Frank Walker Caldwell (1889–1974) was a leading American

propeller A propeller (colloquially often called a screw if on a ship or an airscrew if on an aircraft) is a device with a rotating hub and radiating blades that are set at a pitch to form a helical spiral which, when rotated, exerts linear thrust upon ...

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 Hamilton Standard was an American aircraft propeller parts supplier. It was formed in 1929 when United Aircraft and Transport Corporation consolidated Hamilton Aero Manufacturing and Standard Steel Propeller into the Hamilton Standard Propeller C ...

Propeller Corporation, they won the 1933

Collier Trophy The Robert J. Collier Trophy is an annual aviation award administered by the U.S. National Aeronautic Association (NAA), presented to those who have made "the greatest achievement in aeronautics or astronautics in America, with respect to im ...

for his work on the controllable-pitch propeller. After 25 years of service, he retired in 1955 as director of the

United Aircraft Corporation The PJSC United Aircraft Corporation (UAC) () is a Russian Aerospace manufacturer, aerospace and Arms industry, defense corporation. With a majority stake belonging to the Russian government, it consolidates Russian private and state-owned Russian ...

Research Division.

Early life

Caldwell was born in

Lookout Mountain, Tennessee Lookout Mountain is a town in Hamilton County, Tennessee, United States. The population was 2,058 at the 2020 census. Bordering its sister city of Lookout Mountain, Georgia to the south, Lookout Mountain is part of the Chattanooga, TN– GA ...

, to Frank Hollis Caldwell and Mary Ellis Nellie Walker. His father was president of the Cahill Iron Works and mayor of Chattanooga. He attended the Tome Preparatory School in northeast Maryland and the University of Virginia. In 1912, he graduated from the

Massachusetts Institute of Technology The Massachusetts Institute of Technology (MIT) is a private land-grant research university in Cambridge, Massachusetts. Established in 1861, MIT has played a key role in the development of modern technology and science, and is one of the ...

with a

Bachelor of Science A Bachelor of Science (BS, BSc, SB, or ScB; from the Latin ') is a bachelor's degree awarded for programs that generally last three to five years. The first university to admit a student to the degree of Bachelor of Science was the University of ...

degree in

mechanical engineering Mechanical engineering is the study of physical machines that may involve force and movement. It is an engineering branch that combines engineering physics and mathematics principles with materials science, to design, analyze, manufacture, and ...

. While at MIT, Caldwell and fellow student Hans Frank Lehmann designed a contest winning glider. At that time, MIT did not offer courses in

aeronautics Aeronautics is the science or art involved with the study, design, and manufacturing of air flight–capable machines, and the techniques of operating aircraft and rockets within the atmosphere. The British Royal Aeronautical Society identifies ...

, yet working with Hans Lehmann, Caldwell titled his graduate thesis "Investigation of Air Propellers." After graduation, he worked as foreman and process engineer at

Curtiss Aeroplane and Motor Company Curtiss Aeroplane and Motor Company (1909 – 1929) was an American aircraft manufacturer originally founded by Glenn Hammond Curtiss and Augustus Moore Herring in Hammondsport, New York. After significant commercial success in its first decades ...

Buffalo, New York Buffalo is the second-largest city in the U.S. state of New York (behind only New York City) and the seat of Erie County. It is at the eastern end of Lake Erie, at the head of the Niagara River, and is across the Canadian border from South ...

. In 1916, Caldwell traveled to investigate Army airplane propeller de-lamination at

Columbus, New Mexico Columbus is a village in Luna County, New Mexico, United States, about north of the Mexico–United States border, Mexican border. It is considered a place of historical interest, as the scene of Battle of Columbus (1916), a 1916 attack by 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.

Propeller evolution from World War I

During

World War I World War I (28 July 1914 11 November 1918), often abbreviated as WWI, was one of the deadliest global conflicts in history. Belligerents included much of Europe, the Russian Empire, the United States, and the Ottoman Empire, with fightin ...

, 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 McCook Field was an airfield and aviation experimentation station in Dayton, Ohio, United States. It was operated by the Aviation Section, U.S. Signal Corps and its successor the United States Army Air Service from 1917 to 1927. It was named fo ...

(1918-1927). While at McCook and

Wright Field Wilbur Wright Field was a military installation and an airfield used as a World War I pilot, mechanic, and armorer training facility and, under different designations, conducted United States Army Air Corps and Air Forces flight testing. Loca ...

(1926-1938) he was responsible for all aircraft propeller development. 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. 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: fine pitch for best climb or coarse pitch for improved cruise performance.

Charles A. Lindbergh Charles Augustus Lindbergh (February 4, 1902 – August 26, 1974) was an American aviator, military officer, author, inventor, and activist. On May 20–21, 1927, Lindbergh made the first nonstop flight from New York City to Paris, a distance o ...

's 1927 solo transatlantic aircraft the

Spirit of St. Louis The ''Spirit of St. Louis'' (formally the Ryan NYP, registration: N-X-211) is the custom-built, single-engine, single-seat, high-wing monoplane that was flown by Charles Lindbergh on May 20–21, 1927, on the first solo nonstop transatlant ...

used a ground only adjustable pitch propeller made by Standard Steel Propeller Company.

