Electrical System Flashcards
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 APU Inverter RAT AC GPU receptacle
What components power the DC system?
2 NiCad batteries
3 Transformer Rectifier Units (TRU)
DC GPU receptacle
How does the IDG maintain a stable power output?
A CSD (constant speed drive) attaches the IDG to the AGB (accessory gear box)
What monitors and controls the IDGs?
Generator Control Unit
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
HILOP
If an IDG is manually disconnected can it be reconnected by the flight crew?
No.
Maintenance
What is the primary purpose of the AC generators?
To power the AC buses and AC ESS Bus which…
Power three transformer rectifier units (TRU) 1, 2, and ESS
What is the purpose of the Transformer Rectifier Units?
To convert 115 VAC to 28 VDC
Can the APU replace a failed IDG
Yes
What is the AC electrical system’s priority
Onside IDG
INSIDE APU
OUTSIDE GPU
CROSS-side 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 service 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 button before the next GPU selection
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 are less than 22.5 VDC, or
If battery temp is less than -20 degrees 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 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 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 ESSENTIAL BUSSES and AC STANDBY BUS
What does the RAT power ?
ESSENTIAL BUSSES
What is minimum airspeed for the RAT?
130 KIAS
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 Integrated Control Centers ICC
2 Secondary Power Distribution Assemblies ( 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 be 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 CB’s can only be reset by maintenance
SPDA CB’s can be reset via the MCDU
of networks and why
2
Redundancy
Fault isolation
