Electrical System Flashcards
How many networks make up the electrical system on the aircraft? Why?
- 2 independent networks
* Segregation 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 the DC system?
- 2 NiCad batteries
- 3 Transformer Rectifier Units (TRU)
- DC GPU receptacle
What is the AC electrical systems priority?
- On-side (Respective IDG)
- Inside (APU generator)
- Outside (GPU if on the ground)
- Cross-Side (Opposite IDG)
Which AC source has priority, the APU or GPU?
APU has priority and will automatically switch when the APU is up and running.
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 the GPU button, and MFD electrical page shows a green APU icon.
During “normal operation”, will a failed IDG de-power the respective AC BUS?
No.
How many Display Units (DUs) come to life when you bring the batteries online? Which
ones are they?
2, DU 2 & DU 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 and it’s associated with an EICAS message.
When would the amber IDG oil indicator light illuminate?
- High Oil Temperature, Low Oil Pressure (HOTLOP), or
* Annunciator test button
What action is taken when an amber IDG oil indicator light comes on?
Disconnect the associated IDG per the 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 Transformer Rectifier Units?
To convert AC to DC.
TRU transforms AC to DC, is there a way to change DC 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 generator have the same rating as the IDGs?
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. Connects the 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 Pilot be sure
to do?
Deselect the AC GPU button so the power can be connected the 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 HOT BATT BUS 1.
