ASA Powerplant Oral Study Guide with
Complete Solutions 2024 Graded A+
,1. What is the main advantage of a horizontally opposed engine over a radia
engine for powering modern aircraft?: The horizontally opposed engine has
a much smaller frontal area and is easier to streamline than a radial engine.
2. How many throws are there in the crankshaft of a six-cylinder horizontally
opposed engine?: Six.
3. What kind of connecting rod arrangement is used in a radial engine?: 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.
4. Of what material are most piston rings made?: Gray cast iron.
5. What is the reason for using hydraulic valve lifters in an aircraft engine?:
Hydraulic valve lifters keep all of the clearance out of the valve operatin
mechanism.
This decreases the wear of the valve train components.
6. At what speed does the camshaft turn, relative to the crankshaft speed in
a horizontally opposed engine?: The camshaft turns at one half of the
crankshaft speed.
7. What kind of main bearings are used in a horizontally opposed engine?:
Steel-backed, lead-alloy bearing inserts.
8. On what stroke is the piston of a reciprocating engine when the intake
valve begins to open?: On the exhaust stroke.
9. On what stroke is the piston of a reciprocating engine when the exhaust
valve begins to open?: On the power stroke.
10. Why are both the hot and cold valve clearances given for most rad
engines?: The hot clearance is given for valve timing purposes. The timing is
adjusted with the valves in cylinder number one, set with the hot clearan
When the timing is set, all of the valves are adjusted to their cold clearance.
11. What is meant by a cam-ground piston?: 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 reache
operating temperature, the metal in the piston pin boss expands enough that
the piston becomes perfectly round.
12. Where is the piston in a reciprocating engine when the ignition spa
occurs?: About 30 degrees of crankshaft rotation before the piston reaches top
center on the compression stroke.
13. What is meant by a full-floating wrist pin?: A wrist pin that is not clamped in
either the piston or the connecting rod. Full-floating wrist pins are kept fr
scoring the cylinder walls by soft metal plugs in their ends.
, 14. Why do most aircraft reciprocating engines use more than one spring on
each valve?: By using more than one spring and having the wire diameter and
pitch of the springs different, valve float is minimized. The springs have differen
resonant frequencies, so at least one spring will always be exerting a force on
a valve.
15. Would excessive valve clearance cause the valves to open early or late?:
Excessive valve clearance will cause the valve to open late and close early.
16. What is the purpose of valve overlap in a reciprocating engine?: Va
overlap allows the inertia of the exhaust gases leaving the cylinder to help the
fresh induction charge start flowing into the cylinder.
17. What type of piston rings are installed on the pistons of an aircraft
reciprocating engine?: Compression rings, oil control rings, and oil wiper ring
18. Why are some exhaust valves partially filled with metallic sodium?: 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.
19. What causes detonation in an aircraft engine?: Excessive heat and pressur
in the engine cylinder causes the fuel-air mixture to reach its critical pressure
and temperature. Under these conditions, the mixture explodes rather tha
burns. This explosion is called detonation.
20. Why is a compression check important for determining the condition of
an aircraft reciprocating engine?: 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.
21. What is meant by the compression ratio of a reciprocating engine?: 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.
22. What are the two basic sections of a turbine engine?: The hot section and
the cold section.
23. What are the two basic types of compressors that are used in aircr
turbine engines?: Axial-flow and centrifugal.
24. What is the purpose of the stators in an axial-flow compressor?: Th
stators convert some velocity energy into pressure energy and change th
direction of the air so it is proper for the next stage of rotors.
25. What are three types of combustors used on aircraft turbine engines?:
Can-type, annular-type, and can-annular type.
26. How many igniters are there normally in an aircraft turbine engine?: Two.
Complete Solutions 2024 Graded A+
,1. What is the main advantage of a horizontally opposed engine over a radia
engine for powering modern aircraft?: The horizontally opposed engine has
a much smaller frontal area and is easier to streamline than a radial engine.
2. How many throws are there in the crankshaft of a six-cylinder horizontally
opposed engine?: Six.
3. What kind of connecting rod arrangement is used in a radial engine?: 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.
4. Of what material are most piston rings made?: Gray cast iron.
5. What is the reason for using hydraulic valve lifters in an aircraft engine?:
Hydraulic valve lifters keep all of the clearance out of the valve operatin
mechanism.
This decreases the wear of the valve train components.
6. At what speed does the camshaft turn, relative to the crankshaft speed in
a horizontally opposed engine?: The camshaft turns at one half of the
crankshaft speed.
7. What kind of main bearings are used in a horizontally opposed engine?:
Steel-backed, lead-alloy bearing inserts.
8. On what stroke is the piston of a reciprocating engine when the intake
valve begins to open?: On the exhaust stroke.
9. On what stroke is the piston of a reciprocating engine when the exhaust
valve begins to open?: On the power stroke.
10. Why are both the hot and cold valve clearances given for most rad
engines?: The hot clearance is given for valve timing purposes. The timing is
adjusted with the valves in cylinder number one, set with the hot clearan
When the timing is set, all of the valves are adjusted to their cold clearance.
11. What is meant by a cam-ground piston?: 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 reache
operating temperature, the metal in the piston pin boss expands enough that
the piston becomes perfectly round.
12. Where is the piston in a reciprocating engine when the ignition spa
occurs?: About 30 degrees of crankshaft rotation before the piston reaches top
center on the compression stroke.
13. What is meant by a full-floating wrist pin?: A wrist pin that is not clamped in
either the piston or the connecting rod. Full-floating wrist pins are kept fr
scoring the cylinder walls by soft metal plugs in their ends.
, 14. Why do most aircraft reciprocating engines use more than one spring on
each valve?: By using more than one spring and having the wire diameter and
pitch of the springs different, valve float is minimized. The springs have differen
resonant frequencies, so at least one spring will always be exerting a force on
a valve.
15. Would excessive valve clearance cause the valves to open early or late?:
Excessive valve clearance will cause the valve to open late and close early.
16. What is the purpose of valve overlap in a reciprocating engine?: Va
overlap allows the inertia of the exhaust gases leaving the cylinder to help the
fresh induction charge start flowing into the cylinder.
17. What type of piston rings are installed on the pistons of an aircraft
reciprocating engine?: Compression rings, oil control rings, and oil wiper ring
18. Why are some exhaust valves partially filled with metallic sodium?: 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.
19. What causes detonation in an aircraft engine?: Excessive heat and pressur
in the engine cylinder causes the fuel-air mixture to reach its critical pressure
and temperature. Under these conditions, the mixture explodes rather tha
burns. This explosion is called detonation.
20. Why is a compression check important for determining the condition of
an aircraft reciprocating engine?: 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.
21. What is meant by the compression ratio of a reciprocating engine?: 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.
22. What are the two basic sections of a turbine engine?: The hot section and
the cold section.
23. What are the two basic types of compressors that are used in aircr
turbine engines?: Axial-flow and centrifugal.
24. What is the purpose of the stators in an axial-flow compressor?: Th
stators convert some velocity energy into pressure energy and change th
direction of the air so it is proper for the next stage of rotors.
25. What are three types of combustors used on aircraft turbine engines?:
Can-type, annular-type, and can-annular type.
26. How many igniters are there normally in an aircraft turbine engine?: Two.
