Rotax Aircraft Engines is transitioning its new 915 iS engine design from development to certification, and plans to deliver the new powerplant during the second half of this year.
The four-cylinder, four-stroke liquid/air-cooled engine weighs 185 pounds, including propeller speed reduction unit, turbocharger, intercooler, exhaust system, engine control unit, and fuel injection. A mockup was on display at the Sun 'n Fun International Fly-In and Expo in Lakeland, Florida.
A more powerful extension of the Rotax 912/914 engine family, which has proven itself through more than 50 million flight hours, the 915 iS offers the best power-to-weight ratio of any Rotax engine to date and can produce its rated takeoff power up to 15,000 feet.
“The interesting thing about the 915 is that we will be able to give you takeoff power to 15,000 feet,” Tucker said. Takeoff power is 135 horsepower, and 127 hp is maximum continuous power. For comparison, the Rotax 912 weighs about 145 pounds, and the 914—with turbochargers—is about 165 pounds. “There has been huge demand from people who want to move into higher-performance, two-place [designs] where constant speed propellers can be used.” So initial U.S. customers will be in the experimental sector, and not light sport, where current U.S. rules prohibit the use of adjustable-pitch propellers; manufacturers can seek waivers.
The engine’s performance is being mapped up to 23,000 feet, and some could be used in unmanned aircraft. Customers including General Atomics have bought Rotax engines for drone use.
“These are all built as recreational engines, but we realize some will be used in unmanned aircraft,” Tucker said. “They buy the engine as is; what they do with it is up to them.”
Also on display at Sun ’n Fun is the Searey ATD, for advanced technology demonstrator, a collaboration of RS Aerotech, Progressive Aerodyne Searey, and MT Propeller. Currently equipped with a Rotax 912 iS, the Searey ATD is the first light sport aircraft to be equipped with a constant-speed propeller and a single-lever power control, which the partners say significantly improves performance and dramatically reduces pilot workload. It will receive a new 915 iS immediately after Sun ’n Fun.
Rotax made a spark plug change recently, when longtime supplier NGK decided to leave the aviation market because of liability concerns, Tucker said. The company has shifted to and is already distributing a Rotax-branded spark plug. “Rotax assumes the liability of the spark plugs of Rotax products,” he said. NGK plugs in inventory—or already in aircraft—may continue to be used, he added.
More information on the new engine is available on the Rotax website.