The first documented flying done with a Corvair motor modified for flight was in 1960. A guy named Bernie Pietenpol, who designed small aircraft for himself and other homebuilders, mounted one on a Cub, and then on a plane he had designed and built called "The Air Camper".
Corvair engine cores are getting a bit hard to find, but I picked up three recently. Two for $75 and one for $50. So, for $200 I have the core parts for three air-cooled, 100HP flight engines. True, they will be completely rebuilt before they can be mounted to the front of a small aircraft and expected to deliver safe and reliable flight. The main parts these cores provide are the case, the crankshaft, the cylinders, and the heads. Pretty much everything else gets replaced.
In "How to Keep Your Corvair Alive", Richard Finch explains why the Corvair is such a solid engine design:
1. It has a very short piston stroke which greatly lightens the loads on the pistons, rods, crankshaft and bearings.
2. It is an opposed-cylinder design which practically eliminates loads on the crankshaft main bearings.
3. It is air-cooled which means it theoretically has the whole earth's atmosphere as a cooling supply. Its cooling system cannot deteriorate as can a car with water-cooling and the associated corrosion problems.
4. Its valve-geometry design is almost perfect for a non-overhead cam design and this results in a more efficient cylinder head. Efficiency in this case encourages mechanical longevity.
5. The valve rocker-arm design comes from the most-proved design in the world, the Chevrolet V-8. This ball & stud design came out in 1955 and remains basically unchanged today. It has been copied by many other manufacturers.
6. The toal engine design is simple and simplicity makes for longevity.
Those things are pre-requisites, no doubt. But there are other reasons the Corvair is a good auto-conversion for aircraft. One big reason is that there is a 50 year history of using them in aircraft. That history is important. Even if the spirit of the FAA rule allowing individuals to build experimental aircraft is to EXPERIMENT, meaning if you can demonstrate sufficient airworthiness to an FAA inspector you could fly with a Ford Model A engine, there just aren't as many flight hours on Ford Model A engines (at least documented) as there are on Corvair engines.
While that's important, there's an even more important thing to consider: Substantial testing has been done on Corvair motors as flight engines during the last 15 years by A&P mechanic William Wynn and many others. William in particular however pursues flight testing conversion ideas implemented on Corvairs -- then he PUBLISHES his findings on the Internet and in a Corvair conversion manual that he sells. William's willingness to share his knowledge either for free or for modest price (his manuals or DVDs or parts or services) is remarkable. His dedication to testing design ideas cannot be lauded enough. He may not be the only expert on Corvair engines, nor the only one who shares information, but I have not found any other person that has invested so much in the Corvair engine conversion and contributed so publically to the body of knowledge of what constitues the most reliable and safe Corvair conversion designs.
Visit http://www.flycorvair.com/ for more information on William Wynne's conversion work.
Since I am employed in an engineering field (software), I cannot overstate the importance of testing. An idea that looks very good or even like the best solution on paper may completely fail in practice. An idea that seems plain or less than ideal in theory may work superbly in the crucible of real everyday operation.
Auto engine conversions are by nature experimental, as the engine was not designed for flight. Therefore, any auto engine conversion is an experiment. That is why basing a conversion on the testing (not Internet opinion or assertion, but real in-flight testing) done by others can SUBSTANTIALLY reduce unknown factors and thus risk. Given a design that has been proven to work fairly well in flight, for many hundreds of hours, one can be more confident that following that design will lead to similar performance; on the flipside, even small deviations from a proven design can lead to in-flight failure.
All airplanes are gliders (recently demonstrated to the general public by C.B. Sullenberger and his first officer Jeffrey B. Skiles on US Airways flight 1549).
The gliders that are powered, like an Airbus 320 or single engine pistons like Cessnas or homebuilts, are the ones you don't want to have to glide with no power.
If you're looking to experiment that is fine -- know that your flights will be as a test pilot. There is nothing wrong with that. If you're looking for a reliable air-cooled conversion, the Corvair has a well-established, long, fairly well tested, and highly documented conversion history. Use it.
