The Mazda (Wankel) four-stroke, three-rotor engine can produce up to 350 hp from its small displacement. The power-plant's size and shape easily lends itself to aircraft applications. These engines have been used in aircraft since the mid-1960s and were initially applied in power motorgliders, although the engines have become more plentiful in conventional light airplanes throughout the ensuing years.
The Rotax 914 is a four-stroke liquid/air-cooled engine producing 115 hp at 5,800 RPM. The engine is suitable for turbo-charging and is particularity sporty in the new generation of fiberglass aircraft such as the Glasair. The engine offers good dependability and performance at a attractive price.
As a result of the dependability factor associated with Subaru automotive engines, these power plants have migrated from the road to the air. There are a host of conversion companies that utilize Subaru engines in fixed-wing airplanes. These units produce good power whether they are four- or six-cylinder, and conversion companies typically offer all the necessary bits, such as mounts and engine accessories, allowing the engine to be easily integrated with an appropriate airframe.
Hirth Aircraft engines have been built since 1914 when the company received its first contract from the German Army. Since then, the company has become a major player in the two-stroke engine segment. The engine is typically applied to ultralight aircraft, but Hirth recently has developed and begun to market a three-cylinder version producing between 80 and 100 hp. This engine is very compliant with small home-built aircraft such as the Kit Fox.
Volkswagen (VW) was initially developed and built by Ferry Porsche under contract from Adolf Hitler prior to World War II. The engine and its subsequent car was released as a "peoples car" with the intent of offering the little vehicles to the "German people" by the Nazis as part of their culture retrenchment. Over the years the VW has become a favorite across the world, and the dependability of the little four-cylinder air-cooled engine is well-known. Although it is low on power, the power plant is easy to convert for aircraft use, and in the last 15 years the flying community has seen more and more applications of this innovative approach.