A Townend ring is a narrow- chord cowling ring fitted around the cylinders of an aircraft

radial engine The radial engine is a reciprocating engine, reciprocating type internal combustion engine, internal combustion engine configuration in which the cylinder (engine), cylinders "radiate" outward from a central crankcase like the spokes of a wheel. ...

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 Hubert is a Germanic masculine given name, from ''hug'' "mind" and '' beraht'' "bright". It also occurs as a surname. Saint Hubert of Liège (or Hubertus) (c. 656 – 30 May 727) is the patron saint of hunters, mathematicians, opticians, and m ...

of the

British British may refer to: Peoples, culture, and language * British people, nationals or natives of the United Kingdom, British Overseas Territories and Crown Dependencies. * British national identity, the characteristics of British people and culture ...

National Physical Laboratory in 1929. Patents were supported by

Boulton & Paul Ltd Boulton & Paul Ltd was a British general manufacturer from Norwich, England that became involved in aircraft manufacture. Jeld Wen Inc. bought Boulton & Paul (along with another joinery company John Carr) from the Rugby Group plc in 1999 to ...

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 The NACA cowling is a type of aerodynamic Aircraft fairing, fairing used to streamliner, streamline radial engines installed on airplanes. It was developed by Fred Weick of the National Advisory Committee for Aeronautics (NACA) in 1927. It was a ...

came into general use. Despite suggestions of it exploiting the

Meredith effect The Meredith effect is a phenomenon whereby the aerodynamic drag produced by a cooling radiator may be offset by careful design of the cooling duct such that useful thrust is produced by the expansion of the hot air in the duct. The effect was di ...

, 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.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 Boeing P-26 "Peashooter" is the first American production all-metal fighter aircraft and the first pursuit monoplane to enter squadron service with the United States Army Air Corps. Designed and built by Boeing, the prototype first flew in 1 ...

, the

Vickers Wellesley The Vickers Wellesley was a medium bomber that was designed and produced by the British aircraft manufacturer Vickers-Armstrongs at Brooklands near Weybridge, Surrey. It was one of two aircraft to be named after Arthur Wellesley, 1st Duke of W ...

, the Fokker D.XVI and the central engine on the

Junkers Ju 52 The Junkers Ju 52/3m (nicknamed ''Tante Ju'' ("Aunt Ju") and ''Iron Annie'') is a transport aircraft that was designed and manufactured by German aviation company Junkers. First introduced during 1930 as a civilian airliner, it was adapted int ...

/3m.

Notes

References

External links

The Spotters Glossary
* * * {{Aircraft components Aircraft propulsion components