Electrical Flashcards
Describe the AC electrical system
Two engine driven 115 VAC, 400 hz 3-phase 40 KVA Intergrated Driven Generators provide AC power. APU generator is capable of providing AC power if engines are not running and an ADG is capable of providing emergency power
Describe the DC electrical system
Four Transformer Rectifier Units convert 115 VAC power to 28-VDC power for distribution to the airplanes DC system
Describe the batteries
24 volt APU battery rated at 43 ampere hours and 24 volt main battery rated at 17 ampere hours
Electrical Power Panel:
DC Service switch
Connects the DC service bus to the APU battery direct bus
Electrical Power Panel:
Battery Master Switch
Connects the battery direct buses to the battery bus
Electrical Power Panel:
What does illumination of AVAIL mean on the AC switchlight
External power is connected and usable (correct phase, voltage and frequency)
Electrical Power Panel:
What does illumination of IN USE mean on the AC Switchlight
External power is supplying power to the AC buses
Electrical Power Panel:
IDG 1 and 2 DISC Switchlight (Guarded)
What happens when pressed in
The respective IDG is separated from the accessory gear box. The White DISC light will illuminate
Electrical Power Panel:
IDG 1 and 2 DISC Switchlight (Guarded)
What does illumination of amber FAULT light mean
High oil temp or low oil pressure is detected in the IDG (HOT LOP)
Electrical Power Panel:
IDG 1 and 2 DISC Switchlight (Guarded)
What does the illumination of the DISC light mean
The switchlight has been pressed disconnecting the CSD (constant speed drive) or the CSD has disconnected due to overtorque or temp
Electrical Power Panel:
AC ESS XFER Swtichlight
What happens when pressed
It illuminates and transfers AC ESS bus from AC bus 1 to AC bus 2. Will automatically transfer if a fault is detected on AC bus 1, illuminating the switchlight
Electrical Power Panel:
What does the OFF/RESET position on the Gen1,2 and APU switch mean
Disconnects the generator from its bus and re-arms the generator control circuit
Electrical Power Panel:
AC AUTO XFER switchlight
what does the illumination of the amber FAIL light indicate
Either an AC bus fault, or an over-current condition has occured and the respective bus has been isolated (AC bus 1 or 2)
Electrical Power Panel:
AC AUTO XFER switchlight
What does the illumination of OFF indicate
When pressed the light illuminates indicating that the respective bus has been isolated (manual cross-tie lockout)
ADG Auto Deploy Panel:
Unit switch; tests the transfer relays and the controller logic. What conditions must be met prior to conducting the UNIT test
Both engine generators must be online and both AC buses powed
ADG Auto Deploy Panel:
Unit switch test light; when illuminated what is indicated
Indicates a successful unit test
ADG Auto Deploy Panel:
PWR TXFR OVERRIDE Switch
Removes ADG power from the AC essential bus and allows normal power from AC bus 1 or 2 to the AC essential bus
How can external power be used by the ground crew when the cockpit door is locked
Press the AC PUSH switchlight on the external service panel
What might the DC Service switch be used for
External aircraft lights while repositioning the aircraft without the battery master on
In an aircraft with no power switched on, which buses are powered
APU and main battery direct buses, and the emergency bus
How many AC buses are there
Four
How many DC buses are there
Nine
What normally powers AC bus 1 & 2? And what is the switching priority in an abnormal situation?
GAGE G Onside Generator A APU G Offside Generator E External Power
How many TRU’s are there and what is their maximum power rating?
4 rated at 120 amperes 28 Volts DC
How many DC but ties are there and what are their names?
5
Main tie, cross tie, utility tie, essential tie, essential TRU tie
If the cross tie closes, what else will close?
The main tie and essential tie will close.
What is the DC utility bus shed?
When the main tie or cross tie closes
What items are on the utility bus?
The passenger service units, (primarily reading lights)
How are the DC bus ties controlled?
DC bus tie control is automatically accomplished through the 2 DC power centers (DCPC’s)
When will the essential TRU 2 tie close? (causing it to display on the DC synoptic page)?
With a loss of AC bus 2 and essential TRU 1
What does the DC essential bus primarily provide power for?
The captains flight instruments.
When will the ADG automatically deploy?
Complete AC power failure
What is powered by the ADG?
HEFAS Hydraulic pump 3B Essential AC bus Flaps and Slats at half speed ADG bus Stab trim channel 2
How much power does the ADG produce?
115 volts, 15 KVA
What is the minimum airspeed for ADG operation?
135 kts
Why must the ADG handle be pulled after an auto-deployment?
To continue power through the DC Essential bus once weight on wheels (WOW)
How is normal power restored after an ADG deployment if a generator returns?
By stowing the ADG handle, and pressing the power transfer override button (PWR TXFR OVERRIDE)
Can hydraulic 3b be deselected after an ADG deployment?
No. It is hardwired to the ADG bus for continuous operation.
What items are powered by the DC emergency bus?
Engine fire extinguishers, APU fire extinguishers, fuel shut off valves (SOV) and hydraulic shut off valves
What powers the DC emergency bus?
APU battery direct bus, DC battery bus
When is the DC emergency bus displayed on the DC synoptic’s page?
When power is lost from one or both of its powered sources
When operating only off the batteries in an emergency power situation, how many minutes of battery life does each APU start attempt cost?
6 minutes
Where is the main battery located?
Forward nose compartment
Where is the APU battery located?
Aft equipment bay
