Gemini 100 Sports Impressive Power, Low Weight

Powerplant Developments, a UK company, in a joint development effort with Weslake Air Services and Jade Air, unveiled plans Tuesday at AirVenture 2007 to produce a diesel engine intended for the LSA market.

Tim Archer, President of Powerplant Developments, said the company has been working nonstop over the last seven months to make their idea a reality. Weslake Engineering is known for engineering Formula 1 racing engines, and recently expanded to help build the Gemini. Jade Air, which has been around since the 1970s, specializes in engine overhaul, repair, and engineering consulting.

Derek Graham, Chairman and Co-founder of Powerplant Developments, detailed the build process and outlined many of the engine's features. Graham believes that Europe has been forced to lead in diesel engines because of fuel prices, and the US will be soon to follow.

"The LSA category represents the future of this industry," Graham explains. LSA manufacturers consulting with Powerplant Developments desired an engine capable of 100 horsepower and weighing 150 pounds. Fuel efficiency was a big concern, as well as fuel availability.

The answer lay in a diesel engine that most had forgotten.

As Graham says, "I founded my business on the basis of identifying a market need and satisfying a market need." A lighter engine for the LSA market was the change most LSA manufacturer's desired, so the company began to work on concepts for such an engine. Michael Daniel, head of R&D for Powerplant Developments, had the idea to resurrect a somewhat unconventional engine that Graham says "simply fell off the radar."

Powerplant Developments' Gemini 100 is a supercharged 1.6 liter three cylinder that produces 100 horsepower and weighs a scant 150 pounds. The two-stroke engine has no cylinder heads, valves, rockers, pushrods or camshafts, simplifying design and making the engine extremely maintenance-friendly. The Gemini is supercharged because their design requires forced induction to operate. Since the supercharger saps 30 horsepower (the engine can actually produce 130 horsepower), plans are to eventually upgrade to a turbocharger which would only require five horsepower to run.

The fuel efficiency of the diesel is what essentially motivated Powerplant Developments, and the Gemini 100, at 75% power at 5,000 feet, consumes 4.75 gallons per our of Jet-A compared to 6.6 gallons per hour of Avgas for a Rotax 912. Since the engine employs dual crankshafts as well as some other non-conventional aspects, introducing a training program for this engine will be a priority for the company.

The Gemini 100 sports two pistons in each of its three cylinders; the pistons fire toward each other, the mixture combusts, and they are driven away. Graham notes the technology originally appeared on Lufthansa aircraft in the 1930s, but was abandoned in favor of the turbine engine, though no one had considered its potential as a lightweight engine.

Currently Powerplant Designs is researching a DVD training program, but as the maintenance schedule is small, and the engine is designed for a 2000 hour TBO, the transition should be relatively simple.

"There is very little to do to it," explains Graham.

The first Gemini 100 engines will be available to the experimental market in mid 2008, and the engine will be ASTM certified after that. The prototype engines will fly by the end of September or early October of this year. Cost? "How much will it cost or how much will I sell it for?" says Graham with a laugh. Plans are to offer the Gemini 100 for around $18,500, or about 10% more than the popular Rotax in most LSAs.

The Gemini, which is smaller in every dimension than the Rotax it will compete with, will allow manufacturers more freedom in shaping the cowling of their aircraft and designing engine cooling into the airframe. Current studies by Powerplant Designs have shown that the Gemini Engines could be designed up to a staggering 600 horsepower.

The Gemini 100 may prove popular not only because of its efficiency and light weight, but also because of its simplicity. "The simpler we can make it, the better," says Graham.

FMI: www.jadeair.co.uk/