M1-Airframe Systems & Applications
How are generators rated?
Amperes at rated voltage
If any one generator in a 24-volt dc system shows low voltage, the most likely cause is
An out-of-adjustment voltage regulator.
How is a shunt-wound dc generator connected?
Both fields are shunted across the armature
(1) There are three basic types of dc motors; series, shunt, and compound. (2) In the series motor, the field windings, cosisting of realatively few turns of heavy wire, are connected in series with the armature winding. Which statement(s) are true?
Both.
What is the ratio of turns between the primary coil winding and the secondary coil winding of a transformer designed jto triple its input voltage?
Primary will have one-third as many turns as it secondary
What is the frequency of an alternator dependent upon?
RPM
In an ac circuit with no phase lead or lag, what is true?
Real power equals apparent power.
Electric wire terminals for most aircraft applications must be what type?
Ring
What is the minimum bend radius for an electrical wire bundle?
Ten times the outside diameter of the bundle.
How many cycles of ac voltage are produced in a six-pole alternator of the revolving-field type for each revolution of the rotor?
Three
When attaching a terminal to the end of an electric cable, it should be determined that the strength fo the cable-to-terminal joint is at least eaual to the tensile strength of the cable itself. True or false.
True
a CSD unit drives a generator through the use of
a variable hydrualic pump and hydraulic motor.
The purpose of a rectifier in an electrical system is to change
alternating current to direct current.
Aircraft fuse capacity is rated in
ampers.
An Aircraft electrical circuit control relay is
an electrically operated switch.
During ground operation, aircraft generator cooling is usually accomplished by
an integral fan.
A battery-generator system provides direct current. On installations requiring alternating current from the battery-generator system, it is necessary to have
an inverter.
How does the magnetic brake used to stop rotation of an electric motor armature operation?
A friction brake is applied by a spring and released by a magnet.
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
What is normally used to bond noncontinuous stainless steel aircraft components?
copper jumpers.
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
The primary considerations when selecting electric cable sizes are
current-carrying capacity adn allowable voltage drop.
The inductor-type inverter output voltage is controlled by the
dc stator field current
When a diode is checked for an open circuit or a short circuit, it should be
disconnected from the circuit
If several long lengths of electrical cable are to be installed in rigid conduit, the possiblity fo damage to the cable as it is pulled through the conduit will be reduced by
dusting the cable with powdered soapstone.
A circuit protection device called a current limiter is essentially a slow-blow fuse and is designed to be used in
heavy power circuits.
The starting current of a series-wound dc motor, in passing through both the field and armature windings, produces a
high starting torque.
How should a voltmeter be connected?
in parallel with the load
Aluminum wire must be stripped very carefully becuase
individual strands will break easily after being nicked
AN/MS electrical connectors are specifically designed to meet?
miliary specifications.
A series-wound dc electric motor will normally require
more current at low RPM than at high RPM
CSD driven generators are usually cooled by
oil spray
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
The overvoltage control automatically protects the generaor system when excessive voltage is present by
opening the shunt field circuit
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
opposite the normal directionand through the shunt field in th normal direction.
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
Grounding is electrically connecting a conductive object to th primary structure. One purpose of grounding is to
prevent development of radio frequency potentials.
An ammeter in a battery charging system is for the purpose of indicating the
rate of current used to charge the battery.
The poles of a generator are laminated to
reduce eddy current losses.
if the integrated Drive Generator (IDG) scavenge oil filter is contaminated with metal, you should
remove and replace the IDG
If positive field lead between a generator and a generator contorl panel breaks and is shorted while the engine is running, a voltmeter connected to generatro out-put would indicate
residual voltage.
A voltage regulator controls geneerator voltage by changing the
resistance of the generator field circuit
Bonding connections should be tested for
resistance value.
(refer to Figure 19.) Upon completion of the landing gear extension cycle the green light illumination and the red light remained lit. What is the probably cause?
short in the up limit switch.
The naviation 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 swich is referred to as a
single-pole, single-throw (SPST), Two position switch.
