Electrical Flashcards
The HMG (Hydraulic Motor Generator) provides:
AC power to the AUX TRU and Standby AC Buses
What is the normal AC power source for the AUX TRU and ESS AC bus?
L MAIN AC bus
If the L MAIN AC bus is unpowered, will the AUX TRU and ESS AC bus automatically switch to another power source?
Yes. Both switch to the R MAIN AC bus
What is the “DEAD BUS” power logic for the AUX TRU?
- ESS bus before MAIN
- LEFT side before RIGHT side
What is the purpose of the E-inverter?
Provides AC power for the ESS AC bus (if the ESS AC bus loses power)
What is the normal position of the E INV switch?
AUTO
How long do you wait between selections of L ESS and R ESS when using the HMG?
10 seconds
The 60 Hz converter can be used to:
Power the outlets in the galley and passenger cabin
If you lose L MAIN AC BUS power, what happens automatically?
- AUX TRU transfers to R MAIN AC BUS
- AUX TRU Powers L ESS DC Bus
- ESS AC bus transfers to R MAIN AC Bus
How would you power the L MAIN DC Bus, if you lost the L MAIN AC Bus?
Use the L TRU switch / Push / Observe RAC (switch capsule)
What two (2) sources can power ESS DC buses simultaneously?
- L/R Main batteries
- AUX TRU (when powered by the HMG)
When do you push the RESET switch?
CAS MSG / CHECKLIST says to push it
The MAIN BATTERY switches illuminate ON when the MAIN BATTERIES are being used:
- Powering the ESS buses (batteries are being used)
- When starting the APU
- When AUX pump is operating
Describe a BREAK POWER TRANSFER
A momentary interruption of power to one or several busses
All automatic power transfers will be NBPT’s except between:
External AC power and APU generator
What is the function of BUS TIE ISLN SWITCH?
- Prevents / Allows alternate power sources to power failed bus side
- Allows you to isolate buses
What is the color of the GEN switch if the generator is turned off?
Black - Grey
The ground service bus may be powered on the ground by:
- R MAIN DC BUS, when available
- R battery or directly from external DC power receptacle when using one of three switches
How can you tell if GND SVC Bus is powered?
Beacon is illuminated
Can you look at the Electrical Panel and tell if the GND SVC BUS is powered?
GND SVC BUS capsule will have “ON” illuminated
Is GND SVC BUS powered in flight? And by what?
- Yes
- R MAIN DC bus
What appears in the GEN switch if the GEN FAILED?
- Amber “OFF”
How many GND SVC BUS are there and where are they located?
- 3 (three)
- Forward External Switch Panel Access Door
- Tail Compartment
- Remote Refuel Panel behind Captain seat in cockpit
How do you know the generator has failed by looking at the synoptic?
GEN is outlined in Amber
Will GND SVC BUS turn off automatically?
Yes, when main cabin door, forward external switch panel access door and tail compartment door are all closed
How many E-BATTS are there?
Four (4)
What do the E BATTS power?
- Avionics - (2)
- Emergency Lighting (2)
What do the Avionics E-BATTS Power?
- Clocks
- STBY INST Panel (SFD / EBDI)
- Gear Handle and Indicator
- MCDU’s 1 & 3
- CAPT Audio Panel
Emergency Batteries (E-BATTS) when armed will activate when:
An ESS DC bus power drops below twenty volts
With E-BATTS on, what appears on MCDU 1 & MCDU 3?
MCDU 1 - STBY ENG INST & FUEL
MCDU 3 - BACK UP RADIOS (VHF 1 COM / NAV) and ATC 1
When the aircraft operates on emergency batteries the crew can only tune:
COM 1 / NAV 1 / ATC 1 on MCDU 3
In emergency battery mode the:
Cockpit speakers are not available
ACP on E-BATTS - illuminate
Captain - COM 1 / SPKR ICS + Phone + MIC
Can you plug in AC and DC external power at the same time?
Yes
Which external power source has priority? AC or DC external power?
AC
If you remove AC external power will it Auto Switch to DC external power?
No, you have to deselect EXT PWR switch and RESELECT for DC EXT PWR
Why would you use DC EXT PWR?
Start APU with low battery voltage
