Electrical Flashcards
You Taxi and Park at the Gate.
Ground crew plugs in Externalnpower and you Select GPU.
-With both Engines running what powers AC bus 2?
- Shutdown Engine 2. Now, How is AC BUS 2 powered?
Engine 2- IDG 2
GPU via AC Bus Tie.
In Cruise, you receive an IDG 1 off bus caution message. Where does AC BUS 1 now receive its power ?
You start the APU. Where does the AC BUS TIE now receive its power?
1.) IDG 2 via bus tie
2.) APU
During Descent you receive an
IDG 1 OIL message on the EICAS. What indication will you expect to see on the Electrical Panel?
An Amber Disc light on IDG 1
No
When will GPU AVAIL light Illuminate?
When connected to External power but it’s NOT powering the BUS TIE.
Button can be both pushed in or out
If QRH instructs you to deselect the APU GEN switch, what would this do?
Opens the APU GEN contactor isolating it from the AC BUS TIE.
Disconnects the APU GEN
During OET (one engine taxi) to the gate. With #2 and APU off. What is AC BUS 1 power source?
IDG 1
IDG 1 vía The AC BUS TIE
In Flight: ( APU not Available )
What Normally powers AC BUS 1?
What if IDG 1 was not Available?
IDG 1
IDG 2 via the Bus Tie
What Does the (GPU) IN USE light indicate?
GPU is powering the AC BUS TIE
During cruise QRH directs you to turn AC BUS TIE Selector Switch to
“1 Open” .
What does this Action do?
Will we lose anything.
Opens Bus Tie 1 Contactor- isolating , AC BUS TIE from AC BUS 1
The ability to power AC BUS 1 if IDG 1 fails
What is the priority of the AC BUS TIE
APU, GPU, IDG
What Happens if AC BUS TIE Switch is moved to “2 open”
BUS TIE Contactor 2 opens and isolates AC BUS TIE from AC BUS 2
What does the Yellow light 🟡 below DISC on the IDG switch indicate?
Indicates which IDG to disconnect
Associated with an IDG OIL caution EICAS
How can you Disconnect IDG 1?
Can it be Reconnected in Flight?
Holding the IDG knob in the DISC position for 1 sec.
No, only tech ops can reconnect on the ground.
What happens if a TRU Switch is moved to “OFF”
Would that DC BUS still receive Power?
Isolates TRU from its associated DC Bus
Yes, the DC TIE Contactor will close to provide power.
QRH directs you to move the DC BUS TIE switch to OFF position. How does this affect the DC system?
Opens all DC BUS TIE Contactors
-Restricts the DC system’s capability to Tie DC Buses automatically.
Power Down with NO EXTERNAL power available:
-BATT 1 and BATT 2 are placed into the OFF Position.
….. Have you removed power from ALL the buses on the Aircraft?
NO
HOT BATT BUS 1 and 2 will still be powered through the batteries.
Why is there an AUTO position on BATT 2?
“Auto” allows BATT 2, to power either the:
DC ESS 2 BUS or APU START BUS
How does the AUTO Position of the IDG 1 or IDG 2 Rotary Knob work?
“AUTO” allows IDG Contactor to close, connecting the IDG to it’s AC BUS automatically, according to system logic.
What is the “OFF” function of the IDG rotary knob?
“OFF” opens the IDG Contactor. Isolating the IDG from it’s AC BUS
When will the AVAIL Light ( on the GPU Push Button ) illuminate ?
When AC GPU is connected, but not powering the AC BUS TIE. Regardless of switch position ( In or Out )
Describe the operation of the Essential TRU when in AUTO.
Allows automatic connection of the TRU ESS to the ESS BUS 3
What is the difference between OFF and AUTO on the BATT 2 selector?
OFF- Only the HOT BATT BUS 2 is powered by the BATT 2
AUTO- connects BATT 2 to either the DC ESS BUS 2 or APU START BUS Automatically, according to system logic.
