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Aircraft Engineering > Aircraft Electrical > Flashcards

Aircraft Electrical Flashcards

1
Q

Some electric motors have two sets of field windings wound in opposite directions so that the —

A

Motor can be operated in neither direction

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2
Q

One purpose of a growler test is to determine the presence of

A

A shorted armature

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3
Q

Electric wire terminals for most aircraft applications must be what type?

A

Ring

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4
Q

What is the principal advantage of the series-wound dc motor?

A

High starting torque

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5
Q

If a generator is equipped with a vibrator-type voltage regulator, the actual time the voltage regulator
points remain open

A

Depends on the load carried by the generator

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6
Q

What is a cause of generator brush arcing?

A

Low spring tension

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7
Q

When ac generators are operated in parallel, the —

A

Frequency and voltage must be both equal

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8
Q

The starting current of a series-wound dc motor, in passing through both the field and armature
windings, produces a —

A

High starting torque

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9
Q

Which motor would be most likely to have an armature brake?

A

Landing light retraction motor

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10
Q

The method most often used in overcoming the effect of armature reaction is through the use of —

A

Interpoles

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11
Q

The only practical method of maintaining a constant voltage output from an aircraft generator under
varying conditions of speed and load is to vary the —

A

Strength of the magnetic field

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12
Q

The pole pieces or shoes used in a dc generator are a part of the —

A

Field assembly

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13
Q

How many cycles of ac voltage are produced in a six-pole alternator of the revolving-field type for each
revolution of the rotor?

A

Three

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14
Q

If the reverse current cutout relay contact points fail to open after the generator output has dropped
below battery potential, current will flow through the generator armature —

A

Opposite to the normal direction and through the shunt field in the normal direction

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15
Q

How does the magnetic brake used to stop rotation of an electric motor armature operate?

A

A friction brake is applied by a spring and release by a magnet

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16
Q

In a generator, what eliminates any possible sparking to the brush guides caused by the movement of
the brushes within the holder?

A

The brush pigtail

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17
Q

A series-wound dc electric motor will normally require

A

More current at low rpm than at high rpm

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18
Q

The type of electric wire terminals used for most aircraft applications, in addition to providing good
current carrying capabilities, are designed primarily

A

To prevent circuit failure due to terminal disconnection

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19
Q

Aluminum wire must be stripped very carefully because

A

Individual strands will break easily after being nicked

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20
Q

The commutator of a generator

A

Changes alternating current produced in the armature into direct current as it is taken from the
armature

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21
Q

An ammeter in a battery charging system is for the purpose of indicating the

A

Rate of current used to charge the battery

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22
Q

Which of the following is not one of the purposes of interpoles in a generator?

A

Reduce field strength

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23
Q

To test generator or motor armature windings for opens,

A

A place armature in a growler and connect a 110v test light on adjacent segments; light should light.

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24
Q

What is the color and orientation of the position lights for navigation on civil airplanes?

A

ans. Left side – red , right side – green, rear aft – white

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25
Q

To what depth is the mica insulation between the commutator bars of a dc generator undercut?

A

Equal to the width of the mica

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26
Q

A voltage regulator controls generator output by

A

Varying current flow to generator field coil

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27
Q

Which type of dc generator is not used as an airplane generator?

A

Series wound

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28
Q

What is the most accurate type of frequency-measuring instrument?

A

Integrated circuit chip having a clock circuit

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29
Q

During ground operation, aircraft generator cooling is usually accomplished by

A

An integral fan

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30
Q

What does a rectifier do?

A

Changes alternating current to direct current

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31
Q

What type of instrument is used for measuring very high values of resistance?

A

Megohmmeter

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32
Q

When a diode is checked for an open circuit or a short circuit, it should be

A

Disconnected from the circuit

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33
Q

When handling a high voltage capacitor in an electrical circuit, be sure it

A

It is fully discharge before removing it from the circuit

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34
Q

Which of the following is most likely to cause thermal runaway in a nickel-cadmium battery?

A

Excessive current draw from the battery

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35
Q

How can it be determined if a transformer winding has some of its turns shorted together?

A

Transformer will get hot in normal operation

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36
Q

Which of the following are the major parts of a dc motor?
1. Armature assembly.
2. Field assembly.
3. Brush assembly.
4. Commutator.
5. Pole piece.
6. Rheostat.
7. End frame.

