Radial aircraft engines have been around for more than a century. Predominantly air-cooled, many engines of the last 100 years or so were lighter than their liquid-cooled counterparts that developed similar horsepower. Their characteristic odd-numbered cylinders are arranged in a circular bank, instead of in a straight line. Especially in the 1920s through the 1950s, the radial engine-powered many military and commercial designs. The jet age, plus aeronautical and metallurgical advances overtook radial designs after World War II, as one drawback of an air-cooled radial is that the round bank of cylinders which produces much aerodynamic drag.
Today, very few radial engines are being built. Russia’s Vedeneyev produces the M-14 radial engine, used in many aerobatic aircraft. Many warbirds are powered by radial engines built by Pratt and Whitney and Curtiss-Wright. British manufacturer Bristol developed the Centaurus too.
How many types are you familiar with? You can hover over each photo taken at the 2022 EAA AirVenture to see a wide range of radial engines used in military and civilian designs.