Electrical Flashcards
Does External power have priority over all other generators
Yes
Someone must be present on A/C with APU running
Company limitation (Double check required)
A/C has how many batteries & rating?
1 x 40 amp hr 28VDC Main Battery
1 x 40 amp hr 28VDC AUX Battery
1 x 40 amp hr 28VDC STBY Battery (when equipped with APU)
They provide 1 hr of backup power
Emergency batteries
battery temp limits
50-65 deg is amber
>65 is red
What drives AC generators?
Propellor Reduction gearboxes on respective engine
When is AC power available
Condition levers between min and max range
What are the Battery Start Considerations?
With AC external power, initial start will be on batteries only
Starter Cranking limits
(Charging rate decreases after 3 mins for serviceable batteries)
(Batt temps and charging rates are displayed on MFD and must be monitored while charging)
Does the APU DC Starter Generator power all DC buses when connected?
Yes
A Generator load display indication of +1.05 indicates that
The Generator load is 5% above rated load
What component protects the batteries and generators from faults in the main feeder busses?
EPCU
What is the maximum TRU LOAD limitation in flight or on the ground?
1.0
If the DC GEN#1 caution light illuminates what other aural alert will occur?
One chime from the warning tone generator will sound
Max Battery load meter reading permitted for take off is?
0.1
If both DC Generators fail in flight?
The EPCU will automatically close the main to secondary bus ties powering all busses through the TRU’s
The selection of the BATTERY MASTER switch, with no other switches selected connects the batteries to the?
L & R Essential Busses
The function of the TRU’s is to?
Convert variable AC into DC
The operation of the MAIN BUS TIE switch to the TIE position may be inhibited by?
The Electrical Power Control Unit
The selection of the MAIN BATT or AUX BATT switch without the BATTERY MASTER on will?
Connect the Main & Aux Batteries to the Left Battery Bus or the Standby Battery tot he Battery Bus
The MAIN BUS TIE will always close when?
The EPCU signals it to close
If both TRU’s fail in flight?
The EPCU will automatically close the MAIN to SECONDARY BUS TIES
What is the rated load of the engine driven generators
400 Amp
What buses are powered with AC external power
All AC and DC buses
What is the maximim output rating of the TRU’s
28VDC 300 Amp (26 - 29 V range)
When does auto load shedding of the galley buses occur?
A AC Generator fails
When does the emergency mode of operation occur
Failure of both DC Gen’s and one TRU in the air
Will go into battery power mode
What will the EPCU do when it detects a main bus fault?
Prevents main bus tie and main to secondary bus ties from closing and isolating the affected bus. Also after 5 seconds of persistent fault, sends a TRIP signal to the GCU to isolate the generator and batteries
What will cause the EPCU to react to a main bus fault
Detection and protection of short circuits
What bus does the Main battery connect to when the battery master is switched on?
Right Essential Bus
What bus does the Auxilary battery connect to when the battery master is switched on?
Left essential bus
What bus does the Standby battery connect to when the battery master is switched on?
Right essential bus
What bus does the Main battery connect to when the Main Batt Switch is switched on?
Right Main Bus
What bus does the Aux battery connect to when the Aux Batt Switch is switched on?
Left Main Bus
What bus does the Standby battery connect to when the STBY Batt Switch is switched on?
Left Main Bus
What does the Main Bus Tie Switch actually do? What happens if there is a fault?
Manually ties left and right main buses.
EPCU inhibits the connection if there is a fault.
What does the Bus Fault Reset Switch do?
Re-initialises the EPCU after a bus isolation or fault to enable subsequent bus fault monitoring.
Can battery power be applied to the Secondary Buses? Why?
No it cant, It comes from the TRU’s or through the L & R Main Buses
What does the EPCU do in emergency mode?
The EPCU automatically disconnects the batteries from the main buses. There will be no power on the buses and remaining systems use battery power.
In Emergency mode if you attempt an engine start, what does the EPCU do?
Automatically connects the batteries to the main buses for the duration of the start attempt even if the respective switches are set to off.
Lost services on Left Main DC Bus?
Autopilot and Yaw Damper
Auto Cabin Pressurisation
Stick Pusher
ALT Downlock Indication
L ECS Auto
Rud Sys Isolate
Overhead Glareshield and Pilot Lights
L Flare, L Approach and taxi lights
FPD1
ESID CP, Plt EFIS CP
FMS1, DME1, ADF1
EGPWS, TCAS, ATC1
Flt Attendant Handset
Weather Radar
Lost services on Right Main DC Bus?
Autopilot and Yaw Damper
Stick Pusher
Anti-skid
R ECS Auto
Pilot Window Heat
Deice boot lights
Cntr Console, Co-pilot lights
R Flare, R Approach and Anti-collision lights
Cabin Lights
PFD2, MFD2, ADU2
TCAS, ATC2
VHF2
FMS2, DME2, VOR2
Clock 2
Lost services on Left AC BUS?
Stick Pusher
L Aux fuel pump
L Prop De-icing
L Alpha Vane Heater
L TRU
L Ice Detection Sensor
Pilot windshield Heat
L Engine Intake Heater
L Pitot static heater
Lost services on Right AC BUS?
Stick Pusher
R AUX fuel pump
R prop de-icing
R Alpha Vane Heater
R TRU
R Ice detection sensor
Standby Hyd Pump
Co-pilot windshield Heat
R Engine Intake Heater
R Pitot Static Heater
What two sources power the FADEC?
Primary & Secondary
Primary is the respective PMA located in the accessory drive section
Secondary is the essential power buses
What systems are powered by the HOT BATTERY BUS?
Clocks 1 & 2
Battery Master switch
Battery power for refuelling
Fire bottles discharge squibs
Fuel and Hydraulic shutoff valves via the PULL FUEL / HYD handles
#1 & #2 Engine Fuel Metering units
Fwd and Aft cargo compartment fire systems
APU fire bottle squibs
Boarding and flight deck done lights
Emergency power for PA system
