Aircraft Mechanic Reviewer Philippines PDF

AIRCRAFT MECHANIC REVIEWER PHILIPPINES Some electric motors have two sets of field windings wound in opposite directions so that the ans. Motor can be operated in neither direction One purpose of a growler test is to determine the presence of ans. A shorted armature Electric wire terminals for mo...

AIRCRAFT MECHANIC REVIEWER PHILIPPINES Some electric motors have two sets of field windings wound in opposite directions so that the ans. Motor can be operated in neither direction One purpose of a growler test is to determine the presence of ans. A shorted armature Electric wire terminals for most aircraft applications must be what type? ans. Ring What is the principal advantage of the series-wound dc motor? ans. High starting torque If a generator is equipped with a vibrator-type voltage regulator, the actual time the voltage regulator points remain open ans. Depends on the load carried by the generator What is a cause of generator brush arcing? ES ans. Low spring tension When ac generators are operated in parallel, the ans. Frequency and voltage must be both equal N The starting current of a series-wound dc motor, in passing through both the field and armature windings, produces a ans. High starting torque PI IP Which motor would be most likely to have an armature brake? IL ans. Landing light retraction motor The method most often used in overcoming the effect of armature reaction is through the use of PH ans. Interpoles The only practical method of maintaining a constant voltage output from an aircraft generator under R varying conditions of speed and load is to vary the ans. Strength of the magnetic field AM The pole pieces or shoes used in a dc generator are a part of the ans. Field assembly How many cycles of ac voltage are produced in a six-pole alternator of the revolving-field type for each revolution of the rotor? ans. Three 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 ans. Opposite to the normal direction and through the shunt field in the normal direction How does the magnetic brake used to stop rotation of an electric motor armature operate? ans. A friction brake is applied by a spring and release by a magnet CHORESCA REVIEW MANUAL  AIRCRAFT MECHANIC REVIEWER PHILIPPINES In a generator, what eliminates any possible sparking to the brush guides caused by the movement of the brushes within the holder? ans. The brush pigtail A series-wound dc electric motor will normally require ans. More current at low rpm than at high rpm The type of electric wire terminals used for most aircraft applications, in addition to providing good current carrying capabilities, are designed primarily ans. To prevent circuit failure due to terminal disconnection Aluminum wire must be stripped very carefully because ans. Individual strands will break easily after being nicked The commutator of a generator ans. Changes alternating current produced in the armature into direct current as it is taken from the ES armature An ammeter in a battery charging system is for the purpose of indicating the ans. Rate of current used to charge the battery N Which of the following is not one of the purposes of interpoles in a generator? ans. Reduce field strength PI IP To test generator or motor armature windings for opens, ans. A place armature in a growler and connect a 110v test light on adjacent segments; light should light. IL What is the color and orientation of the position lights for navigation on civil airplanes? ans. Left side – red , right side – green, rear aft – white PH To what depth is the mica insulation between the commutator bars of a dc generator undercut? ans. Equal to the width of the mica R A voltage regulator controls generator output by AM ans. Varying current flow to generator field coil Which type of dc generator is not used as an airplane generator? ans. Series wound What is the most accurate type of frequency-measuring instrument? ans. Integrated circuit chip having a clock circuit During ground operation, aircraft generator cooling is usually accomplished by ans. An integral fan What does a rectifier do? ans. Changes alternating current to direct current What type of instrument is used for measuring very high values of resistance? ans. Megohmmeter CHORESCA REVIEW MANUAL  AIRCRAFT MECHANIC REVIEWER PHILIPPINES When a diode is checked for an open circuit or a short circuit, it should be ans. Disconnected from the circuit When handling a high voltage capacitor in an electrical circuit, be sure it ans. It is fully discharge before removing it from the circuit Which of the following is most likely to cause thermal runaway in a nickel-cadmium battery? ans. Excessive current draw from the battery How can it be determined if a transformer winding has some of its turns shorted together? ans. Transformer will get hot in normal operation Which of the following are the major parts of a dc motor? 1. Armature assembly. 2. Field assembly. ES 3. Brush assembly. 4. Commutator. N 5. Pole piece. 