Selecting an engine for your experimental aircraft


The designers of experimental aircraft have an incredibly wide difference of opinion on the rights of builders to choose their own engine once they buy the plane. I know this personally, I have been in the alternative engine business for the last 25 years, and the designers names I use below are people I have met in person, who directly said these positions to my face.


Moreover, I have done a lot of work over the years on advisory boards and sat through a lot of closed door meetings. I have directly heard many things that were later diluted by PR people until they were non-offensive. I have heard countless well intentioned, but under informed builders relate positions that their favorite designers supposedly held, positions which I know from personal contact, not to represent the designers actual beliefs. I have tried to correct misconceptions, but it is a usually a waste of time to try to expand the understanding of people who are absolutely sure they already know everything.


Examples; Burt Rutan does not like builders using auto engines on his designs, and actively didn’t want anyone doing so to be able to use his name for the plane. On the other end of the spectrum, Randy Schlitter, the founder of Ran’s aircraft told me “They buy it, it belongs to them, they can put a car engine on it if they want, or make a yard decoration if they want, to argue otherwise is to be against private property.”


Between these extremes are all many other companies. Zenith aircraft has been very successful by stating that builders have the right to use any engine they want, just strongly suggesting that the engine be in below a specified all up weight. This is a position very close to Randy Schlitter’s. Richard VanGrunsven, founder of the RV series of aircraft is much closer to Rutan’s position. He was vocally against any engine other than Lycomings. (until he designed the Roxax powered RV-12, which he is vocally against anyone using any other powerplant on.)


VanGrunsven is the largest Lycoming dealer in the country, but I think his adamant insistence on their use is driven by an combination of his belief they are good engines and his attitude that he should be able to say how people use “his” planes, even though these people own them as their private property and are consider the plane’s manufacturer by the FAA. There are many things I admire about the man, but this kind of heavy handed control of others lives while working to be perceived as a ‘nice guy’, isn’t one of them. I actually preferred Rutan’s direct and blunt, ‘do as I say because I am smarter than you and I don’t care if you like me’ approach. I prefer unapologetic dictators over those that seek to be perceived as benevolent.


Between these positions are many companies that like to promote the use of their “Approved” engines for the sole purpose of making money. Most people have no idea that when a builder buys a kit, and later buys a Rotax (or many other imports), the person who sold the kit makes a several thousand dollar kick-back off the engine company. Walk into many kit company’s booths at Oshkosh and tell them you are planning on using a Corvair, and the most common line is “I have met WW and he knows engines, but …(Insert: “Corvairs weigh 350 pounds, they don’t really work. they don’t use 72″ props, they..”) so just do the smart thing and get a Rotax, here I will call lockwood on your behalf”. Look at the math on this; The airframe guy invests 10 minutes having this conversation with a builder six times, one hour total, and then makes a $2,500 kick-back. Yes, they do this not out of the goodness of their hearts, it is for the 2,500 dollar per hour pay-off.  The fact that the kit buyer does not understand the system is what makes it deceitful, and he is unaware of the kit sellers motivation. This system in one of the largest single reasons why conversion engines are not more popular.


If you have ever wondered why we have so many Corvair powered Zenith’s flying, it is not just that it is technically a very good match and that we have done our homework starting with buying a kit for ourselves and building and flying it personally, but the attitude of Zenith is a very big factor. Sebastien Heintz, president of Zenith, has always believed that the builder, as an individual and owner of the kit, has the right to select his own engine. I find it humorously ironic that a guy born in France and raised in Canada turns out to be a much stronger champion of the personal freedom individuals making an educated decision for themselves than many kit company owners who would rather make a buck off builders obediently doing as told while these men try to polish a public image of respecting the freedom and individuality of builders.


Photos from Zenith Aircraft Company's 23rd annual Open Hangar Day & Fly-In at the kit factory in Mexico, Missouri. September 19 & 20, 2014

 Above, the Engine Selection forum from the 2014 Zenith Factory Open House. From the left, the panelists represent, Rob from Rotax, Robert helms from UL power, Corvairs (myself), Pete Krotie from Jabbaru usa, Kim Winner from Continental, and Jann Eggenfelner from Viking. Sebastien Heintz is the moderator, standing by the wing.


In keeping with the Zenith Aircraft perspective, the forum allows builders to directly ask questions to be addressed by the panelists who all represent proven power plant options on Zenith airframes. This approach speaks volumes about how the company views it’s builders; they are seen as adults, capable of making informed choices for themselves. This is very different from companies which dictate to their builders what they will do.


Zenith is an actual dealer for many of the brands of engines that work on their aircraft. They make mounts and cowls for some of these. But this is not a consideration, the goal is to match each builder to the right engine. Each builder is provided with opportunity to get to know many engine providers and make the selection that best matches their goals, budget, time line and philosophy.


I have heard every possible argument for the dictatorial approach, but in the end, traditional homebuilding and real flying, at their very core, are all about learning building and flying, and these are things that are best done as an alert individual, not someone blindly following orders. -ww.


About William Wynne
I have been continuously building, testing and flying Corvair engines since 1989. Information, parts and components that we developed and tested are now flying on several hundred Corvair powered aircraft. I earned a Bachelor of Science in Professional Aeronautics and an A&P license from Embry-Riddle Aeronautical University, and have a proven 20 year track record of effectively teaching homebuilders how to create and fly their own Corvair powered planes. Much of this is chronicled at and in more than 50 magazine articles.

2 Responses to Selecting an engine for your experimental aircraft

  1. Wynne,

    I have been studying your website for several months and have been impressed not only by your product but your overall philosophy of life. I am recently retired and now have the time to build and fly, which I never have had in my 72 years. You have totally convinced me of the viability and desirability of Corvair engines and I will definitely use Corvair to power my future plane.

    This note is not about your engine, but about a practice I have noticed in your testing videos that worries me tremendously. I know that you, your staff, and the many people you invite to share in your activities are very careful people. However, the practice of turning a 5ft propeller at 2500rpm on the ground for extended periods of time without any barriers to prevent human contact, is a practice that is courting disaster. I am not any kind of safety expert. I’m an electrical engineer who used to touch electrical bus bars to see if they were energized, so I’m used to taking unusual risks. Surely you can see the possibility of someone, even a child, walking or running into the spinning prop, even with the noisy environment. It would be an event you would never forgive yourself for. Please provide some sort of barrier for future tests.

    Respectfully yours,
    Robert Hughes

    • Robert,
      Thanks for the note. Your safety note is duly noted. What may not be obvious in the film is that people are further away than you think. Also, if there are any people around as spectators, one person is positioned at the controls, and there is a knife switch that kills the engine almost instantly. I never run an engine in a setting like an airshow, were we have not had a chance to brief everyone present. At colleges, we have a firm rule called “Sunset”: absolutely no prop turns after the sun hits the horizon, and no beer is cracked while the sun is above the horizon. Still your point is well taken, and we may go to a guard at some point. We lost a friend to a prop accident on a Lycoming with a hot mag, you are correct about the dangers of props.

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