Non-standard Engines for Kitfoxes

[rv9ralph]

I would like to fly in a kitfox with the Viking 130hp engine...

So, I was reading an article in the latest Kitplanes about the Zodiac Cruzer. He had a Viking engine. It is worth a read to balance when deciding. He had some issues.

Ralph

[Kitfox Pilot]

Thanks for that Ralph, I don't get kitplanes and can't find the article online but would like to see it because I have been looking at the Viking engines and it hard to find much research on them. I'll see if I can locate the issue. Thanks

[airlina]

Harlan, I just read that article last night(the one that Ralph is reffering to), and believe me you need to find a copy of the June 2020 Kitplanes and read it. And if you can't find one , I'll send you mine. That's how strongly I believe in NOT using "alternative or non-standard engines" in your new Kitfox. Its an eye opener for someone considering going that route. Bruce N199CL

[Kitfox Pilot]

Thanks Bruce , I will get a copy for sure if I can find one.

[genie]

Harlan, I just read that article last night(the one that Ralph is reffering to), and believe me you need to find a copy of the June 2020 Kitplanes and read it. And if you can't find one , I'll send you mine. That's how strongly I believe in NOT using "alternative or non-standard engines" in your new Kitfox. Its an eye opener for someone considering going that route. Bruce N199CL

Thanks to all for your comments.

As for a Viking engine, I discussed this with homebuilder friends. They all dis-endorse the Viking engines as they say that they are made by the same people who used to provide modified Subaru engines for aircraft.

It seems that the consensus is to go for a Rotax engine. I can see three issues with this:

1) Such an engine is usually rather expensive, at least compared to some alternatives.

2) I have heard of reliability issues with Rotaxes as they can fail. They are highly stressed for aircraft engines as they produce more than 1 HP per cubic inch, and in some cases 1.2 HP per cubic inch.

3) Most important: I heard of many Rotax engines being stolen from their aircraft. As they are so good thieves take them. I would like to be able to sleep with peace of mind at nights and not worry about my Rotax engine being stolen.

I understand that Lycoming and Continental engines are very reliable as they have been around since the fifties and sixties and have logged numerous hours in aircraft. Their output is half a horsepower per cubic inch. However I understand that they are somewhat heavy compared to Rotaxes and require lead replacement additives to their fuel.

As for the Belgian engines, they are not less expensive than Rotaxes. ULPower engines provide 2/3rds of a HP per cubic inch, or around 1.5 cu.in per HP. Neither engine type uses reduction gears.

Jabiru engines, I hear, suffer from cooling problems. One can get liquid cooled cylinder heads for them. But in that case they cost more and are no longer standard engines.

I love the looks and sound of Rotec engines. However according to an article which I once read the after sales service of the company was not up to scratch. Besides such engines are heavy and draggy and obscure forward visibility. When compared with the likes of Rotax one can see how much half a century of progress has resulted in.

Unless anyone can find an alternative I reckon that this would give me a choice between a Rotax, a Lycoming and a Continental engine.

George Nielsen

[Av8r3400]

Thanks to all for your comments.

As for a Viking engine, I discussed this with homebuilder friends. They all dis-endorse the Viking engines as they say that they are made by the same people who used to provide modified Subaru engines for aircraft.

It seems that the consensus is to go for a Rotax engine. I can see three issues with this:

1) Such an engine is usually rather expensive, at least compared to some alternatives.

2) I have heard of reliability issues with Rotaxes as they can fail. They are highly stressed for aircraft engines as they produce more than 1 HP per cubic inch, and in some cases 1.2 HP per cubic inch.

3) Most important: I heard of many Rotax engines being stolen from their aircraft. As they are so good thieves take them. I would like to be able to sleep with peace of mind at nights and not worry about my Rotax engine being stolen.

By the Numbers:

1) Comparing a NEW Rotax 912 to a NEW Continental or Lycoming you will find the Rotax very affordable. I can list several people that have purchased low time used engines that are flying them today for less than $7500. Affordable 912 engines are out there, you just need to look for them. By the time they land on Barnstormers they are already sold.
2) Reliability issues with Rotax are easily put into two categories: Owner induced problems and incompetent Mechanic induced. In both cases it is most often people trying to "Fix" something that isn't broken.
3) This is an overblown rarity.

