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HERC CONVERSION > ELECTRICS EXAM REVISION > Flashcards

ELECTRICS EXAM REVISION Flashcards

1
Q

Draw the Schematic

A

In booklet

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2
Q

What are the 3 main subsystems of the electrical system

A
  • Primary AC power
  • Secondary AC power
  • DC power
    systems
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3
Q

What does the external AC power system provide power to?

A

All 3 subsystems (if all switches are closed)

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4
Q

What does the external DC system provide power to?

A
  • The DC power subsystem

- The secondary AC power subsystem

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5
Q

Secondary and Primary AC power voltage?

A

115V

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6
Q

DC power voltage?

A

28V

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7
Q

Describe the generator specs (4)

& what kind of system?

A
  • Aircooled, brushless system,
  • Rated at 40kVA
  • Output voltage of 115V/200V AC
  • 3 phase 400Hz
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8
Q

Location of the engine driven

generators

A

Mounted on the accessory drive pad of each engine reduction gearbox

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9
Q

Three main parts to the generators?

A

PEM

  • Permanent magnet generator
  • Excitation generator
  • Main generator
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10
Q

How are the generators cooled?

A

Combination of internal fans and ram air sourced from air entering the oil cooler scoop

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11
Q

What is the condition/limitation of ram air cooling of the generators?

A

Nil ram air cooling on the ground, generators shouldn’t be run at more than 0.625 continuously on the ground

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12
Q

Why generator disconnect?

What power supplies it?

A

eliminates the need to shut down an engine in flight due to a mechanical generator failure
LH DC

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13
Q

How does a generator disconnect work? (3)

A
  1. Application of 28V DC melts fusible link
  2. a steal plunger drops
  3. causes the drive coupling to shear at two weak points
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14
Q

Positive indication of a generator disconnect

A

Green “disc fired” light illuminates

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15
Q

Where are the GCUs located?

A

(Generator Ctrl Units x5) located aft centre underdeck equipment rack

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16
Q

What is the purpose of the GCU

A

provides complete automatic control and protection for the associated generator

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17
Q

What are the protections provided by a GCU

A
  • Over/Under Voltage
  • Over/Under Freq
  • Differential Fault
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18
Q

Overvoltage specifics (#/what happens/reset?)

A
  • Greater than 130V on any phase
  • De-energises Gen exciter field & opens the contactor
  • Reset: OFF RESET then ON
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19
Q

Undervoltage specifics (#/what happens/reset?)

A
  • Less than 95V on any phase
  • De-energises Gen exciter field & opens the contactor
  • Reset: OFF RESET then ON
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20
Q

Differential Fault (#/what happens/reset?)

A
  • Differential current flow of 35Amps between generator and main distribution panel
  • De-energises Gen exciter field & opens the contactor
  • Reset: Remove DC power OR pull CB (maintenance only & ON GROUND)
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21
Q

Overfrequency (#/what happens/reset?)

A
  • Frq rises above 435Hz
  • De-energises Gen exciter field & opens the contactor
  • Reset: OFF RESET then ON
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22
Q

Underfrequency (#/what happens/reset?)

A
  • Freq less than 370Hz
  • Gen contactor ONLY opens
  • Reset: automatic when frequency rises above 370Hz
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23
Q

What is the LED truth table (&condition)

A

Used to Ident the fault of a tripped generator. Generator needs to be ON to use.

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24
Q

When will you get a GEN OUT light?

What other indications do you get?

