Electrical Flashcards
Alternate Sources of Power for Ground Service Bus?
APU Generator
External Power
Ground Service Bus Powers…
Main Battery Charger
APU Battery Charger
Misc. Cabin & System Loads
Ground Handling Bus Can Be Powered When?
Only on the ground
Ground Handling Bus Only Works If What Are Powered?
APU Generator
or
External Power Source
Ground Handling Bus Provides
Cargo Handling Capability
Equipment Energized During Ground Ops
If Power is Lost to Both Main AC Busses, the Captains Flight Instruments are Powered by the
Hydraulic Driven Generator
What Powers the Transfer Busses Normally?
Their Associated MAIN AC BUSSES
What Powers the Transfer Busses is both AC busses are unpowered?
HDG
Load Shedding That May Be Observed Prior to Engine Start (3)
Electric Hydraulic Pump
Center Tank Fuel Pumps
Utility Busses
Load Shedding That May Be Observed During Non-Normal Operations (3)
Utility Busses After a Generator Failure
Center Tank Fuel Pump after engine start
Cabin ceiling lights after engine failure
The Battery/Standby Power System Consists of the Following Busses (4)
Hot Battery Bus
Main Battery Bus
Standby AC Bus
Standby DC Bus
Name Some Things on Hot Battery Bus
Fire PROTECTION (extinguisher Bottles) Captains Clock APU Fuel Valve Spar Fuel Valve Parking Brake Valve Man Deployment of the RAT All 3 IRUS
Prior to establishing electrical power, the main battery powers what?
The Hot Battery Bus
After electrical power is established, what powers the Hot Battery Bus?
Main Battery CHARGER
After Electrical Power is established what powers the battery bus? What provides a backup source of power?
The Left DC System
The Main Battery
When do we Load Shed?
- During hydraulic pressurization- load sheds c2 pump and two galley busses
- During engine start- ignition goes to ground- lose both galleys both utilities and left electric demand pump
- During inflight with 1 generator down- we load shed galley utility busses and Boeing logic controls the rest
What does the Battery DISCH light illuminated mean?
Battery is discharging
If EICAS powered: MAIN BAT DISCH-
30 MINUTES STANDBY POWER!
What Hydraulic System Powers the Hydraulic Driven Generator?
Center Hydraulic System
Hydraulic Driven Generator provides AC power to what? (4)
Left AC Transfer Bus (Captains)
Right AC Transfer Bus (FO)
Standby AC Bus (through the left AC transfer bus)
The Captains Flight Instrument Transfer Bus
What happens when you bring the throttles aft of the interlock position?
Autothrottles Disengage
Speedbrakes Deploy
REV ISLN light means what?
Fault in the reverser system
this light is inhibited in flight
What happens to the APU bleed valve at 17000’?
It CLOSES
When Arming Speedbrakes what must you have to make them go off on the ground
Main Gear Logic On the Ground
Wheel Spin Up
Thrust Levers to Idle
What are flap positions and their speeds?
UP
1 Just Slats in takeoff position 250
5 Takeoff Flap Position (most common) 230
15 Takeoff Flap Position 210
20 Takeoff Flap Position/Non-Normal Operation 210
25 Normal Landing Flap Position 180
30 Normal Landing Flap Position 170
Cold Dark Airplane
- Check to make sure mx done
- Check logbook
- Supplemental Power Up Procedures 6.1
No Switches on in Electrical System. Whats powered?
Hot Batt Bus
Main Batt Bus
Stb AC Bus
Stb DC Bus
What bus needed to fuel the airplane?
Hot Battery Bus
When you open fueling panel door it uninhibits the the 2 pumps in the Below 50% n2
Switch is left side of the wing - Normal to BATT
Standby Light will be in OFF position
External Power- Tell me about it
1 ON forward aft nose on the right
Leave switches in on position- Boeing System Logic
When does DC Bus Tie work?
When you lose a T/R
What do the GEN CTRL BREAKERs do?
Protects my bus from bad power coming out of generator- Bus is so important
Also protects generator from a bad bus
What turns on the GEN Drive light?
HOT
LOP
There is no auto disconnect
Not able to be reconnected in flight
Only by MX on the ground
How do people vacuum the airplane without me there?
AVAIL light on on the overhead is showing with ground Power plugged in
Ground Service Switch in the forward left galley ON
Walk me through an APU Start
- APU selector to START then spring loads back to ON
- ECU begins start sequence
- FAULT light depicted ON then OFF- (APU fuel valve went full open)
- RUN light will flicker twice (2 self test of circuitry per each battery)
- RUN light will come on at 95% and stay on steady- APU is now started
APU Starting Limitation
3 start attempts in 1 hour allow 1 min cooling between attempts
How do you get the APU to go from External Power to now powering the busses?
You turn external power switch to OFF to get APU to take over
All busses now powered by APU except GROUND HANDLING BUS
**The ground handling bus will still provide power
When will Ground Handling Bus stop running?
- When you go into flight via the main gear ground logic (therefore it only works on the ground) Example: Packs off Takeoff-
- Disconnecting External Power
- Shutting OFF APU
After you disconnect ground power, what is the logic of the electrical system getting power?
Start the right engine, R Main AC bus wants to use the right generator for power obviously –
The Left Main Bus uses the APU Still
Start left engine, L Main AC bus will go to the Left generator for power
L & R AC BTB open to prevent paralleling
IF you turn off APU now you don’t have Ground Handling anymore.
What is shed during an engine start?
C2 Pump & Galley Power
External Power Switch AVAIL Illuminated means what?
- Power Connected
- Acceptable (voltage and frequency)
- Ground Handling Bus is now energized
External Power Switch ON Illuminated means what?
External Power connected to a Main Bus- (you pushed it and wanted it to connect to a Main Bus)
APU Generator OFF Light Indicates?
Generator Manually Selected OFF
or
FAULT on APU Generator
What is the APU Shuffle?
Procedure to prevent inadvertent shutdown by overcoming the check valve
Walk me through the APU Shuffle.
- Turn Bleed Air switch for APU OFF – (Prevents air from going into 4 ducts)
- Packs from AUTO to OFF- (closes both pack valves)
- Turn APU bleed Air Switch back to ON (give control back to Boeing to populate 4 ducts)
What is the Engine Start Duty Cycle?
Continuous for 5 minutes
Must Cool for 30 seconds per minute of operation