A

1,2,3,7

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37
Q

(1) There are three basic types of dc motors; series, shunt, and compound.
(2) In the series motor, the field windings, consisting of relatively few turns of heavy wire, are connected
in series with the armature winding.
Regarding the above statements,

A

Both no. 1 and no. 2 are true

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38
Q

For general electrical use in aircraft, the acceptable method of attaching a terminal to a wire is by

A

Crimping

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39
Q

Which of the following factors must be taken into consideration when determining the wire size to use
for an aircraft installation?
1. Mechanical strength.
2. Allowable power loss.
3. Ease of installation.
4. Resistance of current return path through the aircraft structure.
5. Permissible voltage drop.
6. Current carrying capability of the conductor.
7. Type of load (continuous or intermittent).

A

2,5,6,7

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40
Q

When selecting hardware for attaching bonding connections to an aircraft structure, which of the
following should be considered?
1. Mechanical strength.
2. Allowable power loss.
3. Ease of installation.
4. Permissible voltage drop.
5. Amount of current to be carried.
6. Type of load (continuous or intermittent).

A

1, 3, 5

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41
Q

How should the splices be arranged if several are to be located in an electrical wire bundle?

A

Staggered along the length of the bundle

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42
Q

What is the minimum bend radius for an electrical wire bundle?

A

Ten times the outside diameter of the bundle

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43
Q

When approved, splices may be used to repair manufactured harnesses or installed wiring. The
maximum number of splices permitted between any two connectors is

A

One

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44
Q

AN/MS electrical connectors are specifically designed to meet

A

Military specification

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45
Q

The most common method of attaching a pin or socket to an individual wire in an MS electrical
connector is by

A

Crimping

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46
Q

The pin section of an AN/MS connector is normally installed on

A

The ground side of a circuit

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47
Q

The voltage output of an alternator may be regulated by controlling the

A

Voltage output of the dc exciter

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48
Q

If several long lengths of electrical cable are to be installed in rigid conduit, the possibility of damage to
the cable as it is pulled through the conduit will be reduced by

A

Dusting the cable with powdered soapstone

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49
Q

Grounding is electrically connecting a conductive object to the primary structure. One purpose of
grounding is to

A

Prevent development of radio frequency potentials

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50
Q

What is normally used to bond non-continuous stainless steel aircraft components?

A

Copper jumpers

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51
Q

Aircraft fuse capacity is rated in

A

Amperes

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52
Q

When adding a rheostat to a light circuit to control the light intensity, it should be connected in

A

series with the light

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53
Q

Circuits that must be operated only in an emergency or whose inadvertent activation could endanger a
system frequently employ

A

Guarded switches

54
Q

If one switch is used to control all navigation lights, the lights are most likely connected

A

Parallel to each other and in series with the switch

55
Q

Oil canning of the sides of aluminum or steel electrical junction boxes is considered to be

A

A shorting hazard

56
Q

Electric wiring installed in aircraft without special enclosing means (open wiring) offers the advantages
of ease of installation, simple maintenance, and reduced weight. When bundling open wiring, the
bundles should

A

Be limited as to the number of cables to minimize damage from a single electrical fault

57
Q

During inspection of the terminal strips of an aircraft electrical system, it should be determined that

A

The terminal studs are anchored against rotation

58
Q

What protection to wires and cables does conduit provide when used in aircraft installations?

A

Mechanical

59
Q

Which of the following should be accomplished in the installation of aircraft wiring?

A

Locate the bundle above flammable fluid lines and securely clamp to structure

60
Q

If the (+) terminal of a voltmeter is connected to the (-) terminal of the source voltage and the (-)
terminal of the meter is connected to the (+) terminal of the source voltage, the voltmeter will read

A

Backwards

61
Q

When using the voltage drop method of checking circuit resistance, the

A

Input voltage must be maintained at a constant value

62
Q

The nominal rating of electrical switches refers to continuous

A

Current rating with contacts closed

63
Q

Aircraft electrical junction boxes located in a fire zone are usually constructed of

A

Stainless steel

64
Q

To help minimize radio interference a capacitor will largely eliminate and provide a steady direct current
if the capacitor is connected to the generator in

A

Parallel

65
Q

The primary considerations when selecting electric cable size are

A

Current carrying capacity and allowable voltage drop

66
Q

The navigation lights of some aircraft consist of a single circuit controlled by a single switch which has an
ON position and an OFF position, with no additional positions possible. This switch is referred to as a

A

Single pole single throw (SPST), two position switch

67
Q

Electric circuits are protected from overheating by means of

A

Fuses

68
Q

How does the routing of coaxial cables differ from the routing of electrical wiring?

