1
Q
Difference between primary and secondary batteries?
A
Primary - Unable to be recharges / needs to be replaced
Secondary - Rechargeable
2
Q
Primary and secondary purpose of an aircraft battery?
A
Primary purpose - Emergency power to aircraft
Secondary purpose - To start the aircraft
3
Q
2 most common secondary aircraft batteries?
A
- Sealed lead acid
- NiCad
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
5
Q
Lead acid batteries are made up of what components?
A
- Battery case
- Connectors
- Cells
6
Q
Cells in a lead acid battery are made up of what components?
A
- Plates (pos and neg)
- Separator
- Electrolyte
7
Q
How many cells are found in a lead acid battery?
How much are each cell worth?
A
- 12 cells
- 2v DC each
8
Q
The capacity of a battery is measure in what?
A
Ampere-hour (Ah)
9
Q
What is a C1 rating?
A
Amount of current that a battery can supply flat out for 1 hour
10
Q
How many cells are found in a NiCad battery?
How much are each cell worth?
A
- 20 cells
- 1.2v each
11
Q
How are the cells in a NiCad battery joined together?
A
- Linked in series
- Nickle plated copper used to interlink the cells
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
13
Q
What is SOC?
A
‘State of charge’
- Monitored to maintain the health of an aircraft battery
14
Q
At what temp does the WMC illuminate the ‘batt temp’ warning light?
A
71 degrees celcius +/- 2.8 degrees celcius
15
Q
What is a TRU?
A
Transformer rectifier unit
16
Q
A TRU provides a source of what type of power?
A
DC power
17
Q
Components of a basic TRU?
A
- 3 phase full rectifier
- Cooling circuit
- 3 phase transformer
- Filter unit
- Over temp warning switch
18
Q
What does a voltage regulator do?
A
Regulate DC voltage
19
Q
3 types of voltage regulators?
A
- Carbon pile
- Vibrating point
- Transistor
20
Q
How is a voltage regulator connected?
A
Parallel
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
22
Q
3 basic busbars?
A
- Non-essential
- Essential
- Vital / Emergency
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)
24
Q
What are the 2 DC disruption systems?
A
- Split bus
- Tied bus (parallel)
25
Under a generator fail situation which component in a split bus links the no.1?
Bus tie relay
26
What component in a tied bus ensures the generators are sharing the load?
Equalising voltage controller
27
Advantage of a tied bus system compared to a split bus system?
- Voltage is always constant / 28v across the bus bar regardless of how many generators are lost
28
What is the purpose of an inverter?
Converts DC to AC
29
2 classes of inverters?
- Rotary
- Static
30
Advantages of a static inverter?
- No moving parts
- Light weight
- Smaller in size
31
Static inverter output?
115v AC
32
Components of a static inverter block diagram?
- DC input
- AC output
- Square wave generator
- Power amplifier
- Sinewave shaping network
33
Purpose of a GCU?
- Control frequency
- Regulate voltage
34
What is a GCU?
Generator control unit
35
Fundamental requirements of an AC tied bus system?
- Gens have to be in synch before they are tied together
- Gens must be maintained in synch while in use
36
How are the generators synchronised in an AC tied bus system?
ELMS
37
In an AC tied bus system with 4 generator, if generator 4 fails, what will happen?
- GCB4 will open breaking the circuit to generator 4
- Gen 1, 2 and 3 will supply power to bus 4 (will remain closed)
38
In an AC tied bus system with 4 generators, if generators 2, 3 and 4 fail, What will happen?
- 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
What is ELMS and what does it do?
Electronic load management system
- Controls all the switches
40
3 sources of external DC power supply in an aircraft?
- Battery
- DC generators
- TRU
41
Are primary batteries rechargable?
No, only secondary batteries are
42
Where are primary batteries used in an aircraft?
- Cockpit voice recorder (CVR)
- Flight data recorder (FDR)
- Emergency locator transmitters (ELT)
- Life vest lights
43
When do we service primary batteries?
Specific maintenance schedule as dictated by the equipment / aircraft manufacture
44
Requirements of a secondary battery?
- Large temp variation
- Pressure variation
- Cope well with inversion, vibration and impact
45
Why is nickle cadimum a popular choice in aviation?
