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Change is in the Air as Diesel Engines Advance

By James Wynbrandt

July 20, 2015 - Diesel power has drawn increasing interest in recent years as a viable power option in the GA world, and it’s propelling developments at Superior Air Parts and Engineered Propulsion Systems (EPS) that both companies are touting at EAA AirVenture Oshkosh.

Superior Air Parts (Booth 257), which unveiled its Gemini diesel engine series at the Sun ’n Fun International Fly-In & Expo this year, announced here that American Legend Aircraft Co. will offer the 100-hp Gemini diesel engine as a factory option on its line of Legend Cub light-sport aircraft.

The size and shape of the 100-hp Geminis is smaller than the similarly powered O-200 and Rotax engines, so “it fits in a normal cowling, with room to spare,” said Scott Hayes, Superior’s VP, sales and marketing, one of the reasons Legend opted to offer the engine.

Said Darin Hart, president of American Legend Cub, “Our sales are growing every day in overseas markets,” and “with its high torque, very efficient fuel burn, and the ability to run on Jet A, diesel or bio-diesel fuels, the 100-hp Gemini will be an extremely popular engine option for Legend Cub buyers around the world.”

Superior has a mock-up of the engine installation on the Legend Cub at its display (Booth 257). The two companies anticipate having an engine installed and operating on the airplane by October and hope to have a flying airplane in time for next year’s Sun ’n Fun fly-in. No price for the engine has been set, but Hayes expects it to sell in the $25,000 to $28,000 range.

EPS is developing a diesel engine family in the 320-450 hp range that’s currently undergoing FAA certification, with approval expected in early 2017. The engine is expected to increase fuel economy by 30 to 50 percent over conventional pistons, and have a 3,000-hour TBO (time between overhauls). The engine was first flown at Mojave Air and Space Port this May on a Cirrus SR22 piloted by Dick Rutan, which capped Phase 1 of the development program, said Michael Fuchs, co-founder, president, and CEO of the New Richmond, Wisconsin-based company. An STC (supplemental type certificate) was obtained for the installation, making the SR22 “a prime candidate for future STC activities,” said Fuchs.

The development project is expected to cost about $45 million, and EPS is now fully funded, Fuchs said. Some $22 million has been spent thus far. Cost of the engines hasn’t been determined, but Fuchs estimated the difference over a conventional piston would be similar to that seen in automobile engines. He added that studies indicate operators would enjoy savings in reduced fuel and maintenance costs over the life of the engine that would more than make up the difference.

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