A

Coaxial cable are routed as directly as possible

69
Q

Which of the following copper electrical cable sizes should be selected to replace a No. 6 aluminum
electrical cable?

A

No. 6

70
Q

In installations where the ammeter is in the generator or alternator lead, and the regulator system does
not limit the maximum current that the generator or alternator can deliver, the ammeter can be
redlined at what percent of the generator or alternator rating?

A

100

71
Q

Which statement relating to electric wiring is true?

A

When attaching a terminal to the end of an electric cable , it should be determined that the
strength of the cable to terminal joint is at least equal to the tensile strength of the cable itself.

72
Q

Bonding connections should be tested for

A

Resistance value

73
Q

What kind of switch should you install in a single wire circuit that required the switch to be manually
held in the ON position?

A

Single pole, single throw (SPST), two position normally open (NO)

74
Q

A circuit breaker is installed in an aircraft electrical system primarily to protect the

A

Circuit and should be located as close to the source as possible

75
Q

How should a voltmeter be connected?

A

In parallel with the load

76
Q

A circuit protection device called a current limiter is essentially a slow-blow fuse and is designed to be
used in

A

Heavy power circuits

77
Q

If it is necessary to use an electrical connector where it may be exposed to moisture, the mechanic
should

A

Use a special moisture proof type

78
Q

The three kinds of circuit-protection devices used most commonly in aircraft circuits are

A

Circuit breakers, fuses, and current limiters

79
Q

If a wire is installed so that it comes in contact with some moving parts, what protection should be given
the wire?

A

Pass through conduit

80
Q

In the American Wire Gauge (AWG) system of numbers used to designate electrical wire sizes, the
number assigned to a size is related to its

A

Cross sectional area

81
Q

What is the voltage drop for a No. 18 copper wire 50 feet long to carry 12.5 amperes, continuous
operation?
Use the formula VD = RLA / VD = Voltage drop / R = Resistance per ft = .00644 / L = Length of wires
A = Amperes

A

4v

82
Q

What is the purpose of the selection of derated switches for known continuous load current
applications?

A

To obtain reasonable switch efficiency and service life

83
Q

What is the advantage of a circuit breaker when compared to a fuse?

A

Resettable and reusable

84
Q

What is the advantage of a current limiter?

A

It will take overload for a short period

85
Q

Where electric cables must pass through holes in bulkheads, formers, ribs, firewalls, etc., the wires
should be protected from chafing by

A

Using a suitable grommet

86
Q

In aircraft electrical systems, automatic reset circuit breakers

A

Should not be used as protective devices

87
Q

A certain switch is described as a single-pole, double-throw switch (SPDT). The throw of a switch
indicates the number of

A

Circuits each pole can complete through the switch

88
Q

When considering an alteration, the criteria upon which the selection of electric cable size should be
based are

A

Current carrying and allowable voltage drop

89
Q

What is an important factor in selecting aircraft fuses?

A

Capacity matches the needs of the circuit

90
Q

The circuit breaker in the instrument lighting system protects the

A

Wiring from too much current

91
Q

One advantage of using ac electrical power in aircraft is

A

Greater ease in stepping the voltage up or down

92
Q

Why are the iron cores of most induction coils laminated?

A

To reduce the effects of eddy currents

93
Q

Certain transport aircraft use ac electrical power for all normal operation and battery furnished dc
electrical power for standby emergency use. In aircraft of this type that operate no dc generators, the
batteries are kept charged by

A

Rectifiers which use the aircraft’s ac generator as a source of power

94
Q

The voltage in an ac transformer secondary that contains twice as many loops as the primary will be

A

Greater and the amperage less than in the primary

95
Q

If the positive field lead between a generator and a generator control panel breaks and is shorted while
the engine is running, a voltmeter connected to generator output would indicate

A

Residual voltage

96
Q

What is a method used for restoring generator field residual magnetism?

