Systems Oral Flashcards
(310 cards)
What components power the DC electrical system
2 NiCad batteries (24VDC, 27 AH)
3 Transformer Rectifier Units (TRU) 28VDC, 300 A
DC GPU Receptacle
How does the IDG maintain a stable power supply?
A constant speed drive (CSD) attaches the IDG to the Accessory Gear Box
What will cause the amber IDG light on the overhead panel to illuminate?
High Oil Temperature
Low Oil Pressure
What is the purpose of the Transformer Rectifier Units?
Converts 115VAC to 28VDC
Can the APU replace a failed IDG?
Yes, up to 33,000’
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.
GPU plugged in and outside GPU panel displays IN USE means:
Ground service bus is in use
Cockpit GPU button will display AVAIL even though the ground service bus is in use.
GPU in use and APU started. Next pilot action:
Deselect the GPU button before the next GPU connection
Batteries charge source
Any AC Power Source
Aircraft Batteries endurance (without charging)
10 Minutes
Purpose of the DC GPU receptacle
APU start when batteries
Minimum Battery Temp for APU Start
-20 C
Minimum battery voltage to close battery bus-ties
18 Volts
During APU Start, Battery usage
BATT 1 powers the APU FADEC & EICAS for monitoring
BATT 2 powers the APU Start Bus (including DC Fuel Pump)
What is the purpose of the Inverter?
Converts 28 VDC from batteries to 115 VAC to power the AC STANDBY BUS when an AC source is not available
AC STANDBY BUS powers:
Engine exciters 1A and 2A
When will the RAT deploy?
Automatically if AC BUSSES are not powered
How long after deployment before RAT provides power?
8 Seconds
What prevents total power failure during RAT deployment?
Batteries supply power to the DC ESS BUSSES and AC STANDBY BUS
RAT provides power to:
ESS BUSSES
Minimum RAT airspeed
130 KIAS. Below that speed results in load shedding
What manages the electrical system?
4 Integrated Control Centers (ICC) provides power distribution and protection.
2 Secondary Power Distribution Assemblies (SPDA) distributes electrical loads to aircraft systems according to distribution logic
Can the flight crew reset the ICC and SPDA remote CB’s?
ICC - No, can only be reset my maintenance
SPDA - Yes, via the MCDU
Electrical System Fault Logic
- Onside (Dedicated IDG)
- Inside (APU)
- Outside (GPU)
- Cross Side (Opposite IDG)