Zenith 601XL-3100cc Dr. Andy Elliott


I am going to run a series here called “Flying Planes.” We have an old section on our regular FlyCorvair.com Web site that covered the same topic, but it is out of date, and writing this series will bring it up to speed one story at a time. 

With other types of aircraft, the plane itself is always the centerpiece of the story. With homebuilts, it is different. At the center of every homebuilding story is the builder himself. Looking at the plane can tell you a lot about the builder.  You can get a good take on his workmanship, skills, taste in instrumentation, and creativity. Beyond these observable qualities, you can find out a lot more by getting to know a successful builder and asking why he chose a specific design, how he chose the Corvair, and how his previous experience plays into the aircraft he built. Besides being interesting, asking these questions and learning the answers is how new builders refine their own choices and make decisions on which path to proceed. Even if the answers you come to for your own project are not the same, they can still be honed by contrasting them with a successful builder.

Andy is an aviator of great experience, but his 601XL was his first venture into homebuilding. He holds a degree is aerospace engineering, a doctorate in engineering from MIT, and has several thousand hours of flight time, including a very long stint as a flight instructor in T-38 jets in the Air Force. He has taught as a professor at Embry Riddle Aeronautical University, and today is a full-time working engineer. You can comfortably say that the guy knows something about airplanes.

In our booth at Oshkosh 2011, I stand with three pilots who flew in their Corvair powered Zeniths. From left to right, Shane McDaniels who flew in a 2,700cc CH 650 from Missouri, Woody Harris in a 2,850cc CH 601B from California, and Andy Elliott in a 3,100cc CH 601B from Arizona.

I first met Andy at our 2002 Texas College. He was getting a good look at the Corvair, planning his next move in aviation. After our 601XL flew in 2004, Andy began thinking about the same aircraft, particularly a tailwheel plane like ours. Over time he chose a kit from Zenith and got to work on it. As he made progress, we spoke about Andy buying an engine from us. Our personal 601 had a 3100cc powerplant that I built to demonstrate some of the potential of the engine. It was assembled around a set of 140HP cylinder heads with their larger valves, and a very high compression ratio over 10.75 to 1. All of the systems on the aircraft are our standard Gold items, including the Front Starter System. The engine featured enlarged exhaust ports and very careful internal set up. On the dyno it exceeded 120hp, actually damaging the digital scale with the very strong power pulses from the high compression. Based on the internal changes and the displacement, I was fairly sure this was the most powerful non-turbo Corvair flying. We had it in the plane starting in the 2005 season, and racked up about 220 hours on it, including two trips to Oshkosh.

About the same time Andy needed an engine, another Corvair builder and friend of ours decided to make us an offer on our 601 airframe. A few phone calls and one Solomon like decision later, and our airframe was on a truck to Massachusetts, and we got the 3,100 ready to be shipped to Andy for installation on his 601 nearing completion. Before sending it, I pulled the engine down for inspection and out of general principle had the crank magnafluxed. It passed with flying colors, even though we had flown the aircraft very hard, and most importantly, it had not had a 5th bearing on it. The crank was just nitrided as was our standard practice in engine building. Although we could have sent the engine without the inspection, I thought it was well worth testing, because it had a fair amount of time on a very powerful engine. This was  further confirmation to me that the nitriding was working. At the time, very few 3,100s had flow this amount of hours.

Andy likes to fly a lot, and once his plane was done he flew the test hours off in a very well thought out test program that reflected his professional background. We later had him document this and we printed it in our 2009 Flight Ops Manual. Over the months that followed, Andy built up time, a mixture of short flights in the southwest, and several trips to Oshkosh. In time he modified the airframe with small aerodynamic touches to increase its efficiency and control harmony. This included changing the elevator linkage and installing aileron spades. The engineers from Zenith were impressed enough with the aircraft to take the opportunity to fly it themselves at the west coast Zenith fly in.

Andy’s engine has made four separate trips to Oshkosh. Two under his ownership and two under ours. Pictured above in the 2005 Zenith booth Andy’s 3,100 makes its first Oshkosh appearance on the front of our aircraft.


The engine gave Andy steady service, which he credits to the certified MA3-SPA carb and an exclusive diet of 100LL fuel. (Other Corvairs can be set up for auto fuel, but the compression ratio of this engine makes auto fuel a non-option.) He was careful not to lean the engine at full power nor at low altitude, pointing out that the MA3 runs a very steady air fuel mixture under varying atmospheric conditions, so you don’t have to mess with the mixture if you don’t want to. Before heading to Oshkosh 2011, Andy had racked up 500+ hours on the engine (220 of these were under our ownership, 300 on Andy’s plane). I spoke to him about installing a Weseman 5th bearing on his aircraft, giving him the logic that if he was going to do it eventually, why not now? Although he had not built the engine himself and is not a mechanic, he found the installation straightforward with the tool kit and tech support provided by Jim and Rhonda Weseman. The installation was done over two weekends and the plane flew on to make an appearance at Oshkosh. It was selected to be the aircraft representing the Zodiac series at Aeroshell Square when the EAA presented the Aifetime Achievement Award to Chris Heintz.

Above, Andy’s aircraft at the EAA Chapter 1 Open House, Riverside, Calif.

Today Andy’s engine has more than 600 hours on it, 500 without a 5th bearing, 100+ with the Weseman bearing. He recently pulled the heads off and sent them to Mark Petz at FalconMachine.net for an upgrade to Mark’s specs. I originally had the heads done by SC Performance in California 10 years ago, and they were done to “state of the art” levels for Corvair auto racing guys. SC was a very well respected shop, but they didn’t use the types of seat alloys or valves that Falcon does. Mark inspected the heads carefully before reworking them, and was impressed at Andy’s careful operation; even with an extreme compression ratio the heads showed no signs of detonation. They were just losing compression through the old style exhaust seats. Andy ran the engine at high power settings, but Corvairs don’t have a real problem with this kind of work. Mark feels that considering Andy’s careful operation, the upgraded set of heads will go 1,500 hours. The bottom end of Andy’s engine showed no appreciable wear on the pistons or cylinders.

The upgrade to a 5th bearing and Falcon heads are not expensive modifications by aircraft standards. They each set Andy back about $1,000. You can ask any Rotax or Jabbaru owner if any upgrade on their engines costs this little. Combine this with an initial cost that was about 60% of either of the imports, and the engine still represents an excellent value.

In his travels Andy has met a lot of other builders at airshows, and people have written me privately many time to express how much they thought of the plane and the man. He has represented the Corvair movement in most of the western states, covering Copperstate, EAA chapter #1 Open House, the West Coast Zenith fly ins, and the Contact! alternative engine fly ins in Jean, NV. Additionally, Andy has used the aircraft to cover long trips to visit family and friends, including flights over the mountains in Colorado. He has a lot of praise for both the Zenith and the Corvair. What’s next for Andy? He is giving some serious thought to taking a step up in the speed and agility departments to a single seat Midget Mustang. The engine? The Corvair of course.

 Click here to see a film of Andy’s aircraft in flight

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