ASA POWERPLANT ORAL EXAM 2 LATEST VERSIONS 2024-2025 ACTUAL EXAM COMPLETE 400
QUESTIONS AND CORRECT DETAILED ANSWERS
What is the main advantage of a horizontally opposed engine over a radial engine for powering modern
aircraft? - (answer) smaller frontal area and easier to streamline.
How many throws are there in the crankshaft of a six-cylinder horizontally opposed engine? - (answer)
six
What kind of connecting rod arrangement is used in a radial engine? - (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? - (answer) grey cast iron
What is the reason for using hydraulic valve lifters in an aircraft engine? - (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? - (answer) camshaft is one half the speed of crankshaft
What kind of main bearings are used in a horizontally opposed engine? - (answer) steel backed lead
alloy bearings
On what stroke is the piston of a reciprocating engine when the intake valve begins to open? - (answer)
exhaust
On what stroke is the piston of a reciprocating engine when the exhaust valve begins to open? -
(answer) power
Why are both the hot and cold valve clearances given for most radial engines? - (answer) hot clearance
is for valve timing. timing adjusted with valves in cylinder 1 set with hot clearance then adjusted to cold
clearance
,ASA POWERPLANT ORAL EXAM 2 LATEST VERSIONS 2024-2025 ACTUAL EXAM COMPLETE 400
QUESTIONS AND CORRECT DETAILED ANSWERS
What is meant by a cam-ground piston - (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? - (answer) before top
dead center on the compression stroke
What is meant by a full-floating wrist pin? - (answer) pin not clamped in either piston or connecting rod
Why do most aircraft reciprocating engines use more than one spring on each valve? - (answer) for
different frequencies/rpms
Would excessive valve clearance cause the valves to open early or late? - (answer) open late close early
What is the purpose of valve overlap in a reciprocating engine? - (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? - (answer)
compression, oil control, oil wiper
Why are some exhaust valves partially filled with metallic sodium? - (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? - (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?
- (answer) to check condition of seals between piston ring and cylinder wall and valves and thier seats
, ASA POWERPLANT ORAL EXAM 2 LATEST VERSIONS 2024-2025 ACTUAL EXAM COMPLETE 400
QUESTIONS AND CORRECT DETAILED ANSWERS
What is meant by the compression ratio of a reciprocating engine? - (answer) ratio of volume of
cylinder with piston at bottom vs piston at top
What are the two basic sections of a turbine engine? - (answer) hot and cold
What are the two basic types of compressors that are used in aircraft turbine engines? - (answer) axial
flow and centrifugal
What is the purpose of the stators in an axial-flow compressor? - (answer) convert velocity energy to
pressure energy and change direction of air
What are three types of combustors used on aircraft turbine engines? - (answer) can, annular, can-
annular
How many igniters are there normally in an aircraft turbine engine? - (answer) two
What is the main purpose of the turbine nozzle in an aircraft turbine engine? - (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 - (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 -
(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 - (answer) anti
fiction, ball, roller
QUESTIONS AND CORRECT DETAILED ANSWERS
What is the main advantage of a horizontally opposed engine over a radial engine for powering modern
aircraft? - (answer) smaller frontal area and easier to streamline.
How many throws are there in the crankshaft of a six-cylinder horizontally opposed engine? - (answer)
six
What kind of connecting rod arrangement is used in a radial engine? - (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? - (answer) grey cast iron
What is the reason for using hydraulic valve lifters in an aircraft engine? - (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? - (answer) camshaft is one half the speed of crankshaft
What kind of main bearings are used in a horizontally opposed engine? - (answer) steel backed lead
alloy bearings
On what stroke is the piston of a reciprocating engine when the intake valve begins to open? - (answer)
exhaust
On what stroke is the piston of a reciprocating engine when the exhaust valve begins to open? -
(answer) power
Why are both the hot and cold valve clearances given for most radial engines? - (answer) hot clearance
is for valve timing. timing adjusted with valves in cylinder 1 set with hot clearance then adjusted to cold
clearance
,ASA POWERPLANT ORAL EXAM 2 LATEST VERSIONS 2024-2025 ACTUAL EXAM COMPLETE 400
QUESTIONS AND CORRECT DETAILED ANSWERS
What is meant by a cam-ground piston - (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? - (answer) before top
dead center on the compression stroke
What is meant by a full-floating wrist pin? - (answer) pin not clamped in either piston or connecting rod
Why do most aircraft reciprocating engines use more than one spring on each valve? - (answer) for
different frequencies/rpms
Would excessive valve clearance cause the valves to open early or late? - (answer) open late close early
What is the purpose of valve overlap in a reciprocating engine? - (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? - (answer)
compression, oil control, oil wiper
Why are some exhaust valves partially filled with metallic sodium? - (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? - (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?
- (answer) to check condition of seals between piston ring and cylinder wall and valves and thier seats
, ASA POWERPLANT ORAL EXAM 2 LATEST VERSIONS 2024-2025 ACTUAL EXAM COMPLETE 400
QUESTIONS AND CORRECT DETAILED ANSWERS
What is meant by the compression ratio of a reciprocating engine? - (answer) ratio of volume of
cylinder with piston at bottom vs piston at top
What are the two basic sections of a turbine engine? - (answer) hot and cold
What are the two basic types of compressors that are used in aircraft turbine engines? - (answer) axial
flow and centrifugal
What is the purpose of the stators in an axial-flow compressor? - (answer) convert velocity energy to
pressure energy and change direction of air
What are three types of combustors used on aircraft turbine engines? - (answer) can, annular, can-
annular
How many igniters are there normally in an aircraft turbine engine? - (answer) two
What is the main purpose of the turbine nozzle in an aircraft turbine engine? - (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 - (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 -
(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 - (answer) anti
fiction, ball, roller
