Electrical Flashcards
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
What does the Utility Bus OFF light and associated EICAS message indicate?
Utility bus unpowered
What is the purpose of the bus tie system?
Allows the right and left main AC busses to be isolated or
connected
What does the Generator DRIVE light and L or R GEN DRIVE EICAS message indicate?
Generator Drive Low oil pressure or Generator Drive
high oil temperature
What components are powered from the ground handling bus?
Lower cargo lights, refueling features and cargo handling
When is the ground handling bus powered?
Only on the ground
What does the APU Generator OFF light and APU GEN OFF EICAS message indicate?
APU is running and the generator breaker is open
because of a fault or the APU Generator switch is
selected OFF
What items are powered from the ground service bus?
Main battery charger, APU battery charger, AFT NO.1 E/E
cooling fan, Left forward fuel pump and Main deck cargo
lighting
(757) What busses are powered if both main AC busses fail?
Hot battery bus, Battery bus, Standby DC bus, Standby
AC bus
(757) With the APU supplying both electrical and pneumatics, what occurs as the
first engine is started as it relates to utility bus load shed?
Both utility busses shed
(757) With the APU supplying both electrical and pneumatics, what occurs as the
second engine is started as it relates to utility bus load shed?
Only the respective utility bus sheds
(767) If both left and right AC busses are unpowered, what is the backup power
source?
Hydraulic Driven Generator (HDG)
(767) Which busses are powered from the Hydraulic Driven Generator (HDG)?
Standby AC/DC busses, hot battery bus, battery bus DC,
left and right transfer busses and Captain’s flight
instrument transfer bus
(767) What is the power source for the Hydraulic Driven Generator (HDG)?
The HDG is powered by the center hydraulic system
(767) APU supplying both electrical and pneumatics, what occurs as the second
engine is started as it relates to utility bus load shed?
There is no load shedding of utility busses during engine
start
(767) The loss of which bus or busses will cause the Hydraulic Driven Generator
(HDG) to operate?
The left and right main AC busses
