Electrics Flashcards
How is fuelling powered?
Ground handling bus
What’s the only way to use standby power?
HDG fail
How many AC sources of power does the aircraft have?
5
2IDG’s
APU
HDG
External power
Standby power
How many sources of power on the ground do we need to power the aircraft?
1
How many AC power sources do we need to power the aircraft?
2
What is the load shed order?
Galley Buses
Utility buses
Whatever Boeing deems necessary
Restored in reciprocal order
If we lost the left generator. 1 AC power source remaining. Why does the pressure light on the C2 come on?
Boeing logic load sheds it
What items are on the Hot Battery Bus?
Fire Protection
Captains clock
RAT – deploys below idle RPM with dual engine failure
Set Parking Brake
When will the RAT deploy automatically?
In flight, below idle N2 RPM, Battery Bus ON
*Manual deployment on Hot Battery Bus
How is the aircraft fuelled without power to the ground handling bus?
Fuel Access Panel
Powering up the aircraft what lights come on?
Battery on light
Discharge light
Standby power OFF light
• 2 buses powered
Moving Standby power switch to AUTO powers how many buses are powered?
4
Standby AC
Standby DC
Hot Battery
Battery
What is the purpose of the Flight Instrument Xfer Buses?
Receives cross power for flight instruments with the failure of the bus that powers them normally.
Only works in Non Normal
What is the purpose of the DC BTB?
To provide DC power with the failure of the Transformer Rectifier.
The BTB closes when Transformer rectifier fails.
Works in non normal
What is the purpose of the BTB
Prevents Paralleling
Isolates from a fault
Powers cross side
What does the BTB isolation light mean?
BTB is open and can not be reset in flight.
If the Bus tie switches are not in AUTO, which systems are not available?
2 AC BTB
1 DC BTB
2 Flight instrument Xfer bus
Why are all electrical switches in the auto position?
Allows Boeing logic to control the system. Arms the GCB to automatically close
What does pushing the Generator Drive switch do?
Disconnects the IDG from the engine, it can only be reset on the ground.
What are the only reasons for Generator Drive Light?
High Oil Temp
Low Oil Pressure
What happens/what is seen with the Generator Control Switch off?
Flow bar is NOT in view.
Opens the GCB. Resets fault trip circuitry
What functions can the Generator Control switch perform?
On
Off
Reset
How can you open a GCB?
Select Generator Control Switch Off
External Power connection
Pull the Fire Handle
With the APU generator control switch ON, what happens?
Flow Bar in view
Arms the GCB to automatically close when APU power available
With the APU generator control switch OFF, what do you see/what happens?
Flow bar not in view
Opens GCB
Resets fault trip circuitry
Where do we connect External Power?
Just behind the Nose gear on the right side. 1 connection.
On external power, can you power flight deck lights?
Ground service switch
When external power is connected what is the new bus that is powered?
Ground Handling Bus
The ON light on the External power switch means what?
External power is connected to a main bus
What is the AC Bus priority?
Respective Engine Driven Generator
APU Generator
Cross Side Engine Driven Generator
What are the load shed events?
Overload
Engine Start
Loss of Generator
Why does an overload load shed event occur?
During Pressurisation of HYD – C2 Pump and both galley busses are shed
As HYD reconfigured for flight the electrical primary and demand pumps draw a high load
What is lost when an Engine load shed event occurs?
Left Electric Demand Pump
Both utility busses
What is lost when a Single power source load shed event occurs?
Both Galley buses
Both utility buses
Whatever else Boeing chooses
Starting right engine what should you see?
Engine Valve Light
Spar Valve light
They let you know you have control of the fuel system in the event of needing to shut it down
Shedding occurs when?
Thrust lever advanced with engine shutdown. Must reset
Overload
Start engine
Single power source
**Why is load shedding less for starting second engine?
Engine providing power to buses. APU diverts air to provide 21PSI for start
?????
After engine start where does the Ground Handling Bus get its power from?
APU
After take off how long is the Ground Handling Bus powered?
Powered for take off until the main gear logic confirms airborne
External power switch AVAIL Light on. Where are the BTB?
Open
What happens to the BTB’s on R engine start?
On engine start R BTB opens when R GCB closes. L BTB remains closed to receive power from the APU. Flight instrument transfer BTB’s and DC BTB are open – waiting for fault
With a left bus fault, what lights are ON?
L Bus Tie ISLN
L BTB BUS OFF
L GEN CONT OFF
Utility Bus L + R OFF
With a left bus fault, would you start the APU?
Yes. As a back up for the R Bus in case it fails
What items continue to be powered with dual AC power failure?
HDG – located on the C HYD system, powered automatically
4 Standby Buses
CA Flight Inst Bus
2 ETOPS Buses
On the HDG why is the battery chargers light on?
Battery chargers are more powerful than the power being supplied by the HDG. When the power reduces to the HDG being stronger, the light will go out.
On the HDG what components on the panel are lost?
Upper lower EICAS
Auto Brakes
With the loss of all AC power how are the IRU’s powered?
Hot Battery Bus. After 5 minutes, the right IRU shuts down
With the shut down of the R IRU, what else do we lose?
Captains Heading Flag on the RDMI
In the event of a using standby power, what happens to the fuel?
Suction fuel created by pressure differential. No AC fuel pumps
What items are lost with a dual AC power failure?
Lose the FO’s side
EICAS CRT’s
Auto brakes
Cpt’s Heading RDMI
What no longer remains to be powered with the loss of the L Main AC Bus?
Utility Buses
Galley Buses
Left AC Transfer Bus
Centre AC Bus
What systems are on the Hot Battery Bus
Fire extinguisher bottle - Fire Protection
Captain clock
APU fuel valve
Backup power for IRU’s
If you lose the R Main AC Bus, what happens to the batteries?
No longer charged due to loss of the Ground Service Bus
With the APU generator control switch OFF light displayed, what happens?
Generator Control Breaker Open
