Editing Rotary engine (section)

===Postwar===

By the time the war ended, the rotary engine had become obsolete, and it disappeared from use quite quickly. The British [[Royal Air Force]] probably used rotary engines for longer than most other operators.  The RAF's standard post-war fighter, the [[Sopwith Snipe]], used the [[Bentley BR2]] rotary as the most powerful (at some {{convert|230|hp|abbr=on}}) rotary engine ever built by the [[Allies of World War I]].  The standard RAF training aircraft of the early post-war years, the 1914-origin [[Avro 504]]K, had a universal mounting to allow the use of several different types of low powered rotary, of which there was a large surplus supply. Similarly, the Swedish [[FVM Ö1 Tummelisa]] advanced training aircraft, fitted with a Le-Rhone-Thulin {{convert|90|hp|abbr=on}} rotary engine, served until the mid thirties.

Designers had to balance the cheapness of war-surplus engines against their poor [[fuel efficiency]] and the operating expense of their total-loss lubrication system, and by the mid-1920s, rotaries had been more or less completely displaced even in British service, largely by the new generation of air-cooled "stationary" radials such as the [[Armstrong Siddeley Jaguar]] and [[Bristol Jupiter]].

Experiments with the concept of the rotary engine continued.

The first version of the 1921 [[Michel engine]], an unusual opposed-piston [[cam engine]], used the principle of a rotary engine, in that its "cylinder block" rotated. This was soon replaced by a version with the same cylinders and cam, but with stationary cylinders and the cam track rotating in lieu of a crankshaft. A later version abandoned the cam altogether and used three coupled crankshafts.

By 1930 the Soviet helicopter pioneers, Boris N. Yuriev and Alexei M. Cheremukhin, both employed by ''[[TsAGI|Tsentralniy Aerogidrodinamicheskiy Institut]]'' (TsAGI, the Central Aerohydrodynamic Institute), constructed one of the first practical single-lift rotor machines with their TsAGI 1-EA single rotor helicopter, powered by two Soviet-designed and built M-2 rotary engines, themselves up-rated copies of the [[Gnome Monosoupape]] rotary engine of World War I. The TsAGI 1-EA set an unofficial altitude record of 605 meters (1,985&nbsp;ft) with Cheremukhin piloting it on 14 August 1932 on the power of its twinned M-2 rotary engines.<ref>Savine, Alexandre. [http://www.ctrl-c.liu.se/misc/ram/1-ea.html "TsAGI 1-EA."] {{Webarchive|url=https://web.archive.org/web/20090126202112/http://www.ctrl-c.liu.se/misc/ram/1-ea.html |date=2009-01-26 }} ''ctrl-c.liu.se,'' 24 March 1997. Retrieved 12 December 2010.</ref>