Section V – Electrical Communications Flashcards
When does the Cockpit Voice Recorder system (CVR) automatically operate?
All inputs are recorded continuously anytime AC power is applied to the airplane.
How many VHF radios are installed?
Three independent VHF radios are installed, designated VHF L (left), VHF C
(center), and VHF R (right).
With respect to the Audio Control Panel, how could one switch the microphone source from the boom microphone to the oxygen mask?
By selecting the BOOM/OXY switch to the OXY setting.
What are sources of AC electrical power that can be utilized?
Left and Right IDGs, APU generator, External Power, Hydraulic Driven
Generator (-300ER)
What is the primary purpose of the Bus Tie System?
Prevents paralleling of systems, Isolates faults, and operates automatically to maintain power to both buses.
What is the source order for powering the left and right main buses?
a. Respective IDG
b. APU generator
c. Opposite IDG
What is the power source for the Ground Service Bus?
The right main AC bus. Alternate sources of power for the ground service bus are the APU generator and external power.
What items are powered by the Ground Service Bus?
The main battery charger, APU battery charger, miscellaneous cabin and system loads.
When is the Ground Handling Bus powered? Can it be powered in the air?
What items does the ground handling bus power ?
The ground handling bus is powered from an APU generator or external power source (only needs to be plugged in). It can only be powered on the ground
Cargo compartment systems,lights,maintenance access light and fueling systems
With respect to external power, what does the AVAIL light on the switch indicate when illuminated?
It means that the voltage and frequency are within limits to select external power.
During Autoland operations, what is the power source for the center autopilot?
During Autoland, the buses isolate to allow three independent sources to power the autopilots. The battery/standby system powers the center autopilot.
When a generator is lost above 200 feet RA during Autoland operations, what actions occur?
Both bus tie breakers close and the operating generator powers both left and right AC BUSES. The left main system powers the autopilot. NO LAND 3 appears on the Autoland Status Annunciator.
What is the power source for the Captain’s flight instrument transfer bus in the event of a Left + Right AC bus failure?
Hydraulic Driven Generator
What buses are powered when the battery switch is selected on prior to establishing APU or external electrical power (STBY power selector off)?
The battery bus and hot battery bus
What would cause the BUS OFF light to illuminate on the AC panel?
The BUS OFF light illuminates and the EICAS caution message
L AC BUS OFF or R AC BUS OFF displays if an AC bus is unpowered.
What buses are powered by the Hydraulic Driven Generator when both the left and right main AC buses are unpowered?
Battery bus, hot battery , standby dc , standby ac , left ac transfer , right ac transfer , captains flight instrument transfer bus
What items are on the hot battery bus ?
If you have engines running and you select BAT on the STBY POWER switch what would happen in the system ?
The standby AC and standby DC would not longer be powered by the main ac busses and only powered by the battery bus and inverter for the standby ac bus.
Note : The BAT switch position is only used on the ground to perform a standby power test.
If all generators fail and the HDG is not operating what will power the plane and for how long ?
The main battery can provide 30 minutes of power for the standby power system
What are some items you could lose if the Battery Bus is unpowered ?
Speedbrakes and auto brakes per QRH
