POWERPLANT ASA BAKER SCHOOL FAA
ORAL QUESTIONS ACTUAL PAPER 2026
QUESTIONS WITH SOLUTIONS GRADED A+
⩥ 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, and all other pistons are connected to the master rod with link
rods.
⩥ Of what material are most piston rings made?
Answer: Gray cast iron.
⩥ What is the reason for using hydraulic valve lifters in an aircraft
engine?
Answer: Hydraulic valve lifters keep all of the clearance out of the valve
operating mechanism, decreasing wear of the valve train components.
⩥ At what speed does the camshaft turn relative to the crankshaft speed
in a horizontally opposed engine?
,Answer: The camshaft turns at one half of the crankshaft speed.
⩥ What kind of main bearings are used in a horizontally opposed
engine?
Answer: Steel-backed, lead-alloy bearing inserts.
⩥ On what stroke is the piston of a reciprocating engine when the intake
valve begins to open?
Answer: On the exhaust stroke.
⩥ On what stroke is the piston of a reciprocating engine when the
exhaust valve begins to open?
Answer: On the power stroke.
⩥ Why are both the hot and cold valve clearances given for most radial
engines?
Answer: The hot clearance is given for valve timing purposes, adjusted
with the valves in cylinder number one, set with the hot clearance.
⩥ What is meant by a cam-ground piston?
Answer: A piston that is not perfectly round; its dimension parallel with
the wrist pin is smaller than its dimension perpendicular to the wrist pin.
,⩥ Where is the piston in a reciprocating engine when the ignition spark
occurs?
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?
Answer: A wrist pin that is not clamped in either the piston or the
connecting rod.
⩥ Why do most aircraft reciprocating engines use more than one spring
on each valve?
Answer: To minimize valve float, as different springs have different
resonant frequencies.
⩥ Would excessive valve clearance cause the valves to open late or
early?
Answer: Excessive clearance will cause the valve to open late and close
early.
⩥ What is the purpose of valve overlap in a reciprocating engine?
Answer: Valve overlap allows the inertia of the exhaust gases 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 rings, oil control rings, and oil wiper rings.
⩥ Why are some exhaust valves partially filled with metallic sodium?
Answer: The metallic sodium melts at engine operating temperature and
helps transfer heat from the valve head to the valve stem.
⩥ What causes detonation in an aircraft engine?
Answer: Excessive heat and pressure in the engine cylinder cause the
air-fuel mixture to explode rather than burn.
⩥ Why is a compression check important for determining the condition
of an aircraft reciprocating engine?
Answer: It can determine the condition of the seal between the piston
rings and the cylinder walls, and the seal between the intake and exhaust
valves.
⩥ What is meant by the compression ratio of a reciprocating engine?
Answer: 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.
⩥ What are the two basic sections of a turbine engine?
Answer: The hot section and the cold section.
ORAL QUESTIONS ACTUAL PAPER 2026
QUESTIONS WITH SOLUTIONS GRADED A+
⩥ 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, and all other pistons are connected to the master rod with link
rods.
⩥ Of what material are most piston rings made?
Answer: Gray cast iron.
⩥ What is the reason for using hydraulic valve lifters in an aircraft
engine?
Answer: Hydraulic valve lifters keep all of the clearance out of the valve
operating mechanism, decreasing wear of the valve train components.
⩥ At what speed does the camshaft turn relative to the crankshaft speed
in a horizontally opposed engine?
,Answer: The camshaft turns at one half of the crankshaft speed.
⩥ What kind of main bearings are used in a horizontally opposed
engine?
Answer: Steel-backed, lead-alloy bearing inserts.
⩥ On what stroke is the piston of a reciprocating engine when the intake
valve begins to open?
Answer: On the exhaust stroke.
⩥ On what stroke is the piston of a reciprocating engine when the
exhaust valve begins to open?
Answer: On the power stroke.
⩥ Why are both the hot and cold valve clearances given for most radial
engines?
Answer: The hot clearance is given for valve timing purposes, adjusted
with the valves in cylinder number one, set with the hot clearance.
⩥ What is meant by a cam-ground piston?
Answer: A piston that is not perfectly round; its dimension parallel with
the wrist pin is smaller than its dimension perpendicular to the wrist pin.
,⩥ Where is the piston in a reciprocating engine when the ignition spark
occurs?
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?
Answer: A wrist pin that is not clamped in either the piston or the
connecting rod.
⩥ Why do most aircraft reciprocating engines use more than one spring
on each valve?
Answer: To minimize valve float, as different springs have different
resonant frequencies.
⩥ Would excessive valve clearance cause the valves to open late or
early?
Answer: Excessive clearance will cause the valve to open late and close
early.
⩥ What is the purpose of valve overlap in a reciprocating engine?
Answer: Valve overlap allows the inertia of the exhaust gases 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 rings, oil control rings, and oil wiper rings.
⩥ Why are some exhaust valves partially filled with metallic sodium?
Answer: The metallic sodium melts at engine operating temperature and
helps transfer heat from the valve head to the valve stem.
⩥ What causes detonation in an aircraft engine?
Answer: Excessive heat and pressure in the engine cylinder cause the
air-fuel mixture to explode rather than burn.
⩥ Why is a compression check important for determining the condition
of an aircraft reciprocating engine?
Answer: It can determine the condition of the seal between the piston
rings and the cylinder walls, and the seal between the intake and exhaust
valves.
⩥ What is meant by the compression ratio of a reciprocating engine?
Answer: 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.
⩥ What are the two basic sections of a turbine engine?
Answer: The hot section and the cold section.
