Aircraft Electrical Systems and Components

14 Aircraft Electric Question What is the advantage of a circuit breaker when compared to a fuse? 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? During ground operation, aircraft generator cooling is usually accomplished by Which of the following are considered circuit-protective devices that are used in aircraft electrical systems? A CSD unit drives a generator through the use of Grounding is electrically connecting a conductive object to the primary structure. One purpose of grounding is to Oil canning of the sides of aluminum or steel electrical junction boxes is considered to be A circuit breaker is installed in an aircraft electrical system primarily to protect the A certain switch is described as a single-pole, double-throw (SPDT) switch. The throw of a switch indicates the number of Integrated drive generators (IDG) employ a type of high output AC generator that utilizes An aircraft electrical circuit control relay is Aircraft fuse capacity is rated in In an AC circuit with no phase lead or lag, which is true? The inductor-type inverter output voltage is controlled by the How should a voltmeter be connected? 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 What should be used to protect wires from chafing when they must pass through bulkheads, firewalls, ribs, etc.? What protection to wires and cables does conduit provide when used in aircraft installations? 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 What is the most accurate type of frequency measuring instrument? A voltage regulator controls generator output by 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 What is the maximum amount of time a circuit can be in operation and still be an intermittent duty circuit? (Refer to Figure 18.) Which of the batteries are connected together incorrectly? 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 Where is the generator rating and performance data located? A CSD unit that is disconnected in flight, due to a malfunction such as overtemperature, may be reconnected Answer It is resettable and reusable. Primary will have one-third as many turns as its secondary. an integral fan. Circuit breakers, fuses, and current limiters. a variable hydraulic pump and hydraulic motor. prevent development of radio frequency potentials. a shorting hazard. circuit and should be located as close to the source as possible. circuits each pole can complete through the switch. a brushless system to produce current. an electronically operated switch. amperes Real power equals apparent power. dc stator field current. In parallel with the load. dusting the cable with powdered soapstone. Suitable grommet. Mechanical rectifiers which use the aircraft's AC generators as a source of power. Integrated circuit chip having a clock circuit. varying current flow to generator field coil. the equipment manufacturer. Two minutes. 3 by means of a transformer. Stamped on the generator data plate. only on the ground by maintenance personnel. 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 wire A = Amperes When necessary during operation, CSD disconnect is usually accomplished by What is the advantage of a current limiter? The overvoltage control automatically protects the generator system when excessive voltage is present by In troubleshooting an electrical circuit, if an ohmmeter is properly connected across a circuit component and some value of resistance is read, A series-wound DC electric motor will normally require When selecting hardware for attaching bonding connections to an aircraft structure, which of the following should be considered? If one switch is used to control all navigation lights, the lights are most likely connected Electric wire terminals for most aircraft applications must be what type? The strength of the core of an electromagnet depends upon the material from which it is constructed and which of the following? What is an important factor in selecting aircraft fuses? The circuit breaker in the instrument lighting system protects the (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? How many cycles of AC voltage are produced in a six-pole alternator of the revolving-field type for each revolution of the rotor? If the Integrated Drive Generator (IDG) scavenge oil filter is contaminated with metal, you should The method most often used in overcoming the effect of armature reaction is through the use of To what depth is the mica insulation between the commutator bars of a DC generator undercut? If a generator is equipped with a vibrator-type voltage regulator, the actual time the voltage regulator points remain open Bonding connections should be tested for During inspection of the terminal strips of an aircraft electrical system, it should be determined that The type of electric wire terminals used for most aircraft applications, in addition to providing good current carrying capabilities, are designed primarily Which of the following must be accomplished when installing an anticollision light? A circuit protection device called a current limiter is essentially a slow-blow fuse and is designed to be used in 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 CSD generators are usually cooled by The pin section of an AN/MS connector is normally installed on Static inverters are electronic devices that change DC to AC with the When a diode is checked for an open circuit or a short circuit, it should be 4V. a switch in the cockpit. It will take overload for a short period. opening the shunt field circuit. the component has continuity and is not open. more current at low RPM than at high RPM. Mechanical strength, ease of installation, amount of current to be carried. parallel to each other and in series with the switch. Ring. The number of turns of wire in the coil and the amount of current (amperes) passing through the coil. Capacity matches the needs of the circuit. wiring from too much current. Short in the up limit switch. Three remove and replace the IDG. interpoles Equal to the width of the mica. depends on the load carried by the generator. resistance value. the terminal studs are anchored against rotation. to prevent circuit failure due to terminal disconnection. Install a switch independent of the position light switch. heavy power circuits. a stepdown transformer and a rectifier. oil spray. the ground side of a circuit. use of an oscillator. disconnected from the circuit. How can the direction of rotation of a DC electric motor be changed? 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 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 What kind of switch should you install in a single wire circuit that required the switch to be manually held in the ON position? When handling a high voltage capacitor in an electrical circuit, be sure it If it is necessary to use an electrical connector where it may be exposed to moisture, the mechanic should Circuits that must be operated only in an emergency or whose inadvertent activation could endanger a system frequently employ Electric circuits are protected from overheating by The commutator of a generator How are generators rated? 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 How can it be determined if a transformer winding has some of its turns shorted together? 