A Townend ring is a narrow-chord cowling ring fitted around the cylinders of an aircraft radial engine to reduce drag and improve cooling. It was patented in 1929, and found use on various aircraft of the 1930s and into the 1940s.
Development
The Townend ring was the invention of Dr. Hubert Townend of the British National Physical LaboratoryPatent Specification 320131: Improvements in or relating to aircraft, 8 July 1933 (amended specification from original dated 10 July 1928). in 1929. Patents were supported by Boulton & Paul Ltd in 1929.1930 Canadian patent CA 304755 by Hubert Townend with drawings. In the United States it was often called a "drag ring". It caused a reduction in the drag of radial engines and was widely used in high-speed designs of 1930–1935, before the long-chord NACA cowling came into general use. Despite suggestions of it exploiting the Meredith effect, low airspeeds, low temperature differences and small mass flows make that unlikely,"A History of Aircraft Piston Engines" by Herschel Smith, (Sunflower University Press Manhattan, Kansas, 1981, ), 255 pp. particularly when combined with the lack of flow control as the air exits the cowling.Becker, J.; The high-speed frontier: Case histories of four NACA programs, 1920–1950, SP-445, NASA (1980), Chapter 5: High-speed Cowlings, Air Inlets and Outlets, and Internal-Flow Systems: The ramjet investigation. Although superior to earlier cowlings, and uncowled engines in terms of drag and cooling, above the NACA cowling was more efficient and soon replaced it in general use.
Examples of aircraft with Townend rings include the Boeing P-26 Peashooter, the Vickers Wellesley, the Fokker D.XVI and the central engine on the Junkers Ju 52/3m.
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References
External links
The Spotters Glossary