The Gemini, a promising three-cylinder, six-piston, two-crankshaft two stroke of 100 hp was shown for a few years by Powerplant Developments, a UK company that produced a working prototype/dyno test engine, but ran short of funding for development toward certification. Several LSA (Light Sport Aircraft) manufacturers have expressed strong interest. Opposed piston engines like the Gemini have a built-in obstacle: with ports in the cylinder walls, they have either relatively low power or short lives. The project still exists on hold.
Some other diesel engines have shown promise in experimental in recent years. WAM (Wilksch), of Gloucestershire, England, has flown since 1997 and has freely offered its three-cylinder, two-stroke 120-hp diesels to willing experimental airframers. This direct-drive engine is inverted and has a wet sump; and though it is a two-stroke, it uses a valve for exhaust. In the late 1980s and early 1990s, the Zoche family (of Munich) developed three (70-, 150-, and 300-hp), two-stroke turbocharged diesel engines, but I was told their major funding ceased, and the designs languished.
Certified and experimental
Many companies are planning to stay in the certified marketplace, though some have released power to particular experimentals. DeltaHawk, especially, has several engines flying in many designs, and also has test engines deployed among both experimental designers and certified airframers.
Experimenters (as opposed to volume developers) have flown just about everything, from Citron to Pugeot to Opel to Subaru and beyond, but these are more projects for the hobbyists themselves, and MRO activities are often as not performed in private hangars and garages. Most companies offer some level of factory training on their engines. AMT
DeltaHawk: www.deltahawkengines.com; Centurion: www.centurion-engines.com; Austro: www.austroengine.at; SMA: www.smaengines.com; Continental: www.genuinecontinental.aero; Raikhlin Aircraft Engine Developments (RED): www.red-aircraft.com; Wilksch/WAM: www.wilksch.net; and Zoche: www.zoche.de
Tim Kern is an aviation writer, aircraft builder, and private pilot. He is based in Anderson, IN, and can be reached at firstname.lastname@example.org.
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