This piece originally ran in the September 2021 issue of EAA Sport Aviation magazine.
First produced in 1938, the Lycoming O-145 is a series of four-cylinder, air-cooled aircraft engines that produce 50-75 hp. They were used in a number of classic aircraft, including the Aeronca Chief, a number of Taylorcrafts, the Luscombe 8B, and the J-3L variant of Piper’s Cub. This particular example, rated at 50 hp at 2300 rpm, was used by designer Steve Wittman in his Buttercup, first flown in 1938 and used for more than 50 years as his personal test bed.