ASA POWERPLANT ORALS FINAL EXAM (VERSION A
AND B) QUESTIONS AND VERIFIED ANSWERS ||
LATEST UPDATE 2025/2026
What is the main advantage of a horizontally opposed engine over a radial engine
for powering modern aircraft? - CORRECT ANSWER smaller frontal area and
easier to streamline.
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 other pistons are connected to the master rod with link rods
Of what material are most piston rings made? - CORRECT ANSWER grey cast
iron
What is the reason for using hydraulic valve lifters in an aircraft engine? -
CORRECT ANSWER keep all of the clearance out of the valve operating
mechanism, decreases wear of valve train components
At what speed does the camshaft turn, relative to the crankshaft speed in a
horizontally opposed engine? - CORRECT ANSWER camshaft is one half the
speed of crankshaft
,What kind of main bearings are used in a horizontally opposed engine? -
CORRECT ANSWER steel backed lead alloy bearings
On what stroke is the piston of a reciprocating engine when the intake valve begins
to open? - CORRECT ANSWER exhaust
On what stroke is the piston of a reciprocating engine when the exhaust valve
begins to open? - CORRECT ANSWER power
Why are both the hot and cold valve clearances given for most radial engines? -
CORRECT ANSWER hot clearance is for valve timing. timing adjusted with
valves in cylinder 1 set with hot clearance then adjusted to cold clearance
What is meant by a cam-ground piston - CORRECT ANSWER A piston that is
not perfectly round. . When the piston reaches operating temperature, the metal
expands enough that the piston becomes perfectly round.
Where is the piston in a reciprocating engine when the ignition spark occurs? -
CORRECT ANSWER before top dead center on the compression stroke
What is meant by a full-floating wrist pin? - CORRECT ANSWER pin not
clamped in either piston or connecting rod
Why do most aircraft reciprocating engines use more than one spring on each
valve? - CORRECT ANSWER for different frequencies/rpms
Would excessive valve clearance cause the valves to open early or late? -
CORRECT ANSWER open late 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, oil control, oil wiper
Why are some exhaust valves partially filled with metallic sodium? - CORRECT
ANSWER The metallic sodium melts at engine operating temperature 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 , the mixture explodes rather than burns.
Why is a compression check important for determining the condition of an aircraft
reciprocating engine? - CORRECT ANSWER to check condition of seals
between piston ring and cylinder wall and valves and thier seats
What is meant by the compression ratio of a reciprocating engine? - CORRECT
ANSWER ratio of volume of cylinder with piston at bottom vs piston at top
What are the two basic sections of a turbine engine? - CORRECT ANSWER hot
and cold
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 convert velocity energy to pressure energy and change direction of air
, What are three types of combustors used on aircraft turbine engines? - CORRECT
ANSWER can, annular, can-annular
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 direct gasses as they leave combustors so they will turn
turbine wheel with maximum efficiency
What is meant by a free-turbine turboshaft engine - CORRECT ANSWER A
turboshaft engine that has a turbine wheel, 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 fiction, ball, roller
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.
11. Where can you find the limits of repair allowed for the compressor blades of an
aircraft turbine engine? - CORRECT ANSWER manufacturer service manual
AND B) QUESTIONS AND VERIFIED ANSWERS ||
LATEST UPDATE 2025/2026
What is the main advantage of a horizontally opposed engine over a radial engine
for powering modern aircraft? - CORRECT ANSWER smaller frontal area and
easier to streamline.
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 other pistons are connected to the master rod with link rods
Of what material are most piston rings made? - CORRECT ANSWER grey cast
iron
What is the reason for using hydraulic valve lifters in an aircraft engine? -
CORRECT ANSWER keep all of the clearance out of the valve operating
mechanism, decreases wear of valve train components
At what speed does the camshaft turn, relative to the crankshaft speed in a
horizontally opposed engine? - CORRECT ANSWER camshaft is one half the
speed of crankshaft
,What kind of main bearings are used in a horizontally opposed engine? -
CORRECT ANSWER steel backed lead alloy bearings
On what stroke is the piston of a reciprocating engine when the intake valve begins
to open? - CORRECT ANSWER exhaust
On what stroke is the piston of a reciprocating engine when the exhaust valve
begins to open? - CORRECT ANSWER power
Why are both the hot and cold valve clearances given for most radial engines? -
CORRECT ANSWER hot clearance is for valve timing. timing adjusted with
valves in cylinder 1 set with hot clearance then adjusted to cold clearance
What is meant by a cam-ground piston - CORRECT ANSWER A piston that is
not perfectly round. . When the piston reaches operating temperature, the metal
expands enough that the piston becomes perfectly round.
Where is the piston in a reciprocating engine when the ignition spark occurs? -
CORRECT ANSWER before top dead center on the compression stroke
What is meant by a full-floating wrist pin? - CORRECT ANSWER pin not
clamped in either piston or connecting rod
Why do most aircraft reciprocating engines use more than one spring on each
valve? - CORRECT ANSWER for different frequencies/rpms
Would excessive valve clearance cause the valves to open early or late? -
CORRECT ANSWER open late 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, oil control, oil wiper
Why are some exhaust valves partially filled with metallic sodium? - CORRECT
ANSWER The metallic sodium melts at engine operating temperature 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 , the mixture explodes rather than burns.
Why is a compression check important for determining the condition of an aircraft
reciprocating engine? - CORRECT ANSWER to check condition of seals
between piston ring and cylinder wall and valves and thier seats
What is meant by the compression ratio of a reciprocating engine? - CORRECT
ANSWER ratio of volume of cylinder with piston at bottom vs piston at top
What are the two basic sections of a turbine engine? - CORRECT ANSWER hot
and cold
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 convert velocity energy to pressure energy and change direction of air
, What are three types of combustors used on aircraft turbine engines? - CORRECT
ANSWER can, annular, can-annular
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 direct gasses as they leave combustors so they will turn
turbine wheel with maximum efficiency
What is meant by a free-turbine turboshaft engine - CORRECT ANSWER A
turboshaft engine that has a turbine wheel, 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 fiction, ball, roller
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.
11. Where can you find the limits of repair allowed for the compressor blades of an
aircraft turbine engine? - CORRECT ANSWER manufacturer service manual
