Electrical Flashcards by Dale B

Does External power have priority over all other generators

Yes

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Someone must be present on A/C with APU running

Company limitation (Double check required)

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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

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battery temp limits

50-65 deg is amber
>65 is red

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What drives AC generators?

Propellor Reduction gearboxes on respective engine

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When is AC power available

Condition levers between min and max range

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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)

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Does the APU DC Starter Generator power all DC buses when connected?

Yes

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A Generator load display indication of +1.05 indicates that

The Generator load is 5% above rated load

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What component protects the batteries and generators from faults in the main feeder busses?

EPCU

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What is the maximum TRU LOAD limitation in flight or on the ground?

1.0

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If the DC GEN#1 caution light illuminates what other aural alert will occur?

One chime from the warning tone generator will sound

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Max Battery load meter reading permitted for take off is?

0.1

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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

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The selection of the BATTERY MASTER switch, with no other switches selected connects the batteries to the?

L & R Essential Busses

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The function of the TRU’s is to?

Convert variable AC into DC

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The operation of the MAIN BUS TIE switch to the TIE position may be inhibited by?

The Electrical Power Control Unit

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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