AC electrical Flashcards
(25 cards)
What is the main source of electrical power - AC or DC?
AC
Whats the difference between 757 & 757 ER ELECTRICAL SYSTEM?
ER has HDG (hydraulic driven generator)
What is the electrical system comprised of ?
1) AC MAIN
2) DC MAIN
3) Battery Stby
4) HDG (ER)
What are the main AC POWER SOURCES?
Left & right IDG’s
APU Generator
What are the 2 main features of the IDG’s?
1) Automatic control
2) system protection
What is the priority sequence for AC power?
1) external power
2) onside generator
3) APU
4) opposite side generator
Is there an indication for galley buses?
No
What does the ground service bus power?
1) MAIN BATTERY CHARGER
2) APU BATTERY CHARGER
3) MISCELLANEOUS CABIN & SYSTEM LOADS
What is the purpose of the ground handling bus?
Provided for loads such as cargo handling and equipment energized ONLY during ground ops
How is the ground handling bus powered?
ONLY by APU or EXTERNAL power - ONLY on the GROUND
How are the 3 autopilots powered during autoland?
LEFT MAIN
1) L AUTOPILOT
2) CA FLT INTSTRUMENT TRANSFER BUS
RIGHT MAIN
1) R AUTOPILOT
2) FO FLT INSTRUMENT TRANSFER BUS
BATTERY / STANDBY
1) C AUTOPILOT
DURING AUTOLAND
What happens if loss of GEN above 200’
BUS TIES CLOSE - operating GEN POWERS BOTH AC BUSSES
LEFT MAIN POWERS CENTER AUTOPILOT
NO LAND 3 - appears on autoland status annunciator
DURING AUTOLAND
What happens with loss of GEN BELOW 200’?
BUS TIES REMAIN OPEN
AUTOPILOT ON FAILED GEN SIDE IS UNPOWERED
FLIGHT INSTRUMENTS REMAIN POWERED
AUTOLAND CONTINUES USING 2 AUTOPILOTS
What is the purpose of the FLIGHT INSTRUMENT TRANSFER BUSSES?
TRANSFER POWER TO OPPOSITE MAIN BUS IN CASE OF ASSOCIATED MAIN BUS FAIL
WHAT IS THE PURPOSE OF THE HYDRAULIC DRIVEN GENERATOR ON THE 757 ER ?
IF BOTH MAIN AC BUSES ARE LOST - CA INSTRUMENTS ARE POWERED BY HDG TO COMPLY WITH ETOPS REQUIREMENTS
WHAT IS THE PRIORITY OF ELECTRICAL LOAD SHEDDING?
SHEDS LEAST IMPORTANT ITEMS FIRST
1) GALLEY
2) UTILITY BUSSES
3) INDIVIDUAL EQUIPMENT ITEMS ON MAIN AC
How can you shed UTILITY BUSSES ON THE GROUND WITHOUT ENGINES RUNNING?
How do you reset them?
Advance thrust levers
Push utility BUS BUTTONS OFF THEN ON
What are some important items on the L AC bus?
Some Pitot heat L& C flight directors Flap indicator L& C Autopilot Electronic Engine Control
what does the ISLN light mean?
L or R BUS ISOLATED
What does the DRIVE light on the GEN DRIVE DISC switch mean?
Generator drive oil
temp high
Or
Pressure is low
If you push the GEN DRIVE DISC switch - is it reversible?
No
If you get a MAIN BAT DISCH message - how long do you have before loosing standby bus?
Aprox 30 mins
What does an OFF light on the STBY POWER panel mean?
One or more of the
AC standby
DC standby
Battery bus
Not powered
What are the 3 main functions of the bus tie system?
Prevents paralleling
Maintains bus power
Isolates faults
