AIRCRAFT ELECTRIC CURRENT

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

• Has at least a residual charge before removing it from the circuit.

• Is fully discharged before removing it from the circuit.

• Has a full charge before removing it from the circuit.

Is fully discharged before removing it from the circuit.

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

• Three

• Two

• One

One

The inductor-type inverter output voltage is controlled by the

• Voltage regulator

• DC stator field current

• Number of poles and the speed of the motor

DC stator field current

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

• The output voltage will be high.

• The transformer will get hot in normal operation.

• Measure the input voltage with an ohmmeter

• The transformer will get hot in normal operation.

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

• One-half the width of the mica.

• Equal to twice the width of the mica.

• Equal to the width of the mica.

• Equal to the width of the mica.

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

• Total effective field strength by changing the reluctance of the magnetic circuit.

• Current flowing through the shunt field coils.

• Resistance of the series field circuit.

• Current flowing through the shunt field coils.

If the Integrated Drive Generator (IDG) scavenge oil filter is contaminated with metal, you should

• Remove and replace the IDG.

• Replace the oil and filter at 25-hour intervals.

• Do an oil analysis to diagnose the problem.

• Remove and replace the IDG.

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.

• Increasing the output of the low generator to equal the output of the high generator.

• Decreasing the output of the high generator to equal the output of the low generator.

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

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

• Current-carrying capacity

• Combined resistance and current-carrying capacity

• Cross-sectional area

• Cross-sectional area

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

• Current-carrying capacity and applied voltage.

• Current-carrying capacity and allowable voltage drop.

• Applied voltage and allowable voltage drop.

• Current-carrying capacity and allowable voltage drop.

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

• 3, 5, 6, 7

• 1, 2, 3, 7

• 2, 3, 4, 5

• 1, 2, 3, 7

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

• Centrifugal force releases a rotating brake cog from a stationary notch when the armature reaches a certain speed and magnetic force re-engages the cog when the electrical power is turned off.

• A friction brake is applied by a magnet and released by a spring.

• A friction brake is applied by a spring and released by a magnet.

• A friction brake is applied by a spring and released by a magnet.

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

• Coat the connector with grease.

• Use a special moisture-proof type.

• Spray the connector with varnish or zinc-chromate.

• Use a special moisture-proof type.

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

• Speed of the motor can be more closely controlled.

• Motor can be operated in either direction.

• Power output of the motor can be more closely controlled.

• Motor can be operated in either direction.

What should be used to protect wires from chafing when they must pass through bulkheads, firewalls, ribs, etc.?

• Suitable grommet

• Plastic spiral wrap

• Aerodynamic duct tape

• Suitable grommet

What does a rectifier do?

• Reduces voltage.

• Changes alternating current into direct current.

• Changes direct current into alternating current.

• Changes alternating current into direct current.

Static inverters are electronic devices that change DC to AC with the

• Use of an oscillator.

• Input from an amplifier control by integrated circuits.

• Properties of an exclusive OR gate

• Use of an oscillator.

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

• Crimping and soldering

• Crimping

• Soldering

• Crimping

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

• Wrap with friction tape.

• Wrap with soft wire solder into a shield.

• Pass through conduit.

• Pass through conduit.

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

• In the circuit.

• Disconnected from the circuit.

• Checked with a milliamp ammeter.

• Disconnected from the circuit.

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

• For uncomplicated and rapid circuit connection and disconnection.

• To prevent circuit failure due to terminal disconnection.

• For permanent connection to the circuit.

• To prevent circuit failure due to terminal disconnection.

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). 

• 1, 2, 3

• 1, 3, 5

• 4, 5, 6

• 1, 3, 5

When necessary during operation, CSD disconnect is usually accomplished by

• A switch in the cockpit.

• A shear section in the input shaft.

• Circuit breaker activation.

• A switch in the cockpit.

Electric circuits are protected from overheating by

• Thermocouples

• Fuses

• AN/MS connectors

• Fuses

Where is the generator rating and performance data located?

