Light Stuff

LSAs and the Rotax factor.


A look at whats powering FAA-approved Special Light Sport Aircraft (SLSAs) reveals that most-in fact, more than 73%-of the airplanes on the list come with a Rotax 912 engine. In service, the current domination of the Rotax 912 may be even higher, as the top seller, the Flight Design CT, is one of the many Rotax 912-equipped SLSAs from Europe.

Recently Rotax invited aviation journalists to take a tour of its facilities, which are in Gunskirchen, Austria, and I went, representing KITPLANES. The trip was significant, because in the past, the company was reluctant to allow press visits. Rotax is now part of a new company, Bombardier Recreational Products (BRP), and is the current frontrunner in small aircraft engines. Things have changed.

A Bit of History

Founded in Germany in 1920, Rotax moved to Austria in 1943 and has developed a lengthy line of two- and now four-stroke engines for a wide variety of recreational vehicles. Bombardier acquired Rotax in 1970, and the company’s first aviation engines (Rotax 642 two-strokes) were approved for powering a motorglider under European JAR 22 certification in 1973.

Rotax snowmobile engines began appearing in ultralights, and the company responded in 1975 by producing a line of two-strokes intended for aviation. They included the R-277, -377, -447, -503 and the liquid-cooled R-582. In 1984, development began on Rotaxs first four-stroke aviation engine, the R-912, which features dual ignition, dual carburetors and a dry sump oil system. (Although Rotaxs internal designations include the preceding “R,” well do without from here on, as they’re popularly known by their number designations only.) Introduced in 1987 as an 80-horsepower engine, the 912 was soon offered as the turbocharged, 115-hp 914 and then-by increasing bore by 4.5mm larger bore and the compression ratio by a point and a half (to 10.5:1)-as the 100-hp Rotax 912S. By now, Rotax has produced more than 125,000 aircraft engines, and they are supported by a worldwide network of sales and service facilities. Seventy percent of 912 sales are the 100-hp version.

Rotax continues to improve and produce two- and four-stroke engines-a total of about 200,000 per year-for recreational markets including the BRP Sea-Doo personal watercraft, Ski-Doo snowmobiles, ATVs, motorcycles and go-karts.

The Tour

Rotaxs decision to publicize its products and processes may relate to significant competition in the American LSA market, particularly now that Cessna has decided on a U.S.-produced Continental O-200 for its SkyCatcher. The Cessna LSA unveiled at AirVenture/Oshkosh 2006 was equipped with a Rotax 912ULS. Useful load will be lower in the Continental-equipped Skycatcher, but the slumping dollar/euro exchange rate factor disappears.

Gathering in Wels, Austria, a few miles from tiny Gunskirchen, journalists from the U.S., Canada, Venezuela, the United Kingdom and Germany were taken to the Rotax facility for a briefing by the general manager followed by a tour of the manufacturing plant. Every step toward the final product, from design through production and testing to plans for long-term support, occurs at the Gunskirchen plant.

More than 1200 people work at Rotax. The average employee has been there for 14 years, we were told, but those chosen for the aircraft engine division have even more experience.

Rotax and its suppliers coordinate just-in-time delivery of parts such as carburetors, ignition systems and bearings. Forged blanks and cast components arrive ready for first machining steps. Rotax makes press-fit, multi-piece crankshafts so that light, reliable, single-piece connecting rods can be used. About 160,000 trouble-free, press-fit cranks are made per year.

Computer-controlled machining and initial parts testing are standard, but much of the engine assembly is done by hand. Each engine is test-run and the results are documented. I was surprised to learn that the only difference between the standard 912s (which get a minimum of 20 minutes of run time) and the type-certified versions (required in type-certified aircraft but not in LSAs) is more extensive testing and a complete documentation trail that goes with the engine. (For FAA-approved SLSAs, the Rotax 912UL and 912ULS engines were approved under the ASTM engine consensus standard, precluding the need for the extra tests and paperwork and saving thousands of dollars per engine.) Every Rotax aviation engine is tracked throughout its life.

The Products

Originally concentrating on two-stroke engines, Rotax has seen a complete shift in its market as four-stroke sales have doubled in the last three years. Four years ago, sales were 80% two-strokes and 20% four-strokes. Now the numbers are reversed.

Rotax continues to produce the fan-cooled Rotax 503 and liquid-cooled 582 two-strokes, but 447 production has stopped recently. Now focusing on the 912/914 market, Rotax noted some of the unconventional features. Liquid-cooling the cylinder heads adds to the durability of the valves, valve seats and the heads themselves. The engines can fly for up to an hour without coolant, as the lower liners are air-cooled.

Some pilots who are experienced with geared engines-particularly the GO-300 in the Cessna 175-have questioned the reliability of all geared general aviation aircraft engines including the Rotax 900 series. Rotax gearboxes, however, have proven to be reliable. In our afternoon session about Rotax aircraft engines, we were joined by a representative from one of the European Rotax service centers. I asked what gearbox parts are routinely replaced at engine overhaul time. The answer: gaskets and bearings, not gears or cases. (Phil Lockwood, whose Rotax Service Center performs overhauls in Sebring, Florida, notes that gearbox life depends on proper operation such as setting idle speed up to the recommended rpm.)

Recommended time between overhauls (TBOs) was raised in 2003 to 1500 hours for the Rotax 912 series and 1200 hours for the 914. We were told that Rotax policy is to make good on these numbers, providing compensation or credit for properly maintained engines that fail to make the TBO specs. (Lockwood says some Rotax 912s achieve 2000 hours before overhaul.)

Cake Icing

After lunch at the factory, we journalists and several Rotax managers and public relations people were bused to Linz Airport, where a special airplane waited to fly us to the next phase of the tour. The idea was to provide us with a chance to experience Rotax 912 power in one of three SLSAs: a StingSport, a Tecnam Bravo and a Flight Design CT.

The half-hour low-level flight to Salzburg Airport was aboard a DC-6, the centerpiece of a 23-aircraft collection that resides at Hangar-7 in Salzburg. Hangar-7 is a combination aircraft museum, art museum, world-class restaurant…and an architectural wonder in its own right. The founder of Red Bull, Dietrich Mateschitz, is a pilot and aviation buff…and a Rotax fan. Hangar-7 is open to the public. Admission is free, and if you have more than a few hours in Salzburg, take Bus Line 2 from downtown. Everyone in Salzburg knows Hangar-7. All 23 aircraft are fueled and ready to fly.

Unfortunately, low clouds and windy weather kept the CT and the StingSport away, and Id already flown the Tecnam Bravo. But the trip to Hangar-7 and the late afternoon briefing by Rotax Marketing Director Klemens Dolzer and Aircraft Engines Manager Michael Wagner was a highlight.

Wrapping Up

I asked about ethanol in gasoline. (Premium auto gas is the recommended 912/914 fuel.) The answer: Up to 5% is OK if airframe systems can tolerate it.

I also asked about overhaul costs compared with the price of a new engine. Answer: Most moving parts are replaced, and the cost is about 70% of the original price. (Lockwood said it is closer to 60% at his facility.) Even for pilots like me who have flown dozens of Rotax-powered aircraft, the tour was a confidence-builder.

For more information, visit, and also check out Direct links can be found at

Previous articleJanuary 2008
Next articleTexas Sport Cub
Kitplanes Magazine: Your Homebuilt Aircraft Authority. We cover topics relevant to anyone who has ever dreamed of building or owning a homebuilt experimental aircraft.


Please enter your comment!
Please enter your name here

This site uses Akismet to reduce spam. Learn how your comment data is processed.