Putting the Engine in Engineering
Austrian manufacturer BRP celebrates the 25th Anniversary of its astonishingly successful Rotax 912 engine. The company started the production of aircraft engines in 1973 with the first certified aircraft engine delivered in 1975. AVIATOR chatted with BRP and discovered the history behind this remarkable sports aviation powerhouse.
Which engines were used as aircraft engines before BRP began producing Rotax 912 engines?
The aircraft engines at that stage were spin-offs of snowmobile and industrial engines, which were heavy and themselves based on Continental and VW engines.
Why did BRP decide to develop a new aircraft engine?
The market demand was for a modern, reliable engine that would meet the expected performance. In 1985, the company started the development of a 2-cylinder flat engine especially for the aircraft business. Though the performance of 65 HP was substantially higher than the current aircraft engines with 40 HP, BRP expected more. With the development of a 4- cylinder flat engine, BRP wanted to reach the next level – the 80-HP engine’s category.
The Rotax 912 development was a project dedicated to the aircraft market. For the very first time, all conditions needed on an aircraft engine were considered, like high security, high- quality standards for airplanes, etc. In consideration of the experimental airplanes and gliders, the power-to-weight ratio was one of the main targets to aim.
What was the difference between the Rotax 912 engine and its closest competitors?
The reduction gear was a big advantage over the competitors. Due to the gearbox the propeller speed of 2000 rotations per minute was significantly lower and resulted in a quieter operation. This was an essential remark compared to the direct drive, which was designed on the VW spinoff models (Sauer and Limbach).
A major advantage in the development of the Rotax 912 engine was the opportunity to influence the whole design engineering. The Research & Development effort was considerable but the big advantage was the ability to supervise the project from concept to production. “A lot of our engineers were pilots and they could share their personal experience and theory. Above all that, they understood the essential requirements of an aircraft engine,” reports Francois Tremblay, director, Rotax aircraft engines.
”It is remarkable that about 20 of our employees on the aircraft team are pilots. This way, we are very close to our market and know about the demands in the field,” assured Tremblay.
The first flight tests with the Rotax 912 engines were operated on an airfield in Austria, with the Rotax Falke model, a glider from the German Scheibe company. Later, the engine was installed into a Dimona model from the Hoffmann company (now called Diamond Aircraft).
How did the market react to the new model?
The wow effect on the market was perfect. The engine’s reliability with a time between overhauls (TBO) of 600 hours was twice as high as with a 2-stroke aircraft engine. This implies that the new Rotax 912 engine initiated the aircraft industry’s shift from 2-stroke engine to 4-stroke engines; from the 40 HP engine (used for one-seater ultralight aircraft) to the new 4-stroke with 80 HP that could be used for 2-seat aircrafts.
It was in 1989/90 that the first Rotax 912 engine was delivered out of serial production. The company produced mainly 2-stroke engines up to then. “From the very beginning, when we delivered the 30 first non-certified Rotax 912 aircraft engines in the first year, it was clear that the engine would become a success,“ said Tremblay. The target was the JAR-22 certification (airworthiness requirements for gliders and powered gliders) of the responsible aviation authority (Austrian Type Certification). That was obtained within the first year following the start of production.
In which areas did the engine begin to be recognized as the forerunner of a new era?
The Rotax 912 engine was quickly recognized in the gliding sector (Dimona model, etc.) and substituted Continental and VW spinoffs and other heavy engines. In parallel with the gliding sector, the ultralight (UL) – as well as the advanced UL – and the experimental airplane category were established in 1995. Due to the heavier take-off weight, more power was required (concept – power-to-weight ratio).
At the same time, the General Aviation Revitalization Act was signed in the United States. It was intended to counteract the effects of prolonged product liability on general aviation aircraft manufacturers by limiting the duration of their liability for the aircraft they produce. This meant that more companies invested and therefore more aircraft manufacturers could establish themselves on the market.
Has there been an impact on the whole market?
Gradually, different aircraft manufacturers developed airplanes and installed the new Rotax 912 engine. Without a doubt, this affected the whole aircraft market.
“In 1994, we received the ‘Type Certificate’ for the Rotax 912 F engine, the license regarding FAR 33 and part 23, in the United States. This achievement was to us what a gold medal is to an athlete,” said Tremblay. The Rotax 912 F engine was put in the Katana, a VLA (very light aircraft) model from Diamond Aircraft.
Why is the Rotax 912 engine family still a market leader?
The aircraft market is very conservative and imposes extremely high security and high-quality standards. The overall market volume is too low for a lot of competitors to establish their market.
For the altitude flight test in 1993, the Rotax 912 engine was modified and equipped with a turbocharger. The airplane (HK36 Super Dimona model) powered by the Rotax 912 engine with turbocharger reached an altitude of 33,000 feet (approx. 11,000 m). As a result of this flight test, the Rotax 914 engine’s prototype (Rotax 912 engine with turbocharger) was built. The concept was successful. The company started the development of the Rotax 914 engine and production began a short time later.
In 1996, the certification of the Rotax 914 F engine respecting FAR 33 and JAR-E (a so-called joint certification) was obtained. “Our company was the first with piston engines, followed by other aircraft categories that jumped on the bandwagon. As a consequence the market expanded,” added Tremblay.
Until 1998, the most performing versions were the Rotax 912 UL/A/F engines and then the Rotax 912 S engine was launched on the market (FAR 33). More horsepower was one of the characteristics and the engine was intended for airplanes with a higher load capacity.
In addition, the time between overhauls (TBO) increased from 600 to 1,000 hours. The TBO for the whole Rotax 912 engine family increased in several steps. Since 2009, all Rotax 912 engines provide a TBO of 2,000 hours.
What are the newest developments, based on the Rotax 912 engine?
On March 8th, 2012, BRP launched the new Rotax 912 iS engine – an evolution of the proven Rotax 912 aircraft engines. BRP engineers incorporated technology enhancements such as a modern fuel injection system and digital engine control unit (ECU) to the Rotax 912 engine.
Real-life flight results are showing an improved fuel economy of up to an average of 30% (vs. the Rotax 912 ULS engine) compared to the 21% improvement mentioned at its launch. The Rotax 912 iS engine automatically improves its fuel efficiency by switching to a lean ECO mode once the throttle is pulled back to a throttle setting below 97% after the aircraft’s start and climb phases. This results in lower operating costs. Also, the improved carbon footprint due to lower CO2 emission levels (-38% to -70%) is an additional benefit compared to other aircraft engines.