A
  • When the GCU switch is set to ON & due to a fault, the gen contactor opens, cutting off gen supply
  • MASTER CAUTION & GEN OUT on CAWS
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25
When will you get the APU OUT light? | What is the difference in comparison to GEN OUT?
- When APU is selected ON, but is not powering the ESS BUS | - Nil secondary indication on CAWS
26
Rules for bus switching (4)
1. Any 1 generator can power the ESSENTIAL & MAIN BUSSES 2. Any 2 generators can power all 4 AC busses 3. Sides support sides 4. Inboards support inboards/Outboards support outboards
27
What does the APU have priority over?
Priority over the #2 Generator for powering the ESS BUS
28
What is the AC Bus Tie Switch and can it be used in flight?
- Allows MAIN AC BUS to be powered by the APU generator | - Ground use only
29
When will the BUS OFF indicators illuminate? (#) | What other indications will occur?
- Average phase voltage below 96V - Any one phase voltage below 90V - BUS OFF & MASTER CAUTION
30
External AC power requirements?
- 40kVA at 115/200V AC - 3 Phase 400Hz - Phase rotation A-B-C
31
What is the ground power monitor system?
Monitors external power and if a malfunction occurs, AC power will trip within 1.5secs
32
What is the AC External power switch? | What triggers it to OFF? (4)
- A two-position switch with an override solenoid powered by the battery - Triggers; > APU gen control switch is ON > Ground power monitor system detects a fault in the power supplied > Any engine generator online > Ext power plug not in receptacle
33
How does the AC External power reset switch work?
If power is tripped off by the ground power monitor system, it will stay OFF until the fault corrects an the EXT AC POWER RESET CTRL switch is placed to reset.
34
Two methods of powering the AC secondary BUS
1. LH DC via inverter | 2. ESS AC BUS
35
Secondary AC BUS inverter specs (4) | Location?
- 115V - 1 phase - 400Hz - Rated to 2500VA - Located in electrical control & supply rack under Flight deck floor
36
When will you get the SEL PWR OUT light? | What next?
- Illuminates when the selected power source fails | - Remains illuminated until the ACI & EFC BUS is switched to the ESS AC BUS
37
What does the ACI & EFC buss power
- Engine Temperature datum system - Engine fuel flowmeters - Fuel Qty indicator - LOX Qty indicator - #1 instrument transformer - #2 instrument transformer
38
What is a TRU Rated to? how is it cooled?
- Transformer rectifier unit, converts AC to 28V DC - Rated to 350A - Cooled via internal fans
39
Why are TRUs in pairs?
Load sharing and redundancy
40
Battery specs (6)
- Lead acid type - rated to 24V, - 43 Amp hours - negatively earthed - Min acceptable charge 21V - Provides 3 starts of APU without charging
41
What battery powered circuits must always be considered "live" (FAAJIVEE)
- Fire extinguisher circuit - AC external power switch solenoid - Alarm bells - Jump lights - Isolated DC BUS ON BATTERY light - Voltmeter DC - Emergency depressurisation - Emergency exit lights extinguish button
42
What happens if the battery charge falls below 16V?
The battery relay will drop out and aircraft power will be lost
43
What do the TRU load meters indicate?
The percentage of load output with 100% being 350A
44
TRU Overheat switches - Location - Cause - Reset?
- ABOVE each loadmeter - Automatically shuts off it's overheating TRU by opening the control relay and removing AC power. TRU O/H light will come on - Will auto-reset & resume operation once condition no longer exists
45
TRU TO BUS OPEN indicator - Location - Cause - Reset?
- BELOW each loadmeter - When incorrect current flow is sensed (+350A or -15A), output to bus is grounded (contactor opened) & light illuminates - Manual reset by pressing the switch, resets the TRU to its BUS when the condition no longer exists
46
ISOL/LH DC BUS TIE switch allows? | When?
Allows current flow from the ISO DC BUS to the LH DC BUS when aircraft is on the GROUND
47
RH/LH DC BUS TIE switch allows?
Allows current to flow between the RH and LH DC BUS
48
DC BUS TIE FAIL indicator switch - Cause - Reset
- If RH-LH current is more than 350A in either direction, the tie will open and DC BUS TIE FAIL will illuminate - Reset by pressing the switch; bus tie will close if current is back within limits
49
BUS OFF indicators (LH/RH DC BUS OFF) | What else will occur?
illuminate when the respective BUS is not powered | BUS OFF legend & CAWS illuminate
50
ISOLATED DC BUS ON BATTERY indicator
Indicates that the ISO BUS is being powered by the Battery only, and will drain the battery
51
How are PAVs and CAVs usually powered?
- 3 position NORM/OFF/ALT switch (usually on NORM) - PAVs: LH DC - CAVs: RH DC
52
PAVS & CAVS ALT light
illuminated when the PAVS/CAVS are being powered by their alternate source - PAVS: RH DC - CAVS: LH DC
53
External DC power requirements (3)
400A at 28V DC and negative earthed
54
Where are the touchdown switches located?
Aft face of the Fwd MLG strut (LH & RH)
55
What are the systems controlled by the touchdown switches & what is required? (MEENCCD)
Require one touchdown switch to be operative on the ground; - MFDUs - EIDs - Engine ground stop - Nacelle preheat - CMDs - Clocks - DFDAU
56
What are the systems controlled by the touchdown relay & what is required? (BRAL)
Require both switches to be in air mode to energise the relay. - Brakes (anti-skid threshold control) - Ramp and door control from the flight deck - ADS release - Landing gear lever unlocked
57
Systems controlled by Aux touchdown relay & what is required?
Relay energised as long as one switch is in ground mode. | - ISO/LH DC bus tie control
58
Frq meter limit
380-420 Hz
59
Voltmeter (AC Gens & inverters) limit
110-125V
60
AC loadmeter (engine driven generators) limit
0-1.05 (air) | 0-0.625 (ground)
61
AC Loadmeter (APU) limit
0-1.05
62
DC Voltmeter limit
25-30V
63
DC loadmeter limit
0-1.03
64
Battery voltage min
min 21V
65
Tripped CB rule
Allowed only 1 reset after a 2min cool-down
66
How to isolate the ESS AC BUS?
Pull 9x ESS AC CBs LHS Pilot CB panel, Pull 9x CBs at station 245
67
What is LSGI and how does it affect the generators
Low Stop ground idle. The generators will not be on if engines are in LSGI
68
Describe the LDG lights and their limitation
2x retractable lights on the underside of each wing. White or IR Airspeed limitation with them down: 165KIAS extended
69
Anti-Col Strobe light warnings (2)
- Avoid use of Strobes in IMC conditions as reflection of light from clouds can cause spatial disorientation - All safety precautions WRT the Strobes must be adhered to.
70
List electrically powered anti-ice systems (3)
Pitot heat Windshield anti-ice Prop de-ice
71
What is the pitot anti-ice powered by?
- Pilots pitot: LH DC | - Co pitot: RH DC
72
How does the windshield anti-ice work? | the four layers?
heat provided via LH AC power to a resistance layer in the glass. - Outer glass - conductive layer - Plastic - Inner glass
73
How do the windshields sense temperature? | Temp range for operation?
- Controlled automatically and detected via thermisters | - 43deg to +27deg
74
How do the NESA windshield switches work? | When use HI?
NORM/OFF/HI | Usually in NORM, HI only chosen if ice is accumulating faster than the NORM setting can remove
75
Cold start switches?
Momentary push switches (5sec on, 10sec off), that gradually heat the windshield in extreme cold temps to prevent damage
76
Warning associated with NESA switches
Never touch the outer glass with a bare hand with the switch ON
77
Conditions under with NESA switches must be turned OFF (OPEO)
- OAT greater than 27deg - Panels feel excessively hot - Electrical arcing is observed - One of the panels with a thermister is not heating up (can cause O/H in other panels)
78
Limit if windshield anti-ice is U/S or OFF
Max 187KIAS Below 10,000ft (due bird strike)

HERC CONVERSION (18 decks)

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