Frank Walker Caldwell

Frank Walker Caldwell (1889–1974) was a leading American propeller engineer and designer. As the United States government's chief propeller engineer (1917–1928), he pioneered propeller engineering and propeller testing facilities and techniques. Working at Hamilton Standard Propeller Corporation, they won the 1933 Collier Trophy for his work on the controllable-pitch propeller. His father was president of the Cahill Iron Works and mayor of Chattanooga. At that time, MIT did not offer courses in aeronautics, yet working with Hans Lehmann, Caldwell titled his graduate thesis "Investigation of Air Propellers."

Propeller evolution from World War I During World War I, Caldwell became the chief engineer in the Propeller Research Department of the Airplane Design Section, Aviation Section of the Signal Corps based at McCook Field (1918-1927). Charles A. Lindbergh's 1927 solo transatlantic aircraft the Spirit of St. Louis used a ground only adjustable pitch propeller made by Standard Steel Propeller Company. In 1933, the most modern aircraft in the world, Boeing's Model 247 operated by United Air Lines struggled to reach 6000 feet. After adding Hamilton Standard's hydraulic two position controllable-pitch propeller developed by Caldwell, the Model 247 entered transcontinental service over the Rocky Mountains.

In June 1934 President President Franklin D. Roosevelt congratulated Caldwell at the Oval Office for his two position hydraulic controllable-pitch propeller design that won the 1933 Collier Trophy for the year's greatest achievement in American aviation. 1,000th Controllable Pitch Propeller produced by Hamilton. The 1933 Collier Trophy propeller design team, (Caldwell on the far right).

Hydromatic constant-speed propeller Caldwell and Hamilton Standard invented the automatic pitch-changing propeller. The hydromatic constant-speed propeller uses hydraulic power (normally engine oil) to change pitch while keeping propeller speed constant. Almost all United States Army Air Forces aircraft in World War II used hydromatic constant-speed propellers. Caldwell and Ernest G. McCauley hold three joint patents for propeller innovations.

Prior to Caldwell's hydraulic controllable pitch propeller; [Wallace Rupert Turnbull] a Canadian working in Britain and German engineers focused on mechanical system to change propeller's pitch. Caldwell's hydraulic design, fully developed by 1938, was used in the majority of World War II airplanes. + Patent: Name, Number, Filed, Issued, Title Additionally The Institute granted Caldwell an honorary fellowship in 1946.

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