By Brad Irwin

Piston engines have been around since the early 1770’s when they were first used in steam engines. Nearly a century later, German inventors Nicolaus Otto and Gottlieb Daimler developed a piston engine that would burn gasoline. They were lighter and more reliable than steam engines and had more potential applications.

Engines for airplanes had to be light and still develop plenty of power. This was a problem, since most of the early piston gasoline engines were water-cooled and thus heavier. The advent of air-cooled rotary engines was the first step in developing an aircraft powerplant that was sufficiently light and powerful enough to make them desireable for aircraft applications.

Since the early 1900’s, engine manufactures like Lycoming and Continental have continued to manufacture air-cooled piston engines that been the mainstay of the general aviation industry. Now that the price of av gas in the United States has caught up with the rest of the world, aircraft manufacturers are seriously looking at alternative engine technologies. These include diesel engines, multi-fuel engines, and even small turbine engines adapted for use in smaller general aviation aircraft. Several of these engine technologies were on display in Oshkosh this past summer for those of us interested in seeing first-hand the future of aviation engine technology.

SMA Engines, a French company, has developed a 230 hp air-cooled diesel aircraft engine for general aviation. This engine, like most diesel engines, can burn Jet A and Jet A 1 and has a typical fuel consumption rating of 12 gal/hour at 100% power and 7.9 gal/hour at 65% power in a typical aircraft installation such as a Cessna 182.

A company out of Racine, Wisconsin by the name of DeltaHawk Engines, Inc., has developed a new liquid-cooled two stroke diesel engine for aviation applications. The company was founded in 1996 to develop a “clean sheet” compression-ignition engine for general aviation. A prototype engine first ran on a static Velocity airframe in January 1997.

Mistral Engines SA from Geneva, Switzerland has developed a new rotary aviation engine with cutting-edge proprietary technology which has an excellent power-to-weight ratio, turbine-like smoothness, and extremely low vulnerability to catastrophic failures due to the fewer number of moving parts in a rotary engine versus a comparable piston engine.

One of the most exciting and promising engines recently developed for light general aviation aircraft is the Rolls-Royce RR500. This is a 251 pound turboprop (which includes the installation kit, starter/generator, and oil temp sensor). It can generate up to 400 hp on take-off, maintain 380 hp continuously, and cruise more economically at 270 to 320 shaft hp.

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