Understanding Flying Corvairs Pt. #6, 98% DNA not enough.




If you have not seen the Intro to this series, you can read it here: Understanding Flying Corvairs Pt. #1, Intro., It will explain the goals of the articles. Please take a moment to read it, including the comments section.




“It is said that Humans and Chimpanzees have 98% of their DNA in common. That 2% wrote all the great works of literature, made all the great works of art, made every tool, created writing, went to the Moon, discovered DNA, is capable of incredible acts of kindness and also started all the wars mankind has ever fought. It is the important 1/50 of the total.


Two nearly identical planes can have a two percent difference, one will be a reliable servant under all conditions, and the one that is lesser, by a small, but critical fraction, will not survive it’s first flight.


When looking at a planes airworthiness, do not focus on the percentage of elements that are correct, solely examine the elements which are not. Accidents do not happen because a plane was 100% junk, they happen because 2% of it was not set correctly or up to the task. If this tiny part had been corrected, the laws of the universe would insure that the accident would not happen and the plane in question would offer service identical to the most reliable example. -ww.”




Earlier this year, Zenith 601XL builder Ken Pavlou took his 2700cc Dan bearing equipped Corvair to his airport in Connecticut. His first flight can be described as ‘uneventful’ You can see it filmed in it’s entirety at this link:http://www.youtube.com/watch?v=nK01KhG2CkE&feature=youtu.be. Since that flight, Ken had an uneventful 40 hour test period, and an uneventful round trip to Oshkosh 2014. It now has 145 hours on it, he trusts it enough to fly it at night, (Zenith 601XL flying at night, cockpit video.) and he is planning an Uneventful round trip this coming week to Corvair College #31 in Barnwell South Carolina.


Last week, we had a builder with a plane that was roughly 98% identical to Ken’s destroy his aircraft on the first flight. That person ran his plane up and down the runway many times in something referred as a ‘Crow Hop.’  (Our flight Operations manual specifically states to never do this, as it leads into getting the plane in a position where it is too high to land on the remaining runway, forcing the pilot to make an unplanned flight. See note below.) The pilot did just this, got to tree top altitude and had a sudden loss of power, most likely from very high CHTs leading to detonation. He clipped a tree trying to fly a low pattern and destroyed the plane in the crash. Years of building for 120 seconds of flight.


I exchanged a lot of email with the pilot. He bought the engine second hand, He was reluctant to buy a timing light and did a lot of ground runs without setting it, claiming that he didn’t need to because the original owner said it was once set by me in 2008. When he did check it, it was found to have a several hundred rpm split between A&B. (This is likely caused by someone re-gaping the points to .019″ something the instructions say not to do.) He ‘corrected’ this by resetting the E-side. He also had carb adjustment issues.


He did this over a period of several weeks. He sent me a CHT graph print out of making 7 ‘crow hops’ down the runway with the throttle open for only 30-60 second intervals, which showed escalating CHT’s to 500F. I sent him a short Email including the comment “if I am reading your graph correctly, you have a cylinder running near 500F? that is far too high.” 48 hours later his plane was destroyed. For reasons he has not explained, he had a passenger in the plane on the first flight, something the FAA regards not just as poor judgment, but illegal. I asked him if he had done a two minute ground run test, but he did not respond. (see Understanding Flying Corvairs Pt. #5, Two Minute Test )


By trying to go around, he was essentially running his first two minute test in the air, rather than on the ground. The mechanical things that made this plane different than Ken Pavlou’s are slight adjustments, something less than 2%. The man didn’t need to build a whole new engine, he just needed to slow down and correct some very small things, stuff that probably could have been done in one weekend. Had the pilot just stopped, and spent the time to correct these, the laws that govern the universe would have his airplane run exactly as Ken Pavlou’s does. Instead it is destroyed, and two people were hurt. This accident bears a striking similarity to this one, caused by the builder incorrectly reassembling his carb and then trying a ‘crow hop’: Risk Management, Judgement Error, money in the wrong place.


The concept of correcting the 2% of things that are different from the recognized norm does not just apply to Corvair powered planes, or just to Experimentals.  When a mechanic does an annual on a certified plane, what he is essentially doing is looking for anything on the plane that deviates from the published limits for being in 100% compliance with the Type Certificate Data Sheet for that plane. When he corrects these “Discrepancies”, the plane is judged to be airworthy because the laws of the universe will make it behave just like any other correctly running example, because it has to, it is a machine, and it has no personality, and it has no option but to work.


My experience on these events is that the only thing most aviators at his airport took away from seeing the results was that car engines are bad, and have no place in aircraft. I have been in this business 25 years. I have never come up with a way to salvage the reputation of our work in these instances. -ww




Absolute rule of flight testing #5, from the Corvair Flight Ops manual by ww, 2009,  Section 8, PG 70:


5) Making successive runs back and forth down the runway is a signal that the pilot doesn’t trust the plane. This often leads the pilot into “being forced to go around.” Anytime you read this type of a report, know that the real translation is “I didn’t have a plan, so I just ran up and down the runway until I got my courage up and brain suppressed, and I cast my fate to the wind.”





Above, Ken with his plane on the flight line at Oshkosh.  All week, it was parked with Lynn Dingfelder’s 2700cc 601XL and Pat and Mary Hoyts 2700cc 601XL right behind our tent. The planes are clearly the work of individuals, but the engine installations have the essential common elements that make them Clones of what we have proven to work.


I share this information through these resources:

Flycorvair.com (about 2,000 pages if printed – Free)

Flycorvair.net (589 stories of building, about 500,000 words – Free)

Our Conversion manual (Updated to 250 pages / 104,000 words –$69)

Our Zenith installation manual (About 125 pages –$39)

Our flight operations manual (86 pages, 1/2 on flight testing- $29)

Our peer to peer private information board for Zenith builders and pilots. ‘Zenvair’ Information board formed. ( Free)

Four Corvair Colleges per year.  ( Free)

I answer 4000-5000 Emails and phone calls on technical subjects every year. ( Free)

Appearances at numerous airshows to give technical forums and inspect any builders parts, even if I have to walk all the way to the parking lot after hours to do so. – (Free)

I have made more than 400 house calls (No one was ever charged)


It is hard to suggest that I have not put a good effort to support builders who choose to work with the Corvair, yet many people who saw or heard about the most recent accident will conclude that the builder should have chosen a certified engine, somehow imagining that Continental, a company now owned by the Chinese government, somehow provides better direct service to homebuilders. I have had little success explaining to average EAA people that protection does not come from a little data plate, it comes from exercising good judgment and using available data from qualified sources. -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 www.FlyCorvair.com and in more than 50 magazine articles.

3 Responses to Understanding Flying Corvairs Pt. #6, 983 DNA not enough.

  1. Sarah Ashmore says:

    Just prrof of an old addage “An engine that does not perform correctly on the ground is not likely to perform any better in the air”.

  2. Steve Stahl says:


    Good point!

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