Electrical Flashcards
What does having standby power in off do?
It cuts of all sources of power to the ac and dc stby buses.
What does the standby power switch in auto do?
It gives give the authority to the main ac and dc buses to power the battery bus, stby ac and dc busses. Then it allows the battery to power them as a back up.
What does the standby power switch in bat position do?
It cuts off the main ac and dc power going to the stby ac and dc busses. The battery becomes the only source of power to these busses.
How many sources of ac power do we have?
4
2 engine gens
Apu gen
External power
How do you disconnect an idg?
Idg disconnect switch
Can you reconnect and idg in flight?
No
How many tru do we have?
2
What powers the utility buses?
Respective ac buses
What happens to the utility busses if you become single gen in flight or on takeoff?
They both shed
Can you reconnect the shed utility busses in flight?
Yes by getting another gen back online
How can you reset both the tripped utility buses on the ground?
By having one or both thrust levers at idle and just turning off and on the bus switches
What can happen to the utility if you advance the thrust levers for takeoff with out having the engines running?
advancing both thrust levers before engine start or after engine shutdown can cause a trip off of the utility buses.
Explain the overload load shedding logic?
If the apu or the external power is powering the whole aircraft electrical system and an overload happens, both the utility busses trip off.
If two separate gens are powering the system such as an engine on one side and apu on the other and an over load happens, only utility bus on the side the overload happened trips off.
Explain the engine start load shedding logic?
When the apu is supplying both elctric and pneumatic for the who airplane and and engine is being started, both utility busses get shed.
Once one engine is started, both utility busses come back on.
Then when you start the next engine, only the utility bus on that side shed till the engine is up and running.
How many ac bus ties do we have?
2
How many dc bus ties do we have?
1
What is the power acceptance logic?
Onside gen
Apu
Offside gen
Normally what bus powers the captains flight instruments?
Left main ac bus
Normally what bus powers the first officers flight instruments?
Right main ac bus
Does external power have priority over all the other power sources?
Yes
Which are the only 2 power sources for the ground handling bus?
The apu or external power
Does the apu or external power switches need to be selected for the ground handling bus to be powered?
No. They just have to be available
What bus powers the ground service bus?
Right main ac bus
What is the primary source of dc power?
2 tru
What buses power the tru?
Respective main ac buses
What powers the main dc buses?
The respective tru
How many batteries do we have?
2
What bus charges the battery chargers?
Ground service bus
How many battery chargers do we have?
2
What directly powers the hot battery bus?
Battery
What is the function of the stby busses?
The standby buses power many instruments and systems essential for safe flight during all nor-mal and non-normal operations.
Explain engine start load shedding?
When apu is suppling bleed and electrical power to start the engines, both utility buses are shed during the first start. During starting the other engine, only the utility bus on that side is shed.
What happens if you are in the air or on the ground and all the ac busses are being powered by separate gens and an overload happens on one of the gens?
If a separate generator is supplying each main AC bus (on the ground or in the air), only the utility buses associated with the overloaded generator is shed.
