Guest writer: Phil Maxson, flying a 3100cc Corvair in his 601XL


In this Guest Writer piece we hear from 601XLB builder and flyer Phil Maxson of NJ. Phil has been a stalwart supporter of Corvair power since he finished his 601 in our old hangar six and a half years ago.  Phil has recently had his insights on experimental flying published in Contact! magazine issue #105. Phil’s latest project is to fly Mike Robitaille’s 3100 in Phil’s airframe. This gives a good idea of the quality of people and quality of engines in the Corvair movement. I can hardly imagine two builders of another alternative engine who would install a friends engine in their airframe just to test fly it.

Mike’s 3100 cc Corvair likely one of the last to be built. in the last 3 years almost every builder interested in large displacement Corvairs has opted for our second generation big bore engine, the 3,000 cc. Thousands of hours have been, and will continue to be flown on 3100’s. They are good engines, but the have been superceded by our more recent work.

Above, I stand with Phil in his hangar in NJ in August. I was up visiting my parents and made sure I went out to Phil’s airport for a visit. Unlike the vast majority of aviation businesses, we make house calls. It keeps us in touch with rank and file homebuilders on their home environment. Phil is a native of West Virginia. I always tell him that Chuck Yeager is my second favorite aviator from WV.


On Saturday, I had one of my most enjoyable days flying I’ve had in very long time. It was the first flight in my plane using a new engine. I now have a 3100 Big Boy temporarily installed. Mike Robitaille and I are doing a test with his engine – and what a success it turned out to be! The plane and engine performed flawlessly. Mike did a good job putting it together. It looks nice and runs very nicely.

Mike and I have been collaborating on several projects over the past year, primarily using my hangar to try out some new things. Mike built this engine a couple of years ago and ran it at a previous Corvair College. It had about 2 hours for run time on a test stand prior to installing it on my airframe. For the past year or so, his engine was sitting in my hangar in a crate. We discussed ways to preserving it so it stayed in top condition until his Sonex kit is ready to fly. One day I made the off-hand comment that the best way to preserve it is to fly it, and the idea was hatched.

 When it was time for the annual inspection this year, we started the process of removing my 2700 and installing the Big Boy. I also took the opportunity to make some improvements: I installed 6 CHTs (instead of the two I had before), I upgraded my old oil system to the new gold system, installed a Van’s oil manifold to simplify the plumbing. I also installed an O2 sensor on each exhaust with air/fuel mixture gauge in the panel. When we did the weight and balance, the plane had lost 16 pounds. I think most of that came from eliminating the remote oil system with an older, larger oil filter. We ran several heat cycles of the engine on the ground and we also did several full-power, high-speed taxi trips down the runway. As our final test we ran it for a minute at full power with the tail tied to my wife’s truck.

After so much ground testing, by Saturday morning I was ready to fly! Mike wanted to be there (understandably) and couldn’t make it until 11:00. I was so eager that by the time he got there I had the detailed walk-around done and the plane was fueled and warmed up. Mike grabbed a hand-held radio and headed for the runway.

 The first thing I noticed was about a 100 RPM increase at the first part of the take-off run. It was definitely developing noticeably more thrust based on seat-of-the-pants feel. On climb out I was seeing about a 1000 fpm climb out without pushing it very hard, climbing at about 90 mph. At the top end I’m seeing about a 12 mph increase in speed at the top end, and about 200 RPM increase at full power. The top oil temperature I saw was about the same as on my old engine: about 208 degrees. The CHTs are about the same as I was seeing before, when you account for moving the CHT thermocouples to the top of the engine under the spark plugs. The highest temp I saw was 425 degrees on Cylinder 3. In general the center two cylinders were the hottest.

Mike and I are planning to fly it down to CC24 in a couple of weeks. I need to put on about 3 more hours of testing between now and then, and do a precautionary oil change at about 5 hours. Then we should be ready to go for the nice flight down to Barnwell. That is one of my favorite airports, and Corvair Colleges are one of my favorite events. I look forward to seeing everyone down there.

 Here is a link to a very first run of the engine a few weeks ago:

 Here is a link to a short video of the first flight:



Above, Phil’s 601XL airborne over the Florida coast at Ponce Inlet, 2006.-ww

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