Electrical Flashcards
How many networks make up the electrical system of the aircraft? Why?
- 2 independent networks.
- Segregation and fault isolation.
What components power the AC system (5)?
2 IDGs RAT APU AC GPU receptacle Inverter
What components power the DC system?
2 NiCad batteries
3 Transformer Rectifier units
DC GPU receptacle
What is the AC electrical system priority?
On-side (Respective IDG)
Inside (APU)
Outside (GPU)
Cross-side (Opposite IDG)
Which AC source has priority, APU or GPU?
APU has priority and automatically switches when APU is available.
You receive the aircraft at the gate and it is powered by the AC GPU. You start the APU. Once it is up and running, how can you tell that the APU generator has automatically taken over the electrical load?
AVAIL light on GPU button illuminated, MFD electrical page shows green APU icon.
During normal operation, will a failed IDG de-power the respective AC bus?
No.
How many display units come to life when you bring the batteries online?
2, DUs 2 and 3.
Can one IDG supply the entire electrical system?
Yes.
What are the two lights next to the IDGs?
Tells you which IDG must be disconnected. Its illumination comes with an EICAS message.
When would the amber IDG oil indicator light illuminate?
High oil temperature, low oil pressure (HOTLOP).
Annunciator test button.
What action is taken when an amber IDG oil indicator light comes on?
Disconnect the associated IDG per QRH.
If an IDG is mechanically disconnected can the flight crew reconnect it on the ground or in flight?
No.
What is the primary purpose of the IDGs?
Supply AC power during all operations.
What is a TRU?
Transformer Rectifier Unit
What is the purpose of the TRUs?
To convert AC to DC power.
How is DC power converted to AC?
Inverter
What is the purpose of the inverter?
Converts DC to AC
Can the APU fully replace a failed IDG?
Yes
Does the APU have the same AC rating as the IDG?
Yes.
At the gate, ground power is connected. What does it mean when the switch says AVAIL?
Voltage/amperage/frequency are within limits.
How is it known that an AC GPU is hooked up to the aircraft and ready to provide electricity?
- GPU buttons display 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. Connect AC GPU to the AC BUS TIE according to source priority.
If the airplane is using the AC GPU and the APU is started, what should the pilots be sure to do?
Deselect the AC GPU button so the power can be connected next time it is used.
What happens with the BATT 1 selector ON or OFF?
On: The battery is connected to the DC ESS BUS 1.
Off: The battery supplies power to the HOT BATT BUS 1.
What will charge BATT 1 and BATT 2?
Any AC power source.
In which BATT switch position are the HOT BATTERY BUSSES powered?
The HOT BATT BUSES are always powered regardless of the switch position.
Name a few items on the HOT BATT BUS 1.
- Engline Fire Extinguishers 1A/2A
- Fuel Shutoff Valve 1
- Hydraulic Shutoff Valve 1
- Engine 1 Oil Level Indication
- Courtesy/Service lights FWD
- DC Ceiling Lights
What items are on HOT BATT BUS 2 (7)?
- Engine Fire Extinguishers 2A/2B
- Fuel Shutoff Valve 2
- Hydraulic Shutoff Valve 2
- Engine 2 Oil Level Indication
- Refueling Panel
- Water and Waste System
- CMC
What happens when BATT 2 switched is off?
OFF: The battery supplies power to the HOT BAT BUS 2.
Below what voltage would you have to call maintenance?
-Below 21.0 Volts.
Below what voltage must the batteries be charged?
22.0 Volts. Reference SOP for appropriate charging time.
Is BATT 1 necessary to start the APU?
Yes, BATT 1 powers the APU FADEC.
Why does battery 1 have an ON but no AUTO setting?
Battery 1 does not require automation during APU start.
Why does battery 2 have an AUTO setting?
To allow it to power the APU start bus.
What is the purpose of the DC GPU receptacle?
For APU start when the battery is not available.
Can the DC GPU charge the batteries?
No.
When will the RAT deploy?
Automatically deploys if the AC buses are not powered. Manually deployed (RAT manual deploy handle).
Is there an altitude restriction for RAT operation?
No.
Will the RAT supply power immediately after automatic deployment?
No, there is an 8 second delay during which the batteries supply power.
Is there a total power loss during the 8 seconds that the RAT deploys?
No, the batteries supply power.
Are the power ratings the same for the APU, IDG, and RAT?
No, the RAT provides a lower power output.
When is the RAT icon displayed on the electrical synoptic page?
When the RAT is deployed.
Can the remote electronic CBs in the forward e-bay be monitored?
Yes, via the MCDU.
If you start an engine at the gate with the GPU, is the electrical system split? Why?
Yes. The IDG will power one side and the GPU will power the other.
During an electrical emergency, how long will the batteries last if the RAT doesn’t deploy?
10 minutes
What is available during an electrical emergency (batteries on during power up).
- DU 2 and 3
- IESS
- Captain’s CCD
- FO’s MCDU
- Compass backlight
- Audio control panels
- Guidance panel
- Clock
When the electrical load increases beyond the system limit, what happens?
Load shed galleys and right windshield heating.