- 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
Name of the quick release NiCad battery connector?
Elcon style connector
47
Major danger regarding NiCad batteries?
Thermal runaway
48
2 common forms of protection for DC circuits?
- Current limiters
- Reverse current relay
49
How is a non essential bus isolated during failure of a primary power supply?
Load shed
50
Why is a current limiter used?
Reduces the generator output voltage whenever the maximum safe load is exceeded
51
What is the vital bus directly connected to?
- The aircraft battery
- This ensures power is supplied to the aircrafts emergency loads at all times
52
How is an essential bus isolated and then reconnected?
- By turning the battery switch off
- By turning on the switch
53
Where are split bus commonly used?
Commonly used in light aircrafts with 2 generators
54
Advantages of the tied bus bar?
- Tied together in parallel
- Load is distributed evenly between the aircraft generators, not supplied by an individual generator
55
Difference between split bus and tied bus?
Split - Series
Tied - Parallel
56
What does the equalising voltage controller do?
It ensures that the load carried by the generators is shared evenly
57
What must the voltage be within for the equalising voltage controller?
28v DC
+/- 0.5v
58
When will the non-essential bus be automatically load shed?
When the DC generator fails
59
What are we inspecting when inspecting main and emergency batteries?
- 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
When inspecting a starter generator, what are we looking for?
- Mounting bolts are tight
- Mounting bolts are lock wired if required
- Free of foreign objects
- Secured and positioned correctly
61
When inspecting power relay boxes, what are we looking for?
- 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
2 types of inverters?
- Rotary
- Static
62
Why are inverters required?
Emergency power supply for essential AC loads
63
What are inverters used for?
Convert DC to AC
64
Required AC voltage and frequency used for aircrafts?
115v
400Hz
65
TRU is used to charge what?
- Batteries
- Supply power to DC systems if needed
66
2 components that make up a rotary inverter?
- DC motor
- AC generator
67
What controls the frequency in a rotary inverter?
Speed of rotation of the DC motor
68
Components of a static inverter?
- Diodes
- Transistor
- Capacitor
- Transformer
69
Advantage of a static inverter over a rotary inverter?
- Light weight
- No moving parts
- Less maintenance
70
3 types of voltage regulators?
- 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
What parts of the aircraft run off the non essential busbar?
- Toilet
- Coffee machine
- Anything that is not needed to fly (luxuries)
72
Problem with split bus
Lots of wires and relays
73
Advantage of tied bus
Less moving part, moving in parallel, constant volts
74
What parts of the aircraft are connected to the vital bus?
- Flight controls
- Ejecto seato
- Fire suppressant
75
If you are lost or stuck when troubleshooting, what do you do?
Speak to your supervisor, SPO or SME
76
Where are regulatory requirements for maintenance found?
- Defence aviation safety regulation (DASR)
- Military aviation regulations (MILAVREGs)
- Technical airworthiness regulations (TAREGs).
77
What should be followed when carrying out troubleshooting?
Repair and overhaul manuals
78
What must be carried out after a component is removed or disconnected?
Op test of system
79
Where can the periodic maintenance be found?
Technical maintenance plan (TMP)
80
When inspecting a static inverter what would you be looking for?
- 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
How does a static inverter operate?
They go through a square wave generator, power amplifier, sine wave shaping network and then are monitored through feedback
82
For a static inverter, what is monitored at the feedback stage?
- Voltage
- Frequency
- Current
83
Components of the aircraft diagram for a split bus system?
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
Electrolyte found in a sealed lead acid battery?
Sulphuric acid combine with distilled water
85
What is cold cracking amps of a lead acid battery?
30 seconds at -18 degrees c
(rating and differ from 300A to 1000A depending on the aircraft)
86
Electrolyte found in NiCad battery?
30% potassium hydroxide / 70% distilled water
87
Connector used for lead acid batteries?
MIL Spec
88
What does the capacity of a battery depend on?
- Area of plate in contact with electrolyte
- Quantity and specific gravity of electrolyte
- Type of separater
- General condition of battery
- final limiting voltage
89
Components of a split bus system?
- 2 IDGs
- APU
- GCU
- TRU
- Static inverter
- External power supply
- GCB
- Bus tie breaker
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