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51 Cards in this Set
- Front
- Back
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What are the advantages of using transformers
and transformer rectifiers vice inverters and dynamotors for supplying aircraft power? |
Lightweight, more reliable, and simple to maintain
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What power system requirements do modern
naval aircraft have? |
120-/208-volt ac, 3 phase and 400 Hz
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What determines the voltage frequency of an
ac generator? |
The number of magnetic poles and the rotor rpm
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What are the two types of ac generators?
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The stator
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What supplies the output ac power of a generator?
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Three
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How many phases is an ac generator?
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Brush and brushless
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What are the advantages of a brushless generator
over a brush-type generator? |
Increased reliability and greater operating time between overhaul
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What is a prime mover?
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A device that provides the driving force for a generator
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What is the purpose of a CSD?
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Convert variable engine speed to a constant speed output
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What are inverters?
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An emergency source of ac power when normal ac power fails
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In an inverter, what converts electrical energy
to mechanical energy? |
The dc motor
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On what does the rating of an aircraft inverter
depend? |
The equipment that it will supply
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What is the purpose of a transformer?
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To convert an input ac voltage into a usable ac output voltage by either stepping
up or stepping down that voltage |
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What is the function of a transformer
rectifier? |
To convert ac input voltage to a dc output voltage
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What is the only moving part in a transformer
rectifier? |
The cooling fan
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What is the difference between an autotransformer
and an ordinary transformer? |
An autotransformer has one winding that is common to both primary and
secondary windings |
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Autotransformers offer savings in both size
and costs over conventional units. When are these savings greatest? |
When the turns ratio is less than 2:1
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What are the two general types of instrument
transformers? |
Current and potential
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What are the ways in which emergency power
is supplied to naval aircraft? |
Aircraft storage batteries, auxiliary power units, and hydraulic motor driven
generator |
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Q1-20. What components maintain the aircraft (a/c)
storage battery in a charged state? |
Ac generator and transformer rectifier
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What are the two most common types of a/c
storage batteries in use today and what are the colors of each? |
Lead-acid which have a red case and nickel-cadmium which have a blue case
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What manual is used for information on
securing, storing, servicing, and handling a/c storage batteries? |
NAVAIR 17-15BAD-1
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On a VLAB, what is the purpose of the vent
nozzles? |
The upper nozzle is connected to a tube that supplies definite pressure on the
battery while in flight. The lower nozzle is connected to a negative pressure tube, allowing battery acid to drain without damaging the aircraft |
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The sump jar of a VLAB system contains a felt
pad moistened with what? |
Sodium bicarbonate
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In a VLAB system, what is the purpose of the
sump jar and the felt pad? |
To neutralize the gases and excess battery solution
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What type of electrolyte is used in a SLAB?
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A mixture of sulfuric acid and water
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In a SLAB, how is electrolyte immobilization
accomplished? |
By using a gel or special mats to absorb electrolyte
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What is considered the fundamental unit of a
NICAD battery? |
The cell
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What are the types of cells used in NICAD
batteries? |
Vented and sealed
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What is the nominal value of a NICAD battery
cell? |
1.26 volts dc
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Why can the hydraulic driven emergency
generator only power a small number of circuits? |
The kVA rating is too low
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What causes the rotor in the generator to
turn? |
The hydraulic motor
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What helps to maintain generator output frequency?
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The motor converts 3000 pounds per square inch of fluid to a constant speed
rotation |
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How is the generator cooled?
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By the hydraulic fluid
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What is the purpose of the motor-generator
control? |
It provides voltage regulation and fault detection of the generator output
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What is the function of the solenoid control
valve? |
It is de-energized when primary electrical power is lost and allows hydraulic
fluid to be routed to the hydraulic motor to drive the generator |
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What is the function of an APU?
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To supply pneumatic power for starting engines and operating air conditioning
systems, electrical power for in-flight emergencies, and ground maintenance |
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What is needed for APU starting
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Aircraft battery and fuel
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On a GTCP-95, what drives the generator?
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Shaft power at the main output drive pad
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What are the two main sections of an APU?
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Accessory assembly and compressor/turbine assembly
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The electrical system of an APU consists of
what components? |
Holding relays, oil pressure switch, centrifugal switch assembly, hour meter, and
wiring harness |
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APU ignition cuts out at what rpm?
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95%
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What is the purpose of the centrifugal speed
switch assembly? |
It controls the sequence of operation of various electrical components
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How many sub-switches make up the
centrifugal speed switch assembly? |
Three
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How are the centrifugal speed switches
adjusted? |
By using an adjustment screw to apply spring tension to the lever arm
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What are the functions of each switch?
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35%—shuts the starter down; 95%—arms load control circuit, starts hour meter,
and shuts off ignition; 106%—overspeed protection (shuts down the APU during an overspeed condition) |
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Changing the setting of the 35% switch also
affects what? |
The settings of the 95% and 106% switches
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How does the 106% switch shut down the
APU? |
When the switch is actuated it cuts off fuel flow, causing the APU to shut down
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At what rpm is the starter disengaged?
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35%
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What could happen to the starter if the
dropout relay fails? |
The starter may fail internally due to an overheat or overspeed condition
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Why do we use external electrical power on
aircraft? |
It provides ground crews with electrical power for servicing, fueling, and
performing maintenance actions |
