AIRCRAFT SYSTEMS

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tous Very few free electrons .

ELECTRICS & ELECTRONICS

An electric current is created when electrons are caused to move through a

conductor. et
/flow of
There are six basic means to provide the force which causes electrons to flow:

⑪Friction - static electricity

⑳ Chemical Action - cells and batteries (primary and secondary cells)

③ Magnetism - generators and alternators

⑭ Heat - thermocouples (junction of two dissimilar metals)

⑧
Light - photo electric cell
Pressure - piezoelectric crystals

Of the six basic methods, only Chemical Action (batteries) and Magnetism
(generators) produce electrical power in sufficient quantities for normal daily
needs

Electromotive Force (EMF)

For electric current to flow there must be a force behind it.
Electromotive Force (to
make it flow),In
electrics if the EMF
decreases, the flow of
electrons decreases.
EMF is measured in
units of Voltage.
(DGCA)
The number of volts is a measure of the EMF or Potential Difference (pd)
(the difference in electrical potential between the positive and negative
terminal).
Voltage is given the symbol V or E. .
The source of the voltage can be a battery or a generator.
To measure voltage a voltmeter is used.

Emf↓ flow afcr+

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Current( I )

The current (symbol I) in a conductor is the number of electrons passing any

point in the conductor in one second and is measured in amperes or amps
(symbol A).
Current can be measured by an instrument called an ammeter which is
connected into the circuit so that the current in the circuit passes through the
ammeter.

Effects of an electric current:

Heating Effect. When a current flows through a conductor it always causes the
conductor to become hot - electric fires, irons, light bulbs and fuses.

Magnetic Effect. A magnetic field is always

produced around the conductor when a
current flows through it - motors, generators
and transformers.

Chemical Effect. When a current flows

through certain liquids (electrolytes) a
chemical change occurs in the liquid and any
metals immersed in it - battery charging and
electroplating.

Current is measured by Ammeter,

Ammeter is connected in series and
have low resistance.
Voltage is measured by voltmeter,
Voltmeter is connected in Parallel and
have high resistance.

Resistance /gadhe]

The obstruction in the circuit which opposes the current flow is called
resistance.
UNIT IS OHM(symbol Ω)(DGCA)

Factors Affecting the Resistance R = Pl

-
a

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Type of material. e.g. silver is a better conductor than copper (DGCA)

Length. The longer the wire the greater the resistance

Cross sectional area. The thicker the wire the smaller the resistance

Temperature.
If resistance increases with an increase of temperature, the resistor is said to
have a Positive Temperature Coefficient (PTC). (DGCA)
If resistance decreases with an increase of temperature, the resistor is said to
have a Negative Temperature Coefficient (NTC). PTC TP RY <nat ↓

Resistors NIC T4 RN C ↑

Sometimes resistance is used to adjust the current flow in a circuit by fitting

resistors of known value. These can be either fixed or variable and can be
drawn like this.

-
↑
Ohm’s Law
If the voltage remains constant, any increase in resistance will cause a decrease
in current and vice-versa (current inversely proportional to resistance).

If the resistance remains the same, any increase in voltage will cause an
increase in current and vice- versa (current directly proportional to voltage).

This is expressed as Ohm’s Law:

V = IR

Power
When a Force produces a movement then Work is said to have been done, and
the rate at which work is done is called Power.

In an electric circuit work is done by the voltage causing the current to flow
through a resistance, creating heat, magnetism or chemical action.

The rate at which work is done is called Power and is measured in Watts.

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Watts (W) = Voltage (V) × Amperes (I)

Three formulae for calculating power can be derived from the two basic
formulae V=IR and W=V×I

Voltage unknown W = I2 R W =
iR

Resistance unknown W = V × I W =
V I

Current unknown W = V2 / R W =

v
2
/R

Each electrical circuit in an aircraft will be protected by a fuse or circuit

breaker which will prevent the maximum power rating of a component to be
exceeded by breaking the circuit if the current increases.

