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
What is indicated if the R GEN switch displays an amber OFF light?
The GCU has tripped
If both Generators are inop, which buses does the HMG power?
Both standby AC buses, both ESS DC busses, and the ESS AC bus
What is the rating of the HMG?
10 kVA
How is the HMG powered?
Left hyd system or PTU
Selecting the L Bus tie switch to the ISLN position will:
Isolate the L MAIN AC bus from all power except the left IDG
The minimum main battery voltage is:
22 volts
Which battery is used to close the main door from the outside door switch?
Only the right battery, which is hard-wired to the main door electrical control circuit
The function of the L-R MAIN TRU switch is:
The on-side MAIN AC BUS powers each main TRU. In the unlikely event that the on-side MAIN AC BUS should fail, the L-R MAIN TRU switch can be selected to the opposite side MAIN AC BUS to restore the TRU and its respective MAIN DC BUS.
In what situation can TRU power more than one bus, which buses can it power?
When the HMG and left ESS/right ESS switches are IN/ON, the AUX TRU can power both essential DC buses.
If the right main TRU fails, what should automatically power the right main DC bus?
the AUX TRU
Which batteries are activated when the external battery switch is turned ON?
Both main batteries
What item will be lost with only one AC power source operating in flight?
Galley power
During an emergency evac or ditching after dark, how are emergency lights activated?
By selecting them ON with the emergency battery switch
What will cause the ‘cats eye’ indicator to show white over black in the nav/strob lights?
If one or both strobe lights bulbs should fail
Why are the NAV lights powered by two different power sources and what are they?
If the aircraft has to be towed, the NAV lights can be turned ON with battery power without having to start the APU.
NAV LTS #1 = Left MAIN DC
NAV LTS #2 = Left ESS DC
If the landing light switches are left in during flight, when will the lights turn OFF automatically?
Passing through 18,000’ (or they will change to “PULSE” mode if the pulse light switch is selected
Will the taxi lights turn OFF automatically, if so, when?
Upon gear retraction
How many emergency lighting batteries are installed?
Two
During normal ops, the ground service bus receives power from…
R MAIN DC Bus
From where can the E-Inverter receive power?
L or R ESS DC (Normally it receives power from L ESS DC if E inverter is required)
How are the E-Batts charged?
L Instrument E-Batt - L STBY AC Bus
R Instrument E-Batt - R STBY AC Bus
Forward Lighting E-Batt - L MAIN AC
Aft Lighting E-Batt- R MAIN AC
What items are capable of being powered by the battery tie bus?
Aux Pump
APU Starter
ESS DC Buses
How many TRUs are normally operating in flight?
Four, the AUX TRU is in standby mode, available to pick up any, single TRU
If the Ground Service Bus is selected on with no power on the aircraft, what will power it?
Right Main Battery
Which batteries are activated when the external battery switch is turned on?
Both main batteries
In Flight, how is the ground service bus normally powered?
R MAIN DC
Whenever the GND SVC BUS is turned on, what light illuminates?
Lower beacon
Which buses are powered with only external DC connected?
L - R ESS and MAIN DC
GND SVC Bus
ESS AC (Phase A only - powered thru the E-Inverter)
What electrical components are under the forward floor?
TRUs and E-Inverter
How many TRUs are on the aircraft?
7
5 (L/R MAIN & ESS and AUX)
2 - Battery chargers
How many Circuit Panels are there?
7 POP CPOP LEER L PDB REER - 2 R PDB
Which BPCU (Bus power control unit) controls break power transfer control?
Left BPCU
