Aircraft Electrical Systems 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 either direction.
2
Q
One purpose of a growler test is to determine the presence of…
A
a shorted armature.
3
Q
Electric wire terminals for most aircraft applications must be what type?
A
Ring.
4
Q
What is the principal advantage of the series-wound DC motor?
A
High starting torque.
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.
6
Q
What is a cause of generator brush arcing?
A
Low spring tension.
7
Q
What is required when operating two aircraft AC generators in parallel?
A
Frequency and voltage must both be equal.
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.
9
Q
Which motor would be most likely to have an armature brake?
A
Landing light retraction motor.
10
Q
The method most often used in overcoming the effect of armature reaction is through the use of…
A
interpoles.
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.
12
Q
The pole piece or shoes used in a DC generator are a part of the…
A
field assembly.
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.
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 the normal direction and through the shunt field in the normal direction.
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 released by a magnet.
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.
17
Q
A series-wound DC electric motor will normally require…
A
more current at low RPM than at high RPM.
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.
19
Q
Aluminum wire must be stripped very carefully because…
A
individual stands will break easily after being nicked.
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.
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.
22
Q
Which of the following is not one of the purposes of interpoles in a generator?
A
Reduce field strength.
23
Q
To test generator or motor armature windings for opens,…
A
place armature in a growler and connect a 110V test light on adjacent segments; light should light.
24
Q
What is the color and orientation of the position lights for navigation on civil airplanes?
A
Left side, red; right side, green; rear aft, white.
25
To what depth is the mica insulation between the commutator bars of a DC generator undercut?
Equal to the width of the mica.
26
A voltage regulator controls generator output by...
varying current flow to generator field coil.
27
What type of DC generator is not used as an airplane generator?
Series wound.
28
What is the most accurate type of frequency measuring instrument?
Integrated circuit chip having a clock circuit.
29
During ground operation, aircraft generator cooling is usually accomplished by...
an integral fan.
30
What does a rectifier do?
Changes alternating current into direct current.
31
What type of instrument is used for measuring very high values of resistance?
Megohmmeter.
32
When a diode is checked for an open circuit or a short circuit, it should be...
disconnected from the circuit.
33
When handling a high voltage capacitor in an electrical circuit, be sure it...
is fully discharged before removing it from the circuit.
34
Which of the following is most likely to cause thermal runaway in a nickel-cadmium battery?
Excessive current draw from the battery.
35
How can it be determined if a transformer winding has some of its turns shorted together?
The transformer will get hot in normal operation.
36
What are the major parts of a DC motor?
Armature assembly, field assembly, brush assembly, and end frame.
37
Both 1 and 2 are true.
38
What is the appropriate method for installing pre-insulated terminal lugs and splices to electrical wires?
Using a crimping tool to secure the terminal lug.
39
What must be taken into consideration when determining the wire size to use for an aircraft installation?
Allowable power loss, permissible voltage drop, current carrying capability of the conductor, type of load.
40
When selecting hardware for attaching bonding connections to an aircraft structure, what should be considered?
Mechanical strength, ease of installation, amount of current to be carried.
41
How should the splices be arranged if several are to be located in an electrical wire bundle?
Staggered along the length of the bundle.
42
What is the minimum bend radius for an electrical wire bundle?
Ten times the outside diameter of the bundle.
43
When approved, splices may be used to repair manufactured harnesses or installed wiring. The maximum number of splices permitted between any two connectors is...
one.
44
Electrical connectors used in aircraft assemblies should meet which of the following specifications?
Military Specifications (MS)
45
The most common method of attaching a pin or socket to an individual wire in an MS electrical connector is by...
crimping.
46
The pin section of an AN/MS connector is normally installed on...
the ground side of a circuit.
47
The voltage output of an alternator may be regulated by controlling the...
voltage output of the DC exciter.
48
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....
dusting the cable with powdered soapstone.
