Need Help Contacting the Builder of this Aircraft ASAP.


I was forwarded the image of the modified Pietenpol pictured below.  It is Corvair powered, and I have been told it was signed off by the FAA, but I don’t have a record of working with him.


UPDATE: The builder of the plane has sent a request saying that he wanted the image removed from this story and from our FB ‘Corvair College’ page. He prefers to not discuss his plane in public. I offered to help, meant it. I’m leaving the rest here because first time builders need to understand having a 100 people tell you on FB your plane looks nice isn’t an endorsement of the details.  


Above is the Plane in Question. I do not consider it airworthy, even though the FAA signed it off.  The first thing Piet builders will spot it the tiny weak diagonal cabanes, as I discuss here: Pietenpol Fuel lines and Cabanes and here: Fuel lines and Cabanes, part 2. But that isn’t the main point, it is the Vee shaped lift struts on a parasol with near vertical cabanes and a center section. It is not structurally sound.


In 1989, a guy in my EAA chapter, #288, named Bob Spenk, built a steel tube Grega with a nearly identical lift strut arrangement. To my then-uneducated eye, it looked fine. The Embry-Riddle department chair of engineering was also a #288 member, and he sat down and explained that the new strut arrangement had almost no ability  to resist the wing rotating in relation to the fuselage, and any differential load, such as deflected ailerons, would impart this.  He explained that in a cabin airplane with the same lift struts, the upper longerons contacting the rear spar and the diagonals in the fuselage resist the twisting, and he showed us that one of the largest tubes in a J-3 fuselage does this.  He went on to show that a heath model V parasol has no center section, but it still requires diagonal brace wires from the rear spar lift strut attachment to the motor mount.  He pointed out that a it was superseded by the Heath N, and follow on airplanes like the Baby Ace, with parallel lift struts are required to have the diagonal brace wires between the lift struts, even though they have no center section.  Aircraft structures is a very complicated business, and it doesn’t care if all the local hangar fliers say “I will be alright” and it doesn’t care if all the people on the internet say “Its just a low and slow plane’.  neither of those statements will make the plane right. it doesn’t work that way.


“Hey, William Wynne, you are a jerk, mind your own business, the guy is probably very nice and you are only pissing on his parade. He probably isn’t even a customer of yours. This is why many people think you are an ass.”

 …….In 2016, a lawsuit for $350,000 was tried against me. It came from a person who had a Corvair in their plane, but never bought a single thing from me. If you thought that couldn’t be done, I understand, I didn’t previously believe it was possible either, but yes, it can get to federal court.

  ……..If you work in aviation, or even spend time here, you will have to decide at what level you are Your brothers keeper?  I have long ago decided that I’m fine with many people thinking I’m a jerk for pointing out something like the plane above, but I am unwilling to go to bed at night and try to sleep with a pillow made of justifications and rationalizations.


If you want to read the story of the exact day I learned this, 25 years ago, look here: Effective Risk Management – 2,903 words

“This was the first time I can clearly say I understood the cost of keeping your mouth shut. This was the first step to me becoming the kind of “Bastard” who publicly points out people doing dangerous things.”




16 Replies to “Need Help Contacting the Builder of this Aircraft ASAP.”

  1. I’m trying to envision what you’re describing. Using the pitch-roll-yaw axis, are you saying that the wing can yaw in relation to the fuselage?

    1. Very nice, it was sold because he ‘lost interest’ wonder if this was because someone told him it wasn’t structural? Why is it all the guys selling a project claiming it was built exactly my manual can’t spell my last name?

  2. I rarely spend time trying to figure out fools’ rationale…mostly because I need to concentrate on not becomeing a fool. But I can say, you are my most favorite arrogant bastard ass in the USA. In fact, you are an ‘apostle’ (one who is sent to do the mission of the sender) of aviation and specifically homebuilding. I may never get there, but I know it will not be due to following poor advice. Keep believing in yourself and your mission and, again, thanks for all you do.

  3. looking a little closer based on the link Ryan posted. William didn’t you say not to wrap exhaust pipes? and don’t you specify a 5th bearing?

    1. Also I don’t see exhaust value rotators in the picture. So how is this engine built according to William Wynne?

    2. Also from the image, no exhaust valve rotators, so exactly how is this a William Wynne engine build?

  4. I respect and value your input, William. At least I have learned quite a bit from you.

  5. A quick reminder that when the FAA-authorized DAR signs off your plane, the only thing that *he* signs is that you have demonstrated to his satisfaction that, in fact, >50% of the plane was constructed outside of a factory (not counting the engine or instrumentation/avionics) and that all your paperwork is in order. If you ask for a Repairman certificate, you must also convince him that *you* did >50% of the work.

    That little pink slip you get is only the authorization to enter Phase 1 to test fly the thing. Of course, *most* DARs will at least look over the airplane, and if they think you will kill yourself the first time you try to fly it, they might tell you that. Some might actually *advise* you to fix or change this or that. But that is *not* required. And he cannot deny you the pink slip for stuff he doesn’t like.

  6. That was a good catch! Steve Culp here and that got my attention and I was looking at the pic and see that with the Vee lift struts instead of the parallel cross braced lift struts on most Piets, it makes sense that it puts more force on the cabane struts brace going to the upper motor mount since there is not cross bracing between the cabanes as on most airplanes. The small braces from the top of the front cabane strut to the motor mount looks a bit light for compression loads. Since there is not cross bracing on the Vee struts or cabanes then the wing twisting and fore and aft forces are working those small braces a bit more than what I would consider reasonable. I realize you can’t hardly cross brace the cabanes on a Piet as you would not be able to get into the front cockpit. Hence the forward brace to the upper motor mount. But those parallel struts with the cable cross bracing is strong and has a proven track record. Of course the bottom wings of my planes are attached to a longeron which would be like the parallel lift struts and you can see what I do to keep the top wing in place.

    1. Steve, I have always liked your work. I saw your notes on the Piet FB page sharing thoughts on structures with new builders. You may wish to point out to them that many classic airplanes, like biplanes, which appear to have a center section like a Pietenpol, actually have a one piece upper wing with is a bit structurally different. I think they also miss how if the cabanes are tilted outward at 30 or 45 degrees and braced with real sized wires they can make the wing/fuselage joint very ridgid but lightly built cabanes which are near vertical don’t have the same effect. -thanks, William

  7. Thank you William! I was lucky enough to have guys like Curtis Pitts, Jim Younkin, Steve Wolf, Marion Cole and others to go to for advice. All I had to do was ask and they were all glad to help. Which, when you are building a plane help lessen the scary side of falling out of the sky! My Davis D1K has a similar top wing design as the Piet. But it has cross braces from left top and right top cabanes to the center of the fuselage which with the braces going forwards from the top of those cabanes creats a very strong point to help stabilize the wing. Glad to see a group of people actually trying to help instead of being mean spirited which lead me to throw my opinion in with the mix. Thanks again, Steve Culp

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