• In the Aircraft Maintenance Manual

• In the Pilot Operating Handbook

• Stamped on the generator data plate

• Stamped on the generator data plate

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

• Either side of a circuit (makes no difference).

• The power supply side of a circuit.

• The ground side of a circuit.

• The ground side of a circuit.

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

• Normal operation in vibration-prone areas

• A shorting hazard

• Acceptable operation

• A shorting hazard

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

• Less and the amperage greater than in the primary.

• Greater and the amperage less than in the primary.

• Greater and the amperage greater than in the primary.

• Greater and the amperage less than in the primary.

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). 

• 2, 5, 6, 7

• 2, 4, 6, 7 

• 1, 2, 4, 5

• 2, 5, 6, 7

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

• An appropriately rated fuse is in position at the light to protect the connecting wiring against electrical faults.

• Electrical or mechanical interconnections are provided so that the anti-collision light will operate at all times that the position light switch is in the ON position.

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

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

What is the appropriate method for installing pre-insulated terminal lugs and splices to electric wires?

• Soldering the terminal lug to the end of the wire.

• Using a crimping tool to secure the terminal lug.

• Soldering the exposed wire prior to crimping on the terminal lug.

• Using a crimping tool to secure the terminal lug.

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 to a minimum bend radius of five times the bundle diameter to avoid excessive stresses on the cable insulation.

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

• Include at least one shielded cable to provide good bonding of the bundle to the airframe.

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

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

• Push-pull-type circuit breakers only (no switches)

• Spring-loaded to off toggle or rocker switches

• Guarded switches

• Guarded switches

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

• 50

• 75

• 100

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 graphite.

• Dusting the cable with powdered soapstone.

• Applying a light coat of dielectric grease.

• Dusting the cable with powdered soapstone.

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

• Speed of the alternator

• Voltage output of the dc exciter

• Resistance in the rotor windings

• Voltage output of the dc exciter

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

• Total amperes being used in the airplane.

• Amperage available for use.

• Rate of current used to charge the battery.

• Rate of current used to charge the battery.

Electrical connectors used in the aircraft assemblies should meet which of the following specifications?

• Military Specifications (MS)

• Society of Electrical Specifications (SES)

• Parts Manufacturer Approval (PMA)

• Military Specifications (MS)

Aircraft fuse capacity is rated in

• Ohms

• Volts

• Amperes

• Amperes

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

• Input voltage must be varied.

• Input voltage must be maintained at a constant value.

• Output voltage must be maintained at a constant value.

• Input voltage must be maintained at a constant value.

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.

• Primary will have three times as many turns as its secondary.

• Primary will have twice as many turns as its secondary.

• Primary will have one-third as many turns as its secondary.

To test generator or motor armature windings for opens,

• Check adjacent segments on the commutator with an ohmmeter on the high resistance scale.

• Place armature in a growler and connect a 110V test light on adjacent segments; the light should light.

• Use a 12/24V test light between the armature core segments and the shaft.

• Place armature in a growler and connect a 110V test light on adjacent segments; the light should light.

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

• Circuits each pole can complete through the switch.

• Terminals at which current can enter or leave the switch.

• Places at which the operating device (toggle, plunger, etc.) will come to rest and at the same time open or close a circuit.

• Circuits each pole can complete through the switch.

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

• It controls current flow.

• It is easily replaced.

• It is resettable and reusable.

• It is resettable and reusable.

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

• The frequency of alternating current.

• Direct current to alternating current.

• Alternating current to direct current.

• Alternating current to direct current.

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

• Two minutes

• One minute

• Three minutes

• Two minutes

One advantage of using ac electrical power in aircraft is

• That the effective voltage is 1.41 times the maximum instantaneous voltage; therefore, less power input is required.

• That ac electrical motors can be reversed while dc motors cannot.

• Greater ease in stepping the voltage up or down.

• Greater ease in stepping the voltage up or down.

Why are the iron cores of most induction coils laminated?

• To increase the core permeability.

• To reduce the core reluctance.

• To reduce the effects of eddy currents.

• To reduce the effects of eddy currents.

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

• Correctly

• Low voltage

• Backwards

• Backwards

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

• Depends on the load carried by the generator.

• Is controlled by the reverse-current cutout relay point clearance.

• Is increased when the external load is greater than the generator output.

• Depends on the load carried by the generator.

The nominal rating of electrical switches refers to continuous

• Current rating with the contacts closed.

• Voltage rating with the contacts closed.

• Current rating with the contacts open.

• Current rating with the contacts closed.

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

• Constant current charging of the battery to more than 100 percent of its capacity.

• Excessive current draw from the battery.

• A high internal resistance condition.

• Excessive current draw from the battery.

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

• Left side - red, right side - green, rear aft - white.

• Left side - green, right side - red, rear aft - white.

• Left side - white, right side - green, rear aft - red.

• Left side - red, right side - green, rear aft - white.

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

• Show very low resistance if it is a series field coil.

• Be removed from the generator housing.

• Show high resistance when the meter prods are connected to the terminals of the coil.

• Show very low resistance if it is a series field coil.

How should a coaxial cable be routed?

• Parallel with stringers or ribs.

• Perpendicular to stringers or ribs.

• As directly as possible.

• As directly as possible.

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

• Fifteen times the outside diameter of the bundle.

• Ten times the outside diameter of the bundle.

• Five times the outside diameter of the bundle.

• Ten times the outside diameter of the bundle.

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

• A defective reverse current cutout relay

• An out-of-adjustment voltage regulator

• Shorted or grounded wiring

• An out-of-adjustment voltage regulator

Bonding connections should be tested for

• Amperage value

• Resistance value

• Reactance

• Resistance value

In aircraft electrical systems, automatic reset circuit breakers

• Should not be used as circuit protective devices.

• Are useful where only temporary overloads are normally encountered.

• Must be used in all circuits essential to safe operation of the aircraft.

• Should not be used as circuit protective devices.

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

• Single-pole, single-throw (SPST), single position.

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

• Single-pole, double-throw (SPDT), a single position normally open (NO).

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

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.

• In series with each other and in series with the switch.

• In series with each other and parallel to the switch.

• Parallel to each other and in series with the switch.

CSD driven generators are usually cooled by

• Oil spray

• Both ram air and an integral fan

• An integral fan

• Oil spray

How are generators rated?

• The impedance at rated voltage.

• Amperes at rated voltage.

• Watts at rated voltage.

• Amperes at rated voltage.

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

• Automatically if the temperature falls back into the normal operating range.

• Only on the ground by maintenance personnel.

• Manually by the flight crew.

• Only on the ground by maintenance personnel.

A CSD unit drives a generator through the use of

• A synchronous electric motor.

• An infinitely variable mechanical gearing system.

• A variable hydraulic pump and hydraulic motor.

• A variable hydraulic pump and hydraulic motor.

How should a voltmeter be connected?

• In series with the load.

• In series with the source.

• In parallel with the load.

• In parallel with the load.

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

• No.6

• No.8

• No. 4

• No.6

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

• Suitable for constant speed use

• Low starting torque

• High starting torque

• High starting torque

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

• 1V

• 1/2V

• 4V

• 4V

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

• Zero voltage

• Residual voltage

• Normal voltage

• Residual voltage

The primary considerations when selecting electric cable size are

• Current-carrying capacity and allowable voltage drop.

• The voltage and amperage of the load it must carry.

• The system voltage and cable length.

• Current-carrying capacity and allowable voltage drop.

What is required when operating two aircraft ac generators in parallel?

• Frequency and voltage must both be equal.

• Amperes and frequency must both be equal.

• Amperes and voltage must both be equal.

• Frequency and voltage must both be equal.

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

• Install a switch independent of the position light switch.

• Connect the anti-collision light to the aircraft position light switch.