6. Rheostat. PI IP 7. End frame. ans. 1,2,3,7 IL (1) There are three basic types of dc motors; series, shunt, and compound. PH (2) In the series motor, the field windings, consisting of relatively few turns of heavy wire, are connected in series with the armature winding. R Regarding the above statements, ans. Both no. 1 and no. 2 are true AM For general electrical use in aircraft, the acceptable method of attaching a terminal to a wire is by ans. Crimping 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). ans. 2,5,6,7 CHORESCA REVIEW MANUAL  AIRCRAFT MECHANIC REVIEWER PHILIPPINES 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). ans. 1, 3, 5 How should the splices be arranged if several are to be located in an electrical wire bundle? ans. Staggered along the length of the bundle What is the minimum bend radius for an electrical wire bundle? ans. Ten times the outside diameter of the bundle When approved, splices may be used to repair manufactured harnesses or installed wiring. The ES maximum number of splices permitted between any two connectors is ans. One N AN/MS electrical connectors are specifically designed to meet ans. Military specification PI The most common method of attaching a pin or socket to an individual wire in an MS electrical IP connector is by ans. Crimping IL The pin section of an AN/MS connector is normally installed on ans. The ground side of a circuit PH The voltage output of an alternator may be regulated by controlling the ans. Voltage output of the dc exciter R If several long lengths of electrical cable are to be installed in rigid conduit, the possibility of damage to AM the cable as it is pulled through the conduit will be reduced by ans. Dusting the cable with powdered soapstone Grounding is electrically connecting a conductive object to the primary structure. One purpose of grounding is to ans. Prevent development of radio frequency potentials What is normally used to bond non-continuous stainless steel aircraft components? ans. Copper jumpers Aircraft fuse capacity is rated in ans. Amperes When adding a rheostat to a light circuit to control the light intensity, it should be connected in ans. series with the light CHORESCA REVIEW MANUAL  AIRCRAFT MECHANIC REVIEWER PHILIPPINES Circuits that must be operated only in an emergency or whose inadvertent activation could endanger a system frequently employ ans. Guarded switches If one switch is used to control all navigation lights, the lights are most likely connected ans. Parallel to each other and in series with the switch Oil canning of the sides of aluminum or steel electrical junction boxes is considered to be ans. A shorting hazard 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 ans. Be limited as to the number of cables to minimize damage from a single electrical fault During inspection of the terminal strips of an aircraft electrical system, it should be determined that ans. The terminal studs are anchored against rotation ES What protection to wires and cables does conduit provide when used in aircraft installations? ans. Mechanical Which of the following should be accomplished in the installation of aircraft wiring? N ans. Locate the bundle above flammable fluid lines and securely clamp to structure PI 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 IP ans. Backwards IL When using the voltage drop method of checking circuit resistance, the ans. Input voltage must be maintained at a constant value PH The nominal rating of electrical switches refers to continuous ans. Current rating with contacts closed R Aircraft electrical junction boxes located in a fire zone are usually constructed of ans. Stainless steel AM 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 ans. Parallel The primary considerations when selecting electric cable size are ans. Current carrying capacity and allowable voltage drop The navigation 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 switch is referred to as a ans. Single pole single throw (SPST), two position switch Electric circuits are protected from overheating by means of ans. Fuses How does the routing of coaxial cables differ from the routing of electrical wiring? ans. Coaxial cable are routed as directly as possible CHORESCA REVIEW MANUAL  AIRCRAFT MECHANIC REVIEWER PHILIPPINES Which of the following copper electrical cable sizes should be selected to replace a No. 6 aluminum electrical cable? ans. No. 6 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? ans. 100 Which statement relating to electric wiring is true? ans. When attaching a terminal to the end of an electric cable , it should be determined that the strength of the cable to terminal joint is at least equal to the tensile strength of the cable itself. Bonding connections should be tested for ans. Resistance value What kind of switch should you install in a single wire circuit that required the switch to be manually held in the ON position? ES ans. Single pole, single throw (SPST), two position normally open (NO) A circuit breaker is installed in an aircraft electrical system primarily to protect the N ans. Circuit and should be located as close to the source as possible How should a voltmeter be connected? ans. In parallel with the load PI IP A circuit protection device called a current limiter is essentially a slow-blow fuse and is designed to be used in IL ans. Heavy power circuits PH If it is necessary to use an electrical connector where it may be exposed to moisture, the mechanic should ans. Use a special moisture proof type R The three kinds of circuit-protection devices used most commonly in aircraft circuits are AM ans. Circuit breakers, fuses, and current limiters If a wire is installed so that it comes in contact with some moving parts, what protection should be given the wire? ans. Pass through conduit 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 ans. Cross sectional area 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 / VD = Voltage drop / R = Resistance per ft =.00644 / L = Length of wires A = Amperes ans. 4v CHORESCA REVIEW MANUAL  AIRCRAFT MECHANIC REVIEWER PHILIPPINES What is the purpose of the selection of derated switches for known continuous load current applications? ans. To obtain reasonable switch efficiency and service life What is the advantage of a circuit breaker when compared to a fuse? ans. Resettable and reusable What is the advantage of a current limiter? ans. It will take overload for a short period Where electric cables must pass through holes in bulkheads, formers, ribs, firewalls, etc., the wires should be protected from chafing by ans. Using a suitable grommet In aircraft electrical