12 practice questions from the 246 in this chapter of StudyWren Aviation. Pick an answer and check it to see the explanation and its FAA source.
Reciprocating EnginePAR-02-001
In a four-stroke spark-ignition aircraft engine, in what order do the strokes of the operating cycle occur?
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The answer is C: Intake, compression, power, exhaust
The piston draws in the fuel-air charge (intake), squeezes it (compression), is driven down by combustion (power), and then pushes the burned gases out (exhaust).
The answer is C: Intake, compression, power, exhaust
The piston draws in the fuel-air charge (intake), squeezes it (compression), is driven down by combustion (power), and then pushes the burned gases out (exhaust).
During which stroke of the four-stroke cycle are both valves closed while the piston travels toward the cylinder head?
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The answer is C: Compression
The compression stroke begins when the intake valve closes and the piston moves back up toward the cylinder head, compressing the fuel-air charge with both valves closed. Both valves are also closed on the power stroke, but then combustion drives the piston down, away from the head. On the intake stroke the intake valve is open and the piston moves away from the head, drawing in the charge.
The compression stroke begins when the intake valve closes and the piston moves back up toward the cylinder head, compressing the fuel-air charge with both valves closed. Both valves are also closed on the power stroke, but then combustion drives the piston down, away from the head. On the intake stroke the intake valve is open and the piston moves away from the head, drawing in the charge.
Which engine component, connected to the pistons by connecting rods, converts their back-and-forth motion into the rotary motion that turns the propeller?
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The answer is A: The crankshaft
Connecting rods link each piston to the crankshaft, which converts the pistons' linear (reciprocating) motion into rotation. On most training airplanes the propeller is mounted directly on an extension of the crankshaft.
Connecting rods link each piston to the crankshaft, which converts the pistons' linear (reciprocating) motion into rotation. On most training airplanes the propeller is mounted directly on an extension of the crankshaft.
A four-cylinder, four-stroke engine is running at 2,400 RPM. How many power strokes per minute does EACH individual cylinder produce?
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The answer is B: 1,200
A four-stroke cycle takes two crankshaft revolutions, so each cylinder fires once every two revolutions: 2,400 / 2 = 1,200 power strokes per minute. 4,800 is the total for all four cylinders combined; 2,400 would assume one power stroke per revolution.
A four-stroke cycle takes two crankshaft revolutions, so each cylinder fires once every two revolutions: 2,400 / 2 = 1,200 power strokes per minute. 4,800 is the total for all four cylinders combined; 2,400 would assume one power stroke per revolution.
A six-cylinder, four-stroke engine is turning 2,500 RPM. What is the total number of power strokes per minute delivered by all cylinders combined?
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The answer is C: 7,500
Each cylinder fires once every two revolutions: 2,500 / 2 = 1,250 power strokes per cylinder per minute. Six cylinders x 1,250 = 7,500. 15,000 incorrectly assumes one power stroke per revolution; 1,250 is the figure for a single cylinder.
Each cylinder fires once every two revolutions: 2,500 / 2 = 1,250 power strokes per cylinder per minute. Six cylinders x 1,250 = 7,500. 15,000 incorrectly assumes one power stroke per revolution; 1,250 is the figure for a single cylinder.
What is the main reason the horizontally opposed engine is the most popular reciprocating engine design for small training airplanes?
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The answer is B: A high power-to-weight ratio and small frontal area
Opposed engines have a comparatively small, light crankcase (high power-to-weight ratio) and a compact cylinder arrangement that reduces frontal area and drag. Most use spark ignition, and they always have an even number of cylinders.
The answer is B: A high power-to-weight ratio and small frontal area
Opposed engines have a comparatively small, light crankcase (high power-to-weight ratio) and a compact cylinder arrangement that reduces frontal area and drag. Most use spark ignition, and they always have an even number of cylinders.
A horizontally opposed aircraft engine always has which type of cylinder count?
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The answer is B: An even number of cylinders
Each cylinder on one side of the crankcase 'opposes' a cylinder on the other side, so opposed engines always have an even number of cylinders (commonly four or six in light airplanes).
Each cylinder on one side of the crankcase 'opposes' a cylinder on the other side, so opposed engines always have an even number of cylinders (commonly four or six in light airplanes).
On a typical spark-ignition aircraft engine, where are the magnetos normally mounted?
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The answer is B: On the engine accessory housing
The main parts of the engine are the cylinders (valves, spark plugs, pistons), the crankcase (crankshaft, connecting rods), and the accessory housing, where the magnetos are normally located.
The main parts of the engine are the cylinders (valves, spark plugs, pistons), the crankcase (crankshaft, connecting rods), and the accessory housing, where the magnetos are normally located.
What is the main difference between a spark-ignition engine and a compression-ignition (jet-fueled piston or diesel) aircraft engine?
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The answer is C: The method used to ignite the fuel-air charge
Both designs use cylinders, pistons, and a crankshaft, and either can be air or liquid cooled. Spark-ignition engines fire a premixed charge with spark plugs; compression-ignition engines compress air until it is hot enough to ignite injected fuel.
The answer is C: The method used to ignite the fuel-air charge
Both designs use cylinders, pistons, and a crankshaft, and either can be air or liquid cooled. Spark-ignition engines fire a premixed charge with spark plugs; compression-ignition engines compress air until it is hot enough to ignite injected fuel.
A piston airplane is equipped with a full authority digital engine control (FADEC). Which pilot control would you expect NOT to find in its flight deck?
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The answer is A: A manual mixture control
FADEC computes the injector pulse and ignition timing for each cylinder and adjusts the fuel-air mixture automatically, so it eliminates the need for magnetos, carburetor heat, a mixture control and manual priming. The pilot simply positions a single power lever, and the airplane still has an electrical system with a master switch.
FADEC computes the injector pulse and ignition timing for each cylinder and adjusts the fuel-air mixture automatically, so it eliminates the need for magnetos, carburetor heat, a mixture control and manual priming. The pilot simply positions a single power lever, and the airplane still has an electrical system with a master switch.
Why are air-cooled in-line engines normally limited to four or six cylinders?
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The answer is B: The rearmost cylinders receive very little cooling air
In an in-line air-cooled engine, the cylinders behind the front ones are shielded from the airflow, so the rearmost cylinders get very little cooling air. In-line engines actually have a small frontal area, which is one of their advantages.
The answer is B: The rearmost cylinders receive very little cooling air
In an in-line air-cooled engine, the cylinders behind the front ones are shielded from the airflow, so the rearmost cylinders get very little cooling air. In-line engines actually have a small frontal area, which is one of their advantages.
Each cylinder of a four-stroke engine produces power during only one of its four strokes. How does a four-cylinder engine still deliver continuous crankshaft rotation?
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The answer is A: Each cylinder is on a different stroke, so power strokes are timed in sequence
In a four-cylinder engine each cylinder operates on a different stroke, and the precise timing of the power strokes in each cylinder maintains continuous rotation of the crankshaft.
The answer is A: Each cylinder is on a different stroke, so power strokes are timed in sequence
In a four-cylinder engine each cylinder operates on a different stroke, and the precise timing of the power strokes in each cylinder maintains continuous rotation of the crankshaft.