Sover worst /voltage)

Series and Parallel Circuits (DGCA)

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Questions - Theory

1. All effects of electricity take place because of the existence of a tiny

particle called the:
a. electric
b. proton
c. neutron
- d. electron
-

2. The nucleus of an atom is:

-a. positively charged
b. negatively charged
c. statically charged
d. of zero potential
3. An atom is electrically balanced when:
~a. its protons and electrons balance each other
b. the protons outnumber the electrons
c. the electrons outnumber the protons
d. the electric and static charges are balanced
4. The electrons of an atom are:
a. positively charged
b. neutral
~c. negatively charged
d. of zero potential
5. A material with a deficiency of electrons becomes:
-a. positively charged
b. negatively charged
c. isolated
d. overheated
6. A material with a surplus of electrons becomes:
a. positively charged
- b. negatively charged
c. over charged
d. saturated
7. Heat produces an electric charge when:
a. like poles are joined
b. a hard and soft glass is heated
-c. the junction of two unlike metals is heated
d. hard and soft material are rubbed together
8. Friction causes:

MANSIMRAN SINGH
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a. mobile electricity
b. basic electricity
~
c. static electricity
d. wild electricity
9. Chemical action produces electricity in:
a. a light meter
b. a generator
-c. a primary cell
d. starter generator
10. A photo electric cell produces electricity when:
a. two metals are heated
-b. exposed to a light source
c. a light source is removed
d. exposed to the heat of the sun

Questions - Units 1

1. The difference in electric potential is measured in:

a. kVARs
b. watts
c. amps
~d. volts
2. Electrical power is measured in:
- a. watts
b. amperes
c. ohms
d. volts
3. The unit measurement of electrical resistance is:
a. the volt
b. the watt
~ c. the ohm
d. the ampere
4. An ammeter measures:
- a. current
b. power dissipation

MANSIMRAN SINGH
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c. differences of electrical potential

d. heat energy
5. Materials containing ‘free electrons’ are called:
a. insulators
b. resistors
c. collectors
-d. conductors
6. The unit used for measuring the EMF of electricity is:
a. the ohm
b. the ampere
~c. the volt
d. the watt
7. The unit used for measuring:
a. current - is the volt
~ b. resistance - is the ohm
c. electric power - is the capacitor
d. EMF - is the amp
8. Three resistors of 60 ohms each in parallel give a total resistance of:
a. 180 ohms
b. 40 ohms
c. 30 ohms
~d. 20 ohms
9. A voltmeter measures:
-
a. electromotive force
b. the heat loss in a series circuit
c. the current flow in a circuit
d. the resistance provided by the trimming devices
10. Watts =
a. resistance squared × amps
- b. volts × ohms
c. ohms × amps
d. volts × amps
Questions - Units 2
1. The total resistance of a number of power consumer devices connected in
series is:
- a. the addition of the individual resistances
b. the addition of the reciprocals of the individual resistance
c. twice the reciprocal of the individual resistances
d. the reciprocal of the total
2. The total resistance of a number of resistances connected in parallel is:

MANSIMRAN SINGH
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a. R = R1 + R2 + R3 + R4
b. 1 R2 1 R1 = + + + 1 RT 1 R3 1 R4
c. = + + + 1 RT R1 R3 R2 R4
d. = + + + R T1 1 R 1 R R2 1 R4 1
3. Ohm’s Law states:
a. Resistance in ohms Electromotive force in volts Current in amps =
b. Current in amps Electromotive force in volts Resistance in ohms =
c. Electromotive force in volts Resistance in ohms Current in amps =
4. A device consuming 80 watts at 8 amps would have a voltage supply of:
a. 640 volts
W
=

V)
b. 12 volts
- c. 10 volts
d. 8 volts
5. In a simple electrical circuit, if the resistors are in parallel, the total current
consumed is equal to:
a. the sum of the currents taken by the resistors divided by the number
of resistors
- b. the sum of the currents taken by the resistors
c. the average current taken by the resistors times the number of the
resistors
d. the sum of the reciprocals of the currents taken by the resistors
6. The symbol for volts is:
a. E or W
- b. V or E
c. I or V
d. R or W
7. Electrical potential is measured in:
a. watts
b. bars
~ c. volts
d. ohms
8. If a number of electrical consuming devices were connected in parallel, the
reciprocal of the total resistance would be:
a. the sum of the currents
- b. the sum of the reciprocals of the individual resistances
c. the sum of their resistances
d. volts divided by the sum of the resistances
9. The current flowing in an electrical circuit is measured in:
a. volts
b. ohms

