Wallace Rupert Turnbull (Canadian Aviation Pioneer)

Birthdate: October 16, 1870
Birth Place: St. John, New Brunswick
Year Inducted: 1976
Death Date: November 24, 1954

"The patient application of his aeronautical theses to a number of problems unique to flight, and more especially his invention of the successful variable pitch propeller, have been of outstanding benefit to Canadian aviation."

W. Rupert Turnbull graduated in mechanical engineering from Cornwall University in 1893 and undertook post graduate work in physics at the Universities of Berlin and Heidelberg, Germany. In 1902 he built the first wind tunnel in Canada. During the next decade he continued researching the stability of aircraft and investigated many forms of airfoils. During WWI Turnbull was employed by Frederick and Company aircraft builders in England where he designed a number of propellers, the most successful being the variable pitch propeller. His interests extended into many fields, such as hydroplanes, torpedo screens, bomb sights and consolidated and tidal power, but his systematic approach to aeronautical engineering remains his greatest contribution.

One of W. Rupert Turnbull's early contributions to aviation was the construction in 1902 of the first wind tunnel in Canada, and one of the earliest in the world. At his home in Rothesay, New Brunswick, the Canadian engineer built a basic wind tunnel out of an old packing case, and used it to experiment with propellers and various types of engines. "His research strongly influenced the design of aircraft for the next century, concludes Captain Howe of the Canadian Air Force. "General aviation aircraft today are still designed upon the foundational work he did."

Turnbull's involvement in aeronautical engineering research spans over a period of more than four decades and touched on many aspects of flight. Undoubtedly, his main contribution to the world of aviation was the invention of the variable pitch propeller, a device that has become a milestone in the evolution of aircraft.

"An early aircraft with a fixed propeller was like a vehicle with no transmission," explains Master Corporal Tim Beaudoin, an instructor at the Canadian Forces School of Aerospace Technology and Engineering (CFSATE). The Aviation Systems instructor compares flying an aircraft equipped with a fine pitch propeller to driving a car in first gear all the time, while an aircraft with a coarse pitch propeller would be equivalent to having a high gear only.

"It was Turnbull's genius that brought us the variable pitch propeller. The ability to adjust the propeller pitch in flight provided better acceleration when needed and improved fuel consumption, which allowed for greater payloads to be efficiently and safely carried through the skies."

"For people in Borden, there is a very good reason for taking interest in Mr. Turnbull's achievements. It was right here in Borden, on June 6, 1927, that with the help of the Royal Canadian Air Force, W. Rupert Turnbull tested his variable pitch propeller in flight for the first time. That day was an important milestone in the evolution of powered flight, and certainly a proud moment in the history of aviation at Camp Borden."

Although Bush Pilots during the 1920s flew thousands of miles and performed incredible feats of bravery and entrepreneurship to serve the remote areas of Canada's north, W. Rupert Turnbull, working in his own laboratory at Rothesay, New Brunswick, was, in fact, Canada's first aviation pioneer. His interest began even before the end of the nineteenth century and his invention of the variable pitch propeller in 1927 revolutionized the aircraft industry. By 1900 he believed that the airplane was imminent. He shared his interest in aviation with such pioneers as Dr. Samuel Langley, who advanced the theory of flight; Otto Lilienthal, who experimented with gliders; and Gustave Eiffel, who built the world's first wind tunnel. He was reluctant to admit his conviction, however, for fear of being considered a "crank."

In 1902 he left General electric to return to Rothesay where he established himself as a consulting engineer and built a laboratory. There he built Canada's first wind tunnel out of an old packing case and experimented with lift devices, internal combustion as well as turbine engines and propellers, the latter taking him, in 1906, to visit Alexander Graham Bell at Baddeck, Nova Scotia. He thought Bell's belief in kites was wrong because of the excessive drift factor. That same year he applied for his first of what would eventually number 17 patents. Most of these dealt with aeronautics; the first was broadly titled "Improvements in Aeroplanes and Hydroplanes."

In 1909, for his study published in Scientific American on power absorbed by the airscrew, he won a bronze medal. Two years later he wrote the Laws of Airscrews that scientifically identified today's wellknown laws of air propellers. By then he had also filed a broad patent on a double curvature aerofoil to be executed by a British company, but the deal fell through and the patent lapsed.

When World War I began, he closed his lab and went to Britain to volunteer his services to several aircraft manufacturers without remuneration, but also without success. Later, he joined Sage and Company which the Admiralty had commissioned to manufacture aircraft. For the duration of the war Turnbull remained with Sage. Initially he was an aircraft inspector but later was given a free hand to work on various wartime devices including air propellers, bomb sights, and torpedo screens.

Returning to Canada at war's end, he concentrated his interest in the variable pitch propeller which he had considered originally in 1916. His first model, developed partly in England, was brought back to Canada to be completed at Rothesay, December 1922. In the same year Turnbull obtained a Canadian patent for it and interested the R. C.A. F. in testing it in an Avro trainer. I ri February 1923, the propeller won a silver medal at the Inventions Show in New York City, but later that year, when it was tested with a mechanical brake control, it proved impractical. In October the propeller was destroyed in a hangar fire at Camp Borden.

By then Turnbull was already working on a new design with alternative control mechanisms. One design retained brake shoes; the other was an experimental model using an electrical motor drive. The R.C.A.F. through its research committee, selected the second unit. Canadian Vickers Limited made the blades, and Turnbull developed the electrical control unit at Rothesay. The results at Camp Borden in 1927, of a test that included an assessment of takeoff, cruising speed, and fuel consumption were "remarkably good" wrote J.H. Parkin in the Canadian Aeronautical Journal in 1956. Changing the angle of a propeller in flight, in relation to the air, had a profound effect on air transport and completely changed the face of aviation history. Ability to adjust propeller pitch allowed greater payloads to be carried efficiently and safely in the skies.

Within months of the test Turnbull applied for patents in Canada, the US, and Great Britain and began negotiations with firms for the rights to his invention. He sold the patent in December 1929 to the Reed Propeller Company, a subsidiary of the Curtis Aeroplane and Motor Company which was, in turn, a division of the Curtis-Wright Corporation of the United States. In 1935 the export division of that company reached an agreement with the Bristol Aeroplane Company of England and royalties were paid until the US Government purchased the patents outright in 1944.

Turnbull, meanwhile, pursued other interests. As early as 1919, he had proposed a scheme to utilize tidal power at the confluence of the Petitcodiac and Memramcook Rivers of his home province and, while further studies proved his idea had merit, the availability of cheap coal won out. He was, however, invited to be a director of the Petitcodiac Tidal Power company when it was organized in 1928, and his interest in tidal power remained throughout the rest of his life. He also served on the board of the Turnbull Real Estate company as well as the Turnbull Home for Incurables.

In 1936, when the Associate Committee on Aeronautical Research announced plans for a museum at Ottawa, Turnbull donated some of his early and priceless inventions and memorabilia including his model of the variable pitch propeller which was brought back from a museum in England.

Although Turnbull was better known and respected outside Canada as one of the world's outstanding pioneer scientists in aeronautics, his own country finally honoured him as an achiever when the University of New Brunswick conferred an Honorary Doctor of Science upon him in 1942. As well, the Engineering Institute of Canada named him an honorary member in 1951, three years before his death at the General Hospital in Saint John, New Brunswick.

Canada Post honored W. Rupert Turnbull with a stamp in October 2022.