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Thread: Rotax 2 Stroke Engine, best choice for low cost flying?

  1. #1

    Rotax 2 Stroke Engine, best choice for low cost flying?

    I'm looking to buy an Experimental for low-cost time building. One of the commonalities of many under $15K planes is Rotax 2 stroke engines. I am trying to determine if a 4 stroke is worth the extra cost because I am planning to purchase this plane as a first plane, not as a long-term plane.

    My plans for the plane are:
    Own 2 years or less and Fly 200-350 hours.

    This will mean that I will pass TBO on a 2 stroke Rotax, so I will need to budget for at least 1 overhaul. I have a mechanical background, so I am confident that I can do the overhaul myself, but I want to budget based on me removing the engine and sending it off for an overhaul. I am concerned about know that I will experience an overhaul, but I also find the low cost of overhaul or replacement appealing because it means that unexpected expenses like an engine failure or prop strike will cost less than on an O-200.

    Because it has a huge impact on every decision we make about airplanes my planned mission is:
    Fly enough qualify for a commercial ticket - Primary Goal
    25% - Local, in/out of same airport flights during the day (Just fly)
    25% - Daytime VFR XC Flights
    15% - Night VFR XC Flights
    15% - IFR XC Flights, including IFR training - Planning to rent a plane for these, unless there are low-cost options to fly in my experimental
    10% - Just Fly Night Flights
    10% - Carrying Friends on Overnights and Vacations - Planning to Rent for these, due to needing to carry more than 1 passenger

    My questions are: Is there anything I am overlooking with this plan? Is the Rotax 2 stroke the best option for this plan, or is there a cheaper way to fly (even if it means more up front)? What should I budget for an overhaul, or should I just budget for a replacement engine after TBO? What questions am I forgetting to even ask (aka, what don't I know that I don't know)?

  2. #2
    I'm certainly no expert but I think I would just get a Cessna 150. If you look around you will probably find one that is IFR.

  3. #3
    rwanttaja's Avatar
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    Quote Originally Posted by thisadviceisworthles View Post

    25% - Local, in/out of same airport flights during the day (Just fly)
    25% - Daytime VFR XC Flights
    15% - Night VFR XC Flights
    15% - IFR XC Flights, including IFR training - Planning to rent a plane for these, unless there are low-cost options to fly in my experimental
    10% - Just Fly Night Flights
    10% - Carrying Friends on Overnights and Vacations - Planning to Rent for these, due to needing to carry more than 1 passenger
    Personally, I haven't heard of any IFR-qualified planes using a two-stroke engine. You've got 40% of your flying either night or IFR flying. I'm not that familiar with two-stroke engines, but one quick online search says that the Rotax 582 has a 170 watt generator. That's 15 amps to run a full IFR panel, radio, transponder, ADS-B, position lights, strobe, and landing light, plus charge the battery back up from starting the airplane.

    To me, this sounds like a serious stretch. Now, *maybe*, with modern electronics, LED lighting, etc, this is doable. But if I understand the two-stroke Rotaxen, the same generator is powering the ignition system. You could go all '50s on us and run most of the gauges with vacuum, but you'd need a venturi since I don't believe there's a vacuum pump for the Rotax.

    The other factor is just out-and-out safety. Statistically, aircraft with two-stroke engines suffer the loss of engine power about twice as often as traditional engines. And since this is based on accident statistics, and most two-stroke-powered airplanes are easy-to-force-land ultralights (which are less likely to result in a reportable accident, the actual rate is probably worse.

    It's a risk that many two-stroke pilots are willing to take. However, again, you're talking about 40% of your flying being IFR or at night. Pulling off a successful forced landing will be difficult. Combining the higher risks associated with night/IFR operations with the lower reliability of a two-stroke really doesn't sound like a good idea.

    Ron Wanttaja

  4. #4

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    Most 2 strokes have touchy carb jets. In the desert where I live it can be around 100 degrees in the daytime and 65 Degrees at night. if your jets are set for 100 Degrees for the day and go into the night you'll have problems with leaning out and overheating or not getting up to temp, or running rich and flooding out. Most 2 stroke failures are Jet related or old gas or water and crude in the carb causing jets to plug up. Rotax has a pretty good chart for jets needed at altitudes and outside air temps. I'm sure all of them have charts for carb jet settings.

  5. #5

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    Based solely on anecdotal evidence, I can say that being a mechanic is a big plus when owning a two stroke engine.

    As much as it pains me to say it, I think you'd be better off purchasing a spam can (C150, C172) if you're going to go IFR.
    The opinions and statements of this poster are largely based on facts and portray a possible version of the actual events.

  6. #6

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    Some operators get double TBO or more with the two-stroke. Two-stroke uses more fuel and oil.
    Night VFR is same as IFR if it quits or many other hazards of night, so not recommended by me.

  7. #7
    Sam Buchanan's Avatar
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    I have about 250 hours two-stroke time. There is no way I would fly a two-stroke at night or IMC.
    Sam Buchanan
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