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Powerplant Writtens > Engine Electrical Systems > Flashcards

Engine Electrical Systems Flashcards

1
Q

What device is used to convert alternating current, which has been induced into the loops of the rotating armature of a DC generator, to direct current?

A

A commutator.

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2
Q

A certain direct current series motor mounted within an aircraft draws more amperes during start than when it is running under its rated load. The most logical conclusion that may be drawn is what?

A

The condition is normal for this type of motor.

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3
Q

The stationary field strength in a direct current generator is varied…

A

according to the load requirements.

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4
Q

What type of electric motor is generally used with a direct-cranking engine starter?

A

Direct current series-wound motor.

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5
Q

Upon what does the output frequency of an AC generator (alternator) depend?

A

The speed of rotation and the number of field poles.

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6
Q

A high surge of current is required when a DC electric motor is first started. As the speed of the motor increases,…

A

the counter EMF builds up and opposes the applied EMF, thus reducing the current flow through the armature.

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7
Q

Alternators (AC generators) that are driven by a constant-speed drive (CSD) mechanism are used to regulate the alternator to a constant what?

A

Hertz output (constant frequency).

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8
Q

What is used to polish commutators or slip rings?

A

Double-zero sandpaper.

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9
Q

If a generator is malfunctioning, its voltage can be reduced to residual by actuating the what?

A

Generator master switch.

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10
Q

If the points in a vibrator-type voltage regulator stick in the closed position while the generator is operating, what will be the probable result?

A

Generator output voltage will increase.

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11
Q

Why is a constant-speed drive used to control the speed of some aircraft engine-driven generators?

A

So that the frequency of the alternating current output will remain constant.

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12
Q

According to the electron theory of the flow of electricity, when a properly functioning DC alternator and voltage regulating system is charging an aircraft’s battery, the direction of current flow through the battery…

A

is into the negative terminal and out the positive terminal.

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13
Q

Aircraft that operate more than one generator connected to a common electrical system must be provided with what?

A

Individual generator switches that can be operated from the cockpit during flight

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14
Q

The most effective method of regulating aircraft direct current generator output is to vary, according to the load requirements, the what?

A

Strength of the stationary field.

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15
Q

Electric motors are often classified according to the method of connecting the field coils and armature. Aircraft engine starter motors are generally of which type?

A

Series.

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16
Q

As the generator load is increased (within its rated capacity), the voltage will what?

A

Remain constant and the amperage output will increase.

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17
Q

As the flux density in the field of a DC generator increases and the current flow to the system increases, the…

A

force required to turn the generator increases.

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18
Q

What is the purpose of a reverse-current cutout relay?

A

It opens the main generator circuit whenever the generator voltage drops below the battery voltage.

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19
Q

Generator voltage will not build up when the field is flashed and solder is found on the brush cover plate. These are most likely indications of what?

A

An open armature.

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20
Q

Why is it unnecessary to flash the field of the exciter on a brushless alternator?

A

Permanent magnets are installed in the main field poles.

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21
Q

One way that the automatic ignition relight systems are activated on gas turbine engines is by a what?

A

Drop in compressor discharge pressure.

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22
Q

How are the rotor windings of an aircraft alternator usually excited?

A

By a variable direct current.

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23
Q

What precaution is usually taken to prevent electrolyte from freezing in a lead-acid battery?

A

Keep the battery fully charged.

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24
Q

What is the ampere-hour rating of a storage battery that is designed to deliver 45 amperes for 2.5 hours?

A

112.5 ampere-hour.

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25
Q

How many hours will a 140 ampere-hour battery deliver 15 amperes?

A

9.33 hours.

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26
Q

What is basic advantage of using AC for electrical power for a large aircraft?

A

AC systems operate at higher voltage than DC systems and therefore use less current and can use smaller and lighter weight wiring.

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27
Q

What are two types of AC motors that are used to produce a relatively high torque?

A

Three-phase induction and capacitor start.

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28
Q

(1) Alternators are rated in volt-amps, which is a measure of the apparent power being produced by the generator.

(2) Alternating current has the advantage over direct current in that its voltage and current can easily be stepped up or down.

A

Both 1 and 2 are true.

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29
Q

What is the frequency of most aircraft alternating current?

A

400 hertz.

30
Q

The reason for flashing the field in a generator is to what?

A

Restore residual magnetism to the field frame.

31
Q

The part of a DC alternator power system that prevents reverse flow of current from the battery to the alternator is the what?

A

Rectifier.

32
Q

The generating system of an aircraft charges the battery by using what?

A

Constant voltage and varying current.

33
Q

The constant current method of charging a nickel-cadmium battery…

A

is the method most effective in maintaining cell balance.

34
Q

(Refer to Figure 4) The following data concerning the installation of an electrical unit is known: current requirements for continuous operation - 11 amperes; measured cable length - 45 feet; system voltage - 28 volts (do not exceed 1 volt drop); cable in conduit and bundles. What is the minimum size copper electrical cable that may be selected?