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 When approved, splices may be used to repair manufactured harnesses or installed wiring. The maximum number of splices permitted between any two connectors is When using an ohmmeter to check the continuity of a generator field coil, the coil should Which of the following is not one of the purposes of interpoles in a generator? When using the voltage drop method of checking circuit resistance, the What is a method used for restoring generator field residual magnetism? Some electric motors have two sets of field windings wound in opposite directions so that the The most common method of regulating the voltage output of a compound DC generator is to vary the The pole pieces or shoes used in a DC generator are a part of the What is required when operating two aircraft AC generators in parallel? One advantage of using AC electrical power in aircraft is What does a rectifier do? An ammeter in a battery charging system is for the purpose of indicating the One purpose of a growler test is to determine the presence of What is the appropriate method for installing pre-insulated terminal lugs and splices to electric wires? The poles of a generator are laminated to Reverse the electrical connections to either the field or armature windings. cross-sectional area. single-pole, single-throw (SPST), two-position switch. Single-pole, single-throw (SPST), two-position normally open (NO). is fully discharged before removing it from the circuit. use a special moisture-proof type. guarded switches. fuses. changes alternating current produced in the armature into direct current as it is taken from the armature. Amperes at rated voltage. strength of the magnetic field. The transformer will get hot in normal operation. be limited as to the number of cables to minimize damage from a single electrical fault. one show very low resistance if it is a series field coil. Reduce field strength. input voltage must be maintained at a constant value. Flash the fields. motor can be operated in either direction. current flowing through the shunt field coils. field assembly. Frequency and voltage must both be equal. greater ease in stepping the voltage up or down. Changes alternating current into direct current. rate of current used to charge the battery. a shorted armature. Using a crimping tool to secure the terminal lug. reduce eddy current losses. Which of the following copper electrical cable sizes should be selected to replace a No. 6 aluminum electrical cable? What is the principal advantage of the series-wound DC motor? What is the minimum bend radius for an electrical wire bundle? Electrical connectors used in the aircraft assemblies should meet which of the following specifications? No. 6. Which of the following are the major parts of a DC motor? Armature assembly, field assembly, brush assembly, and end frame. In a generator, what eliminates any possible sparking to the brush guides caused by the movement of the brushes within the holder? During inspection of an anticollision light installation for condition and proper operation, it should be determined that The most common method of attaching a pin or socket to an individual wire in an MS electrical connector is by The purpose of a rectifier in an electrical system is to change Which of the following should be accomplished in the installation of aircraft wiring? Which motor would be most likely to have an armature brake? The starting current of a series-wound DC motor, in passing through both the field and armature windings, produces a When considering an alteration, the criteria upon which the selection of electric cable size should be based are What is a cause of generator brush arcing? Which statement relating to electric wiring is true? 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 What is the color and orientation of the position lights for navigation on civil airplanes? 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 Which of the following factors must be taken into consideration when determining the wire size to use for an aircraft installation? A voltage regulator controls generator voltage by changing the What type of instrument is used for measuring very high values of resistance? 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 The primary considerations when selecting electric cable size are The voltage output of an alternator may be regulated by controlling the What is normally used to bond noncontinuous stainless steel aircraft components? If any one generator in a 24-volt DC system shows low voltage, the most likely cause is The voltage in an AC transformer secondary that contains twice as many loops as the primary will be High starting torque. Ten times the outside diameter of the bundle. Military Specifications (MS). The brush pigtail. the anticollision light can be operated independently of the position lights. crimping. alternating current to direct current. Locate the bundle above flammable fluid lines and securely clamp to structure. Landing light retraction motor. high starting torque. current-carrying capacity and allowable voltage drop. Low spring tension. 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. opposite the normal direction and through the shunt field in the normal direction. Left side, red; right side, green; rear aft, white. increasing the output of the low generator and decreasing the output of the high generator until they are equal. Allowable power loss, permissible voltage drop, current carrying capability of the conductor, type of load. resistance of the generator field circuit. Megohmmeter. residual voltage. current-carrying capacity and allowable voltage drop. voltage output of the dc exciter. Copper jumpers. an out-of-adjustment voltage regulator. greater and the amperage less than in the primary. 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. How should the splices be arranged if several are to be located Staggered along the length of the bundle. in an electrical wire bundle? In aircraft electrical systems, automatic reset circuit breakers should not be used as circuit protective devices. individual strands will break easily after being Aluminum wire must be stripped very carefully because nicked. If a wire is installed so that it comes in contact with some Pass through conduit. moving parts, what protection should be given the wire? The nominal rating of electrical switches refers to continuous current rating with the contacts closed. If the (+) terminal of a voltmeter is connected to the (-) terminal of the source voltage and the (-) terminal of the backwards meter is connected to the (+) terminal of the source voltage, the voltmeter will read To help minimize radio interference a capacitor will largely eliminate and provide a steady direct current if the capacitor parallel. is connected to the generator in Aircraft electrical junction boxes located in a fire zone are stainless steel. usually constructed of A battery-generator system provides direct current. On installations requiring alternating current from the batteryan inverter. generator system, it is necessary to have What is the purpose of the selection of derated switches for To obtain reasonable switch efficiency and service known continuous load current applications? life. Which type of DC generator is not used as an airplane Series wound. generator? When adding a rheostat to a light circuit to control the light series with the light. intensity, it should be connected in Which of the following is most likely to cause thermal runaway Excessive current draw from the battery. in a nickel-cadmium battery? Residual voltage is a result of magnetism in the field shoes. Why are the iron cores of most induction coils laminated? To reduce the effects of eddy currents. How should a coaxial cable be routed? As directly as possible. How does the magnetic brake used to stop rotation of an A friction brake is applied by a spring and released electric motor armature operate? by a magnet. How is a shunt-wound DC generator connected? Both fields are shunted across the armature. What is the frequency of an alternator dependent upon? RPM.