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AV Fundies > AES > Flashcards

AES Flashcards

1
Q

Difference between primary and secondary batteries?

A

Primary - Unable to be recharges / needs to be replaced

Secondary - Rechargeable

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2
Q

Primary and secondary purpose of an aircraft battery?

A

Primary purpose - Emergency power to aircraft

Secondary purpose - To start the aircraft

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3
Q

2 most common secondary aircraft batteries?

A
  • Sealed lead acid
  • NiCad
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4
Q

Methods to keep batteries held in position during flight?

A

Hold down points manufactured into the lid of the battery case lid: Used to secure into battery tray or aircraft frame

No hold down points available: Positioned using brackets

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5
Q

Lead acid batteries are made up of what components?

A
  • Battery case
  • Connectors
  • Cells
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6
Q

Cells in a lead acid battery are made up of what components?

A
  • Plates (pos and neg)
  • Separator
  • Electrolyte
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7
Q

How many cells are found in a lead acid battery?

How much are each cell worth?

A
  • 12 cells
  • 2v DC each
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8
Q

The capacity of a battery is measure in what?

A

Ampere-hour (Ah)

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9
Q

What is a C1 rating?

A

Amount of current that a battery can supply flat out for 1 hour

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10
Q

How many cells are found in a NiCad battery?

How much are each cell worth?

A
  • 20 cells
  • 1.2v each
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11
Q

How are the cells in a NiCad battery joined together?

A
  • Linked in series
  • Nickle plated copper used to interlink the cells
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12
Q

Define thermal runaway?

A
  • Uncontrollable increase in the temperature of a battery
  • Leads to discharge or toxic fumes or ignition

High temp / high changing rate = battery becomes unstable

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13
Q

What is SOC?

A

‘State of charge’

  • Monitored to maintain the health of an aircraft battery
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14
Q

At what temp does the WMC illuminate the ‘batt temp’ warning light?

A

71 degrees celcius +/- 2.8 degrees celcius

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15
Q

What is a TRU?

A

Transformer rectifier unit

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16
Q

A TRU provides a source of what type of power?

A

DC power

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17
Q

Components of a basic TRU?

A
  • 3 phase full rectifier
  • Cooling circuit
  • 3 phase transformer
  • Filter unit
  • Over temp warning switch
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18
Q

What does a voltage regulator do?

A

Regulate DC voltage

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19
Q

3 types of voltage regulators?

A
  • Carbon pile
  • Vibrating point
  • Transistor
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20
Q

How is a voltage regulator connected?

A

Parallel

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21
Q

What is the purpose of a reverse current relay?

A

To stop back current damaging the generator by returning to the generator on engine shut down

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22
Q

3 basic busbars?

A
  • Non-essential
  • Essential
  • Vital / Emergency
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23
Q

Under a generator fail situation, which busbar will become offline first and what components disengages it?

A
  • Non-essential
  • Relay is de-energised (GCB)
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24
Q

What are the 2 DC disruption systems?

A
  • Split bus
  • Tied bus (parallel)
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25
Q

Under a generator fail situation which component in a split bus links the no.1?

A

Bus tie relay

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26
Q

What component in a tied bus ensures the generators are sharing the load?

A

Equalising voltage controller

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27
Q

Advantage of a tied bus system compared to a split bus system?

A
  • Voltage is always constant / 28v across the bus bar regardless of how many generators are lost
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28
Q

What is the purpose of an inverter?

A

Converts DC to AC

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29
Q

2 classes of inverters?

A
  • Rotary
  • Static
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30
Q

Advantages of a static inverter?

A
  • No moving parts
  • Light weight
  • Smaller in size
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31
Q

Static inverter output?

A

115v AC

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32
Q

Components of a static inverter block diagram?

A
  • DC input
  • AC output
  • Square wave generator
  • Power amplifier
  • Sinewave shaping network
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33
Q

Purpose of a GCU?