A

No. 12.

35
Q

Which of the following aircraft circuits does NOT contain a fuse/circuit breaker?

A

Starter circuit.

36
Q

The maximum number of terminals that may be connected to any one terminal stud in an aircraft electrical system is what?

A

Four.

37
Q

What is the maximum number of bonding jumper wires that may be attached to one terminal grounded to a flat surface?

A

Four.

38
Q

Starter brushes should be replaced when they are worn down to what?

A

One-half of the original length.

39
Q

When installing an electrical switch, under which of the following conditions should the switch be derated from its nominal current rating?

A

Direct current motor circuits.

40
Q

The resistance of the current return path through the aircraft is always considered negligible, provided the what?

A

Structure is adequately bonded.

41
Q

In order to reduce the possibility of ground shorting the circuits when the connectors are separated for maintenance the AN and MS electrical connectors should be installed with the what?

A

Pin section on the ground side of the electrical circuit.

42
Q

When does current flow through the coil of a solenoid-operated electrical switch?

A

Continually, as long as the control circuit is complete.

43
Q

When a 28-volt, 75 ampere generator is installed on an aircraft, an electrical load analysis ground check is performed and it is determined that the battery is furnishing 57 amperes to the system, with all electrical equipment operating. This indicates what?

A

The load will be within the generator load limit.

44
Q

What type of lubricant may be used to aid in pulling electrical wires or cables through conduits?

A

Soapstone talc.

45
Q

Which of the following is regulated in a generator to control its voltage output?

A

The strength of the field.

46
Q

Bonding jumpers should be designed and installed in such a manner that they what?

A

Provide a low electrical resistance in the ground circuit.

47
Q

When the starter switch to the aircraft gas turbine engine starter-generator is energized and the engine fails to rotate, one of the probable causes would be the what?

A

Starter solenoid is defective.

48
Q

Arcing at the brushes and burning of the commutator of a motor may be caused by what?

A

Weak brush springs.

49
Q

The maximum allowable voltage drop between the generator and the bus bar is what?

A

2 percent of the regulated voltage.

50
Q

ON-OFF two position engine electrical switches should be installed how?

A

So the ON position is reached by a forward or upward motion.

51
Q

When selecting an electrical switch for installation in an aircraft circuit utilizing a direct current motor, what?

A

A derating factor should be applied.

52
Q

When installing electrical wiring parallel to a fuel line, the wiring should be what?

A

Above the fuel line.

53
Q

(Refer to Figure 4.) In a 28-volt system, what is the maximum continuous current that can be carried by a single No. 10 copper wire 25 feet long, routed in free air?

A

35 amperes.

54
Q

What speed must an eight-pole AC generator turn to produce 400 hertz AC?

A

6,000 RPM

55
Q

Which Federal Aviation Regulation specifies that each resettable circuit protective device requires a manual operation to restore service after the device has interrupted the circuit?

A

14 CFR Part 23

56
Q

Which Federal Aviation Regulation requirement prevents the use of automatic reset circuit breakers?

A

14 CFR Part 23

57
Q

The time/current capacities of a circuit breaker or fuse must be what?

A

Below those of the associated conductor.

58
Q

(1) Most modern aircraft use circuit breakers rather than fuses to protect their electrical circuits.

(2) Part 23 requires that all electrical circuits incorporate some form of circuit protective device.

A

Only 1 is true.

59
Q

Electrical switches are rated according to the what?

A

Voltage and the current they can control.

60
Q

Electrical circuit protection devices are installed primarily to protect the what?

A

Wiring.

61
Q

(1) Electrical circuit protection devices are rated based on the amount of current that can be carried without overheating the wiring insulation.

(2) A “trip-free” circuit breaker makes it impossible to manually hold the circuit closed when excessive current is flowing.

A

Both 1 and 2 are true.

62
Q

Which of the following Federal Aviation Regulations require that all aircraft using fuses as the circuit protective devices carry “one spare set of fuses, or three spare fuses of each kind required”?

A

14 CFR Part 91.

63
Q

What is the smallest terminal stud allowed for aircraft electrical power systems?

A

No. 10.

64
Q

A typical barrier type aircraft terminal strip is made of what?

A

Paper-base phenolic compound.

65
Q

A term commonly used when two or more electrical terminals are installed on a single lug of a terminal strip is what?

A

Stacking.

66
Q

(1) Electrical wires larger than 10 gauge use uninsulated terminals.

(2) Electrical wires smaller than 10 gauges use uninsulated terminals.

A

Only 1 is true.

67
Q

Aircraft electrical is manufactured in sizes according to a standard known as what?

A

American Wire Gauge (AWG).

68
Q

Aircraft wire size is determined by using a what?

A

Wire gauge.

69
Q

Aircraft copper electrical wire is coated with tin, silver, or nickel in order to what?

A

Prevent oxidation.

70
Q

How many basic types of circuit breakers are used in powerplant installation electrical systems?

A

Three.

Powerplant Writtens (28 decks)

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