The type of electric wire terminals used for most aircraft applications, in addition to providing good current carrying capabilities, are designed primarly
to prevent circuit failure due to terminal disconnection.
If it is necesary to use an electrical connector where it may be exposed to moisture, the mechanic should
use a special moisture-proof type.
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.
1,2,3, and 7
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 alterantor rating?
100
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, and 7
(refer to Figure 18.) What batteries are connected together incorrectly?
3
What is the volatage drop for a No. 18 copper wire 50 feet long to carry 12.5 amperes, continuous operation? Use formula VD=RLA VD= voltage drop R= resistance per ft= .00644 L= Length of wire A= Amperes
4V.
How does the routing of coaxial cables differ from the routing of electrical wiring?
Coaxial cables are routed as directely as possible
To what depth is the mica insulation between the commutator bars of a dc generator undercut?
Equal to the width of the mica.
What is most likely cause of thermal runaway in a nickel-cadmium battery?
Excessive current draw from the battery.
How can it be determined if a transformer winding has some of its turns shorted together?
The transformer will get hot in normal operation.
What is a method used for restoring generator field residual magnetism?
Flash the fields.
What is required when operating two aircraft ac generators in parallel?
Frequency and voltage must both be equal.
What is the principle advantage of the series-wound dc motor?
High starting torque
The following must be accompished when installing an anticollision light?
Install a switch independent of the position light switch.
What is the most accurate type of frequency-measuring instrument?
Integrated circuit ship having a clock circuit
What is the purpose fo the selection of derated switches for known continuous load current applications?
To obtain reasonable switch efficency and service life.
Why are the iron cores of most induction coils laminated?
To reduce the effects of eddy currents.
What is the advantage of a current limiter?
It will take overload for a short period.
What motor will be most likely to have an armature brake?
Landing light retraction motor.
What is the color and orientation of the position lights for navigation on civilian airplanes?
Left side- red, right side-green, rear aft- white.
What should be accomplished in the installation of aircraft wiring?
Locate the bundle above flammable fluid lines and securely clamp to structure.
What is a cause of generator brush arcing?
Low spring tension.
What protection to wires and cables does conduit provide when used in aircraft installations?
Mechanical.
What type of instrument is used for measuring very high values of resistance?
Megohmmeter
What copper electical cable sizes should be selected to replace a No. 6 aluminum electrical cable?
No. 6
Static inverters are electronic devices that change DC to AC with the
Us of an oscillator.
If a wire is installed so that it comes in contact with some moving parts, what protection should be given the wire?
Pass through conduit
What is the advantage of a circuit breaker when compared to a fuse?
Resettable and reusable.
How can the direction of rotation of a dc electric motor be changed?
Reverse the electrical connections to either the field or armature windings.
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), two-position normally open (NO)
How should the splices be arranged if several are to be located in an electrical wire bundle?
Staggered along the length of the bundle.
Integrated drive generators (IDG) emply a type of high output ac generator that utilizes
a brushless system to produce current
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 stepdown transformer and a rectifier.
When necessary during operation, CSD disconnect is usually accomplished by
a switch in the cockpit.
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.
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 bundle should
be limited s the number of cables to minimize damage from a single electrical fault.
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.
Residual voltage is a result of magnetism in the
field shoes
The generator rating is usually found stamped of the
generator
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 th output of the low generator and decreasing the output of the high generator until they are equal.
A CSD unit that is disconnected in flight, due to a malfunction such as overtemperature, may be reconnected
only on the ground by maintenance personnel.
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.
To test generator or motor armature windings for opens,
place armature in a growler and connect a 110V test light on adjacent segments; light should light.
Certain transport aircraft use ac electrical power for all normal operation and battery furnishied dc electrical power for standby emergency use. In aircraft of this type that operate no dc generator, the batteries are kept charged by
rectifiers which use the aircraft's ac generators as a source of power.
During inspeciton of an anticollision light installation for condition and proper operation, it should be determined that
the anticollision light can be operated independently of the position lights.