49
Grounding is electrically connecting a conductive object to the primary structure. One purpose of grounding is to...
prevent development of radio frequency potentials.
50
What is normally used to bond noncontinuous stainless steel aircraft components?
Copper jumpers.
51
Aircraft fuse capacity is rated in...
amperes.
52
When adding a rheostat to a light circuit to control the light intensity, it should be connected in...
series with the light.
53
Circuits that must be operated only in an emergency or whose inadvertent activation could endanger a system frequently employ...
guarded switches.
54
If one switch is used to control all navigation lights, the lights are most likely connected...
parallel to each other and in series with the switch.
55
Oil canning of the sides of aluminum or steel electrical junction boxes is considered to be...
a shorting hazard.
56
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...
be limited as to the number of cables to minimize damage from a single electrical fault.
57
During inspection of the terminal strips of an aircraft electrical system, it should be determined that...
the terminal studs are anchored against rotation.
58
What protection to wires and cables does conduit provide when used in aircraft installations.
Mechanical.
59
What should be accomplished in the installation of aircraft wiring?
Locate the bundle above flammable fluid lines and securely clamp to structure.
60
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...
backwards.
61
When using the voltage drop method of checking circuit resistance, the...
input voltage must be maintained at a constant value.
62
The nominal rating of electrical switches refers to continuous...
current rating with the contacts closed.
63
Aircraft electrical junction boxes located in a fire zone are usually constructed of...
stainless steel.
64
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...
parallel.
65
The primary considerations when selecting electric cable size are...
current-carrying capacity and allowable voltage drop.
66
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...
single-pole, single throw (SPST), two-position switch.
67
Electrical circuits are protected from overheating by...
fuses.
68
How should a coaxial cable be routed?
As directly as possible.
69
What copper electrical cable sizes should be selected to replace a No. 6 aluminum electrical cable?
No. 6.
70
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?
100.
71
What statement relating to electric wiring (terminals) is true?
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
Bonding connections should be tested for...
resistance value.
73
What kind of switch should you install in a single wire circuit that required the switch to be manually held in the ON position?
Single-pole, single-throw (SPST), two-position normally open (NO).
74
A circuit breaker is installed in an aircraft electrical system primarily to protect the...
circuit and should be located as close to the source as possible.
75
How should a voltmeter be connected?
In parallel with the load.
76
A circuit protection device called current limiter is essentially a slow-blow fuse and is designed to be used in...
heavy power circuits.
77
If it is necessary to use an electrical connector where it may be exposed to moisture, the mechanic should...
use a special moisture-proof type.
78
What is considered circuit protective devices that are used in aircraft electrical systems?
Circuit breakers, fuses, and current limiters.
79
If a wire is installed so that it comes in contact with some moving parts, what protection should be given to the wire?
Pass through a conduit.
80
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...
cross-sectional area.
81
4V.
82
What is the purpose of the selection of derated switches for known continuous load current applications?
To obtain reasonable switch efficiency and service life.
83
What is the advantage of a circuit breaker when compared to a fuse?
It is resettable and reusable.
84
What is the advantage of a current limiter?
It will take overload for a short period.
85
What should be used to protect wires from chafing when they must pass through bulkheads, firewalls, ribs, etc.?
Suitable grommet.
86
In aircraft electrical systems, automatic reset circuit breakers...
Should not be used as circuit protective devices.
87
A certain switch is described as a single-pole, double throw (SPDT) switch. The throw of a switch indicates the number of...
circuits each pole can complete through the switch.
88
When considering an alteration, the criteria upon which the selection of electric cable size should be based are...
current-carrying capacity and allowable voltage drop.
89
What is an important factor in selecting aircraft fuses?
Capacity matches the needs of the circuit.
90
The circuit breaker in the instrument lighting system protects the...
wiring from too much current.
91
One advantage of using AC electrical power in aircraft is...
greater ease in stepping the voltage up or down.
92
Why are the iron cores of most induction coils laminated?
To reduce the effects of eddy currents.
