Townend ring

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Polish sports plane PZL Ł.2 with a Townend ring

A Townend ring is a narrow-chord cowling ring fitted around the cylinders of an aircraft radial engine to reduce drag and improve cooling.

Development[edit]

The Townend ring was the invention of Dr. Hubert Townend of the British National Physical Laboratory[1] in 1929. Patents were supported by Boulton & Paul Ltd in 1929.[2] 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,[3] particularly when combined with the lack of flow control as the air exits the cowling.[4]}} Although superior to earlier cowlings, and uncowled engines in terms of drag and cooling, above 217 kn (402 km/h; 250 mph) the NACA cowling was more efficient and soon replaced it in general use.[5]

Examples of aircraft with Townend rings include the Boeing P-26 Peashooter, the Vickers Wellesley, the Fokker D.XVI and the centre engine on the Junkers Ju 52/3m.

Notes[edit]

References[edit]

  1. ^ Patent Specification 320131: Improvements in or relating to aircraft , 8 July 1933 (amended specification from original dated 10 July 1928)
  2. ^ 1930 Canadian patent CA 304755 by Hubert Townend with drawings
  3. ^ "A History of Aircraft Piston Engines" by Herschel Smith, (Sunflower University Press Manhattan, Kansas, 1981, ISBN 0-89745-079-5), 255pp.
  4. ^ Becker, J.; The high-speed frontier: Case histories of four NACA programs, 1920- SP-445, NASA (1980), Chapter 5: High-speed Cowlings, Air Inlets and Outlets, and Internal-Flow Systems: The ramjet investigation
  5. ^ 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. Archived from the original on 2004-10-31. Retrieved 2007-04-28.[failed verification]

External links[edit]