MANSIMRAN SINGH
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c. inductance
~d. amps
10. Electromotive force is measured in:
a. amps × volts
b. watts
c. ohms
~
d. volts
Questions - General

1. Ohm’s Law is given by the formula:

a. RV I =
b. RI V =
c. VR I =
d. R = V × I
2. The current flowing in a circuit is:
a. directly proportional to resistance, indirectly proportional to voltage
b. directly proportional to temperature, inversely proportional to
resistance
c. inversely proportional to resistance, directly proportional to voltage
d. inversely proportional to applied voltage, directly proportional to
temperature
3. The unit of EMF is the:
a. ampere
~b. vol
c. watt
d. ohm
4. Potential difference is measured in:
a. amps
~b. volts
c. watts
d. ohms
5. The unit of current is the:
-a. ampere
b. volt
c. watt
d. ohm
6. The unit of resistance is the:
a. ampere
b. volt
c. watt
-d. ohm

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7. Electrical power is measured in:

a. amperes
b. volts
- c. watts
d. ohms
8. 1250 ohms may also be expressed as:
a. 1250 k ohms
b. 1.25 k ohms
c. 1.25 M ohms
d. 0.125 k ohms
9. 1.5 M ohms may also be expressed as:
a. 15 000 ohms
b. 1500 ohms
c. 150 000 ohms
d. 1500 k ohms
10. 550 k ohms may also be expressed as:
a. 550 000 M ohms
b. 0.55 M ohms
c. 55000 ohms
d.
↑ 0.55 ohms
11. If the voltage applied to a simple resistor increases:
a. current will decrease but power consumed remains constant
b. resistance and power decrease
- c. current flow will increase and power consumed will increase
d. current flow increases and power consumed decreases

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MANSIMRAN SINGH
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Circuit Protection

In an electrical circuit, abnormal conditions may arise for a variety of reasons,

which can cause overcurrent or overvoltage conditions. therefore necessary to
protect circuits against all such faults, by the use of fuses and circuit breakers.

Circuit Protection Devices

There are a number of protection devices used in aircraft electrical systems but
only 2 basic types are discussed here:

Fuses
Circuit breakers

A fuse normally opens the circuit before full fault current is reached,
(DGCA)

whereas the circuit breaker opens after the full fault current is
reached. (DGCA)
This means that when circuit breakers are used as the protection
device, both the circuit breaker and the component must be capable of
withstanding the full fault current for a short time.
The circuit breaker has the capability, which the fuse has not, of opening
and closing the circuit, and can perform many such operations before
replacement is necessary.

 Fuses

There are 3 basic types of fuse currently in use on aircraft:

Cartridge fuse
High rupture capacity (HRC) fuse
Current limiter fuse

 The Cartridge Fuse

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The cartridge type fuse consists of a tubular glass or

ceramic body, 2 brass end caps and a fuse element.
A fuse operates when the current flowing through it
is sufficient to melt the wire or strip element, the
time taken varying inversely with the current.
Fuses are rated in ‘amps’.(DGCA)
A blown fuse may be replaced with another of the correct rating once
only.
If it blows again when switching on, there is a defect in the system and
the fuse must not be changed again until the circuit has been
investigated.

 High Rupture Capacity (HRC) Fuses

The high rupture capacity (HRC) fuse is an improvement on the
cartridge type fuse.
It is used mainly for high current rated circuits.

 Current Limiters
Current limiters, as the name suggests, are
designed to limit the current to some
predetermined amperage value.
They are also thermal devices, but unlike
ordinary fuses they have a high melting
point, so that their time/ current characteristics permit them to carry a
considerable overload current before rupturing.
For this reason their application is confined to the protection of heavy-
duty power distribution circuits.
The output of a Transformer Rectifier Unit would be a prime location
for a current limiter to be used.
converts Ac to DC

Inventor i convert DLAoAL

 Circuit Breakers
Circuit breakers combine the function of fuse and
switch and can be used for switching circuits on
and off in certain circumstances.
They are fitted to protect equipment from damage
resulting from overload, or fault conditions.