A
  • Control frequency
  • Regulate voltage
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34
Q

What is a GCU?

A

Generator control unit

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35
Q

Fundamental requirements of an AC tied bus system?

A
  • Gens have to be in synch before they are tied together
  • Gens must be maintained in synch while in use
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36
Q

How are the generators synchronised in an AC tied bus system?

A

ELMS

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37
Q

In an AC tied bus system with 4 generator, if generator 4 fails, what will happen?

A
  • GCB4 will open breaking the circuit to generator 4
  • Gen 1, 2 and 3 will supply power to bus 4 (will remain closed)
38
Q

In an AC tied bus system with 4 generators, if generators 2, 3 and 4 fail, What will happen?

A
  • GCB2, GCB3 and GCB4 will open, breaking the circuit to generator 2, 3 and 4
  • Gen 1 is not capable of powering itself and 3 other generators on its own, therefore bus 2, 3 and 4 will remain disengaged
39
Q

What is ELMS and what does it do?

A

Electronic load management system

  • Controls all the switches
40
Q

3 sources of external DC power supply in an aircraft?

A
  • Battery
  • DC generators
  • TRU
41
Q

Are primary batteries rechargable?

A

No, only secondary batteries are

42
Q

Where are primary batteries used in an aircraft?

A
  • Cockpit voice recorder (CVR)
  • Flight data recorder (FDR)
  • Emergency locator transmitters (ELT)
  • Life vest lights
43
Q

When do we service primary batteries?

A

Specific maintenance schedule as dictated by the equipment / aircraft manufacture

44
Q

Requirements of a secondary battery?

A
  • Large temp variation
  • Pressure variation
  • Cope well with inversion, vibration and impact
45
Q

Why is nickle cadimum a popular choice in aviation?

A
  • Good starting current
  • Deliver a linear output
  • Handle extreme temps reasonably well
  • Maintenance is simplified as you can open the case and replace individual cells without having the replace them all
46
Q

Name of the quick release NiCad battery connector?

A

Elcon style connector

47
Q

Major danger regarding NiCad batteries?

A

Thermal runaway

48
Q

2 common forms of protection for DC circuits?

A
  • Current limiters
  • Reverse current relay
49
Q

How is a non essential bus isolated during failure of a primary power supply?

A

Load shed

50
Q

Why is a current limiter used?

A

Reduces the generator output voltage whenever the maximum safe load is exceeded

51
Q

What is the vital bus directly connected to?

A
  • The aircraft battery
  • This ensures power is supplied to the aircrafts emergency loads at all times
52
Q

How is an essential bus isolated and then reconnected?

A
  • By turning the battery switch off
  • By turning on the switch
53
Q

Where are split bus commonly used?

A

Commonly used in light aircrafts with 2 generators

54
Q

Advantages of the tied bus bar?

A
  • Tied together in parallel
  • Load is distributed evenly between the aircraft generators, not supplied by an individual generator
55
Q

Difference between split bus and tied bus?

A

Split - Series
Tied - Parallel

56
Q

What does the equalising voltage controller do?

A

It ensures that the load carried by the generators is shared evenly

57
Q

What must the voltage be within for the equalising voltage controller?

A

28v DC
+/- 0.5v

58
Q

When will the non-essential bus be automatically load shed?

A

When the DC generator fails

59
Q

What are we inspecting when inspecting main and emergency batteries?

A
  • Examine physical damage (to metal enclosed batteries)
  • Check for tripped circuit breakers
  • Check quick disconnect plugs
  • Check cables for damage, defects, security and cleanliness
60
Q

When inspecting a starter generator, what are we looking for?

A
  • Mounting bolts are tight
  • Mounting bolts are lock wired if required
  • Free of foreign objects
  • Secured and positioned correctly
61
Q

When inspecting power relay boxes, what are we looking for?

