Electrical Non-normals Flashcards
How is electrical power ensured for essential loads?
The backup power system (consisting of 2 backup generators)
Essential loads are powered by ?
The L & R transfer busses
Essential loads include ?
- Instrument & panel lighting
- Captain & FOs nav & communication radios
- L & C pitot & engine probe heat
Transfer busses are normally powered by ?
The L & R Main AC busses
What do the XFER busses connect to when their respective AC busses are unpowered ?
One of the back up generators
Backup Power System Provides for:
- Loss of 1 Main AC bus
- Loss of both Main AC busses
- Only 1 Main generator available
- Autoland
In the event of a loss of ALL main & backup generators ?
A standby system powers critical AC & DC equipment
Critical AC equipment?
- C ILS
- Radio Alt
- Marker beacon L
- ATC transponder L
- VOR L
- Engine igniters
Critical DC loads?
Captain & FOs flight instruments & displays
The standby system consists of ?
- The battery busses
- Captain’s & FOs instrument busses
- An AC standby bus
The busses in the standby power system are normally powered from ?
The L & R AC XFER busses directly or, through the TRUs
If the transfer busses become unpowered, (in the standby power system) how do you get power?
A RAT (ram air turbine) provides DC power through the TRUs
The standby AC bus is powered from the battery bus through a standby inverter
Why would you deploy the RAT in flight?
To provide electrical & hydraulic power simultaneously (in a standby power situation)
What is the primary source of standby electrical power if all normal sources are lost?
The RAT - Ram Air Turbine
3 things about the RAT:
- Located in aft R fairing
- Non-time-limited source of power
- < 1/10 power of IDG
The RAT is deployed automatically if:
- Both XFER busses are unpowered
- All 3 hydraulic system pressures are low
- Dual EF & C hydraulic pressure low
If the RAT doesn’t deploy automatically ?
It can be deployed manually
The ‘PRESS’ light on the RAT illuminates when?
The RAT is producing a minimum of 1,500 psi for the flight controls
If the RAT is unable to maintain hydraulic pressure what is sacrificed?
Electrical load is shed until hydraulic pressure is satisfactory
When RAT electrical loads are shed, or prior to RAT deployment, what powers the standby power system?
The Main Battery
When the RAT provides electrical power which busses are powered?
Both Captain’s & FOs flight instrument busses
When the battery provides standby power which busses are powered?
Only the Captain’s flight instrument bus
What is the primary source for the transfer busses?
Main AC busses
If all main & backup generators fail, what is the primary source of power for the standby electrical system?
RAT