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Generally, the CB incorporates an automatic thermo-sensitive tripping

device and a manually or electrically operated switch.
CBs are common on the flight deck of modern aircraft and can be
categorized as either:
Rana noga)
a Non-trip Free Circuit Breaker, or /Manually tri
a Trip Free Circuit Breaker. (DGCA)

The non-trip free circuit breaker may be held in under fault

conditions and the circuit will be made, this is clearly dangerous.
The trip free circuit breaker if held in under the same
circumstances, the circuit can not be made.
Pressing the re-set button will reset either CB if the fault has been
cleared.

Questions - Circuit Breakers

1. In a circuit fitted with a non-trip free circuit breaker if a fault occurs and
persists:
-a. if the reset button is depressed and held in, the circuit will be made
b. the trip button may be pressed to reset, but not permanently
c. a non-trip free circuit breaker can never be bypassed
d. the reset button may be pressed to make the circuit permanent
2. A trip free circuit breaker that has tripped due to overload:
a. can be reset and held in during rectification
b. can never be reset
c. can be reset after overhaul

I
d. may be reset manually after fault has been cleared
3. Circuit breakers and fuses:
a. are used in DC circuits only
b. are used in AC or DC circuits
c. are used in AC circuits only

MANSIMRAN SINGH
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d. are used in low current circuits only

·
4. A trip free circuit breaker is one which:
a. cannot be reset by holding the lever in while the fault persists
b. can be reset by holding the lever in while the fault persists
c. must be held in during checks to find faults
d. can be bypassed
5. If the reset button is pressed in the trip free circuit breaker, the contacts
with the fault cleared will:
- a. be made and kept made
b. only be made if there is a fuse in the circuit
c. reset itself only after a delay of 20 seconds
d. not be made and the reset will remain inoperative
6. A circuit breaker is a device for:
a. controlling rotor movement only
u b. isolating the service on overload
c. isolating the battery when using the ground batteries
d. earthing the magnetos when switching off

-
7. A non-trip free circuit breaker is:
a. one which can make a circuit in flight by pushing a button
b. a wire placed in a conductor which melts under overload
c. another type of voltage regulator
d. an on-off type tumbler switch
⑧
8. A non-trip free circuit breaker that has tripped due to overload:
a. can never be reset
b. can only be reset on the ground by a maintenance engineer
c. can be reset and held in if necessary
~ d. cannot be reset while the fault is still there

X
9. A thermal circuit breaker works on the principle of:
a. differential expansion of metals
b. differential thickness of metals
c. differential density of metals
d. differential pressure of metals
10. Circuit breakers are fitted in:
X a. series with the load
b. parallel with the load
c. across the load
d. shunt with the load
Questions - Fuses

1. A fuse is said to have blown when:

MANSIMRAN SINGH
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a. an excess current has burst the outer cover and disconnected the
circuit from the supply
b. the circuit is reconnected
~ c. a current of a higher value than the fuse rating has melted the
conductor and disconnected the circuit from the supply
d. the amperage has been sufficiently high to cause the fuse to trip out
of its holder and has therefore, disconnected the circuit from the supply
2. In a fused circuit the fuse is:
a. in parallel with the load
-b. in series with the load
c. in the conductor between generator and regulator
d. only fitted when loads are in series
3. Overloading an electrical circuit causes the fuse to ‘Blow’. This:
a. increases the weight of the insulation
b. fractures the fuse case
c. disconnects the fuse from its holder
~d. melts the fuse wire
4. What must be checked before replacing a fuse?
a. The ohms of the circuit
b. The amps being used in the circuit
ic. The amps capacity of the consuming device in the circuit
d. The correct fuse volt or watts rating
⑧5. The size of fuse required for an electrical circuit whose power is 72 watts
and whose voltage is 24 volts is:
a. 24 amps
b. 10 amps
c. 5 amps
d. 15 amps
6. When selecting a fuse for an aircraft circuit the governing factor is:
a. the voltage of the circuit
b. cable cross-sectional area
c. resistance of the circuit
~
d. power requirements of the circuit
7. A fuse in an electrical circuit is ‘blown’ by:
a. cooler air
b. the breaking of the glass tube
c. excess voltage breaking the fuse wire
/d. excess current rupturing the fuse wire
8. A fuse is used to protect an electrical circuit, it is:
- a. of low melting point

