{{short description|1920s British piston aircraft engine}} <!-- This article is a part of Wikipedia:WikiProject Aircraft. Please see Wikipedia:WikiProject Aircraft/page content for recommended layout. --> {{infobox aero engine |name= R |image= File:PobjoyR.JPG |caption= Preserved Pobjoy R at the Shuttleworth Collection |engine_type=Piston radial aero-engine |manufacturer=Pobjoy Airmotors |first_run=1926 |major_applications=BA Swallow<br>Comper Swift }}

The '''Pobjoy R''' is a British seven-cylinder air-cooled radial aircraft engine designed and built by Pobjoy Airmotors.<ref>Lumsden 2003, p.178.</ref> Introduced in 1926, it was a popular engine for ultralight and small aircraft in the 1930s. A notable feature of the Pobjoy R was the propeller reduction gear which allowed the small engine to operate at more desirable higher speeds.

The engine was license produced in Czechoslovakia by Walter Aircraft Engines as the '''Walter Mira'''.<ref>[https://kramerius.army.cz/search/i.jsp?pid=uuid:562acded-5f0d-11e9-b4d6-005056b73ae5#periodical-periodicalvolume-periodicalitem-page_uuid:562acded-5f0d-11e9-b4d6-005056b73ae5 ''Letecvi'' magazine, (Walter engine range advertisement, 1935) 1934, Volume 10, No. 12] Retrieved: 27 November 2021</ref>

==Variants== ;Walter Mira R :License produced version of Pobjoy R. ;Walter Mira I-R :Renaming of Mira R. ;Walter Mira II-R :Developed version of the Mira R producing 95 hp (70 kW).

==Applications== {{columns-list|colwidth=30em| * British Aircraft Swallow * Cierva C.25 * Comper Kite * Comper Swift * Cosmopolitan Light Plane * Couzinet 101 * Farman F.239 * Fauvel AV.10 * Fieseler F 3 * General Aircraft Monospar * Hendy Hobo * Kay Gyroplane * Landgraf H-2 * Letov Š-139 * Lippisch Delta IV * Mauboussin M.121P Corsaire Major * Miles Satyr * Nicholas-Beazley Pobjoy Special * Nozawa X-I * Pander Multipro * Praga E.214 * Přikryl-Blecha PB-5 Racek * Savoia-Marchetti SM.80bis * Short Scion * Short Scion Senior * Spartan Clipper * Swanson-Fahlin SF-1 }}

;Walter Mira * Letov Š-39 * Letov Š-139

==Engines on display== A preserved Pobjoy R engine is on display at the Shuttleworth Collection, Old Warden, Bedfordshire.{{cn|date=May 2018}}

Two Pobjoy R engines, one installed in the remains of Comper Swift (R222 / LV-FBA) will be soon on display at the National Aviation Museum in Buenos Aires Province, Argentina.{{cn|date=May 2018}}

==Specifications (Pobjoy R)== {{pistonspecs |<!-- If you do not understand how to use this template, please ask at Wikipedia talk:WikiProject Aircraft --> <!-- Please include units where appropriate (main comes first, alt in parentheses). If data are missing, leave the parameter blank (do not delete it). For additional lines, end your alt units with </li> and start a new, fully-formatted line with <li> --> |ref=''Lumsden''. |type=7-cylinder air-cooled, radial, left-hand tractor |bore=3.03 in (77 mm) |stroke=3.43 in (87 mm) |displacement=173.05 cu in (2.84 L) |length= |diameter={{Convert abbreviated|25.5|in}} |width= |height= |weight=135 lb |valvetrain= |supercharger= |turbocharger= |fuelsystem= |fueltype= |oilsystem=Dry sump |coolingsystem=Air-cooled |power=85 hp |specpower=0.5 hp/cu in |compression= |fuelcon=4.9 imp. gallons per hour |specfuelcon= |oilcon= |power/weight= 0.63 hp/lb }}

==See also== {{aircontent <!-- other related articles that have not already linked: --> |see also=

<!-- designs which were developed into or from this aircraft: --> |related= *Pobjoy Niagara <!-- aircraft that are of similar role, era, and capability as this design: --> |similar aircraft=

<!-- relevant lists that this aircraft appears in: --> |lists= * List of aircraft engines

<!-- For aircraft engine articles. Engines that are of similar to this design: --> |similar engines= * Rotec R2800

<!-- See WP:Air/PC for more explanation of these fields. --> }}

==References== {{commons category}}

===Notes=== {{reflist}}

===Bibliography=== {{refbegin}} * Guttery, T.E. ''The Shuttleworth Collection''. London: Wm. Carling & Co, 1969. SBN 901319-01-5 * Lumsden, Alec. ''British Piston Engines and their Aircraft''. Marlborough, Wiltshire: Airlife Publishing, 2003. {{ISBN|1-85310-294-6}}. {{refend}}

{{Pobjoy aeroengines}} {{Walter aeroengines}}

R Category:1920s aircraft piston engines Category:Aircraft air-cooled radial piston engines Category:Seven-cylinder engines