ASA Powerplant Oral Study Guide Questions
And Answers
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.
,ASA Powerplant Oral Study Guide Questions
And Answers
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.
Why are both the hot and cold valve clearances given for most
radial engines? -
correct answer ✅The hot clearance is given for valve timing
purposes. The timing is adjusted with the valves in cylinder number
,ASA Powerplant Oral Study Guide Questions
And Answers
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
, ASA Powerplant Oral Study Guide Questions
And Answers
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 a valve.
Would excessive valve clearance cause the valves to open early or
late? -
correct answer ✅Excessive valve 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.
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
And Answers
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.
,ASA Powerplant Oral Study Guide Questions
And Answers
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.
Why are both the hot and cold valve clearances given for most
radial engines? -
correct answer ✅The hot clearance is given for valve timing
purposes. The timing is adjusted with the valves in cylinder number
,ASA Powerplant Oral Study Guide Questions
And Answers
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
, ASA Powerplant Oral Study Guide Questions
And Answers
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 a valve.
Would excessive valve clearance cause the valves to open early or
late? -
correct answer ✅Excessive valve 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.
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
