Asa Powerplant Oral Exam Latest Exam | All Questions And Correct
Answers | Already Graded A+ | Verified Answers | Study This One!
What is the main advantage of a horizontally opposed engine over a radial engine for powering
modern aircraft? - (CORRECT 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? -
(CORRECT ANSWER)Six
What kind of connecting rod arrangement is used in a radial engine? - (CORRECT 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? - (CORRECT ANSWER)Gray cast iron
What is the reason for using hydraulic valve lifters in an aircraft engine? - (CORRECT
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? - (CORRECT ANSWER)The camshaft turns at one half of the crankshaft speed
What kind of main bearings are used in a horizontally opposed engine? - (CORRECT
ANSWER)Steel-backed, lead-alloy bearing inserts
On what stroke is the piston of a reciprocating engine when the intake valve begins to open? -
(CORRECT ANSWER)On the exhaust stroke
On what stroke is the piston of a reciprocating engine when the exhaust valve begins to open? -
(CORRECT ANSWER)On the power stroke
1
,Why are both the hot and cold valve clearances give for most radial engine? - (CORRECT
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? - (CORRECT 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? - (CORRECT
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? - (CORRECT 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? -
(CORRECT 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? - (CORRECT
ANSWER)Excessive clearance will cause the valve to open late and close early
What is the purpose of valve overlap in a reciprocating engine? - (CORRECT 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? -
(CORRECT ANSWER)Compression rings, oil control rings, and oil wiper rings
2
,Why are some exhaust valves partially filled with metallic sodium? - (CORRECT
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? - (CORRECT 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? - (CORRECT 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? - (CORRECT 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? - (CORRECT ANSWER)The hot section
and the cold section
What are the two basic types of compressors that are used in aircraft turbine engines? -
(CORRECT ANSWER)Axial-flow and centrifugal
What is the purpose of the stators in an axial-flow compressor? - (CORRECT 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? - (CORRECT
ANSWER)Can-type, annular-type, and can-annular-type
3
, How many igniters are there normally in an aircraft turbine engine? - (CORRECT
ANSWER)Two
What is the main purpose of the turbine nozzle in an aircraft turbine engine? - (CORRECT
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? - (CORRECT 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? -
(CORRECT 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? -
(CORRECT ANSWER)Anti-friction bearings, such as ball bearings or roller bearings
What is meant by a turbofan engine? - (CORRECT 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? - (CORRECT 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? - (CORRECT ANSWER)If the engine is shut down while
4
Answers | Already Graded A+ | Verified Answers | Study This One!
What is the main advantage of a horizontally opposed engine over a radial engine for powering
modern aircraft? - (CORRECT 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? -
(CORRECT ANSWER)Six
What kind of connecting rod arrangement is used in a radial engine? - (CORRECT 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? - (CORRECT ANSWER)Gray cast iron
What is the reason for using hydraulic valve lifters in an aircraft engine? - (CORRECT
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? - (CORRECT ANSWER)The camshaft turns at one half of the crankshaft speed
What kind of main bearings are used in a horizontally opposed engine? - (CORRECT
ANSWER)Steel-backed, lead-alloy bearing inserts
On what stroke is the piston of a reciprocating engine when the intake valve begins to open? -
(CORRECT ANSWER)On the exhaust stroke
On what stroke is the piston of a reciprocating engine when the exhaust valve begins to open? -
(CORRECT ANSWER)On the power stroke
1
,Why are both the hot and cold valve clearances give for most radial engine? - (CORRECT
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? - (CORRECT 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? - (CORRECT
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? - (CORRECT 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? -
(CORRECT 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? - (CORRECT
ANSWER)Excessive clearance will cause the valve to open late and close early
What is the purpose of valve overlap in a reciprocating engine? - (CORRECT 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? -
(CORRECT ANSWER)Compression rings, oil control rings, and oil wiper rings
2
,Why are some exhaust valves partially filled with metallic sodium? - (CORRECT
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? - (CORRECT 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? - (CORRECT 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? - (CORRECT 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? - (CORRECT ANSWER)The hot section
and the cold section
What are the two basic types of compressors that are used in aircraft turbine engines? -
(CORRECT ANSWER)Axial-flow and centrifugal
What is the purpose of the stators in an axial-flow compressor? - (CORRECT 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? - (CORRECT
ANSWER)Can-type, annular-type, and can-annular-type
3
, How many igniters are there normally in an aircraft turbine engine? - (CORRECT
ANSWER)Two
What is the main purpose of the turbine nozzle in an aircraft turbine engine? - (CORRECT
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? - (CORRECT 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? -
(CORRECT 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? -
(CORRECT ANSWER)Anti-friction bearings, such as ball bearings or roller bearings
What is meant by a turbofan engine? - (CORRECT 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? - (CORRECT 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? - (CORRECT ANSWER)If the engine is shut down while
4
