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Flashcards in Electrical Deck (32):

What does an External Power "AVAIL" light indicate when illuminated?

External power is available and is of acceptable quality (voltage and frequency).


When selected manually, what electrical power source will trip off any existing power source?

External power.


What does an illuminated APU Gernerator "OFF" light indicate?

APU generator control breaker is open because of a fault with the APU running.

APU Generator control switch is selected OFF.


What does an Engine Generator "OFF" light indicate when illuminated?

The generator control breaker is open.


What does an illuminated Generator "DRIVE" light indicate?

The respective generator oil temperature is high
The respective generator oil pressure is low.


When can a disconnected IDG be reconnected?

On the ground by maintenance only.


What happens during an AUTOLAND if one of the Generators fails below 200 ft.?

-Both bus tie breakers remain open (L/Standby/R systems are isolated for autoland).

-The autopilot associated with a failed generator is unpowered.

-The flight instruments remain powered through the flight instrument transfer buses.

-The autoland continues using the remaining two autopilots.


What is the purpose of the Bus Tie System in AUTO?

Arms automatic transfer of buses in case of bus or power failures.

Arms automatic AC bus tie circuits.
Arms automatic DC bus tie circuits.
Arms automatic flight instrument transfer buses.


What are the priorities for automatically powering the left and right main buses?

1. Respective Generator
2. APU
3. Opposite Generator


What happens to the Electrical System when the engines are started with APU electrical power in use?

When the associated IDG's come online, the bus tie closes powering the main AC bus from that IDG.


What does an illuminated AC bus "ISLN" light indicate when the Bus Tie switch is in the "AUTO" position?

Fault has occured, automatically opening the AC bus tie breaker.


With a left AC bus fault, witll the Captain's Flight Instruments lose power?

No, the FO instrument bus will automatically provide power to the Captain's flight instruments.


With the Bus Tie Switches in "AUTO," what happens to a DC bus if it's respective T/R fails?

The DC tie switch closes allowing the other bus to provide power to the bus.


What items are normally powered by the Ground Handling Bus?

Lower cargo doors and equipment (aircraft fueling panel) and is energized only on the ground and only from the APU generator or external power.


How is the Ground Handling Bus powered?

APU or External power.


What is the normal source of power for the Aircraft Battery Charger?

Ground Service Bus


What items are normally powered by the Ground Service Bus?

Main Battery Charger
APU Battery Charger
Miscellaneous cabin and system loads


What is the normal source of power for the Ground Service Bus?

Right Main AC Bus.


What are the alternate sources of power for the Ground Service Bus?

APU Generator & External Power


What normally powers the left and right utility buses?

Their respective main AC bus.


What conditions would cause Utility Bus Load shedding?

The loss of a generator or engine.


What happens to the utility buses when a single engine generator is powering the electrical system and an additional power source becomes available?

They are load shed. If load permits the system will automatically restore power to the shed utility bus with the addition of another power source.


What is the purpose of Automatic Load Shedding?

To ensure power to critical components critical to flight.


What is the function of the "OFF" position of the STBY power selector?

The standby busses are unpowered.


What is the function of the "BAT" position of the STBY power selector?

The standby busses are powered by the main battery.


How is the STBY DC bus normally powered (electrical power established on all busses)?

Left DC bus via the left AC bus.


How is the STBY AC bus normally powered(electrical power established on all busses)?

Left main AC bus via the left engine generator.


How is the STBY AC bus powered during standby power operations?

The main battery and standby inverter.


What electrical component is capable of providing temporary power to the Standby Power System should a loss of all generators occur?

The main battery.


How long is the Main Battery capable of powering the Standby Power System?

30 minutes.


What causes the Standby Power Bus "OFF" light to illuminate?

Either the DC or AC stand by bus(es) are unpowered.


What items remain powered when operating on Standby Power?

Right IRU, Fuel Indicators, Electrical Standby Instrument System, Capt. Marker Beacon/Audio, Manual Speedbrakes, Alternate Stab Trim, Engine/APU Fire Detection & Protection, Left VHF (PA and Intercom), Manual Pressurization, Master Warning Lights, Standby Engine Instruments, Gear Lights, Flap Handle serves as Indicator, Fuel Control Switches, Center ILS & Control Head.