Rotax is the brand name for a range of internal combustion engines developed and manufactured by the Austrian company BRP-Rotax GmbH & Co KG (until 2016 BRP-Powertrain GmbH & Co. KG), in turn owned by the Canadian Bombardier Recreational Products. Under the Rotax brand, the company is one of the world's largest producers of light piston engines.
Rotax four-stroke and advanced two-stroke engines are used in a wide variety of small land, sea and airborne vehicles. Bombardier Recreational Products (BRP) use them in their own range of such vehicles. Since the 1990s, Rotax has been the world's dominant supplier of engines for ultralight aircraft and light sport aircraft, and a major producer of engines for other light aircraft.
History
The company was founded in 1920 in Dresden, Germany, as ROTAX-WERK AG. In 1930, it was taken over by Fichtel & Sachs and transferred its operations to Schweinfurt, Germany. Operations were moved to Wels, Austria in 1943, and finally to Gunskirchen, Austria in 1947. In 1959, the majority of Rotax shares were taken over by the Vienna-based Lohner-Werke, a manufacturer of car and railway wagon bodies.
In 1970, Lohner-Rotax was bought by the Canadian Bombardier Inc. The former Bombardier branch, Bombardier Recreational Products, now an independent company, uses Rotax engines in its ground vehicles, personal water craft, and snowmobiles.
Applications
Snowmobiles
The original application for Rotax engines, Ski-Doo snowmobiles from Bombardier Recreational Products are equipped with Rotax engines, including two-stroke and four-stroke, turbocharged and naturally aspirated, two- and three-cylinder models.
Aircraft
Rotax is one of the world's principal suppliers of aircraft engines for ultralight aircraft, light aircraft and unmanned aerial vehicles. Between 1985 and 1995, 60,000 Rotax engines were sold for aircraft propulsion. In the light aircraft class, in 1998 Rotax outsold all other aero engine manufacturers combined. Their four-stroke engines powered most U.S.-certified light sport aircraft when they first appeared around 2004. Over two decades later, Rotax engines remain the most popular line of engines for light sport and ultralight aircraft, and the second-most-popular (after Lycoming Engines) for U.S. Experimental / Amateur-Built (E/A-B) aircraft.
Two-stroke aircraft engines
Rotax air-cooled, two-stroke engines began appearing on ultralight aircraft in the early 1980s, with a pair of single-cylinder, 9.5-horsepower Rotax 185s powering the single-seat Lazair ultralight by 1982. Soon, the 26-horsepower, single-cylinder Rotax 277 became the most widely used engine powering U.S. ultralight aircraft (and remains, for many, the only Rotax engine they can use to adequately power the aircraft and still remain within the FAA-mandated weight limits for ultralight aircraft which can be operated without a pilot's license).
Two-stroke Rotax model numbers approximated the engine's displacement (in cubic centimeters), and the first two digits (from the 277, on) are very roughly similar to the engine's horsepower (e.g.: The Rotax 447 engine displaces 437 cc, and is rated at 40 hp).
Subsequent evolutions of the early designs included the two-cylinder, two-stroke Rotax 377, Rotax 447, and Rotax 503, all in production by 1985 (the last of these, the 503, was discontinued in 2010-2011, by then the most popular engine it its class, and still widely used as of 2023). Later two-stroke designs included the Rotax 532 (circa 1984) and Rotax 582, both of which augmented the air-cooling with liquid-cooled cylinder heads.
Most Rotax two-stroke engines were rated, recommended, or reported with a TBO (time between overhauls) of about 150-300 hours (compared to 1200-2000 hours for government-certified, conventional, four-stroke, light aircraft engines), though later models improved upon that some.
Four-stroke aircraft engines
Moving towards more demanding aircraft applications, Rotax, by 1989, developed a four-stroke, four-cylinder, engine: the Rotax 912, with versions eventually ranging from 80 to over 100 horsepower, followed by a turbocharged 115 horsepower Rotax 914.
Rotax four-stroke engines differ from conventional four-stroke aircraft engines by their unusually small displacement for the amount of horsepower -- compensated for by higher than normal rotational speed (over 5,000 rpm). To reduce propeller-shaft speeds to normal aircraft propeller rotational speeds, (around 2300-2400 rpm) the engines use a reduction gearbox. They are also designed to accept motor spirit, with up to 10% Ethanol content.
