Reciprocating Engine Oral Exam Questions and Answers

October 14, 2026 · Based on FAA-S-ACS-1 and FAA-H-8083-32B, Powerplant · Updated October 18, 2026

Practice explaining a reciprocating engine from its cylinder arrangement to its operating cycle. Use these ten prompts to check your component descriptions, timing terms, and calculations. Answer aloud first, then compare your explanation with the cited FAA handbook page. Keep a small sketch nearby if it helps you describe motion clearly.

What should my answer explain?

Start this rehearsal with a drawing rather than a memorized paragraph. Label the cylinder head, barrel, piston, connecting rod, and crankshaft, then explain the relationship between them. For each answer, check whether you have described the component’s function as well as named it.

Use a separate pass for timing and volume terms. Say what a term measures before trying an example. Keep the handbook’s qualifiers in your spoken answer: if it says generally, most, or for example, say so too. Reserve detailed ignition-system, fuel-metering, and lubrication practice for their own topic sessions.

FAA-S-ACS-1, AM.III.A, p. 44

For the wider exam, read the Powerplant oral questions overview. Use the ACS codes guide when reviewing the ACS codes on your Airman Knowledge Test Report (AKTR).

Which ACS elements do these questions practice?

The table identifies the elements used for the practice questions below. It is not a prediction of your assigned questions.

Which oral exam questions can I practice?

These practice questions are built from ACS elements; they are not actual FAA test questions. The short explanations are study answers, not complete aircraft maintenance procedures.

1. How does the handbook classify reciprocating engines by cylinder arrangement and cooling method?

ACS: AM.III.A.K1

By cylinder arrangement, the handbook lists inline, V-type, radial, and opposed engines. By cooling method, it distinguishes liquid-cooled and air-cooled engines. In an air-cooled engine, heat moves directly from the cylinders to the air. In a liquid-cooled engine, heat passes to coolant, which travels through tubing to a radiator in the airstream. Most reciprocating aircraft engines are air cooled, with thin metal fins on the cylinders to increase the surface for heat transfer.

FAA-H-8083-32B, Powerplant, p. 1-3

2. How are the cylinders and crankshaft arranged in an opposed engine?

ACS: AM.III.A.K4

The opposed-type engine has two banks of cylinders directly opposite each other with a crankshaft in the center. Pistons from both banks connect to that single crankshaft. The engine can be air cooled or liquid cooled, although the air-cooled version is used predominantly in aviation. The engine is generally mounted with the cylinders in a horizontal position.

FAA-H-8083-32B, Powerplant, p. 1-4

3. What cylinder arrangement defines a radial engine, and what is a double-row radial?

ACS: AM.III.A.K5

The radial engine consists of a row, or rows, of cylinders arranged radially about a central crankcase. A row may contain three, five, seven, or nine cylinders. Some radial engines have two rows of seven or nine cylinders, one in front of the other; the handbook calls those double-row radials. One type of radial engine has four rows of seven cylinders, for a total of 28 cylinders.

FAA-H-8083-32B, Powerplant, p. 1-4

4. For an air-cooled opposed engine, what are the cylinder’s two major parts and their roles?

ACS: AM.III.A.K4

The air-cooled cylinder assembly has two major parts: the head and the barrel. The head provides a place for combustion and helps conduct heat for cooling. The piston operates in the barrel. At assembly, the heated head is screwed down on a chilled barrel; when the head cools and the barrel warms, a gastight joint results. The handbook says the majority of cylinders are built this way, with an aluminum head and a steel barrel.

FAA-H-8083-32B, Powerplant, p. 1-14 · FAA-H-8083-32B, Powerplant, p. 1-15

5. When explaining opposed-engine construction, what does the crankshaft do and what are its three main parts?

ACS: AM.III.A.K4

The crankshaft changes the reciprocating motion of the piston and connecting rod into rotary motion for the propeller. Its three main parts are the journal, crankpin, and crank cheek. The journal rotates in a main bearing. The connecting rod attaches to the crankpin. The crank cheek joins the crankpin to the main journal.

FAA-H-8083-32B, Powerplant, p. 1-8

6. What completes one operating cycle in a four-stroke reciprocating engine?

ACS: AM.III.A.K2

The strokes are intake, compression, power, and exhaust. Completing them takes two crankshaft revolutions, or 720 degrees; each cylinder fires once during those two revolutions. The handbook separately lists five events in order: intake, compression, ignition, power, and exhaust. Ignition is an event, not a fifth stroke: the charge is fired by an electric spark as the piston approaches TDC on the compression stroke.

