# Powerplant Part 5

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1. 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
2. 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 condition is normal for this type of motor.
3. The stationary field strength in a direct current generator is varied
4. What type of electric motor is generally used with a direct-cranking engine starter?
Direct Current, Series-wound motor
5. Upon what does the output frequency of an ac generator (alternator) depend?
The speed of rotation and the number of field poles.
6. 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 builds up and opposus the applied EMF, thus reducing the current flow through the armature.
7. Alternators (ac generators) that are driven by a constant-speed drive (CSD) mechanism are used to regulate the alternator to a constant
Hertz Output
8. What is used to polish commutators or slip rings?
Very Fine Sandpaper
9. If a generator is malfunctioning, its voltage can be reduced to residual by actuating the
Generator Master Switch
10. 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.
11. 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.
12. 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 negative terminal and out the positive terminal
13. 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.
14. 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.
15. 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
16. As the generator load is increased (within its rated capacity), the voltage will
Remain constant and the amperage output will increase.
17. As the flux density in the field of a dc generator increases and the current flow to the system increases, the
Force required to turn the generator increases.
18. 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.
19. 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
An open armature.
20. Why is it unnecessary to flash the field of the exciter on a brushless alternator?
Permanent magnets are installed in the main field poles.
21. One way that the automatic ignition relight systems are activated on gas turbine engines is by a
Drop in compressor discharge pressure.
22. How are the rotor windings of an aircraft alternator usually excited?
By a variable direct current.
23. What precaution is usually taken to prevent electrolyte from freezing in a lead acid battery?
Keep the battery fully charged.
24. What is the ampere-hour rating of a storage battery that is designed to deliver 45 amperes for 2.5 hours?
112.5 Ampre-hour
25. How many hours will a 140 ampere-hour battery deliver 15 amperes?
9.33 Hours
26. What is a basic advantage of using ac for electrical power for a large aircraft?
AC systems operate at a higher voltage than DC systems and therefore use less current and can use smaller and ligher wiring.
27. What are two types of ac motors that are used to produce a relatively high torque?
Three phase induction and capacitor start.
28. (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 No.2 are true
29. What is the frequency of most aircraft alternating current?
400 Hertz
30. The reason for flashing the field in a generator is to
Restore correct polarity and/or residual magnetism to the field poles.
31. The part of a dc alternator power system that prevents reverse flow of current from the battery to the alternator is the
Rectifier
32. The generating system of an aircraft charges the battery by using
Constant voltage and varying current
33. The constant current method of charging a ni-cad battery
Is the method most effective in maintaining cell balance.
34. (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
35. Which of the following aircraft circuits does NOT contain a fuse/circuit breaker?
Starter Circuit.
36. The maximum number of terminals that may be connected to any one terminal stud in an aircraft electrical system is
Four
37. What is the maximum number of bonding jumper wires that may be attached to one terminal grounded to a flat surface?
Four
38. As a general rule, starter brushes are replaced when they are approximately
One-half their original length.
39. When installing an electrical switch, under which of the following conditions should the switch be derated from its nominal current rating?
Direct-current motor circuits.
40. The resistance of the current return path through the aircraft is always considered negligible, provided the
41. 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.
42. When does current flow through the coil of a solenoid-operated electrical switch?
Continually, as long as the control circuit is complete.
43. 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
44. What type of lubricant may be used to aid in pulling electrical wires or cables through conduits?
Soapstone Talc
45. Which of the following is regulated in a generator to control its voltage output?
The strength of the field
46. Bonding jumpers should be designed and installed in such a manner that they
Provide a low electrical resistance in the ground circuit.
47. 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.
48. Arcing at the brushes and burning of the commutator of a motor may be caused by
Weak brush springs.
49. The maximum allowable voltage drop between the generator and the bus bar is
2 percent of the regulated voltage.
50. ON-OFF two position engine electrical switches should be installed
So the ON position is reached by a forward or upward motion
51. When selecting an electrical switch for installation in an aircraft circuit utilizing a direct current motor,
A derating factor should be applied
52. When installing electrical wiring parallel to a fuel line, the wiring should be
Above the fuel line.
53. (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 Ampres
54. What speed must an eight-pole ac generator turn to produce 400-Hertz ac?
6,000 RPM
55. How many basic types of circuit breakers are used in powerplant installation electrical systems?
Three
56. 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
57. Which Federal Aviation Regulation requirement prevents the use of automatic reset circuit breakers?
14 CFR Part 23
58. The time/current capacities of a circuit breaker or fuse must be
Below those of the associated conductor
59. (1) Most modern aircraft use circuit breakers rather than fuses to protect their electrical circuits.