• Use shielded electrical cable to assure fail-safe operation.

• Install a switch independent of the position light switch.

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

• Drum-wound armatures in combination with a negatively connected series field

• Shaded poles

• Interpoles

• Interpoles

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 operates no dc generators, the batteries are kept charged by

• Rectifiers which use the aircraft’s ac generators as a source of power.

• Alternators which use the aircraft’s generators as a source of power.

• Inverters which use the aircraft’s ac generators as a source of power.

• Rectifiers which use the aircraft’s ac generators as a source of power.

A voltage regulator controls generator output by

• Shorting out field coil in the event of overload.

• Introducing a resistance in generator-to-battery lead in the event of overload.

• Varying current flow to generator field coil.

• Varying current flow to generator field coil.

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

• Series/parallel

• Parallel

• Series

• Parallel

Residual voltage is a result of magnetism in the

• Armature

• Field windings

• Field shoes

• Field shoes

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

• Strength of the magnetic field

• Speed at which the armature rotates

• Number of conductors in the armature

• Strength of the magnetic field

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.

• Electrical unit in the circuit and should be located as close to the source as possible.

• Circuit and should be located as close to the unit as possible.

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

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

• Heavy power circuits

• 400 cycle AC circuits

• Starter-generator circuits

• Heavy power circuits

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 open.

• Either the component or the circuit is shorted.

• The component has continuity and is not open

• The component has continuity and is not open

An aircraft electrical circuit control relay is

• Any conductor which receives electrical energy and passes it on with little or no resistance.

• An electronically operated switch.

• A device that converts electrical energy to kinetic energy.

• An electronically operated switch.

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

• Rotate the positive brush one commutator segment.

• Reverse the electrical connections to either the field or armature windings.

• Interchange the wires which connect the motor to the external power source.

• Reverse the electrical connections to either the field or armature windings.

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

• Shunt-type ohmmeter

• Multimeter

• Megohmmeter

• Megohmmeter

How is a shunt-wound dc generator connected?

• The field and armature are shunted with a capacitor.

• Both fields are shunted across the armature.

• One field is shunted across the other.

• Both fields are shunted across the armature.

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

• Electromagnetic

• Structural

• Mechanical

• Mechanical

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

• Aluminum sheets

• Carbon steel

• Stainless steel

• Stainless steel

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

• Armature assembly

• Brush assembly

• Field assembly

• Field assembly

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

• A shorted armature

• A broken field lead

• An out-of-round commutator

• A shorted armature

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 an inverter.

• By means of a transformer.

• By means of a rectifier.

• By means of a transformer.

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

• The FAA.

• Aircraft technical orders.

• The equipment manufacturer.

• The equipment manufacturer.

The poles of a generator are laminated to

• Increase flux concentration

• Reduce eddy current losses

• Reduce flux losses

• Reduce eddy current losses

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

• Series with the light.

• Parallel with the light.

• Series-parallel with the light switch.

• Series with the light.

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

• Overcome armature reaction.

• Reduce field strength.

• Reduce arcing at the brushes.

• Reduce field strength.

What is the cause of generator brush arcing?

• Seating brushes with No. 000 sandpaper

• Carbon dust particles

• Low spring tension

• Low spring tension

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

• The number of turns of wire in the coil and the amount of current (amperes) passing through the coil.

• The size (cross-section) and the number of turns of wire in the coil and the applied voltage.

• The number of turns of wire in the coil and the applied voltage.

• The number of turns of wire in the coil and the amount of current (amperes) passing through the coil.

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

• Support the bundle to structure and/or solid fluid lines to prevent chafing damage.

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

• Provide adequate slack in the wire bundle to compensate for large changes in temperature.

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

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

• Splicing within wire bundles is not permitted.

• Grouped together to facilitate inspection.

• Staggered along the length of the bundle.

• Staggered along the length of the bundle.

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

• Compound wound

• Series wound

• Externally grounded

• Series wound