FAA-H-8083-32B, Powerplant, p. 1-25 · FAA-H-8083-32B, Powerplant, p. 1-26 · FAA-H-8083-32B, Powerplant, p. 1-27

7. What is valve overlap, and why is it used?

ACS: AM.III.A.K2

The intake valve opens before TDC on the exhaust stroke, and exhaust-valve closing is delayed until after the piston has passed TDC and started the intake stroke. This timing is called valve overlap: for a moment both valves are open at the same time, at the end of the exhaust stroke and the beginning of the intake stroke. The handbook describes overlap as helping internal cooling, increasing the inducted air-fuel charge, and scavenging combustion byproducts from the cylinder.

FAA-H-8083-32B, Powerplant, p. 1-18 · FAA-H-8083-32B, Powerplant, p. 1-26

8. How is valve-event timing expressed, and does opening timing mean the valve is fully open?

ACS: AM.III.A.K2

Valve-event timing is specified in degrees of crankshaft travel. A valve needs some crankshaft travel to open fully, so the specified opening timing marks the start of opening, not the fully open position. The valve events vary considerably in different engines, so the handbook’s timing chart is only an example; it says it is most important to follow the engine manufacturer’s recommendations in maintenance and overhaul.

FAA-H-8083-32B, Powerplant, p. 1-26

9. What is piston displacement, and how do bore and stroke enter its calculation?

ACS: AM.III.A.K7

When a piston moves from BDC to TDC, it displaces a specific volume, known as piston displacement; it is expressed in cubic inches for most American-made engines. The bore of a cylinder is its inside diameter. The stroke is the distance the piston moves from one end of the cylinder to the other, specifically from top dead center (TDC) to bottom dead center (BDC), or vice versa. The bore gives the cross-sectional area: the radius is half the bore, and the area is pi times the radius squared. For one cylinder, multiply that area by the stroke. For a multicylinder engine, multiply that product by the number of cylinders to get the total piston displacement.

FAA-H-8083-32B, Powerplant, p. 1-28 · FAA-H-8083-32B, Powerplant, p. 1-25

10. What does compression ratio compare?

ACS: AM.III.A.K7

The compression ratio of an engine is a comparison of the volume of space in a cylinder when the piston is at the bottom of the stroke to the volume of space when the piston is at the top of the stroke. This comparison is expressed as a ratio, hence the term compression ratio. In the handbook’s example, those volumes are 140 and 20 cubic inches, giving 140:20, or 7:1. Compression ratio is a controlling factor in the maximum horsepower an engine develops, but it is limited by present-day fuel grades and by the high engine speeds and manifold pressures required for takeoff. Together with manifold pressure, it sets the cylinder pressure just before ignition; the handbook warns that if that pressure becomes too high, pre-ignition or detonation occur and produce overheating.

FAA-H-8083-32B, Powerplant, p. 1-29

How do I answer it out loud?

Work through three groups: engine arrangements and construction; the four-stroke cycle and valve events; then displacement and compression ratio. For each group, write one sentence naming the idea you need to explain. After rehearsal, compare your sentence with the answer outline and its cited page. Mark any term you used without defining it.

How should I check my practice answer?

Draw a piston at the top and bottom of its travel. Label the bore and stroke, then write separate explanations for displacement and compression ratio. Next, draw a four-stroke sequence and speak through it without notes. Compare it with the cited pages, paying particular attention to the distinction between strokes and events. Repeat the answer you found hardest, and remember to say that valve timing varies between engines and follows the manufacturer’s recommendations.

Check the explanation in the handbook during study, then close it for the spoken rehearsal. The ACS states that reference material is not allowed for answering oral questions.

“the applicant is not allowed to use any reference material to answer the oral questions asked by the examiner.”

FAA-S-ACS-1, Appendix 1, p. A-1

Which guide should I read next?

• Engine Inspection Oral Exam Questions
• Turbine Engine Oral Exam Questions

Which sources support these answers?

References show the printed handbook pages. The links open the corresponding PDF pages.

• FAA-H-8083-32B, Powerplant
• FAA-S-ACS-1, AM.III.A and Appendix 1

About this guide: drafted with AI from the FAA sources listed on this page and checked claim by claim against them. Not reviewed by an A&P mechanic or DME. How we make our guides