General aviation engines too stagnant for you? Superior Air Parts has an affordable cure coming in their just announced Gemini diesel at $24,900. First application is on the Super Legend Cub as we learned in a joint announcement from Superior and Legend Cub this morning at AirVenture.
No clone this, the new Gemini – it is a water cooled, two-crankshaft, opposed piston 3-cylinder 2-stroke. That means three cylinder bores, each with two pistons reciprocating towards each other. The dual crankshafts live at the outer ends of the engine where the valves and rocker arms normally found in typical horizontally-opposed aircraft engines.
The two crankshafts are mated through a geartrain terminating at the prop shaft in the engine’s center. This allows thrust-making 4000 engine and 2500 propeller rpm. With the engine mounted in a flat configuration Superior says the packaging and weight are favorable to the timeless Continental O-200 so the Gemini should easily package under numerous existing cowlings.
Superior has worked with Weslake, an English consultancy, on the Gemini. Advantages to the design are remarkably tight packaging, a very rigid block, short, lightweight and stiff crankshafts and reported notably smooth running. Gear noise is said to be minimal, with the engine essentially silent behind the usual propeller noise.
Superior is debuting the Gemini in naturally-aspirated, 100 hp form via the Super Legend Cub with a series of follow-on turbocharged engines following. First of these is rated at 125 hp and future engines will add cylinders (remember, two pistons per cylinder in 3-, 4- and 5-cylinder form) to reach 550 hp.
Superior says the engine will be built in their Coppell, Texas facility with parts sourced from best-case suppliers (German forgings, U.S. machining).
There is still a long way to go before the Gemini is a proven quantity but the program is well underway with dyno mules already running. Expect the bare Super Legend Cub airframe wearing the mock-up Gemini engine at Air Venture to be flying at Sun-and-Fun next spring.
Check out this video by Paul Berorelli from our sister publication AVweb: