(and how it applies to my Zenith CH 750 build)
Between 1959 and 1969 General Motors built approximately 1.8 million Corvair vehicles. The Corvair air-cooled engine was constructed mostly of aluminum — a cutting-edge technology for passenger car engines at the time. In October 1957, GM broke ground on the engine foundry at Massena, New York to specifically build the Corvair engine castings. Each engine required 92 lbs. of aluminum which was supplied by the nearby Reynolds Metals aluminum plant. The metal was delivered to the foundry in a molten state by trucks carrying very large ladles of liquid aluminum. Once delivered these ladles (moved around the foundry via overhead cranes) were directly used in the casting process to pour the liquid metal into sand molds which formed the required engine parts.
After the aluminum cooled the castings were separated from the sand molds and the newly-formed engine parts were cleaned, inspected, packaged and shipped to the Tonawanda Engine Plant in Buffalo, New York. GM workers there then machined the parts and performed the final assembly into finished Corvair engines. 1)Section reviewed and edited by Mike McKeel, Engineer, and Eva “Corvair Lady” McGuire, Corvair Historian
In 1960, as soon as Corvairs were being sold, Bernard Pietenpol went to a Chevrolet dealer in Spring Valley Minnesota and ordered an engine. Bernard was one of the earliest homebuilt aircraft pioneers, and he intended to convert the Corvair engine for aircraft use. Pietenpol had created his Pietenpol Air Camper airplane by trial and error during 1927 -1928. 2) Pietenpol Manual, Donald D Pietenpol, 1991, History pVI and p51 It was designed explicitly for homebuilders with basic woodworking skills. He sold plans for it in magazines, had built them to order, and had continuously developed them with various auto conversion and aircraft engines for 18 years. Then in 1948 he stopped building them.
Pietenpol focused on other things for a long time until the Corvair engine came along. Apparently its design rekindled his interest in automotive engine conversions for aircraft.
His first Corvair conversion in 1960 was put on a Piper J-3 Cub for development and testing. After figuring out it would work, he put the Corvair on an Air Camper that had been built in 1937. Testing showed excellent performance characteristics. From that success Pietenpol was inspired to build two more Air Campers, both with Corvair power. One was completed in 1964; his final plane, today known as “The Last Original”, was completed in 1966.3)Ibid, p 51
In 1989 William Wynne began to seriously look at the Corvair as a potential engine to power light aircraft. He was particularly interested in the increasingly difficult problem of finding affordable power plants for experimental aircraft because companies like Teledyne-Continental had ceased producing engines for small planes. With determination — and ingenious insight — William realized that the Corvair motor was in many ways a strong candidate for further development as an aircraft conversion. As a first year student at Embry Riddle, he immediately set to work building a Pietenpol aircraft and working on a modernized Corvair aircraft engine conversion. In 1993 he graduated as an A&P, with an Associate of Science in Aviation Maintenance, and with a Bachelor of Science in Aeronautics. With this solid education and a strong vision, he began his own personal and very significant contribution in the arena of experimental aviation. 4) William Wynne, personal communications, June 2020; WW FlyCorvair Youtube “Perceptions — Motivation and the Transformative Process“, June 21, 2019
Thirty-plus years later Corvair flight engines have powered many experimental aircraft — about 500 are flying today. The vast majority of those plane’s power plants are directly attributable to the work and teachings of William. Those planes sticking closest to William’s developments have by far fared the best and have performed with enviable reliability.
Parts are not an issue because cylinders, pistons, connecting rods, and even things like crankshafts and camshafts can be had new when required. All the little bits and bobs in the conversion are also available new. Core engines are still widely available for teardown, reconditioning, and rebuild.
If you want the challenge of inventing everything yourself in experimental aviation you can do that. The Wright brothers, while eventually having no choice but to learn the reality of aerodynamics and aircraft construction on their own, did not start that way. They started by learning everything they could from every authoritative source they could find. And so, needing an engine, they wrote letters to automobile manufacturers in seven different states — but none of those engines met their weight and power needs. They therefore turned to their machinist friend Charlie Taylor, who had worked with gasoline engines of varying sorts. Charlie wound up building the engine for the very first airplane to fly under its own power.5) The Wright Brothers, David McCullough, Simon & Schuster, 2015, pp 86-88.
Eighty-odd years later, in an unexpected economic twist, William Wynne identified a coming lack of affordable power plants for light aircraft; having the skills himself and preferring to create his own story in aviation rather than being part of another person’s or enterprise’s story, he took on the task of developing the next generation of Corvair flight conversions. Guided by standard aviation maintenance and aeronautics practices and a stubborn devotion to testing and quality, his work has lead to a mature and highly reliable automobile conversion.
I have followed the Wright’s lead. I have sought out expertise and the best authority I can find regarding a power plant I can build myself. That power plant is the Corvair, and that authority is William Wynne. Hundreds of his engines are flying reliably and successfully. I want to share in that success, not be defeated by variations I invent myself or are invented by someone who’s never flown a Corvair but might be an absolute expert constructing high power Corvair racing engines.
Learn, build, fly: How well the first two things are done will determine the outcome of the last.
After long study of all kinds of small homebuilt types, I found myself ever returning to the Zenith STOL aircraft designed by Chris Heintz. At first enthralled by the CH 701, I was somewhat frustrated that the Corvair seemed outside its ideal weight range. Then in 2007 or so I became aware of the CH 750. It was the middle brother between the 2 place CH 701 and the 4 place CH 801. Zenith claimed it was designed in part to give more engine options than the CH 701 had — specifically including the Corvair.
Studying the engine and airframe options extensively, I decided to let my choice of plane be driven by compatibility with the Corvair. Even though it’s possible to fly a CH 701 with a Corvair, weight limitations cause some performance restrictions. There are currently many flying examples of CH 750s using Corvairs, and I therefore chose to build the Zenith CH750 STOL.
Fifty odd years after Corvair production ceased I found a rusted out Corvair hulk at John’s Salvage Yard south of Seguin, Texas. It was scheduled for crushing when I intervened; I had TZero (my engine’s nickname) pulled from the car for $350 bucks.
Like my engine, the CH 750 I’m building is made almost entirely of aluminum: Sheets, angles, spars, ribs, rivets. The parts will be either formed by myself the old-fashioned way or made by Zenith.
Fifty years ago, whoever drove that Corvair I found at John’s Salvage off the lot had no idea their engine would wind up in my shop as a rusted derelict. They had no idea that the engine powering them down the road would wind up pulling my plane through the air. They were way too busy with their own time under the sun, their own story: Hands on the wheel, hair blowing in the wind — and smiling. They were definitely smiling. And one day soon I will be looking down on John’s Salvage Yard from the air, wagging my wings, smiling, pulled through the air by the same engine core that pulled the original buyer down the road in their brand new, shiny Corvair.
References [ + ]
|1.||↑||Section reviewed and edited by Mike McKeel, Engineer, and Eva “Corvair Lady” McGuire, Corvair Historian|
|2.||↑||Pietenpol Manual, Donald D Pietenpol, 1991, History pVI and p51|
|3.||↑||Ibid, p 51|
|4.||↑||William Wynne, personal communications, June 2020; WW FlyCorvair Youtube “Perceptions — Motivation and the Transformative Process“, June 21, 2019|
|5.||↑||The Wright Brothers, David McCullough, Simon & Schuster, 2015, pp 86-88.|