In troubleshooting an electrical circuit, if an ohmeter is properly connected across a circuit component and some value of resistanc is read
the component has continuity and is not open.
Major adjustments on equipment such as regulators, contactors, and inverters are best accomplished outside the airplane on test benches with necessary instruments and equpment. Adjustment procedure should be as outlined by
the equipment manufacturer.
The strength of the core of an electromagnet depends upon the material from which it is contructed and which of the following?
the number of turns of wire in the coil and the amount of current (amperes) passing through the coil
What is the maximum amount of time a circuit can be in operation and still be an intermittent duty circuit?
two minutes.
In a generator, what eliminates any possible sparking to the brush guides caused by the movement of the brushes within the holder?
The brush pigtail.
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 if load (continues of intermittent)
1,3, and 5
What does a rectifier do?
Changes alternating current into direct current.
One purpose of a growler test is to determine the presence of
a shorted armature.
Oil canning of the sides of aluminum or steel electrical junction boxes is considered to be
a shorting hazard.
What is an important factor in selecting aircraft fuse?
capacity matches the needs of the circuit.
The communicator of a generator
changes alternating current produced in the armature into direct current as it is taken from the armature..
A circuit breaker is installed in an aircraft electrical system primarly to protect the
circuit and should be located as close to the source as possible.
The three kinds of circuit-protection devices used most commonly in aircraft circuits are
circuit breakers, fuses, and current limiters.
The most common method of attaching a pin or socket to an individual wire in an MS electrical connector is by
crimping
For general electrical use in aircraft, the acceptable method of attaching a terminal to a wire is by
crimping.
In the American Wire Gauge (AWG) system of numbers used to designate electrical wire sizes, the mumber assigned to a size is realated to its
cross-sectional area.
The nominal rating of electrical switches refers to continues
current rating with the contacts closed
When condidering an alteration, the criteria upon which the selection of electric cable size should be based are
current-carrying capacity and allowable voltage drop
If a generator is equipped with a vibrator-type voltage regulator, the actual time the voltage regulator points remain open
depends o the load carried by the generator.
The pole pieces or shoes used in a dc generator are a part of the
field assembly
Electric circuits are protected from overheating by means of
fuses
One advantage of using ac electrical power in aircraft is
greater ease in stepping the voltage up or down.
The voltage in an ac transformer secondary taht contains twice a many loops as the primary will be
greater than the amperage less than the primary.
Circuits that must be operated only in an emergency or whose inadvertent activation could endanger a system frequently employ
guarded switches.
When using the voltage drop method of checking circuit resistance, the
input voltage mus be maintained at a constant value.
The method most often used in overcoming the effect of armature reaction is through the use of
interpoles.
When handling a high voltage capacitor in an electrical circuit, be sure it
is fully discharged before removing it from the circuit
Some electric motors have two sets of field windings wound in opposite directions so that the
motor can be operated in either direction.
What is not one of the purposes of interpoles in a generator?
reduce field strength.
When adding a rheostat to a light circuit to control th light intensity, it should be connected in
series with the light
What type of dc generator is not used as an airplane generator?
series wound
In aircraft electrical systems, automatic reset circuit breakers
should not be used as circuit protective devices.
When using an ohmeter to check the continuity of a generator field coil, the coil should
show very low resistance if it is a series field coil
Aircraft electrical junction boxes located in a fire zone are usually contructed of
stainless steel
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.
The pin section of an AN/MS connector is normally installed on
the ground side of a circuit
During inspection of the terminal strips of an aircraft electrical system, it should be determined that
the terminal studs are anchored against rotation
Where electric cables must pass through holes in bulkheads, formers, ribs, firewalls, etc., the wires should be protected form chafing by
using a suitable grommet.
A voltage regulator controls generator output by
varying current flow to generator field coil.
The voltage output of an alternator may be regulated by controlling the
voltage output of the dc exciter.
The circuit breaker in the instrument lighting system protects the
wiring from too much current
