Engine Electrical Flashcards
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 commutator
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?
The condition is normal for this type of motor
The stationary field strength in a direct current generator is varied
According to the load requirements
What type of electric motor is generally used with a direct-cranking engine starter?
Direct current , series wound motor
Upon what does the output frequency of an ac generator (alternator) depend?
The speed of rotation and the number of field poles
A high surge of current is required when a dc electric motor is first started. As the speed of the motor
increases,
the current EMF builds up and opposes the applied EMF, thus reducing the current flow through the
armature
Alternators (ac generators) that are driven by a constant-speed drive (CSD) mechanism are used to
regulate the alternator to a constant
Hertz output
What is used to polish commutators or slip rings?
A very fine sand paper
If a generator is malfunctioning, its voltage can be reduced to residual by actuating the
Generator master switch
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 increase
Why is a constant-speed drive used to control the speed of some aircraft engine-driven generators?
. So that the frequency of the alternating current output will remain constant
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
As in to negative terminal and out the positive terminal
Aircraft that operate more than one generator connected to a common electrical system must be
provided with
. Individual generator switches that can be operated from the cockpit during flight
The most effective method of regulating aircraft direct current generator output is to vary, according to
the load requirements, the
Strength of the stationary field
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
As the generator load is increased (within its rated capacity), the voltage will
Remain constant and the amperage of the output will increase
As the flux density in the field of a dc generator increases and the current flow to the system increases,
the
The force require to turn the generator increase
What is the purpose of a reverse-current cutout relay?
.It opens the main generator circuit whenever the generator voltage drops below the battery
voltage
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
Open armature
Why is it unnecessary to flash the field of the exciter on a brushless alternator?
Permanent magnets are installed in the main field poles
One way that the automatic ignition relight systems are activated on gas turbine engines is by a
Drop in compressor discharge pressure
How are the rotor windings of an aircraft alternator usually excited?
By a variable direct current
What precaution is usually taken to prevent electrolyte from freezing in a lead acid battery?
Keep battery fully charged
What is the ampere-hour rating of a storage battery that is designed to deliver 45 amperes for 2.5
hours?
112 amperes per hour
How many hours will a 140 ampere-hour battery deliver 15 amperes?
9.33 hours
What is a basic advantage of using ac for electrical power for a large aircraft
AC system operates at a higher voltage than dc systems and therefore use less current and can use
smaller and lighter weight wiring
What are two types of ac motors that are used to produce a relatively high torque?
Three phase induction and capacitor start
(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
Both no.1 and 2 are true.
What is the frequency of most aircraft alternating current?
400 hertz
The reason for flashing the field in a generator is to
Restore the polarity and/or residual magnetism to the field poles
The part of a dc alternator power system that prevents reverse flow of current from the battery to the
alternator is the
Rectifier
The generating system of an aircraft charges the battery by using
Constant voltage and varying current
The constant current method of charging a ni-cad battery
Is the method maintaining cell balance
(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?
No. 12
Which of the following aircraft circuits does NOT contain a fuse/circuit breaker?
Starter circuit
The maximum number of terminals that may be connected to any one terminal stud in an aircraft
electrical system is
4
What is the maximum number of bonding jumper wires that may be attached to one terminal grounded
to a flat surface?
Four
As a general rule, starter brushes are replaced when they are approximately
One half their original length
When installing an electrical switch, under which of the following conditions should the switch be
derated from its nominal current rating?
Direct current motor circuit
The resistance of the current return path through the aircraft is always considered negligible, provided
the
Structure is adequately bonded
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
When does current flow through the coil of a solenoid-operated electrical switch?
Continually as long as the control circuit is complete
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
The load will be within generator load limit
What type of lubricant may be used to aid in pulling electrical wires or cables through conduits?
Soapstone talc
Which of the following is regulated in a generator to control its voltage output?
The strength of the field
Bonding jumpers should be designed and installed in such a manner that they
Provide a low resistance in the ground circuit
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
Starter solenoid is defective
Arcing at the brushes and burning of the commutator of a motor may be caused by
Weak brush spring
The maximum allowable voltage drop between the generator and the bus bar is
2 percent of regulated voltage
ON-OFF two position engine electrical switches should be installed
So the on position is reached by a forward or upward motion
When selecting an electrical switch for installation in an aircraft circuit utilizing a direct current motor,
a derating factor should be applied
When installing electrical wiring parallel to a fuel line, the wiring should be
Above the fuel line
(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
35 amperes
What speed must an eight-pole ac generator turn to produce 400-Hertz ac?
6000 rpm
How many basic types of circuit breakers are used in powerplant installation electrical systems?
Three
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
Which Federal Aviation Regulation requirement prevents the use of automatic reset circuit breakers?
14 CFR part 23
The time/current capacities of a circuit breaker or fuse must be
Below those of the associated conductor
(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 1 is true
Electrical switches are rated according to the
Voltage and current they can control
Electrical circuit protection devices are installed primarily to protect the
Wiring
(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,
Both no. 1 and no. 2 is true
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 91
What is the smallest terminal stud allowed for aircraft electrical power systems?
No. 10
A typical barrier type aircraft terminal strip is made of
Paper base phenolic compound
A term commonly used when two or more electrical terminals are installed on a single lug of a terminal
strip is
Stacking
(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 1 is true
Aircraft electrical wire size is measured according to the
American wire gauge system
Aircraft copper electrical wire is coated with tin, silver, or nickel in order to
Prevent oxidation