1933 Collier Trophy

In 1929, Caldwell transitioned from the US Army Air Service to the

Propeller Corporation where he further developed the controllable-pitch propeller. The controllable-pitch or variable-pitch propeller tied together the major aeronautical advances of aerodynamic drag reduction and increased engine power. In 1933, the most modern aircraft in the world, Boeing's Model 247 operated by

United Air Lines United Airlines, Inc. (commonly referred to as United), is a major American airline headquartered at the Willis Tower in Chicago, Illinois.

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. The Boeing Model 247 main competitor the

Douglas DC-2 The Douglas DC-2 is a 14-passenger, twin-engined airliner that was produced by the American company Douglas Aircraft Company starting in 1934. It competed with the Boeing 247. In 1935, Douglas produced a larger version called the DC-3, which b ...

, also used Caldwell's controllable-pitch propeller. 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." In June 1934 President President

Franklin D. Roosevelt Franklin Delano Roosevelt (; ; January 30, 1882April 12, 1945), often referred to by his initials FDR, was an American politician and attorney who served as the 32nd president of the United States from 1933 until his death in 1945. As the ...

congratulated Caldwell at the

Oval Office The Oval Office is the formal working space of the President of the United States. Part of the Executive Office of the President of the United States, it is located in the West Wing of the White House, in Washington, D.C. The oval-shaped room ...

for his two position hydraulic controllable-pitch propeller design that won the 1933

for the year's greatest achievement in American aviation.

Hydromatic constant-speed propeller

Caldwell and Hamilton Standard invented the automatic pitch-changing propeller. The hydromatic

constant-speed propeller In aeronautics, a variable-pitch propeller is a type of propeller (airscrew) with blades that can be rotated around their long axis to change the blade pitch. A controllable-pitch propeller is one where the pitch is controlled manually by the p ...

uses hydraulic power (normally engine oil) to change pitch while keeping propeller speed constant. This design included the ability to streamline (feather) the propeller blade reducing drag from propellers on failed engines. Almost all

United States Army Air Forces The United States Army Air Forces (USAAF or AAF) was the major land-based aerial warfare service component of the United States Army and ''de facto'' aerial warfare service branch of the United States during and immediately after World War II ...

aircraft in

World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...

used hydromatic constant-speed propellers. The constant-speed propeller was popularly known as the "gearshift of the air." Caldwell and Ernest G. McCauley hold three joint patents for propeller innovations. In 1990, the Hydromatic Propeller, on display at the New England Air Museum of

Windsor Locks Windsor Locks is a town in Hartford County, Connecticut, United States. As of the 2020 census, its population was 12,613. It is the site of Bradley International Airport, which serves the Greater Hartford-Springfield region and occupies approxim ...

, was pronounced as an International Historic Mechanical Engineering Landmark by the American Society of Mechanical Engineers. Prior to Caldwell's

hydraulic Hydraulics (from Greek: Υδραυλική) is a technology and applied science using engineering, chemistry, and other sciences involving the mechanical properties and use of liquids. At a very basic level, hydraulics is the liquid counter ...

controllable pitch propeller; allace Rupert Turnbulla Canadian working in Britain and German engineers focused on

mechanical system A machine is a physical system using Power (physics), power to apply Force, forces and control Motion, movement to perform an action. The term is commonly applied to artificial devices, such as those employing engines or motors, but also to na ...

to change propeller's pitch. Caldwell's hydraulic design, fully developed by 1938, was used in the majority of World War II airplanes. Hamilton Standard produced 500,000 hydraulic controllable pitch propellers for World War II.

Sylvanus Albert Reed Award (1935)

The Institute of Aeronautical Sciences, forerunner to the

American Institute of Aeronautics and Astronautics The American Institute of Aeronautics and Astronautics (AIAA) is a professional society for the field of aerospace engineering. The AIAA is the U.S. representative on the International Astronautical Federation and the International Council of ...

(AIAA), presented Caldwell with the 1935

Sylvanus Albert Reed Sylvanus Albert Reed (8 April 1854 – 1 October 1935) was an American aerospace engineer who developed the modern metal aircraft propeller. Early life and career Reed Graduated from Columbia University in 1874. He worked as an engineer special ...

Award. This annual award recognizes "Experimental or theoretical investigations having a beneficial influence on the development of practical aeronautics". Additionally The Institute granted Caldwell an honorary fellowship in 1946.

Family and death

Caldwell married Gertrude Sweigert Heisel (1896–1977) on September 28, 1918; their son Walter Hollis Caldwell (1924–2003) was born in

Dayton, Ohio Dayton () is the sixth-largest city in the U.S. state of Ohio and the county seat of Montgomery County. A small part of the city extends into Greene County. The 2020 U.S. census estimate put the city population at 137,644, while Greater Day ...

. He later married Majorie Snodgrass (1897–1976), their son Frank Walker Allen Caldwell (1934–1962) was born in

West Hartford, Connecticut West Hartford is a town in Hartford County, Connecticut, United States, west of downtown Hartford. The population was 64,083 at the 2020 census. The town's popular downtown area is colloquially known as "West Hartford Center," or simply "The C ...

. Caldwell died on December 23, 1974, at age 85.

Publications

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References

External links

History of the First 50 Years of Flight "We Saw It Happen" - United Aircraft Corporation
Brief film clip of Frank W. Caldwell at time counter +01:25:25:23 * {{DEFAULTSORT:Caldwell, Frank W. 1889 births 1974 deaths People from Chattanooga, Tennessee MIT School of Engineering alumni American aerospace engineers Collier Trophy recipients Aviation inventors American manufacturing businesspeople 1933 in aviation 20th-century American inventors Aviation history of the United States Aviation pioneers