel
- Water and Waste System
