Rotary engine technology takes off in general aviation

So, while designs are well proven, motors require some 70 or 80 moving parts and still use 100-octane low-leaded (100 LL) fuel that has long been displaced by kerosene for commercial aircraft. Thanks to EUREKA project E! 2743 KERO, advances in combustion chamber design and electronic management systems are making it possible to develop a reliable rotary engine for small planes running on standard kerosene jet fuel.

Swiss project leader Mistral Engines saw a major market for a safer, more reliable motor that could be easily adapted to any model of light aircraft and able to run on industry standard fuel. The design is based on the Wankel rotary engine developed in Germany in the 1930s but emerged at the wrong time. So far, it has only really been developed and commercialised by Japanese car maker Mazda in its RX-8 and previous models.

Safety and reliability are key factors in aviation. Advantages of the design include excellent reliability as there are few moving parts, a high power-to-weight ratio, compactness and smooth running compared with conventional piston-engine designs. Moreover, the engine will run on widely available standard commercial aviation fuels. The Wankel engine has a rotor instead of reciprocating pistons, doing away with any need for crankshafts, pistons and springs and reducing the number of moving parts to only two or three. Modern electronics has now made it possible to overcome timing and injection control complications, resulting also in similar fuel consumption figures to piston engines.

Several partners are involved in the EUREKA project. The Ecole Polytechnique Fédérale de Lausanne (EPFL) is studying the best combustion conditions for the kerosene in terms of combustion-chamber design, injection and ignition. “We are also now developing a special exhaust silencer with the EPFL to limit the noise, using active and passive noise- reduction technologies able to work at very high temperatures,” adds Geles. “This has not been done before.”

EUREKA labelling played a key role in obtaining funding for the KERO project. “While we managed to start the work with ‘pocket money’”, explains Claude Geles, chairman of Mistral. “EUREKA labelling enabled us to put together the10 million euro in private equity financing that we needed to see the project through to a fully certified product ready for manufacture.” Most of the technical problems have already been overcome –one problem still being tackled is pushing away the detonation, or pre-ignition, limit. Nevertheless, Geles predicts full FAA certification within 18 months of the project ending. The sky is then literally the limit!