Electrical Flashcards
The HMG provides power to
5 Buses
L and R ESS DC Buses thru the AUX TRU
L and R Standby AC Buses
EMER ESS AC Bus thru the E-Inverter
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? Which one?
Yes. Both switch to the R MAIN AC bus
What is the purpose of the E-inverter?
Provides AC power for the ESS AC bus (if the ESS AC bus loses power)
How long do you wait between selections of L ESS and R ESS when using HMG?
10 Secs
If you lose L MAIN AC Bus, how would you power the L MAIN DC bus?
Depress the L TRU switch. Observe ‘RAC’ illuminate in the capsule
What two power sources can power the ESS DC Bus simultaneously?
L/R Main batteries AUX TRU (When powered by the HMG)
When do the MAIN Battery switches illuminate?
- When they are powering the ESS buses
- When starting the APU
- When AUX pump is operating.
All automatic power transfers will be NBPTs except between…
External AC and APU power.
What appears in the GEN switch capsule if the GEN FAILED?
Amber “OFF”
The Ground service bus may be powered on the ground by:
- R MAIN DC
2. R Batt or Ext DC when using one of the three Ground Service Bus switches.
How can you tell if the Ground Service Bus is powered?
Beacon is on
Can the Crew tell if the Ground service bus is on by looking at the cockpit electrical panel?
Yes. The GND SVC BUS capsule will have “ON” illuminated
Is GND SVC BUS powered inflight? If so, by what?
Yes / R MAIN DC
How many GND SVC BUS switches and where?
3
- Fwd Ext Switch Panel
- Tail Compartment.
- Remote Refuel Panel
When will the GND SVC BUS automatically shut off?
On the ground, with main door closed and forward external switch service panel AND tail compartment door are closed.
What do the Avionics E-Batts power?
1. Clocks 2, 3. STBY INST Panel (SFD/EBDI) 4. Gear Handle and indicator 5,6. MCDU 1 and 3 7. CAPT Audio Panel
Emer Batts when armed will activate…
when an ESS DC power drops below 20 Volts
With E-Batts on, what appears on the MCDU 1 and MCDU 3?
MCDU 1 - STBY ENG INST and FUEL
MCDU 3 - BACK UP RADIOS (VHF 1 COM/NAV) and ATC
When operating on E-Batts which comm can be tuned and how?
COM 1 / NAV 1 / ATC 1 on MCDU 3
Can you plug in Ext AC and DC power simultaneously? Which has priority?
Yes.
AC has priority
If you plug in Ext AC and DC simultaneously, AC will take priority and power the aircraft. If removed Ext AC power, will DC power automatically pick up the load?
No. You have to deselect Ext AC and reselect for DC Ext Power
Why would you use DC EXT Power?
Start the APU with low battery voltage
When should an open circuit breaker be reset?
If the affected component is required for safe flight and landing
