Until recently, I’d never understood the distinctions between the various types of aircraft engines, and how they all worked. So I decided to write a guide to both common aircraft engines and niche, wildly-impractical engines.

Nearly all aircraft engines have a common input and output. They use petroleum-based fuel, which is a wonderfully compact source of chemical energy. They produce thrust. The only difference is in the conversion from fuel to forward motion.

 Piston engines

A simple and popular propulsion system is the piston engine attached to a propeller. This is the setup used by the Wright brothers on their first flight at Kitty Hawk, and it’s still used in the Cessna 172, the most widely-flown airplane today.

Pistons are neat devices. Fuel is burned and pushes down a piston. The downward motion is converted into rotation with a crankshaft, exactly the same way as when you...