Stephan's Sonex #1627 Builder's Log

116.40 hours
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Who am I?
My name is Stephan Edelman and I live in the city of Mississauga, about 30 minutes west of Toronto, Ontario Canada. I have been a small business owner since 1998 and have been completely absorbed in its development and growth ever since. Although there are many successes that I have been able to claim, it has increasingly forced me in a direction where I receive fewer and fewer joys. I spend the bulk of my time developing (intangible) software products. The engine and Content Management System that drives this very website is one of those products that I developed. I'm very much a hands on guy and at the end of the day, I yearn to work with my hands again and create something tangible instead of just vaporware.


Although I have only recently started flying, it is something that has been in the back of my head for as long as I can remember. It is one of those things that I've always known I was going to do. After a while, you realize you have to follow your dream if you want to make it happen, so I started learning to fly. I'm currently working on obtaining my private pilots license. I hope to be certified sometime this year (2013).


Why Sonex?

 I really wanted to build a VANS RV-7. I liked the looks of it and the performance and the company's track record. I set out on a year long due dilligence journey that I initially used to justify my decision to build the RV. During the course of that journey, I realized that the RV was outside my budget, but more importantly, outside my skillset. I knew that I was trying to bite off more than I could chew. So, I removed the RV from my list of possible options and focussed on reviewing the other options that I had come across. These included the Sonex and the Zenair Zodiac CH650.


I really liked the Zodiac, because it had some resemblence to the RV in terms of physical appearance and because the manufacturer is just 1.5 hours north of me, in Perkensfield, ON Canada. I did all my prelimimary research and called up Zenair to talk about the options, the build process and the cost. I spent about 45 minutes talking to Michael Heintz, who patentiently and meticuously answered each and all of my questions. Michael is the son of the designer of the Zodiac, Chris Heintz. The company has been in business since 1974. I was sold. I was pretty sure that after I had done all my due dilligence, I was going to build the Zodiac. 


This did not happen, of course. In researching the Zodiac, I came across several builder's websites and blogs commenting on the Zodiac CH601 areodynamic flutter problems and mid-air break ups. In all 11 deaths had been attributed to the problem prompting a recommendation by the NTSB to ground all Zodiacs -which the FAA refused to do- but the FAA agreed to start a thorough investigation of the root cause of the accidents. Several countries in Europe, including the Netherlands, grounded the entire fleet of Zodiac CH601XL as a precaution. I was born in the Netherlands and lived there until I was 18, and know from experience that the government more often than not acts in the best interest of public safety than in the interest of a commercial company or its reputation. They would have not made this decision lightly. It got my attention.


I was particularly troubled by Zenair's position with respect to the accidents. The company insisted that if the builder had built the plane to the manufacturer's specifications, that areodynamic flutter would not result in a catastrophic breakup. This sounded a bit like: if you have a Zodiac that hasn't broken up yet in flight, then you have plane built to manufacturer's specifications, but when your plane does break up, it is not built to manufacturer's specifications.


The decision to toss the Zodiac as a serious option came after reviewing the FAA Special Report on the flutter related problems. The company maintained that their plane design was safe, but at the same time created an upgrade kit containing over 200 design changes. It was obvious to me that they wanted to limit their liability by not admitting to any design deficiencies. Although the FAA Special Report did not reveal a specific root cause, the report did reveal a startling finding: "The manufacturer’s analysis used an assumption that the lift distribution has a purely elliptical shape. This assumption is often used in academic evaluations, but is incorrect for compliance to ASTM F 2245 § Several more appropriate methods exist for estimating the distribution of wing lift. Some of these methods are listed in advisory circular (AC) 23-19 Airframe Guide for Certification of Part 23 Airplanes" (4.1 Load Analysis - Page 13). In other words, the manufacturer had used a simpler academic model to calculate wing loading. This put doubt in my mind whether the company has the know-how to actually design a safe airplane, otherwise they would have undoubtedly used the correct model. For me, the Zodiac option was out.


The issues with the Zodiac option hightened my due dilligence with the Sonex. I searched for every possible negative blog or comment about the Sonex design or the company, but could only find inconsequential comments relating to Sonex's position on making modifications to the design (and calling it a Sonex), use of non-approved engines and the prop hub design on the AeroVee conversion engine. I tried to find any and all possible reasons to dismiss the Sonex as a serious option, but could not. Further research on the proprietors, Jeremy and John Monnett, revealed that they are professional, safety focused and conservative, which is fully reflected in the design of the Sonex. As an example, the Turbo option development for the Aerovee was announced in 2010, but as of 2013, no official package is available from Sonex. This highlights the conservative nature of the company, in my opinion, as the AeroVee engine is an auto conversion engine for which a number of Turbo options are currently already available for racing. I am left to conclude that they haven't completed all necessary testing and that's why they haven't brought it to market yet. Of course, this is just speculation, but I would be interested in a Turbo, so it's reasonable to conclude that there's a market for it.


The last remaining hurdle for a Sonex selection was to find local builders, from whom I could possibly draw on for support, if needed. I determined that there were at least 5 builders in my direct area (50km), who were either actively building or already flying the Sonex. It was clear to me, the Sonex was going to be my build project.

Last Updated 2013/05/06 09:35:49PM