DC electrical Flashcards
What are the requirements for DC power Transfer?
BOTH bus tie switches in AUTO
How is the DC system powered?
Through 2 TRU’s (Transformer rectifier units)
powered by The Main AC BUSES
Are there any flight deck controls for the MAIN DC system?
No. (Except for bus tie switches)
What is the Battery/Standby power system for?
Provide AC & DC POWER to critical flight instruments - communications - navigation systems & other critical systems
IN CASE OF LOSS OF BOTH MAIN AC & DC systems
What are the 4 buses of the BATTERY/standby power system?
1) HOT BATTERY BUS
2) BATTERY BUS
3) STANDBY DC BUS
4) STANDBY AC BUS
What powers the HOT BATTERY BUS - before establishing electrical power? After?
Main Battery
After ext pwr or GEN online main battery charger powers HOT BATTERY BUS
What powers the BATTERY BUS before electrical power established? After?
With the Battery switch on the BATTERY BUS POWERED by MAIN BATTERY
After electrical power established (Ext pwr or GEN online) BATTERY BUS is powered by LEFT DC
What indicates MAIN BATTERY DISCHARGING?
DISCH light on overhead panel
If EICAS powered MAIN BAT DISCH displayed
What indications will you get if you turn off battery switch after electrical power established?
battery OFF light on overhead
BATTERY OFF on EICAS
What powers the DC STANDBY BUS when STBY POWER switch is in AUTO?
(Before and after establishing electrical power)
PRIOR - with the BAT switch on - powered by MAIN BATTERY
AFTER - LEFT DC SYSTEM
If you get a STBY POWER OFF LIGHT - does that mean DC STBY BUS is not powered?
Not always
How is the STANDBY AC BUS powered by the DC system?
Through the MAIN DC BATTERY and an INVERTER
How can the STBY BUSSES still be powered if the standby bus OFF light is on and you have a STANDBY BUS OFF message?
If power is lost to the BATTERY BUS you will receive these indications eventhough the STBY BUSES are still powered through the Main systems
On the 757 ER - which hydraulic system powers the HDG?
Left
Why would you get a temporary battery DISCH light even with the HDG Operating?
The HDG does not put out as much power as a fully charged battery - so it takes some time before the battery discharges to the lower output level of the HDG
