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ASA POWERPLANT ORALS FINAL 2026 100%
PASS ASSURED EXAMINATION SOLUTIONS
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
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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
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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
, 4 | Page
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
ASA POWERPLANT ORALS FINAL 2026 100%
PASS ASSURED EXAMINATION SOLUTIONS
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
,2 | Page
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
,3 | Page
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
, 4 | Page
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
