ENGINE ELECTRIC CURRENT

AIRFRAME RATING

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

• Generator circuit

• Air-conditioning circuit

• Starter circuit

• Starter circuit

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

• 112.5 ampere-hour

• 90.0 ampere-hour

• 45.0 ampere-hour

• 112.5 ampere-hour

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

• Technical Standard Order (TSO)

• American Wire Gauge (AWG)

• Military Specification (MS)

• American Wire Gauge (AWG)

Electrical circuit protection devices are installed primarily to protect the

• Switches

• Wiring

• Units

• Wiring

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

• Generator speed.

• Strength of the stationary field.

• Number of rotating armature loops in use.

• Strength of the stationary field.

ON-OFF two position engine electrical switches should be installed

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

• So that the toggle will move in the same direction as the desired motion of the unit controlled.

• Under a guard.

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

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? 

• Generator output voltage will decrease. 

• Generator output voltage will not be affected. 

• Generator output voltage will increase

• Generator output voltage will increase

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

• Voltage drop across the circuit is checked. 

• Generator is properly grounded. 

• Structure is adequately bonded.

• Structure is adequately bonded.

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 

• Is into the positive terminal and out the negative terminal. 

• Cycles back and forth with the number of cycles per second being controlled by the rotational speed of the alternator.

• Is into the negative terminal and out the positive terminal.

• Is into the negative terminal and out the positive terminal.

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

• An automatic device that will isolate non-essential loads from the system if one of the generators fails.

• Automatic generator switches that operate to isolate any generator whose output is less than 80% of its share of the load.

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

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

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

• To eliminate uncontrolled surges of current to the electrical system.

• So that the voltage output of the generator will remain within limits.

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

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

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’?

• 14 CFR Part 23

• 14 CFR Part 43

• 14 CFR Part 91

• 14 CFR Part 91

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

• Four

• Three

• Two

• Four

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?

• An inverter.

• A commutator.

• A rectifier.

• A commutator.

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

• Generator master switch

• Rheostat

• Master solenoid

• Generator master switch

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

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

Regarding the above statements,

• Only No. 2 is true.

• Only No. 1 is true.

• Neither No. 1 nor No. 2 is true.

• Only No. 1 is true.

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

• Silicone grease

• Soapstone talc

• Rubber lubricant

• Soapstone talc

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

• Strapping

• Piggy backing

• Stacking

• Stacking

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 

• That the generator load will exceed the generator limit. 

• The load will be within the generator load limit.

• The load exceeds the maximum system percentage capacity.

• The load will be within the generator load limit.

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

• 14 CFR Part 91

• 14 CFR Part 21

• 14 CFR Part 23

• 14 CFR Part 23

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

• No. 6

• No. 10

• No. 8

• No. 10

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?

• Series

• Compound

• Shunt (parallel)

• Series

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

• Prevent oxidization.

• Improve conductivity.

• Add strength.

• Prevent oxidization.

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

• Continually, as long as the aircraft's electrical system master switch is on.

• Only until the movable points contact the stationary points.

• Continually, as long as the control circuit is complete.

• Continually, as long as the control circuit is complete.

(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.

Regarding the above statements, 

• Only No. 1 is true. 

• Only No. 2 is true.

• Both No. 1 and No. 2 are true.

• Both No. 1 and No. 2 are true.

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

• Generator amperage decreases.

• Force required to turn the generator increases.

• Generator voltage decreases.

• Force required to turn the generator increases.

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

• The counter emf increases proportionally.

• The counter emf decreases proportionally.

• The counter emf builds up and opposes the applied emf, thus reducing the current flow through the armature.

• The counter emf builds up and opposes the applied emf, thus reducing the current flow through the armature.

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

• Excessive brush spring tension

• Weak brush springs

• Low mica

• Weak brush springs

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

• Beside the fuel line.

• Below the fuel line.

• Above the fuel line.

• Above the fuel line.

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

• Three

• Two

• Four

• Four

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

• Hertz output

• Voltage output

• Amperage output

• Hertz output

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

• A derating factor should be applied.

• A switch designed for dc should be chosen.

• Only switches with screw-type terminal connections should be used.

• A derating factor should be applied.

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

• Pin section on the ground side of the electrical circuit.

• Socket section on the ground side of the electrical circuit.

• Pin section on the positive side of the electrical circuit.

• Pin section on the ground side of the electrical circuit.

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

• 1.40 hours

• 14.0 hours

• 9.33 hours

• 9.33 hours

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

• By a constant ac voltage from the battery.

• By a constant ac voltage.

• By a variable direct current.

• By a variable direct current.

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

(2) Federal Aviation Regulations Part 23 requires that all electrical circuits incorporate some form of circuit protective device. Regarding the above statements, 

• Only No. 1 is true.

• Only No. 2 is true.

• Both No. 1 and No. 2 are true.

• Only No. 1 is true.

