Electrical Flashcards
What is the purpose of the DC GPU receptacle
For APU start
Can you use the DC GPU to start the APU
YEs, as long as BATT 1 still works.
What does the AC System compose of
- 2 IDG
- APU
- AC External power receptacle
- RAT
- Inverter
What does the DC System compose of
- 2 22.5v NiCad Batteries
- DC External Receptacle
- 3 TRUs
Placing the IDG in the OFF position does what to the system?
It isolates that generator from its bus.
Placing the IDG in the DISC position does what?
It disconnects the IDG from Accessory gear box
Placing the AC BUS TIES in the open position does what?
It segregates that bus from the rest of the system
When does the available light illuminate in the AC GPU button
when ground power is properly suppling the correct Voltage, Amps, frequency to the system.
What happens when you place the TRU switch in the off position?
It isolates that TRU from its reactive bus.
Putting the DC BUS TIES in OFF position does what?
It opens the Ties removing them from the Auto logic.
When would the IDG Icon be White
When switch is in the off position or engine not running.
When would the AC GPU be white
When power is connected but the button is not pushed in.
What voltage does the battery ICON Turn white
Below 18v
The IDGs and APU Generator is rated at?
115V, 40kva, 400hz
When does the RAT come out?
When both AC BUS 1 and AC BUS 2 are not being powered
What BUS does the RAT power?
AC ESS BUS
When you get an IDG 1 (2) OIL EICAS msg, what other indication do you get
an amber light next to the IDG telling you which one to disconnect.
If disconnecting the IDG hold it for how many seconds
Hold it for 1 seconds. No more than 3 seconds.
Does the IDG auto disconnect?
Yes, IDG oil temperature reaches 366°F
Lets say your on AC ground power and you start the APU what does the auto logic do?
It removes the ground power and has the APU take over the electrical system, the ““IN USE” white light of the GPU turns to “AVAIL”. You must push out that button.
How can ground personnel have power to light up the plane for cleaning.
push the button on the front ramp panel or on the flight attendant panel at the forward right galley.
What does the Inverter do?
Converts DC Power to AC power to power the AC STBY BUS
What electrical power does the RAT provide
115v, 15kva, 400hz
How long does it take the RAT to power and what does it power?
It powers the AC ESS BUS and it takes 8 seconds.
When total electrical failure occurs and the RAT pops out, what powers the system while the RAT comes online
The batteries Power the DC ESS BUSes and also power the AC STBY BUS via the inverter.
What basic Items does the RAT provide power to
- ACMP 3A
- High lift devices.
- Avionics
- Communication and
- Battery Recharging.
What is the Minimum speed for the RAT? And what happens if we go below that?
130kts. If we below that speed, the RAT can only Power the AC ESS BUS and the batteries will provide power to the DC ESS BUSES eventually load shedding.
The DC GPU can supply power to only what BUS
The APU START BUS only.
What do the TRUs do?
They convert 115v AC power to 28v DC power for the DC system, at 300 amps
What happens if one TRU fails?
As long as the system is in auto, the ties will close to have no systems degradation.
Explain the Batteries
2 NiCad batteries rated at 22.8v 27 Amps, they can be charged by any AC source.
The batteries can provide Emergency power for how long?
10 minutes
What is the min temperature to use the batteries
-20
On the ground if the batteries are the only source of power a horn will sound after?
5 minutes
When would you use A DC GPU for APU Start?
if the outside temp is less than -20, or Battery 2 is less than 21 volts
What will cause an Amber Light on the IDG panel?
High Oil Temp
Low Oil Pressure
Can an APU replace a Failed IDG, up to what Altitude
yes, up to 33,000 feet.
What is the AC electrical Power Priority
- Onside IDG
- APU
- GPU
- Opposite Side IDG
How do you know if the GPU is ready to provide AC electrical load?
You get the “AVAIL” light on the over head panel and the GPU shows up on the EICAS Page.
What batteries are used for APU start?
Both batteries are used.
BAT 1 Powers EICASE and FADEC
BAT 2 powers the APU START BUS
What is the purpose of the inverter and what does it power.
It converts 28VDC to 115VAC it powers the AC STANDBY BUS any time AC power is not available.
The AC STANDBY BUS has the Igniters for DC Engine start.
What is on the AC STANDBY BUS
Engine exciters 1A and 2A
When will the RAT deploy?
- Any time the AC BUSES are not boing powered.
2. Manually by the pilot
Why does BATT 2 Normal position AUTO
Because it isolates the APU BUS for APU starts and acts as a backup to the DC ESS BUSES. Also for DC GPU start.
When only the Batteries are powering the system what do you see in the cockpit
- Screens 2 and 3
- IESS
- CLOCK
- MCDU #2
- Compass Light
Can one AC power source power the entire system?
yes
What are the batteries rated at?
22.8v and 27 amps.
What 2 EICAS messages do you see when you are on RAT power.
- Emergency Power
2. BATT DiSCH -> this goes away when RAT is powering AC ESS BUS
What speed do you need to be at when the RAT comes out for it to power the system?
150kts when it first comes out. Once out than 130kts.
If the RAT is deployed, does it give you back the AC ESS BUS if you establish AC power with APU or IDG?
No, once RAT comes out it locks into AC ESS BUS and does not let go.
How do the batteries get charged during Electrical Emergency Condition (RAT is out)
The RAT power the AC ESSN BUS, the AC ESS BUS power the TRU ESS which than charge the batteries, and the BATT DISC message goes away.
Describe the IDG Switch Positions?
- Off - Disconnects IDG From the BUS
- Auto - Allows IDG to pick up power per power priority.
- DISC - Spring loaded switch. disconnects from Engine.
