Reciprocating engines are commonly used to power private and commercial airplanes. Also known as piston engines, they are characterized by the use of reciprocal-motion pistons. The piston or pistons “reciprocate” inside of the engines while simultaneously converting combustion-generated pressure into rotary motion. While all reciprocating engines use this same basic design, they are available in several different types. Below is a breakdown of the three primary types of reciprocating airplane engines.

#1) Radial Reciprocating Engines

Radial reciprocating engines are those that feature radial-motion cylinders. The cylinders move outwards from the crankcase. Radial reciprocating engines are typically used in small narrow-body passenger airplanes. You won’t find them in many wide-body airplanes. Radial reciprocal engines can have anywhere from a half-dozen to 30 cylinders, all of which are mounted in a perimeter around the crankcase. During use, the cylinders move outwards from the crankcase that they surround.

#2) In-Line Reciprocating Engines

Another common type of reciprocating engine is in-line. In-line reciprocating engines are those that feature banks of cylinders. In other words, the cylinders are installed in columns, with one cylinder behind another cylinder. This is in stark contrast to other types of engines, which feature one or more rows of cylinders. The banks of in-line reciprocating engines typically have a maximum of six cylinders each. Some of them have fewer cylinders, but the banks of most in-line reciprocating engines have no more than six cylinders each.

#3) Flat Reciprocating Engines

There are flat reciprocating engines as well. Also known as horizontally opposed engines, flat reciprocating engines are characterized by the placement of their cylinders. They feature horizontally aligned cylinders. The cylinders are placed on opposite ends of the engine. Each of the cylinders has a pair of pistons, which come together at the combustion chamber. Some of the benefits of flat reciprocating engines include a lower operating temperature, a shorter length and a lower center of mass when compared to other types of engines.

In Conclusion

Not all reciprocating airplane engines are the same. There are three primary types of reciprocating engines used to power airplanes, including radial, in-line and flat. Radial reciprocating engines live up to their namesake by performing radial movements with their cylinders. In-line reciprocating engines, on the other hand, feature banks of cylinders. Flat reciprocating engines feature horizontally aligned cylinders. There are other types of airplane engines. For reciprocating engines, though, most consist of either radial, in-line or flat.