The 1905 patent by Alfred Büchi, a Swiss engineer working at Gebrüder Sulzer (now simply called Sulzer) is often considered the birth of the turbocharger. This patent was for a compound radial engine with an exhaust-driven axial flow turbine and compressor mounted on a common shaft. The first prototype was finished in 1915 with the aim of overcoming the power loss experienced by aircraft engines due to the decreased density of air at high altitudes. However, the prototype was not reliable and did not reach production. Another early patent for turbochargers was applied for in 1916 by French steam turbine inventor Auguste Rateau, for their intended use on the Renault engines used by French fighter planes. Separately, 1917 testing by the American National Advisory Committee for Aeronautics and Sanford Alexander Moss showed that a turbocharger could enable an engine to avoid any power loss (compared with the power produced at sea level) at an altitude of up to above sea level. The testing was conducted at Pikes Peak in the United States using the V12 Liberty aircraft engine.