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)?

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.

Quote:

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Originally Posted by thisadviceisworthles

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

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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

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.

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.

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.

I have about 250 hours two-stroke time. There is no way I would fly a two-stroke at night or IMC.

I would check out a few options. If you are invested in the project, then an automotive engine conversion may be worth checking out. You can get an automotive engine for pretty cheap (especially compared to aircraft grade stuff...) and there plenty of small startups that make reduction drives. Subaru engines are a relatively common choice, as they are light, make good power and are reliable. You can also easily find reduction drives for the Subaru engines. I am looking into scratch building a plane with Mazda Wankel rotary engines, which can have good power to weight ratios (300hp for roughly 225lbs), but they burn oil and can be very finicky if not treated right. I am currently looking at the turbo 13B from the RX - 7. If you are interested in the Wankel, then I have several companies that make reduction drives for them.

Christian L.

As waltermitty said, a Cessna 150 that is IFR equipped is going to be your best affordable option for what you describe. You would have to have more guts that I do to fly a 2-stroke powered plane at night or IFR. These engines were designed for ultralights and other very light planes. They do not have the reliability or the electrical systems needed for night or IFR flight, and I dare say you will have a hard time finding a 2-stroke powered plane that is IFR legal.

Similarly, auto-engine conversions do not enjoy as good a safety record as certificated engines. That is just a fact. I personally know of five inflight engine failures of auto engine airplanes. These have their place but it is not at night or in IMC.

$15K is a pretty tight budget for what you are trying to accomplish, but don't get sucked into something that isn't safe just to save a little money.