Only No.1 is true
60. Electrical switches are rated according to the
Voltage and the current they can control
61. Electrical circuit protection devices are installed primarily to protect the
Wiring
62. (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 are true
63. 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
64. What is the smallest terminal stud allowed for aircraft electrical power systems?
No.10
65. A typical barrier type aircraft terminal strip is made of
Paper base phenolic compound
66. A term commonly used when two or more electrical terminals are installed on a single lug of a terminal strip is
stacking
67. (1) Electrical wires larger than 10 gauge use uninsulated terminals.
Only No.1 is true.
68. Aircraft electrical wire size is measured according to the
American Wire Gauge System
69. Aircraft copper electrical wire is coated with tin, silver, or nickel in order to
Prevent Oxidization
70. Which of the following fire detectors are commonly used in the power section of an engine nacelle?
Rate-of-temperature-rise detectors
71. What is the function of a fire detection system?
To activate a warning device in the event of a powerplant fire.
72. (Refer to Figure 2.) Determine the fire-extinguisher container pressure limits when the temperature is 75°F.
338 minimum and 424 maximum
73. How are most aircraft turbine engine fire-extinguishing systems activated?
Electrically Discharged cartridges.
74. How does carbon dioxide (CO(2)) extinguish an aircraft engine fire?
Contact with air converts the liquid into snow and gas which smothers the flame.
75. What retains the nitrogen charge and fire-extinguishing agent in a high rate of discharge (HRD) container?
Breakable disk and Fusible disk.
76. A continuous-loop fire detector is what type of detector?
Overheat Detector
77. What is the operating principle of the spot detector sensor in a fire detection system?
A bimetallic thermoswitch that closes when heated to a high temperature.
78. How is the fire-extinguishing agent distributed in the engine section?
Spray Nozzles and Preforated Tubing.
79. Which of the following is the safest fire-extinguishing agent to use from a standpoint of toxicity and corrosion hazards?
Bromotrifluoromethane (Halon 1301)
80. Which of the following is NOT used to detect fires in reciprocating engine nacelles?
Smoke Detectors.
81. What is the principle of operation of the continuous-loop fire detector system sensor?
Core resistance material which prevents current flow at normal temperatures.
82. The most satisfactory extinguishing agent for a carburetor or intake fire is
Carbon Dioxide
83. The explosive cartridge in the discharge valve of a fire-extinguisher container is
A life-dated unit
84. Why does one type of Fenwal fire detection system use spot detectors wired in parallel between two separate circuits?
So that a single fault may exist in the system without sounding a false alarm.
85. Which of the following fire detection systems measures temperature rise compared to a reference temperature?
Thermocouple
86. The pulling out (or down) of an illuminated fire handle in a typical large jet aircraft fire protection system commonly accomplishes what events?
Closes fuel shutoff, closes hydraulic shutoff, disconnect the generator field, and arms the fire-extinguishing system.
87. A fire detection system operates on the principle of a buildup of gas pressure within a tube proportional to temperature. Which of the following systems does this statement define?
Lindberg continuous-element system
88. The fire detection system that uses a single wire surrounded by a continuous string of ceramic beads in a tube is the
Fenwal System
89. The fire detection system that uses two wires imbedded in a ceramic core within a tube is the
Kidde System
90. A fuel or oil fire is defined as a
Class B Fire
91. A fire detection system that operates on the rate-of-temperature rise is a
Thermocouple System
92. A fire involving energized electrical equipment is defined as a
Class C fire
93. Two continuous-loop fire detection systems that will not test due to a broken detector element are the
Kidde System and Fenwal System
94. In a fixed fire-extinguishing system, there are two small lines running from the system and exiting overboard. These line exit ports are covered with a blowout type indicator disc. Which of the following statements is true?
When the yellow indicator system is missing, it indicates the fire-extinguishing system has been normaly discharged.
95. The most satisfactory extinguishing agent for an electrical fire is
Carbon Dioxide
96. Which of the following fire detection systems will detect a fire when an element is inoperative but will not test when the test circuit is energized?
the Kidde System and the Fenwal System
97. Which of the following fire detection systems uses heat in the normal testing of the system?
The thermalcouple system and the Lindberg system
98. After a fire is extinguished, or overheat condition removed in aircraft equipped with a Systron-Donner fire detector, the detection system
Automaticaly Resets
99. The use of water on class D fires
will cause the fire to burn more violently and can cause explosion
100. For fire detection and extinguishing purposes, aircraft powerplant areas are divided into fire zones based on
The volume and smoothness of the airflow through engine compartments.
101. (Refer to Figure 3.) What are the fire-extinguisher container pressure limits when the temperature is 50°F?
475- 625 PSIG
 Author: robsok ID: 101193 Card Set: Powerplant Part 5 Updated: 2011-09-12 04:58:20 Tags: Powerplant Folders: Description: Engine Fire Protection Systems and Engine Electrical Systems Show Answers: