Fred A. Thaheld (1902-1981) was a self-taught engineer born in Austria, who first became acquainted with engines due to his involvement with German motorcycle racing after World War I. Thaheld worked his way as a seaman on merchant ships to South America, and then on to Southern California in 1921. He settled in Brea, California, and began building a low-wing monoplane in the garage of William Tremaine, pilot and co-founder of the Brea Air Club; that aircraft was flown in air meets in Southern California in 1924-1925. Thaheld then built for Tremaine the Tremaine Humming Bird "Spirit of John Rodgers" for his planned non-stop flight to Japan. Instead, the "Spirit of John Rodgers" was used by Naval Lieutenants George Covell and Richard Waggener for their entry in the Dole Air Race. Unfortunately, they crashed the aircraft at Point Loma, California, on the way to the start of the race in Oakland, California. The loss of "The Spirit of John Rodger," ended Thaheld's aeronautical engineering with Tremaine, and Thaheld began his work of designing and building diesel aircraft engines. In 1929, Thaheld was the Chief Engineer of the Guiberson Diesel Engine Company where he directed aircraft diesel engines development, and built the following engines for aircraft: Guiberson Diesel A-980 185-hp 9-Cylinder Radial; Guiberson Diesel A-918 240-hp & A-980 185-hp Radials; and Guiberson Diesel T-1020 9-Cylinder Radial Tank Engine. While the engines were installed and successfully flown in aircraft, they were not a commercial success and Guiberson and Thaheld instead sold their various diesel engines to the US Army for tanks. Thaheld then became the principal in Diesel Power Inc., a division of Shaffer Tool Works of Brea, California, and during the mid-1940s, designed a 90 horsepower diesel engine for light aircraft which he used in his Stinson 10-A. Thaheld held over 30 patents in engine design and become a naturalized US citizen in 1943.