A
  • Check security of mounting
  • Examine looms, harnesses for correct bend radius and routing
  • Signs of over heading
  • Terminals are secured, correctly fitted and free of foreign objects
62
Q

2 types of inverters?

A
  • Rotary
  • Static
62
Q

Why are inverters required?

A

Emergency power supply for essential AC loads

63
Q

What are inverters used for?

A

Convert DC to AC

64
Q

Required AC voltage and frequency used for aircrafts?

A

115v
400Hz

65
Q

TRU is used to charge what?

A
  • Batteries
  • Supply power to DC systems if needed
66
Q

2 components that make up a rotary inverter?

A
  • DC motor
  • AC generator
67
Q

What controls the frequency in a rotary inverter?

A

Speed of rotation of the DC motor

68
Q

Components of a static inverter?

A
  • Diodes
  • Transistor
  • Capacitor
  • Transformer
69
Q

Advantage of a static inverter over a rotary inverter?

A
  • Light weight
  • No moving parts
  • Less maintenance
70
Q

3 types of voltage regulators?

A
  • Vibrating point (Sparking - overcomes spring tension, 50-200 times a second - feedback path is through the resistor)
  • Carbon pile (Carbon wears down)
  • Transistor (electronic switch connected to an earthing point so when the contact open and close it stops the return path)
71
Q

What parts of the aircraft run off the non essential busbar?

A
  • Toilet
  • Coffee machine
  • Anything that is not needed to fly (luxuries)
72
Q

Problem with split bus

A

Lots of wires and relays

73
Q

Advantage of tied bus

A

Less moving part, moving in parallel, constant volts

74
Q

What parts of the aircraft are connected to the vital bus?

A
  • Flight controls
  • Ejecto seato
  • Fire suppressant
75
Q

If you are lost or stuck when troubleshooting, what do you do?

A

Speak to your supervisor, SPO or SME

76
Q

Where are regulatory requirements for maintenance found?

A
  • Defence aviation safety regulation (DASR)
  • Military aviation regulations (MILAVREGs)
  • Technical airworthiness regulations (TAREGs).
77
Q

What should be followed when carrying out troubleshooting?

A

Repair and overhaul manuals

78
Q

What must be carried out after a component is removed or disconnected?

A

Op test of system

79
Q

Where can the periodic maintenance be found?

A

Technical maintenance plan (TMP)

80
Q

When inspecting a static inverter what would you be looking for?

A
  • Inspect it for signs of overheating, security, damage, or defects
  • Pay attention to sign of contamination around the vent holes
  • Inspect the receptacle for signs of damage, corrosion and foreign objects
81
Q

How does a static inverter operate?

A

They go through a square wave generator, power amplifier, sine wave shaping network and then are monitored through feedback

82
Q

For a static inverter, what is monitored at the feedback stage?

A
  • Voltage
  • Frequency
  • Current
83
Q

Components of the aircraft diagram for a split bus system?

A

a) External power relay
b) Auxiliary power relay
c) GCB (Generator control breaker)
d) INV (Inverter)
e) TRU 1 (Transformer rectifier unit)
f) TRU 2

84
Q

Electrolyte found in a sealed lead acid battery?

A

Sulphuric acid combine with distilled water

85
Q

What is cold cracking amps of a lead acid battery?

A

30 seconds at -18 degrees c

(rating and differ from 300A to 1000A depending on the aircraft)

86
Q

Electrolyte found in NiCad battery?

A

30% potassium hydroxide / 70% distilled water

87
Q

Connector used for lead acid batteries?

A

MIL Spec

88
Q

What does the capacity of a battery depend on?

A
  • Area of plate in contact with electrolyte
  • Quantity and specific gravity of electrolyte
  • Type of separater
  • General condition of battery
  • final limiting voltage
89
Q

Components of a split bus system?

A
  • 2 IDGs
  • APU
  • GCU
  • TRU
  • Static inverter
  • External power supply
  • GCB
  • Bus tie breaker

AV Fundies (11 decks)

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