Frank W. Caldwell | |
|---|---|
.jpg) Frank W. Caldwell being congratulated on winning the 1933 Collier Trophy (visible in the background) for his work with Hamilton Standard on the controllable-pitch propeller.[1] | |
| Born | (1889-12-20)December 20, 1889[2] |
| Died | December 23, 1974(1974-12-23) (aged 85) |
| Education | Mechanical engineering (B.S.) |
| Alma mater | University of Virginia Massachusetts Institute of Technology |
| Occupation | Aircraft propeller engineer |
| Known for | Variable-pitch propeller |
| Spouses |
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| Children | Walter H. Caldwell (1924–2003) Frank W. A. Caldwell (1934–1962)[2] |
| Parent(s) | Frank Hollis Caldwell Mary Ellis Nellie Walker |
| Awards | Collier Trophy (1933) Sylvanus Albert Reed Award (1935) |
Frank Walker Caldwell (1889–1974) was a leading Americanpropeller 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 atHamilton Standard Propeller Corporation, they won the 1933Collier Trophy for his work on the controllable-pitch propeller.[1] After 25 years of service, he retired in 1955 as director of theUnited Aircraft Corporation Research Division.[3]
Caldwell was born inLookout Mountain, Tennessee, to Frank Hollis Caldwell and Mary Ellis Nellie Walker.[2] His father was president of theCahill Iron Works and mayor of Chattanooga.[4] He attended theTome Preparatory School in northeast Maryland and the University of Virginia.[4][5] In 1912, he graduated from theMassachusetts Institute of Technology with aBachelor of Science degree inmechanical engineering.[3] While at MIT, Caldwell and fellow studentHans Frank Lehmann designed a contest winning glider.[4] At that time, MIT did not offer courses inaeronautics, yet working with Hans Lehmann, Caldwell titled his graduate thesis "Investigation of Air Propellers."[4][5] After graduation, he worked as foreman and process engineer atCurtiss Aeroplane and Motor Company inBuffalo, New York. In 1916, Caldwell traveled to investigate Army airplane propeller de-lamination atColumbus, New Mexico, near the Mexican border. Realizing that propellers glued in New York delaminated in the southwest heat, he developed a new glue that improved propeller reliability.[5]
DuringWorld War I, Caldwell became the chief engineer in the Propeller Research Department of the Airplane Design Section, Aviation Section of theSignal Corps based atMcCook Field (1918-1927).[6] While at McCook andWright Field (1926-1938) he was responsible for all aircraft propeller development.[3] In Ohio, Caldwell designed the whirl test by mounting the subject propeller on a fixed stand to measure thrust, endurance, speed, efficiency, and structural strength.[3] Post war propeller design moved from wood to metal and fixed pitch to variable pitch. Caldwell pushed propeller development to individual detachable blades joined to a central hub allowing, on the ground, pre-flight adjustment of the blades to satisfy performance goals:[3] fine pitch for best climb or coarse pitch for improved cruise performance.[7]Charles A. Lindbergh's 1927 solo transatlantic aircraft theSpirit of St. Louis used a ground only adjustable pitch propeller made byStandard Steel Propeller Company.[3]
In 1929, Caldwell transitioned from the US Army Air Service to theHamilton Standard Propeller Corporation where he further developed thecontrollable-pitch propeller. The controllable-pitch or variable-pitch propeller tied together the major aeronautical advances of aerodynamic drag reduction and increased engine power.[3][8] In 1933, the most modern aircraft in the world,Boeing's Model 247 operated byUnited Air Lines struggled to reach 6000 feet. After adding Hamilton Standard's hydraulic two positioncontrollable-pitch propeller developed by Caldwell, the Model 247 entered transcontinental service over the Rocky Mountains.[4] TheBoeing Model 247 main competitor theDouglas DC-2, also used Caldwell's controllable-pitch propeller.[3]
In 1933 the Collier Trophy was awarded to "Hamilton Standard Aircraft Propeller Co, with particular credit to Frank W Caldwell, Chief Engineer, for development of a controllable-pitch propeller."[9]
In June 1934 President PresidentFranklin D. Roosevelt congratulated Caldwell at theOval Office for his two position hydraulic controllable-pitch propeller design that won the 1933Collier Trophy for the year's greatest achievement in American aviation.[3][10]
Caldwell and Hamilton Standard invented the automatic pitch-changing propeller. The hydromaticconstant-speed propeller uses hydraulic power (normally engine oil) to change pitch while keeping propeller speed constant.[7] This design included the ability to streamline (feather) the propeller blade reducing drag from propellers on failed engines.[3][11] Almost allUnited States Army Air Forces aircraft inWorld War II used hydromatic constant-speed propellers.[3] The constant-speed propeller was popularly known as the "gearshift of the air."[12][13][14] Caldwell andErnest G. McCauley hold three joint patents for propeller innovations.[6] In 1990, the Hydromatic Propeller, on display at the New England Air Museum ofWindsor Locks, was pronounced as an International Historic Mechanical Engineering Landmark by the American Society of Mechanical Engineers.[11][6]
Prior to Caldwell'shydraulic controllable pitch propeller; [Wallace Rupert Turnbull] a Canadian working in Britain and German engineers focused onmechanical system to change propeller's pitch. Caldwell's hydraulic design, fully developed by 1938, was used in the majority of World War II airplanes.[11] Hamilton Standard produced 500,000 hydraulic controllable pitch propellers for World War II.[13][15]
| Adjustable Pitch Propeller | Pat. No. 1,404,269 | Filed: May 5, 1921 | Issued: January 24, 1922 | Title: Variable-pitch or Reversible Propeller |
| Hydraulic Propeller | Pat. No. 1,893,612 | Filed: May 25, 1929 | Issued: January 10, 1933 | Title: Propeller[14] |
| Patent Assignee: Hamilton Standard Propeller Company |
The Institute of Aeronautical Sciences, forerunner to theAmerican Institute of Aeronautics and Astronautics (AIAA), presented Caldwell with the 1935Sylvanus Albert Reed Award. This annual award recognizes "Experimental or theoretical investigations having a beneficial influence on the development of practical aeronautics".[16] Additionally The Institute granted Caldwell an honorary fellowship in 1946.[3]
Caldwell married Gertrude Sweigert Heisel (1896–1977) on September 28, 1918; their son Walter Hollis Caldwell (1924–2003) was born inDayton, Ohio.[2] He later married Majorie Snodgrass (1897–1976), their son Frank Walker Allen Caldwell (1934–1962) was born inWest Hartford, Connecticut.[2]
Caldwell died on December 23, 1974, at age 85.[3][5]
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