Electrical Flashcards
What are the AC power sources listed in the EPC?
2 IDGs (Integrated Drive Generators), 1 APU Generator, 1 ACGPU (Ground Power Unit), 1 RAT (Ram Air Turbine), 1 Inverter.
What is the power output of the IDGs?
T15VAC, 400Hz, 40KVA.
What is the power output of the APU Generator?
115VAC, 400Hz, 40KVA.
What is the power output of the ACGPU?
115VAC, 400Hz, 40KVA.
What is the power output of the RAT?
115VAC, 400Hz, 15 KVA.
What is the voltage of the Inverter?
250V.
Can one IDG power both AC buses?
Yes, one IDG can power both AC buses on ground and in flight.
Can the APU power both AC buses?
Yes, the APU can power both AC buses on ground and in flight up to FL330.
Can the GPU power both AC buses?
Yes, the GPU can power both AC buses.
What is the primary AC power source?
IDGs (Integrated Drive Generators).
What is the function of the AUTO setting on an IDG?
System logic controls contactor.
What happens when the IDG is set to OFF?
Opens contactor.
What does DISC do on an IDG?
Mechanically disconnects the CSD (Constant Speed Drive) from the IDG.
Who can reconnect the IDG?
Flight crew cannot reconnect the IDG; it is a maintenance function only.
What does an amber light with an EICAS oil message indicate?
IDG disconnect is required.
What is the secondary AC power source?
APU (Auxiliary Power Unit).
What is required for ARU start?
DC PU are required for ARU start.
What is the minimum voltage required to close the battery contactor?
18.0 VDO.
What is the minimum BATT 2 temperature for start?
-20°C.
What is the AC GPU?
The AC GPU (Ground Power Unit) is a secondary AC power source.
How can the AC GPU be turned ON?
The AC GPU can be turned ON via three different buttons: one on the AC GPU panel, one opposite the FWD lav, and one in the cockpit on the overhead panel.
What happens when the parking brake is released with the AC or DC GPU connected?
A CAS message (GPU CONNECTED), Master Caution flasher, and an aural warning will occur.
What does the AVAIL indication mean?
AVAIL indicates that the GPU is properly connected and power requirements are satisfied.
What does the IN USE indication mean?
IN USE means that the GPU is powering the AC system.
What is the normal AC electrical priority order?
The normal AC electrical priority is: Onside (IDG), Inside (APU), Outside (GPU), Cross-Side (Other IDG).
What is the function of the inverter?
The inverter powers the AC STANDBY BUS when the normal AC power source is not available.
What is the RAT?
The RAT (Ram Air Turbine) is an emergency AC power source.
What are the deployment conditions for the RAT?
The RAT has no altitude or airspeed restriction for deployment and automatically deploys if both AC buses lose power during flight.
What happens during RAT deployment?
During deployment (approximately 8 secs), the aircraft’s batteries provide power.
What is the minimum airspeed required for RAT to provide power?
A minimum of 130 knots airspeed is required.
What happens below 130 knots with the RAT?
Below 130 knots, the RAT will provide power only to AC ESS, while batteries will provide power to DC ESS and AC STANDBY.
What is the DC electrical power configuration?
The DC electrical power configuration includes 13 TRUs (Transformer Rectifier Units), 2 Batteries, and 1 DC GPU.
What is the function of TRUs?
TRUs are the primary DC power source that converts 115VAC into 28VDC.
How do TRUs operate?
Each TRU works in isolation from the other.
What type of power source are batteries considered?
Secondary DC power source
How many NiCad batteries are used?
2 NiCad batteries
What is the purpose of the batteries?
Back-up for DC ESS
How are the batteries charged?
Charged via any AC power source through the TRUs
What is the minimum voltage required to close the battery contactor?
18.0 volts minimum required to close the battery contactor
How long will the batteries provide power during an electrical emergency?
Will provide 10 minutes of power during an electrical emergency
What does the DC GPU do?
Hooks directly to the APU start bus and replaces BATT 2 during APU start
How can the DC GPU be turned on?
Can only be turned on by a ground ramp button
Can the DC GPU charge BATT 2?
Cannot charge BATT 2
What is the ICC?
Integrated Control Center
How many ICCs are installed?
4 (Installed in various Electronics Bays)
What is a characteristic of the ICC?
Line-replaceable (plug-n-play like a computer’s motherboard)
What are SPDAs?
Secondary Power Distribution Assemblies
What is the function of the SPDAs?
An electrical load management unit
Where do SPDAs receive power from?
Receives power from ICCs
What do SPDAs do with the power?
Distributes power according to system logic
What do SPDAs perform on many items?
Performs BITs on many items
In simple terms, what do ICCs and SPDAs do?
The ICCs collect and confirm the power is safe and then sends it to the SPDAs, which distributes it.
What are the items on the Hot Battery Bus?
DC HOT BUS 1 and DC HOT BUS 2
What are the 6 things on 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 are the 7 things on DC Hot bus 2?
Engine 1b/2b fire extinguisher
Engine fuel shutoff valve 2
Hydraulic shutoff valve 2
Engine 2 oil level indication
CMC
Panel refuel
Water and waste system
How many networks make up the electrical system on the airplane?
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 Units (TRU), DO 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 BUSES and AC ESS BUS which…
Power the 3 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 (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.
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 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 < 22.0 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 an AC source is not available.
What is on the AC STANDBY BUS?
Engine exciters 14 and 24.
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 or manually by pilot.
How long after deployment before the RAT will supply power?
6 seconds.
Is there a total loss of power during the 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.
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) and 2 Secondary Power Distribution Assemblies (SPDA).
What is an 1007?
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 ICCs) that distributes electrical loads to aircraft systems according to distribution logic and performs BITs on many components.
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.