93
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...
rectifiers which use the aircraft's AC generators as a source of power.
94
The voltage in an AC transformer secondary that contains twice as many loops as the primary will be...
greater and the amperage less than in the primary.
95
If the positive field lead between a generator control panel breaks and is shorted while the engine is running, a voltmeter connected to generator out-put would indicate...
residual voltage.
96
What is a method used for restoring generator field residual magnetism?
Flash the fields.
97
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...
by means of a transformer.
98
What must be accomplished when installing an anti-collision light.
Install a switch independent of the position light switch.
99
The inductor-type inverter output voltage is controlled by the...
DC stator field current.
100
When using an ohmmeter to check the continuity of a generator field coil (if it is a series field coil), the coil should...
show very low resistance if it is a series field coil.
101
The strength of the core of an electromagnet depends upon the material from which it is constructed and what else?
The number of turns in the coil and the amount of current (amperes) passing through the coil.
102
A voltage regulator controls generator voltage by changing the...
resistance of the generator field circuit.
103
The over-voltage control automatically protects the generator system when excessive voltage is present by...
opening the shunt field circuit.
104
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...
increasing the output of the low generator and decreasing the output of the high generator until they are equal.
105
What is the maximum amount of time a circuit can be in operation and still be intermittent duty circuit?
Two minutes.
106
The most common method of regulating the voltage output of a compound DC generator is to vary the...
current flowing through the shunt field coils.
107
Which of the batteries are connected together incorrectly?
3.
108
Upon completion of the landing gear extension cycle, the green light illuminated and the red light remained lit. What is the probable cause?
Short in the up limit switch.
109
If any one generator in a 24-volt DC system shows low voltage, the most likely cause is...
an out-of-adjustment voltage regulator.
110
How can the direction of rotation of a DC electric motor be changed?
Reverse the electrical connections to either the field or armature windings.
111
Static inverters are electronic device that change DC to AC with the...
use of an oscillator.
112
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 step-down transformer and a rectifier.
113
During inspection of an anti-collision light installation for condition and proper operation, it should be determined that...
the anti-collision light can be operated independently of the position lights.
114
Major adjustments on equipment such as regulators, contractors, and inverters are best accomplished outside the airplane on test benches with necessary instruments and equipment. Adjustment procedure should be outlined by...
the equipment manufacturer.
115
A battery-generator system provides direct current. On installations requiring alternating current from the battery-generator system, it is necessary to have...
an inverter.
116
An aircraft electrical circuit control relay is...
an electrically operated switch.
117
The purpose of a rectifier in an electrical system is to change...
alternating current to direct current.
118
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?
Primary will have one-third as many turns as its secondary.
119
In an AC circuit with no phase lead or lag, which is true?
Real power equals apparent power.
120
How are generators rated?
Amperes at rated voltage.
121
How is a shunt-wound DC generator connected?
Both fields are shunted across the armature.
122
The poles of a generator are laminated to...
reduce eddy current losses.
123
What is the frequency of an alternator dependent upon?
RPM.
124
Where is the generator rating and performance data located?
Stamped on the generator data plate.
125
Residual voltage is a result of magnetism in the...
field shoes.
126
In troubleshooting an electrical circuit, if an ohmmeter is properly connected across a circuit component and some value of resistance is read...
the component has continuity and is not open.
127
CSD generators are usually cooled by...
oil spray.
128
A CSD unit drives a generator through the use of...
a variable hydraulic pump and hydraulic motor.
129
Integrated drive generators (IDG) employ a type of high output AC generator that utilizes...
a brushless system to produce current.
130
If the Integrated Drive Generator (IDG) scavenge oil filter is contaminated with metal, you should...
remove and replace the IDG.
131
When necessary during operation, CSD disconnect is usually accomplished by...
a switch in the cockpit.
132
A CSD unit that is disconnected in flight due to a malfunction such as over-temperature, may be reconnected...
only on the ground by maintenance personnel.