MANSIMRAN SINGH
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b. of high capacity
c. of high melting point
d. of low resistance
9. Fuses: -

a. protect the load

b. protect the cable
c. protect the generator
~ d. protect both the circuit cable and load
10. A current limiter:
a. is a fuse with a low melting point

~
b. is a circuit breaker
c. is a fuse with a high melting point
d. is a fuse enclosed in a quartz or sand

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CAPACITANCE

 Capacitors
 Introduction:
A capacitor can perform three basic functions:

Stores an electrical charge by creating an electrical field between the

plates.
Will act as if it passes Alternating Current LGhar pe astah)
Blocks Direct Current flow (Battery se miltikais

 Construction:
In its simplest form a capacitor
consists of two metal plates
separated by an insulator called a
dielectric.
Wires connected to the plates
allow the capacitor to be
connected into the circuit.

Capacitance

The capacitance (C) of a capacitor measures its ability to store an

electrical charge.
The unit of capacitance is the FARAD (F).
Factors Affecting Capacitance:
Area of the plates - a large area gives a large capacitance

Distance between the plates - a small distance gives a large capacitance

Material of the dielectric - different materials have different values of

capacitance.

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MANSIMRAN SINGH
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Batteries

The purpose of a battery in an aircraft is to provide an emergency source of

power when the generator is not running and to provide power to start the
engine.

A battery is made up of a number of cells which convert chemical energy into

electrical energy.
Primary Cell
A primary cell consists of two electrodes immersed in
a chemical called an electrolyte.
The electrolyte encourages electron transfer between
the electrodes until there is a potential difference
between them.
When the electron transfer ceases the cell is fully
charged and the potential difference is approximately 1.5 volts between the
two electrodes.
When the positive and negative terminals are
connected to an external circuit electrons flow
from the negative terminal to the positive
terminal through the circuit.
As this circulation of electrons continues, the
negative electrode slowly dissolves in the
electrolyte until it is eventually eaten away and the
cell is then “dead” and is discarded.
Primary cells cannot be recharged.
Secondary Cells
Secondary cells work on the same principle as primary cells but the chemical
energy in the cell can be restored when the cell has been discharged by passing
a “charging current” through the cell in the reverse direction to that of the
discharge current.

In this way the secondary cell can be discharged and recharged many times
over a long period of time.(DGCA)

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During recharging electrical energy is converted into chemical energy which is

retained until the cell is discharged again.

The Capacity of a cell is a measure of how much current a cell can provide in a
certain time.
Capacity is measured in Ampere hours (Ah) (DGCA)

A cell with a capacity of 80 Ah should provide a current of 8 A for 10 hours, or

80 A for 1 hr.

Capacity is normally measured at the 1 hour rate.

Cells in Series Cells in Parallel

positive terminal of one cell is positive terminals are joined
connected to the negative terminal together and the negative terminals
are joined together
total voltage is the sum of the total voltage is that of one cell
individual cell voltages

But the capacity is that of one cell. capacity is the sum of the individual
cell capacities.

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Lead Acid Battery

One of the most common types of
secondary cell is the Lead Acid cell.

The active material of the positive plate is

lead peroxide and the negative plate is
spongy lead, both plates are immersed in an
electrolyte solution of water and sulphuric
acid.

The state of charge of a lead acid cell can be determined by measuring the
strength of the electrolyte solution.

Hydrometer which measures the specific gravity (SG). Electrolyte Ra sample

A fully charged cell will have a SG of 1.27, a discharged cell will have a SG of
1.17. (DGCA)

When the SG has fallen to 1.17 and the voltage to 1.8 volts the cell should be
recharged.

To charge a cell it is connected to a battery charger which applies a slightly

higher voltage to the cell and causes current to flow in the reverse direction
through the cell.

While this is happening the lead sulphate which had been deposited on the
plates is removed and the SG of the electrolyte rises to 1.27.
The on load/nominal voltage of each cell of a lead acid battery is 2 volts.

The off load voltage of each cell of a lead acid battery is 2.2 volts.

Electrolytes are highly corrosive and if spilled in aircraft can cause extensive
damage.

The neutralizing agent to be used for an acid electrolyte is a sodium

bicarbonate solution.

