Electrical Flashcards
(39 cards)
During an autoland, if a loss of the left generator below 200 feet (with no APU
operating) occurs, the left autopilot and left main AC bus become unpowered. Will
thee to have flight instruments displayed?
Yes. Flight instruments remain powered through the
flight instrument transfer busses.
(757) During engine start when the APU is used for both electrical and pneumatic
power, what utility bus(ses) load shed(s)?
When the first Engine Start selector is moved to GND,
both utility busses trip. When the second Engine Start
selector is moved to GND, only the respective utility bus
trips.
(767) The amount of DC power produced by the HDG is less than the DC power
produced by a fully charged battery. Which of the following indications might you
get until the battery power decreases to the power level produced by the HDG?
The Battery DISCH light.
(767) Which hydraulic pump is inhibited during engine start?
Le electric demand pump is inhibited on the ground
during engine start of either engine.
(757) Which hydraulic pump load sheds automatically to reduce electrical loads
when operating on one generator with both Center Electric Pump switches ON?
The C2 pump load sheds
What does the Engine Generator OFF light and EICAS message indicate?
Generator control breaker is open
What three conditions shed the utility busses on a B757?
Engine start, generator loss and overload
What are the power sources for the ground handling bus?
External power or APU
(757) What is the normal source of power to the Captain’s flight instruments?
Left main AC bus
Cycling the Generator Control switch (OFF then ON) has what effect?
OFF ‐ resets trip circuitry and ON arms generator to close
automatically when generator power is available
What occurs if the Generator Drive Disconnect switch is pushed?
Disconnects generator and drive from engine and cannot
be reset by the flight crew
What does the BUS OFF light and associated EICAS message indicate?
Indicated AC bus is unpowered
What are the priorities for powering the left and right main AC busses?
Respective IDG, APU generator and opposite IDG
When does the generator load shed protection arm regarding a generator loss?
Aircraft in flight or both thrust levers moved into the
takeoff range
What occurs following a failure of one engine‐driven generator during a multiautopilot
approach, APU operating?
AC bus is powered by the APU when the associated bus
tie breaker closes
What does the External Power AVAIL light indicate?
External power is plugged in and power is acceptable
What is the normal power source for the ground service bus?
Right main AC
What does the Battery DISCH light and MAIN BAT DISCH EICAS message indicate?
Battery is discharging
What does the Standby Power Bus OFF light and STANDBY BUS OFF EICAS message
indicate?
Standby AC and/or DC bus not powered and/or battery
bus and/or Standby Power selector in OFF
Which of the following will cause the Generator DRIVE light to illuminate?
Generator drive oil temperature is high
What can power a utility bus?
Respective main AC bus only
What busses power the autopilots during a coupled ILS approach (autoland) after selecting APP (approach switch)?
Left main AC powers left autopilot, right main AC powers
right autopilot and standby/battery powers center
autopilot
How are both standby busses powered when the Standby Power selector is
positioned to BAT?
Standby busses are powered from the hot battery bus
What does the AC Bus ISLN light indicate?
Indicates fault or Bus Tie switch is OFF
