Electrical Flashcards
Recall the power sources for the AC Buses (AC BUS 1, 2, and AC ESS BUS) during normal operating conditions.
o AC Buses 1 & 2:
▪ Respective Engine Generator (IDG 1 or 2).
▪ External power
▪ APU generator
o AC ESS Bus:
▪ Normally by AC Bus 1
▪ AC Bus 2 manually, when AC ESS FEED pb is selected to ALTN
▪ AC Bus 2 automatically, via the auto switching logic
Describe the electrical system’s power priority.
Same side
External power
APU
Opposite side
BUS TIE pb.
AUTO (light out)
OFF
AUTO (light out) – Power priority order logic is active.
OFF – Power priority order logic is deactivated.
- AC Bus 1 and 2 can only be powered by their respective engine generator.
- External or APU generator power cannot be applied to the aircraft.
AC ESS FEED pb.
The AC ESS FEED pb is used to manually command AC Bus 2 to power the AC ESS Bus.
When in the “light out” configuration:
▪ AC Bus 1 powers AC ESS Bus. This the normal configuration.
▪ Should AC Bus 1 fail, AC Bus 2 automatically powers AC ESS BUS.
When selected to ALTN:
▪ AC Bus 2 is commanded to power AC ESS Bus regardless of the status of AC Bus 1.
▪ ALTN appears only when the pb is selected.
Explain the information provided by the electrical power legends on the ECAM ELEC page.
o GEN 1 & GEN 2 and APU GEN:
- Percentage of Output
- Voltage
- Frequency
o EXT PWR:
- Voltage
- Frequency
NOTE: The EXT PWR legend appears whenever the external power cord is connected to the aircraft and Volts and Freqs meet requirements.
Recall the display on the ECAM ELEC page of an unpowered AC or DC ESS SHED Bus.
The word SHED (amber) appears under AC ESS or DC ESS buses only when the respective SHED Bus has automatically shed.
(Shed meaning unpowered).
GALLEY SHED display on the ECAM ELEC page.
o In-flight – When on single generator power, GALLEY SHED indicates that the galley’s main bus
has been automatically depowered. However, its secondary bus remains powered.
o On the Ground – With either external or APU generator power in use, both main and secondary galley buses
remain powered.
o When the GALLEY pb is selected OFF, GALLEY SHED indicates that the galley’s main and secondary buses are depowered.
Recall the cautions associated with selecting the guarded IDG 1 and IDG 2 pbs.
To avoid damage to the IDG disconnect mechanism DO NOT:
▪ Disconnect unless the engine is operating or is wind-milling.
▪ Hold the pb(s) for more than three (3) seconds.
Explain the color coding convention of the circuit breakers.
Green
Black
Yellow
Red
Green: Monitored by FWC’s, ECAM message when CB is open for more than 1 minute
Black:
- Circuit breaker is not monitored by the FWCs therefore, no “C/B TRIPPED” message is generated.
- The system which the circuit breaker supports may be monitored by the FWCs
Yellow: Pulled when flying on batteries
Red:
- Red cap prevents CB from being reset.
- Provide circuit protection to the Wing Tip Brakes (WTB).
GEN 1 LINE pb is selected OFF.
o Opens generator 1’s line contactor, in affect isolating it from the remainder
of the aircraft’s electrical system.
o Generator 1 is limited to only powering one fuel pump in each wing tank.
Two methods of activating the emergency generator.
o Automatically:
▪ Loss of power to AC Bus 1 and 2 in flight will automatically deploy the Ram Air Turbine (RAT) and activate the
emergency generator.
o Manually:
▪ Selecting the red guarded MAN ON pb on the EMER ELEC PWR panel will manually deploy the Ram Air Turbine
(RAT) and activate the emergency generator.
NOTE: Selecting the RAT MAN ON pb on the HYD panel will deploy the RAT but
will not activate the emergency generator.
Emergency Electrical Configuration
AC 1 and AC 2 unpowered
Emergency generator is powering:
AC ESS BUS
DC ESS BUS
AC and DC ESS SHED buses through their ESS buses
Explain what occurs to the emergency generator when the landing gear is lowered.
aircraft batteries become the sole source of electrical power.
NOTE: A red FAULT light illuminates on the EMER ELEC PWR panel when AC Buses 1 and 2 are unpowered and the RAT is deployed but the emergency generator is not supplying power
Recall the location and use of the MAINT BUS switch
▪ Located on the electrical panel on the ceiling of the forward galley.
▪ When selected ON, allows external power for ground servicing without energizing the entire aircraft’s electrical
system.
▪ Only requires external power to be connected and have good Volts and Freqs
The APU AVAIL light indicates:
The ON light indicates:
That the APU is “On Speed”
External power has been selected
Recall the power source when:
- both engines are shut down
- the APU START pb indicates AVAIL (green)
- the EXT PWR pb indicates AVAIL (green)
APU generator
avail light on ext pwr only indicates good volts and freqs connected
ext pwr must always be manually selected to be used
