The engines powering the vast majority of personal airplanes are air-cooled. This means they don’t have a radiator and a liquid-based system like most automobiles we might drive to the airport. Yes, piston powerplants like those in the Rotax line, as well as many diesel engines designed for aircraft, are liquid cooled. But these more modern designs are in a distinct minority. In fact, besides the metallurgy, the basic configuration of aircraft piston engines has changed little since before World War II: Flat, horizontally opposed or radial designs from that era predominate.
Any time we ignite fuel inside a piston engine’s cylinders, we generate heat, which has to go somewhere—be dissipated—before increasing to the point damage is done. Air cooling an aircraft engine has the advantage of relatively light weight—the radiator, associated plumbing and relatively heavy liquid aren’t needed—and an endless supply of coolant. For most applications, we’re of the opinion putting a liquid-cooled engine on a personal airplane is akin to cooling a submarine with air. But no matter how simple air cooling a piston engine can be, pilots have found ways to screw it up.
