Electrical Flashcards
How many NiCad batteries are there on the aircraft?
Three.
How many engine-driven DC starter-generators are there on the aircraft?
Two.
How many transformer rectified units (TRUs) are there on the aircraft?
Two.
How many APU generators are there on the aircraft?
One.
T or F: the electrical system comprises both a direct current (DC) system and an alternating current (AC) system.
True.
T or F: DC power to the electrical system is supplied by two-engine driven DC generators only.
False, it is also supplied by three NiCad batteries, two TRUs, and an APU generator.
T or F: circuit breaker panels can be found in the left and right main landing gear wheel wells.
True.
How many circuit breaker panels are there in the flight compartment?
Four.
Which of the following are NOT electrical buses?
There is no emergency bus.
These are buses: battery bus, left and right essential buses, left and right main buses, left and right secondary buses.
The aircraft is equipped with which of the following battteries?
Three 24V batteries: main, auxiliary, standby.
Which batteries are used for engine starting when ground power is not available?
Main and auxiliary.
How long will the batteries power the aircraft if normal electrical power fails?
60 minutes.
How many battery switches are there?
Four (one for each battery and a master).
T or F: if the battery master is in the OFF position, the other batteries can still be used to power the aircraft.
False.
T or F: when the battery master is in the OFF position, all battery power is turned off no matter what position the other switches are in.
True.
If the battery is being charged at a 100% rate of charge, how will it be depicted on the MFD battery page?
1.00
How is a battery that is discharging displayed on the MFD electrical page?
A negative number.
When the battery temperature is within limits, what color does it display on the MFD electrical page?
White.
When the battery temperature exceeds normal limits, what colors would display on the MFD electrical page?
Yellow then red.
If any battery temperature is 50 - 65ºC, what color does the battery temperature display as on the MFD battery page?
Yellow.
Where can the GPU be connected to the aircraft for DC power?
Left forward fuselage.
When connected to external power on the ground, DC EXT PWR ON is displayed in what color?
Green.
T or F: the EPCU protects the system from too high and too low DC power voltage from the DC external power source?
True.
After engine start, how many volts does the DC generator provide?
28V DC.
Where are the transformer rectifier units (TRUs) located?
In the nose.
TRUs change 3-phase 115v AC to what?
28V DC.
During normal operation, which busses do the TRUs power?
Left or right secondary bus.
A L TRU caution light will illuminate when what happens?
The left TRU is offline or has failed.
On the ground, what busses does the APU generator provide power for?
Left and right main, essential, and secondary buses.
What does it mean when a plus sign (+) is displayed in front of a value on the MFD electrical page?
An overload of the power source.
The entire DC electrical system can still be powered when up to how many power sources have failed?
Two.
When does the EPCU send a signal to the generator to trip it offline during a main DC bus fault?
After 5 seconds.
If the right main bus has a bus fault, which battery is disconnected from the system?
Main battery.
T or F: if a secondary bus fault occurs, the increased current will trip the circuit breaker for the respective TRU.
True.
In addition to an inoperative TRU, what is required for the EPCU to enter emergency mode?
Airplane is in the air, both DC generators are not available.
In addition to a dual DC generator failure, what is required for the EPCU to enter emergency mode?
Airplane is in the air, at least one TRU is not available.
T or F: in EPCU emergency mode, the batteries are the main source of power.
True.
When in EPCU emergency mode, which busses automatically disconnect from the batteries?
Main buses.
What is the voltage output of the AC generators?
Three-phase 115V AC.
Where are the AC generators mounted on the aircraft?
Propeller reduction gearbox.
How many external AC power ports are there on the aircraft?
One.
When the aircraft is powered by external DC power, which busses are powered?
Left and right main, essential, and secondary buses.
T or F: when a DC generator fails, the main bus tie switch must be manually selected to keep the associated main DC bus powered.
False, the EPCU can override switch position.
Which switch should pilots use to connect the main battery to its associated main feeder bus?
MAIN BATT.
T or F: the electrical system has a single hot battery bus to keep certain items powered at all times.
True.
T or F: the hot battery bus can be powered by any of the three batteries.
False.
At what point will DC electrical bus load shedding begin?
Three DC sources fail.
In EPCU emergency mode, the ____ are the main power source for the available DC busses.
Batteries.
The AC generators connect to the system when the engines are running, Gen 1 and 2 switches are selected on, and ____.
Condition levers are in the MIN to MAX range.
Which of the following statements regarding the AC cross tie function is most accurate?
It works automatically to ensure both AC buses are powered in the even of an AC generator failure.