A

Flash the fields

97
Q

The major advantages of alternating current (AC) over direct current (DC) is the fact that its current and
voltage can easily be increased or decreased

A

By means of a transformer

98
Q

Which of the following must be accomplished when installing an anti-collision light?

A

Install a switch independent of the position light switch

99
Q

The inductor-type inverter output voltage is controlled by the

A

Dc stator field current

100
Q

When using an ohmmeter to check the continuity of a generator field coil, the coil should

A

Show very low resistance if it is a series field coil

101
Q

The strength of the core of an electromagnet depends upon the material from which it is constructed
and which of the following?

A

The number of turns of wire in the coil and the amount of current (ampere) passing through the coil

102
Q

A voltage regulator controls generator voltage by changing the

A

Resistance of the generator field circuit

103
Q

The overvoltage control automatically protects the generator system when excessive voltage is present
by

A

Opening the shunt field circuit

104
Q

What is the maximum amount of time a circuit can be in operation and still be an intermittent duty
circuit?

A

Two minutes

105
Q

(Refer to Figure 18.) Which of the batteries are connected together incorrectly?

A

3

106
Q

(Refer to Figure 19.) Upon completion of the landing gear extension cycle, the green light illuminated
and the red light remained lit. What is the probable cause?

A

Short in the up limit switch

107
Q

If any one generator in a 24-volt dc system shows low voltage, the most likely cause is

A

An out of adjustment voltage regulator

108
Q

How can the direction of rotation of a dc electric motor be changed?

A

Reverse the electrical connections to either the field or armature windings

109
Q

Aircraft which operate only ac generators (alternators) as a primary source of electrical power normally
provide current suitable for battery charging through the use of

A

A step down transformer and a rectifier

110
Q

During inspection of an anti-collision light installation for condition and proper operation, it should be
determined that

A

The anti-collision light can be operated independently of the position lights

111
Q

Major adjustments on equipment such as regulators, contactors, and inverters are best accomplished
outside the airplane on test benches with necessary instruments and equipment. Adjustment procedure
should be as outlined by

A

The equipment manufacturer

112
Q

A battery-generator system provides direct current. On installations requiring alternating current from
the battery-generator system, it is necessary to have

A

An inverter

113
Q

A relay is

A

Magnetically operated switch

114
Q

The purpose of a rectifier in an electrical system is to change

A

Alternating current to direct current

115
Q

What is the ratio of turns between the primary coil winding and the secondary coil winding of a
transformer designed to triple its input voltage?

A

Primary will have one third as many turns as its secondary

116
Q

In an ac circuit with no phase lead or lag, which is true?

A

Real power equals apparent power

117
Q

How are generators rated?

A

Amperes and rated voltage

118
Q

How is a shunt-wound dc generator connected?

A

Both fields are shunted across the armature

119
Q

The poles of a generator are laminated to

A

Reduce by eddy current losses

120
Q

What is the frequency of an alternator dependent upon?

A

Rpm

121
Q

The generator rating is usually found stamped on the

A

Generator

122
Q

Residual voltage is a result of magnetism in the

A

Field shoes

123
Q

In troubleshooting an electrical circuit, if an ohmmeter is properly connected across a circuit component
and some value of resistance is read,

A

The component has continuity and is not open

124
Q

CSD driven generators are usually cooled by

A

Oil spray

125
Q

A CSD unit drives a generator through the use of

A

A variable hydraulic pump and hydraulic motor

126
Q

Integrated drive generators (IDG) employ a type of high output ac generator that utilizes

A

A brushless system to produce current

127
Q

If the IDG scavenge oil filter is contaminated with chunks or pieces of metal

A

Remove and replace the IDG

128
Q

When necessary during operation, CSD disconnect is usually accomplished by

A

A switch in the cockpit

129
Q

A CSD unit that is disconnected in flight, due to a malfunction such as overtemperature, may be
reconnected

A

Only on the ground by maintenance personnel

130
Q

When dc generators are operated in parallel to supply power for a single load, their controls include an
equalizer circuit to assure that all generators share the load equally. The equalizer circuit operates by

A

Increasing the output of the low generator and decreasing the output of the high generator until
they are equal

131
Q

The most common method of regulating the voltage output of a compound dc generator is to vary the

A

Current flowing through the shunt field coils

Aircraft Engineering (12 decks)

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