Electrical Flashcards
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
or
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?
- Respective Generator
- APU
- 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.
