Gemini Engine Moving Toward Production

By Scott Spangler on January 12th, 2009

JetWhine_Gemini_Test Designing, testing, certifying, and producing a new aircraft engine is never an easy process. A sour economy that sends investors into hiding just makes the process that more challenging. But the three-cylinder, six piston diesel/Jet A  Gemini 100 (see Gemini Diesel Engine Attracts Industry’s Eye) is gaining on that goal, says Tim Archer, president of Powerplant Development USA.

jetwhine-tecnam-p92-eaglet Being developed in Britain, the company just received the UK equivalent of a small business loan that will put the Gemini 100 into limited production in April 2009. The first engines will be going to Tecnam, which will use its Eaglet to evaluate both the 100 and, at a later date, the turbocharged Gemini 125. “I don’t think we’ll make Sun ‘n Fun,” Archer says, but the Gemini Tecnam should be ready for AERO Friedrichshafen 2009, Europe’s leading GA trade show, and EAA AirVenture Oshkosh.

Fuel is, perhaps, first among the reasons why aviation needs a production piston powerplant that efficiently drinks a turbine’s favorite liquid.  Compared to diesel/Jet A, 100 LL avgas is a drop in the refiner’s bucket, and environmental agencies and groups have it in their sights as the work to rid the world of the last leaded fuel. 

Before Gemini 100 production begins, it must complete its test stand program in Hastings UK, which is now focusing on mapping the fuel system. With its unique opposed-piston design (two pistons in one cylinder), Powerplant Developments had to design its own fuel system, says Archer. Being unique, there were no data points to compare it to and more quickly determine the optimum fuel quantity and spray pattern for each engine rpm and horsepower setting.

Creating this map is time consuming and involves a lot of minute changes to the high pressure fuel nozzles, Archer says. The good news is that the mapping effort is nearly complete. “We’re at 90 percent engine rpm and approximately 80 percent power.” To determine the final spray patterns and injection timing, PPD is testing the system on a separate test rig. When this testing is complete, the system returns to the engine to complete the fuel mapping process.

The only other engineering challenge is designing the new supercharger mounting interface. For initial testing PPD modified an off-the-shelf belt-driven unit to accept a drive shaft. The production unit should be ready by the time the fuel mapping is done. Once the Gemini 100 is in limited production, PPD will turn its attention to the Gemini 125, basically the same engine with a turbocharger. It should follow the 100 by three or four months. —Scott Spangler


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9 Responses to “Gemini Engine Moving Toward Production”

  1. Jeffrey Sigmon Says:

    I’m all for these diesel engines! I hope they don’t follow in the same footsteps as Thielert and their engine used in the Diamond Twinstar.

  2. Dale Kettring Says:

    Go diesel!!!

    I, too, am all for getting these engines certified. Then move forward to getting bio-diesel fuels certified as well.


  3. Vernia Haider Says:

    I don’t often respond on blogs until now! I’ve added you to my reader, thanks :)

  4. andre Maertens Says:

    I am a retired diesel engineer and say that it is time for those engines to hit the market.i my opinion they should have been there 50 years ago.For those who may ask Yes I know the junkers Jumo it was a marvellous engine.Thanks for copying some of it.Hope the Gemini comes soo we need them NOW!

  5. Mike Says:

    Good on you PPD. The Gemini engine will fit comfortably under the cowling of my Robin ATL, and weighs slightly less than my time expired Limbach 80 HP. Guess I will just have to wait and hope the Gemini becomes available for retrofit soon.

  6. ron brothers Says:

    ITS about time for this type of technology to come back, for piston engines, i would say that is is the ultimate engineering for pistons, so many pluses with little drawbacks.

  7. Bill Izard Says:

    looking forward to your engine going into my Omega aircraft

  8. AirVenture Update: Gemini Diesel Engine | RENT-A-PLANE Says:

    […] diesel engine (Gemini Diesel Engine Attracts Industrys Eye), with an update in January 2009 (Gemini Engine Moving Toward Production). Because readers are still discussing the engine in the comment sections of these posts, here is […]

  9. Leif G Alstadseter Says:

    Is there somebody who knew were I can get a answer what the price is for the Gemini Diesel and delvery time?
    I have tried to call and send a e-mail….


    Leif G Alstadseter

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