Alkaline Battery (Nickel Cadmium, NiCad)

MANSIMRAN SINGH
 Baric Acid-Nitrileyins Agent 150

Lead acid batteries are still used in some

smaller aircraft but have been largely
replaced by Nickel Cadmium (alkaline type)
batteries.
The plates are nickel oxide and cadmium and
the electrolyte is potassium hydroxide.

The SG of the electrolyte is 1.24 - 1.30.

The on-load voltage of one cell is about 1.2 volts.

Unlike the lead acid battery, the relative SG

of the nickel-cadmium battery electrolyte
does not change and the voltage variation
from “fully charged” to “fully discharged,” is
very slight.
The terminal voltage remains substantially
constant at 1.2 volts throughout most of the
discharge.

NiCad batteries have a low thermal capacity; the heat generated in certain
conditions is faster than it can dissipate, so causing a rapid increase in
temperature. heat dispital mahi Gopata

This condition is known as a thermal runaway, and can cause so much heat
that the battery may explode.(DGCA)
Battery Checks
The Capacity of a battery is the product of the load in amperes that the
manufacturers state it will deliver, and the time in hours that the battery is
capable of supplying that load.

The capacity is measured in ampere hours (Ah).(DGCA)

A 40 Ah battery when discharged at the 1 hour rate should supply 40 amps for
the 1 hour. This is known as the ‘rated load’.

A Capacity Test, a test to determine the actual capacity of aircraft batteries, is

carried out every 3 months and the efficiency must be 80% or more for the
battery to remain in service.DGCA

MANSIMRAN SINGH
 Impact
northe many ato
e

151

This capacity will ensure that essential loads can be supplied for a period of 30
minutes following a generator failure. (DGCA)

Battery Charging

A Constant Voltage Charging system is employed with most lead acid batteries
to maintain the battery in a fully charged condition during flight. With this
system the output voltage of the generator is maintained constant at 14 volts
for a 12 volt battery and 28 volts for a 24 volt battery.

The generator voltage exceeds the battery voltage by 2 volts for every 12 volts
of battery potential.(DGCA)
NOTE: After starting an engine using the aircraft’s battery, whether it is a lead
acid battery or an alkaline battery, the generator, when it is on line, recharges
that battery.

A high charge rate could result in a battery overheating and subsequent

damage.

main bhi Yehl battery has

SHELF LIFE:(DGCA)
~
Lead acid batteries are stored in a charged state to prevent deterioration of
the battery by sulphation.
NiCad batteries can be stored in a discharged state with no detrimental effect
to the battery and therefore have a longer storage life or ‘shelf life’.

MANSIMRAN SINGH
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Questions - Batteries 1

1. Battery voltage is tested with:

a. a megometer
b. a voltmeter on rated load
c. an ammeter with a rated voltage
~
d. a hygrometer
2. Two 12 V 40 Ah batteries connected in series will produce:
a. 12 V 80 Ah
b. 12 V 20 Ah
c. 24 V 80 Ah
-d. 24 V 40 Ah
3. Two 12 V 40 Ah batteries connected in parallel will produce:
-a. 12 V 80 Ah
b. 24 V 80 Ah
c. 12 V 20 Ah
d. 24 V 40 Ah
4. A battery capacity test is carried out:
a. 6 monthly
b. 2 monthly
-c. 3 monthly
d. every minor check

MANSIMRAN SINGH
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5. An aircraft has three batteries each of 12 volts with 40 Ah capacity

connected in series. The resultant unit has:
a. a voltage of 36 and a capacity of 120 Ah
b. a capacity of 120 Ah and a voltage of 12
c. a capacity of 36 Ah and 120 watts
~ d. a voltage of 36 and a capacity of 40 Ah
6. An aircraft has a battery with a capacity of 40 Ah. Assuming that it will
provide its normal capacity and is discharged at the 10 hour rate:
a. it will pass 40 amps for 10 hrs
b. it will pass 10 amps for 4 hrs
~c. it will pass 4 amps for 10 hrs
d. it will pass 40 amps for 1 hr ⑧
7. Battery capacity percentage efficiency must always be:
a. 10% above saturation level
b. above 70%
~c. 80% or more
d. above 90%
⑧
8. The method of ascertaining the voltage of a standard aircraft lead acid
battery is by checking:
a. the voltage on open circuit
b. the current flow with a rated voltage charge
c. the voltage off load
-d. the voltage with rated load switched ON
9. A battery is checked for serviceability by:
a. using an ammeter
-b. measuring the specific gravity of the electrolyte
c. a boric acid solution
d. using an ohmmeter
⑧
10. In an AC circuit:
a. the battery is connected in series
b. a battery cannot be used because the wire is too thick
~ c. a battery cannot be used because it is DC
d. only NiCad batteries can be used
Questions - Batteries 2

