ASA POWERPLANT ORALS EXAM 2
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What is used to maintain a constant frequency of alternating current that is produced by an AC
alternator driven by an aircraft turbine engine?
A hydraulic constant-speed drive unit between the engine and the alternator
What three things must be synchronized before a three-phase AC generator can be connected to a bus
that is being served by another generator?
The voltage, the frequency, and the phase rotation of the generators
What must be done to reverse the direction of rotation of the armature of a DC electric motor?
The current flow must be reversed through the armature or the field windings, but not through both of
them
Does a series-wound DC motor have a high or a low starting torque?
A high starting torque
Which aircraft electrical circuit does not normally contain a fuse or circuit breaker?
The starter motor circuit
When removing a battery from an aircraft, which connection should be removed first?
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,The ground connection must be disconnected first and connected last
What is meant by the effective voltage of sine wave alternating current?
The value of the alternating current that is needed to produce the same amount of heat as this value of
direct current
What is a starter-generator that is used with many of the smallest gas turbine engines?
A single-engine-mounted component that serves as a starter for starting the turbine engine. When the
engine is running, the circuitry can be shifted so it acts as a compound-wound generator
When should aircraft wiring be installed in a conduit?
When the wiring passes through an area in the aircraft where open wiring could likely be damaged, such
as through a wheel well
What is meant by the viscosity of engine lubricating oil?
The resistance of the oil to flow
What is meant by a wet sump lubrication system?
A lubrication system in which the oil is carried inside the engine itself
What is meant by a dry sump lubrication system?
A lubrication system in which the oil is carried in a tank that is not a part of the engine
How is oil temperature controlled in an aircraft reciprocating engine?
Hot oil is directed through the core of the oil cooler, but cold oil is directed around the outside of the
core so it will not be further cooled
Is the oil temp shown on the aircraft instrument panel the temp of the oil entering the engine or of the
oil leaving the engine?
It is the temp of the oil entering the engine
What is the purpose of oil dilution in a reciprocating engine?
When very cold weather is anticipated, gasoline can be mixed with the lubricating oil before the engine
is shut down. This reduces the viscosity of the oil and makes starting easier. When the engine is running,
the gasoline evaporates out of the oil
What is the function of the hopper in the oil tanks used with some reciprocating engine?
Hoppers are a part of the oil dilution system. Only the oil in the hopper is diluted. This speeds up dilution
and requires less gasoline
What happens to the gasoline that is used to dilute the oil in the crankcase of an aircraft reciprocating
engine?
When the engine is running and the oil is warm, the gasoline evaporates out of it
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,What is the purpose of the sludge plugs in the crankshaft of a reciprocating engine?
They trap sludge that is in the oil and hold it until the engine is disassembled at overhaul
Which pump is the larger in a dry-sump lubricating system, the pressure pump or the scavenger pump
The scavenger pump has a greater volume
Why do full-flow oil filters have a spring-operated bypass valve in them?
In case the filter should plug up so it cannot pass any oil, the bypass valve will open and allow unfiltered
oil to flow through the system
What is the function of a fuel-oil heat exchanger in the lubrication system of a turbojet engine?
This allows heat from the oil to warm the fuel so ice will not form on the fuel filters
What kind of oil is used in most turbojet engines?
Synthetic oil
Where are the last chance oil filters located in a turbojet engine?
They are located inside the engine just ahead of the nozzles that spray oil onto the bearings
Where is the oil tank in a dry-sump reciprocating engine vented?
To the engine crankcase
What information must be displayed around the oil filter opening for a turbojet engine?
The word "oil" and the permissible oil designations, or references to the Airplane Flight Manual for the
permissible oil designations
What is the function of the oil control rings on the piston of an aircraft reciprocating engine?
They maintain the proper quantity of oil between the piston and the cylinder wall
What is meant by a spectrometric oil analysis?
It is a program in which a sample of oil is taken from the engine at regular intervals and sent to a
laboratory, where it is burned in an electric arc. The resulting light is analyzed for the wavelengths of the
elements that are present in the oil sample. Traces of aluminum, copper, and iron in the oil indicate
wear of the pistons or wrist pin plugs (aluminum), cylinder walls or piston rings (iron), main bearings or
bushings (copper). A single sample is meaningless. there must be a series of samples taken at regular
intervals to measure the change in the amounts of these metals
What indication would a pilot have if his oil supply was low?
The oil temp would be high and the oil pressure would be low
What is meant by a hot-tank lubrication system?
A lubrication system in which the oil cooler is located in the pressure subsystem
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, What is meant by a cold-tank lubrication system?
A lubrication system in which the oil cooler is located in the scavenge subsystem. The oil that is returned
to the tank has been cooled
What is the main advantage of a magneto ignition system over a battery ignition system for an aircraft
reciprocating engine?
A magneto has its own source of electrical energy, and it is not dependent upon the battery
What is the function of the capacitor in a magneto?
The capacitor minimizes arcing at the breaker points, and it speeds up the collapse of the primary
current as the breaker points open
What is a compensated magneto cam, and on what kind of engine is one used?
A compensated cam is a special cam used in magnetos mounted on high-performance radial engines.
The cam has one lobe for each cylinder, and the lobes are ground in such a way that the breaker points
open when the pistons in the different cylinders are the same linear distance from top center
What is the significance of the numbers on the distributor of an aircraft magnet?
These numbers are the sparking order of the magneto, not the firing order of the engine
What happens in a magneto ignition system when the ignition switch is placed in the Off position?
The primary circuit is connected to ground
What is the reason for having a low-tension ignition system on some aircraft?
Low-tension magnetos are used on aircraft that fly at high altitues where there is a problem with flash-
over in the high-tension magneto distributer
What is the basic difference between a low-tension magneto and a high-tension magneto?
The low-tension ignition system has only one coil in the magneto, and it used a carbon-brush-type
distributor. Low voltage is distributed to high-tension transformers that are located on the heads of
each cylinder. A high-tension magneto produces high voltage in the magneto coil, and it is sent to the
correct spark plug by the built-in high voltage distributor
What is meant by an All Weather spark plug?
A shielded spark plug that has a recess in the shielding in which a resilient grommet on the ignition lead
forms a watertight seal
What is meant by the reach of a spark plug?
The length of the threads on the spark plug that screw into the cylinder head
What is the difference between a hot spark plug and a cold spark plug?
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