Townend ring

Development

The Townend ring was the invention of Dr. Hubert Townend of the British National Physical Laboratory in 1929. Patents were supported by Boulton & Paul Ltd in 1929. 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, particularly when combined with the lack of flow control as the air exits the cowling. Although superior to earlier cowlings, and uncowled engines in terms of drag and cooling, above 217 kn 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.

Notes

References

References

1. [http://v3.espacenet.com/publicationDetails/originalDocument?CC=GB&NR=320131A&KC=A&FT=D&date=19291010&DB=EPODOC&locale=en_gb ''Patent Specification 320131: Improvements in or relating to aircraft''], 8 July 1933 (amended specification from original dated 10 July 1928).
2. [https://wayback.archive-it.org/all/20110827041209/http://brevets-patents.ic.gc.ca/opic-cipo/cpd/eng/patent/304755/summary.html#view_or_download_imagesOriginal 1930 Canadian patent CA 304755 by Hubert Townend with drawings].
3. "Means for reducing eddy formation in the airflow passing aircraft bodies".
4. "A History of Aircraft Piston Engines" by Herschel Smith, (Sunflower University Press Manhattan, Kansas, 1981, {{ISBN. 0-89745-079-5), 255 pp.
5. Becker, J.; ''The high-speed frontier: Case histories of four NACA programs, 1920–1950'', SP-445, NASA (1980), [http://www.hq.nasa.gov/pao/History/SP-445/ch5-5.htm Chapter 5: High-speed Cowlings, Air Inlets and Outlets, and Internal-Flow Systems: The ramjet investigation].
6. Hansen, James R.. "Engineering Science and the Development of the NACA Low-Drag Engine Cowling". From Engineering Science to Big Science: The NACA and NASA Collier Trophy Research Project Winners.