systems, automatic reset circuit breakers ans. Should not be used as protective devices A certain switch is described as a single-pole, double-throw switch (SPDT). The throw of a switch ES indicates the number of ans. Circuits each pole can complete through the switch When considering an alteration, the criteria upon which the selection of electric cable size should be N based are ans. Current carrying and allowable voltage drop What is an important factor in selecting aircraft fuses? PI IP ans. Capacity matches the needs of the circuit IL The circuit breaker in the instrument lighting system protects the ans. Wiring from too much current PH One advantage of using ac electrical power in aircraft is ans. Greater ease in stepping the voltage up or down R Why are the iron cores of most induction coils laminated? ans. To reduce the effects of eddy currents AM 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 operate no dc generators, the batteries are kept charged by ans. Rectifiers which use the aircraft’s ac generator as a source of power The voltage in an ac transformer secondary that contains twice as many loops as the primary will be ans. Greater and the amperage less than in the primary 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 ans. Residual voltage What is a method used for restoring generator field residual magnetism? ans. Flash the fields CHORESCA REVIEW MANUAL  AIRCRAFT MECHANIC REVIEWER PHILIPPINES 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 ans. By means of a transformer Which of the following must be accomplished when installing an anticollision light? ans. Install a switch independent of the position light switch The inductor-type inverter output voltage is controlled by the ans. Dc stator field current When using an ohmmeter to check the continuity of a generator field coil, the coil should ans. Show very low resistance if it is a series field coil The strength of the core of an electromagnet depends upon the material from which it is constructed and which of the following? ans. The number of turns of wire in the coil and the amount of current (ampere) passing through the coil A voltage regulator controls generator voltage by changing the ES ans. Resistance of the generator field circuit The overvoltage control automatically protects the generator system when excessive voltage is present by N ans. Opening the shunt field circuit PI 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 IP ans. Increasing the output of the low generator and decreasing the output of the high generator until they are equal IL What is the maximum amount of time a circuit can be in operation and still be an intermittent duty PH circuit? ans. Two minutes The most common method of regulating the voltage output of a compound dc generator is to vary the R ans. Current flowing through the shunt field coils AM (Refer to Figure 18.) Which of the batteries are connected together incorrectly? Ans. 3 CHORESCA REVIEW MANUAL  AIRCRAFT MECHANIC REVIEWER PHILIPPINES (Refer to Figure 19.) Upon completion of the landing gear extension cycle, the green light illuminated and the red light remained lit. What is the probable cause? ES N ans. Short in the up limit switch PI If any one generator in a 24-volt dc system shows low voltage, the most likely cause is IP ans. An out of adjustment voltage regulator How can the direction of rotation of a dc electric motor be changed? IL ans. Reverse the electrical connections to either the field or armature windings PH 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 ans. A step down transformer and a rectifier R During inspection of an anti-collision light installation for condition and proper operation, it should be AM determined that ans. The anti-collision light can be operated independently of the position lights 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 ans. The equipment manufacturer A battery-generator system provides direct current. On installations requiring alternating current from the battery-generator system, it is necessary to have ans. An inverter A relay is ans. Magnetically operated switch The purpose of a rectifier in an electrical system is to change ans. Alternating current to direct current CHORESCA REVIEW MANUAL  AIRCRAFT MECHANIC REVIEWER PHILIPPINES 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? ans. Primary will have one third as many turns as its secondary In an ac circuit with no phase lead or lag, which is true? ans. Real power equals apparent power How are generators rated? ans. Amperes and rated voltage How is a shunt-wound dc generator connected? ans. Both fields are shunted across the armature The poles of a generator are laminated to ans. Reduce by eddy current losses What is the frequency of an alternator dependent upon? ans. Rpm ES The generator rating is usually found stamped on the ans. Generator N Residual voltage is a result of magnetism in the ans. Field shoes PI In troubleshooting an electrical circuit, if an ohmmeter is properly connected across a circuit component IP and some value of resistance is read, ans. The component has continuity and is not open IL CSD driven generators are usually cooled by ans. Oil spray PH A CSD unit drives a generator through the use of ans. A variable hydraulic pump and hydraulic motor R Integrated drive generators (IDG) employ a type of high output ac generator that utilizes AM ans. A brushless system to produce current If the IDG scavenge oil filter is contaminated with chunks or pieces of metal ans. Remove and replace the IDG When necessary during operation, CSD disconnect is usually accomplished by ans. A switch in the cockpit A CSD unit that is disconnected in flight, due to a malfunction such as overtemperature, may be reconnected ans. Only on the ground by maintenance personnel CHORESCA REVIEW MANUAL