1. The specific gravity of a fully charged lead acid cell is:

~ a. 1.270
b. 1.090
c. 1.120
d. 0.1270

MANSIMRAN SINGH
 154

2. The nominal voltage of the lead acid cell is:

a. 1.2 volts
b. 1.5 volts
- c. 1.8 volts
d. 2.0 volts
3. A lead acid battery voltage should be checked:
a. on open circuit
b. using a trimmer circuit
c. with an ammeter
~d. on load
4. In an aircraft having a battery of 24 volts nominal off load and fully
charged the voltmeter would read:
a. 22 volts
b. 24 volts
c. 26 volts
- d. 28 volts
5. The system used to maintain aircraft batteries in a high state of charge is
the:
a. constant current system
b. constant load system
c. constant resistance system
~ d. constant voltage system
6. If you connect two identical batteries in series it will:
a. double the volts and halve the capacity
b. reduce the voltage by 50%
- c. double the volts and leave the capacity the same
d. double the volts and double the amps flowing in a circuit with twice
the resistance
7. The nominal voltage of an alkaline cell is:
a. 2.2 volts
b. 1.8 volts
~c. 1.2 volts
d. 0.12 volts
8. The specific gravity of a fully charged alkaline cell is:
a. 0.120 - 0.130
b. 1.160
-c. 1.240 - 1.30
d. 1.800
9. The electrolyte used in the lead acid cell is diluted:
a. hydrochloric acid

MANSIMRAN SINGH
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~
b. sulphuric acid
c. boric acid
d. potassium hydroxide
⑧
10. The electrolyte used in an alkaline battery is diluted:
a. saline solution
b. sulphuric acid
~

c. cadmium and distilled water

~d. potassium hydroxide solution
Questions - Batteries 3
⑧
1. The number of lead acid cells required to make up a twelve volt battery is:
a. 8
b. 12
~ c. 6
d. 10
⑧2. A voltmeter across the terminals of a battery with all services off will
indicate:
~ a. electromotive force
b. resistance
c. a flat battery
d. residual voltage
⑧3. The voltage of a secondary cell is:
a. determined by the number of plates
b. determined by the area of the plates
c. determined by the diameter of the main terminals
~ d. determined by the active materials on the plates
⑧ 4. The level of the electrolyte must be maintained:
a. just below the top plate
b. above the plates level with the filler cap
c. one inch below the top of the plates
- d. just above the top of the plates
⑧ 5. To top up the electrolyte add:
a. sulphuric acid
~ b. distilled water
c. sulphuric acid diluted with distilled water
d. boric acid
6. Non-spill vents are used on aircraft batteries to:
-a. prevent spillage of electrolyte during violent manoeuvres
b. stop spillage of the water only
c. prevent the escape of gases

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d. prevent spillage during topping-up

7. The capacity of a lead acid battery is:
-a. determined by the area of the plates
b. determined by the active materials on the plates
c. determined by the size of the series coupling bars
d. determined by the number of separators
8. Acid spillage in an aircraft can be neutralized by using:
a. caustic soda
b. soap and water
c. soda and water
-
d. bicarbonate of soda and water
⑧
9. When the battery master switch is switched off in flight:
a. the generators are disconnected from the bus bar
b. the ammeter reads maximum
c. the battery is isolated from the bus bar
d. the battery is discharged through the bonding circuit diodes

·
10. When the generator is on line the battery is:
a. in parallel with the other loads
b. in series with the generator
c. in series when the generator is on line and is relayed when the
generator is off line
d. load sharing

Answers - Batteries 1
1 2 3 4 5 6 7 8 9 10

b d a c d c c d b c

Answers - Batteries 2

1 2 3 4 5 6 7 8 9 10

a d d c d c c c b d

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 157

Answers - Batteries 3

1 2 3 4 5 6 7 8 9 10

c a d d b a a d c a

MANSIMRAN SINGH