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Crankshaft rotation per four-stroke cycle

Aviation Mechanic Powerplant (AMP) practice question 2 of 13 on Reciprocating Engines. ACS element AM.III.A.K2 · difficulty: recall. Want to answer it in a timed quiz? Use the Aviation Mechanic Powerplant (AMP) practice mode.

Question bank updated 2026-09-22

QUESTIONHow many degrees of crankshaft rotation are required to complete the four strokes of one operating cycle in a cylinder?

  1. A360 degrees
  2. B720 degrees
  3. C1,080 degrees
Show the answer and explanation

Correct answer: B. 720 degrees

  • A — incorrect One revolution completes only two of the four strokes; that figure describes the two-stroke cycle, which finishes its cycle in one revolution.
  • B — correct Two complete revolutions of the crankshaft, or 720 degrees, are required for the four strokes of one cycle.
  • C — incorrect Three revolutions is more rotation than the four-stroke cycle requires; the cycle is finished after two.

BACKGROUND

The vast majority of certified aircraft reciprocating engines operate on the four-stroke cycle, sometimes called the Otto cycle. Four strokes are required to complete the series of events in each cylinder, and two complete revolutions of the crankshaft, 720 degrees, are needed to produce them. As a result, each cylinder of a four-stroke engine fires once in every two revolutions of the crankshaft. The two-stroke cycle, by contrast, completes its operating cycle in one revolution because intake and exhaust are accomplished during the same stroke.

STUDY TIP

Tie the number 720 to the fact that each cylinder fires only once per two crankshaft revolutions; that relationship also feeds the power-stroke count used in horsepower formulas.

KEY POINTS

  • The four-stroke cycle needs two crankshaft revolutions, or 720 degrees.
  • Each cylinder therefore fires once every two revolutions.
  • A two-stroke engine completes its cycle in a single revolution.

SOURCES

  • FAA-H-8083-32B ch01 "Four-Stroke Cycle"
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MORE ON RECIPROCATING ENGINES

SkyDrill is not affiliated with the FAA. This is an original practice item based on FAA-H-8083-32B Aviation Maintenance Technician Handbook – Powerplant, and 14 CFR part 43. Regulations and handbooks are revised; confirm details against the current edition.