CURRENTLY TESTING EXAMS QUESTIONS OF ASA Powerplant Orals EXAM 2 WITH ACTUAL CORRECT DETAILED ANSWERS
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Course
ASA Powerpla
Institution
ASA Powerpla
CURRENTLY TESTING EXAMS QUESTIONS
OF ASA Powerplant Orals EXAM 2 WITH
ACTUAL CORRECT DETAILED ANSWERS CURRENTLY TESTING EXAMS QUESTIONS
OF ASA Powerplant Orals EXAM 2 WITH
ACTUAL CORRECT DETAILED ANSWERS CURRENTLY TESTING EXAMS QUESTIONS
OF ASA Powerplant Orals EXAM 2 WITH
ACTUAL CORREC...
CURRENTLY TESTING EXAMS QUESTIONS
OF ASA Powerplant Orals EXAM 2 WITH
ACTUAL CORRECT DETAILED ANSWERS
What is the main advantage of a horizontally opposed engine over a radial engine for powering modern
aircraft? - ANSWER-The horizontally opposed engine has a much smaller frontal area and is easier to
streamline than a radial engine
How many throws are there in the crankshaft of a six-cylinder horizontally opposed engine? -
ANSWER-Six
What kind of connecting rod arrangement is used in a radial engine? - ANSWER-A master rod connects
the single throw of the crankshaft with a piston. All of the other pistons are connected to the master
rod with link rods
Of what material are most piston rings made? - ANSWER-Gray cast iron
What is the reason for using hydraulic valve lifters in an aircraft engine? - ANSWER-Hydraulic valve
lifters keep all of the clearance out of the valve operating mechanism. This decreases the wear of the
valve train components
At what speed does the camshaft turn, relative to the crankshaft speed in a horizontally opposed engine?
- ANSWER-The camshaft turns at one half of the crankshaft speed
What kind of main bearings are used in a horizontally opposed engine? - ANSWER-Steel-backed, lead-
alloy bearing inserts
,On what stroke is the piston of a reciprocating engine when the intake valve begins to open? -
ANSWER-On the exhaust stroke
On what stroke is the piston of a reciprocating engine when the exhaust valve begins to open? -
ANSWER-On the power stroke
Why are both the hot and cold valve clearances give for most radial engine? - ANSWER-The hot
clearance is given for valve timing purposes. The timing is adjusted with the valves in cylinder number
one, set with the hot clearance. When the timing is set, all of the valves are adjusted to their cold
clearance.
What is meant by a cam-ground piston? - ANSWER-A piston that is not perfectly round. Its dimension
parallel with the wrist pin is several thousandths of an inch less than its dimension perpendicular to the
wrist pin. When the piston reaches operating temperature, the metal in the piston pin boss expands
enough that the piston becomes perfectly round
Where is the piston in a reciprocating engine when the ignition spark occurs? - ANSWER-About 30
degrees of crankshaft rotation before the piston reaches top center on the compression stroke
What is meant by a full-floating wrist pin? - ANSWER-A wrist pin that is not clamped in either the
piston or the connecting rod. Full-floating wrist pins are kept from scoring the cylinder walls by soft
metal plugs in their ends
Why do most aircraft reciprocating engines use more than one spring on each valve? - ANSWER-By
using more than one spring and having the wire diameter and pitch of the springs different, valve float is
minimized. The springs have different resonant frequencies, so at least one spring will always be exerting
a force on the valve
Would excessive valve clearance cause the valves to open early or late? - ANSWER-Excessive clearance
will cause the valve to open late and close early
What is the purpose of valve overlap in a reciprocating engine? - ANSWER-Valve overlap allows the
inertia of the exhaust gases leaving the cylinder to help the fresh induction charge start flowing into the
cylinder
,What type of piston rings are installed on the pistons of an aircraft reciprocating engine? - ANSWER-
Compression rings, oil control rings, and oil wiper rings
Why are some exhaust valves partially filled with metallic sodium? - ANSWER-The metallic sodium
melts at engine operating temperature and sloshes back and forth inside the hollow valve. It picks up
heat from the valve head and transfers it into the valve stem, so it can be transferred to the cylinder
head through the valve guide
What causes detonation in an aircraft engine? - ANSWER-Excessive heat and pressure in the engine
cylinder causes the fuel-air mixture to reach its critical pressure and temperature. Under these
conditions, the mixture explodes rather than burns. This explosion is called detonation
Why is a compression check important for determining the condition of an aircraft reciprocating engine?
- ANSWER-A compression check can determine the condition of the seal between the piston rings and
the cylinder walls, and the seal between the intake and exhaust valves and their seats
What is meant by the compression ratio of a reciprocating engine? - ANSWER-The ratio of the volume
of the cylinder with the piston at the bottom of its stroke to the volume with the piston at the top of its
stroke
What are the two basic sections of a turbine engine? - ANSWER-The hot section and the cold section
What are the two basic types of compressors that are used in aircraft turbine engines? - ANSWER-
Axial-flow and centrifugal
What is the purpose of the stators in an axial-flow compressor? - ANSWER-The stators convert some
velocity energy into pressure energy and change the direction of the air so it is proper for the next
stage of rotors
What are three types of combustors used on aircraft turbine engines? - ANSWER-Can-type, annular-
type, and can-annular-type
How many igniters are there normally in an aircraft turbine engine? - ANSWER-Two
, What is the main purpose of the turbine nozzle in an aircraft turbine engine? - ANSWER-The turbine
nozzle directs the hot gases as they leave the combustors so they will turn the turbine wheel with
maximum efficiency
What is meant by a free-turbine turboshaft engine? - ANSWER-A turboshaft engine that has a turbine
wheel, or stage of turbine wheels, that is not used to drive the compressor of the gas generator section
of the engine. This free turbine drives the propeller in a turboprop engine or the transmission and rotor
of a helicopter
Why do some axial-flow turbine engines have more than one set of turbines and compressors? -
ANSWER-A two-spool turbine engine has a low-pressure and a high-pressure compressor, each driven
by its own turbine. The two independent systems operate at the speed at which they are most efficient
What kind of bearings are used to support the rotor shaft of an aircraft turbine engine? - ANSWER-
Anti-friction bearings, such as ball bearings or roller bearings
What is meant by a turbofan engine? - ANSWER-An axial-flow turbine engine in which the first stage of
compressor blades are lengthened, so they can force air around the outside of the gas generator portion
of the engine
Where can you find the limits of repair allowed for the compressor blades of an aircraft turbine engine?
- ANSWER-In the FAA-approved service manual issued by the manufacturer of the engine
Why is it important that a turbojet engine be allowed to cool before it is shut down after it has been
operated at a high power setting? - ANSWER-If the engine is shut down while it is hot, there is a
possiblity that the shroud will contract around the turbine wheel and seize the rotor
What is meant by a hung start in a turbine engine? - ANSWER-A start in which ignition occurs, but the
engine does not accelerate to a self-sustaining speed
What is meant by a hot start in a turbine engine? - ANSWER-A start in which ignition occurs, but the
internal temperatures go high enough that they can damage the engine
What is meant by creep of the turbine blades? - ANSWER-A condition of permanent elongation of the
turbine blades. Creep is caused by the high temperatures and the high centrifugal loading imposed on
the blades
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