Electrical switches are rated according to the

• Voltage and the current they can control.

• Resistance rating of the switch and the wiring.

• Resistance and the temperature rating.

• Voltage and the current they can control.

What is the frequency of most aircraft alternating current?

• 115 Hertz

• 60 Hertz

• 400 Hertz

• 400 Hertz

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

• Armature shaft bearings overheating.

• Excessive brush arcing.

• An open armature

• An open armature

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

• 2% of the regulated voltage.

• Less than the voltage drop permitted between the battery and the bus bar.

• 1% of the regulated voltage.

• 2% of the regulated voltage.

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?

• 14 CFR Part 23

• 14 CFR Part 43

• 14 CFR Part 91

• 14 CFR Part 23

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

• Reverse current relay

• Rectifier

• Voltage regulator

• Rectifier

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

• It prevents fluctuations of generator voltage.

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

• It eliminates the possibility of reversed polarity of the generator output current.

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

A typical barrier type aircraft terminal strip is made of

• Paper-base phenolic compound.

• Layered aluminum impregnated with compound.

• Polyester resin and graphite compound.

• Paper-base phenolic compound.

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

• Prevent buildup of a static electrical charge between the airframe and the surrounding atmosphere.

• Provide a low electrical resistance in the ground circuit.

• Are not subjected to flexing by relative motion of airframe or engine components.

• Provide a low electrical resistance in the ground circuit.

Aircraft wire size is determined by using the

• Wire gauge

• Ohmmeter

• Dial caliper

• Wire gauge

What is used to polish commutators or slip rings?

• Double-0 sandpaper

• Emery cloths

• Stiff bristle brushes

• Double-0 sandpaper

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

• Speed of the armature.

• Number of windings in the armature.

• The strength of the field.

• The strength of the field.

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

• Brushless alternators do not have exciters.

• The exciter is constantly charged by battery voltage.

• Permanent magnets are installed in the main field poles.

• Permanent magnets are installed in the main field poles.

The generating system of an aircraft charges the battery by using

• Constant current and varying voltage

• Constant voltage and varying current

• Constant voltage and constant current

• Constant voltage and varying current

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

• Direct current, series-wound motor

• Synchronous motor

• Direct current, shunt-wound motor

• Direct current, series-wound motor

Starter brushes should be replaced when they are worn down to

• One-quarter of the original length.

• One-half of the original length.

• Three-quarters of the original length.

• One-half of the original length.

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

• Drop in compressor discharge pressure.

• Sensing switch located in the tailpipe.

• Drop in fuel flow.

• Drop in compressor discharge pressure.

The constant current method of charging a ni-cad battery

• Will bring it up to fully charged in the shortest amount of time.

• Will lead to cell imbalance over a period of time.

• Is the method most effective in maintaining cell balance.

• Is the method most effective in maintaining cell balance

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

• Capacitive circuits

• Conductive circuits

• Direct-current motor circuits

• Direct-current motor circuits

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

• Remove the battery and keep it under constant charge.

• Keep the battery fully charged.

• Place the aircraft in a hangar.

• Keep the battery fully charged.

(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. Regarding the above statements,

• Only No. 2 is true.

• Only No. 1 is true.

• Both No. 1 and No. 2 are true.

• Both No. 1 and No. 2 are true.

The reason for flashing the field in a generator is to

• Restore residual magnetism to the field frame.

• Ensure proper operation of the capacitor.

• Relieve the unit of any residual electrical energy.

• Restore residual magnetism to the field frame.

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

• Two

• Three

• Four

• Three

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

• The speed of rotation and the strength of the field.

• The speed of rotation, the strength of the field, and the number of field poles.

• The speed of rotation and the number of field poles

• The speed of rotation and the number of field poles

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

• Equal to those of the associated conductor.

• Below those of the associated conductor.

• Above those of the associated conductor.

• Below those of the associated conductor.

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

• AC systems operate at higher voltage than dc systems and therefore use more current and can use smaller and lighter weight wiring.

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

• AC systems operate at lower voltage than dc systems and therefore use less current and can use smaller and lighter weight wiring.

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

What speed must an eight-pole ac generator turn to produce 400-Hertz ac?

• 1,200 RPM

• 400 RPM

• 6,000 RPM

• 6,000 RPM

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

• Shaded pole and shunt field

• Shunt field and single phase

• Three-phase induction and capacitor start

• Three-phase induction and capacitor start

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

• The brushes are floating at operating RPM because of weak brush springs.

• The starting winding is shorted.

• The condition is normal for this type of motor.

• The condition is normal for this type of motor.

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

• Decrease and the amperage output will increase.

• Remain constant and the amperage output will decrease.

• Remain constant and the amperage output will increase.

• Remain constant and the amperage output will increase.

The stationary field strength in a direct current generator is varied

• Because of generator speed.

• According to the load requirements.

• By the reverse-current relay.

• According to the load requirements.