If you enjoy the build and the experimentation of Experimental Aircraft, choose your own crazy engine and enjoy it! If you are more interested in flying, go with an engine that is supported by your Kit manufacturer and has some following among builders. This will give you the best chance of success.

As to Viking, the day Jan Eggenfellner starts paying back the money he stole from all of his Subaru customers, I will take him seriously. Until then, I'm not interested.

[aviator79]

HP/cubic inch isn't actually a very good indicator of engine reliability. Because Rotaxes run at much higher RPM, you could say that they are spreading that stress over more cycles. Brake Mean Effective Pressure (BMEP) is more closely correlated to engine reliability. As it turns out, it's just some constant times TORQUE/cubic inch. Here are some BMEPs:
Conti O-200 - 147 psi
Lycosaur IO-360 - 147 psi
Rotax 912ULS - 165 psi

Now, you might say, surely making the engine turn faster induces some stress too, and you'd be right. Mean Piston Speed is also correlated to engine reliability and longevity. However, because Rotax engines have a shorter stroke, the penalty isn't what you might expect:
Conti 0-200 - 1778 ft/min
Lycosaur IO-360 - 1967 ft/min
Rotax 912ULS - 2320 ft/min

In both cases, you'll see that the Rotax does run a little "harder", but not as dramatically as the HP/ci numbers would make you believe. The Rotax is also a comparatively more modern liquid cooled engine, and really has established a good record of reliability if they are maintained like Rotax engines and not like Lycontinentals. They are well-designed engines purpose-built for airplanes. They aren't inexpensive, but there are multiple sources for parts across the globe, and an enormous wealth of community technical support available. There is a reason they are the de facto standard for Kitfoxes, and pretty much the entire light sport market.

[genie]

I would like to thank everybody for your replies. I found them all very interesting. The above one provided me with very useful information about BMEPs and piston speeds of the most widespread light aircraft engines.

My main priority is flying and not the build and experimentation of experimental aircraft. Therefore should I get as far as building a Kitfox I will choose a standard engine: a Rotax, a Continental or a Lycoming. If it is one of the last two I would never get it brand new as it does not pay to do so. One with 1500 hours or even 2000 hours would be perfectly well suited for me. I will keep away from Viking and Rotec engines.

I love the looks and sound of Rotec engines. but due to their weight and drag penalties and reputation for inadequate customer support by this company I do not think it would be a suitable choice for me. Of course I love it if others get such beautiful engines so people who have the courage are welcome for my sake to get one of these or a Viking engine.

In my opinion a diesel engine would be well suited for touring aircraft. But as no such engine is available this option would be for those who enjoy the build and experimentation process. The Continental ex-Thielert is not sold to homebuilders and I believe that few if any are available second hand. The Delta Hawk is very expensive. I heard some people have adapted automotive diesel engines for use in aircraft. Good luck to those who try.

As long as we are on this subject: those who really enjoy experimenting with aircraft and engines could consider a Vija engine. It comes from France and is based on Suzuki engines and is cooled by oil and air. The trouble is that the company which produces it has closed. thus it must be difficult to find one and product support is non-existent. For further information see: https://vija-engines.wixsite.com/vija-en

[genie]

This is an interesting comment. Since my previous entry I managed to locate the article you are mentioned, I believe. I believe that it comes from Kitplanes June 2020 pp 18 - 25. Initially the builder chose a Viking 130 HP 1.5-litre Honda Fit engine. After experiencing many problems with it he replaced it with a ULPower 350iS. From what I understand from this article one should avoid the former. Using Google I found that many people have written about Viking engine problems.

George Nielsen

[Dave S]

Another point to consider when thinking about an auto conversion engine: Call up the insurance carrier who you would have insure the plane and ask them about it.

Before I sent in my order for my kit - called the guys up and the answer I got was they really, really liked kitfox airplanes with a rotax 4 stroke and trigear.

Auto engines are not necessarily shown the same consideration by insurers as engines designed for aircraft in the first place; and, that can translate into cost and insurability.......but it depends.

Just a thought