Pobjoy R

The Pobjoy R is a British seven-cylinder air-cooled radial aircraft engine designed and built by Pobjoy Airmotors.^[1] 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.

R
Preserved Pobjoy R at the Shuttleworth Collection
Type	Piston radial aero-engine
Manufacturer	Pobjoy Airmotors
First run	1926
Major applications	BA Swallow Comper Swift

The engine was license produced in Czechoslovakia by Walter Aircraft Engines as the Walter Mira.^[2]

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

• 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.^{[citation needed]}

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.^{[citation needed]}

Specifications (Pobjoy R)

Data from Lumsden.

General characteristics

• 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)
• Diameter: 25.5 in (647.7 mm)
• Dry weight: 135 lb

Components

• Oil system: Dry sump
• Cooling system: Air-cooled

Performance

• Power output: 85 hp
• Specific power: 0.5 hp/cu in
• Fuel consumption: 4.9 imp. gallons per hour
• Power-to-weight ratio: 0.63 hp/lb

See also

Related development

• Pobjoy Niagara

Comparable engines

• Rotec R2800

Related lists

• List of aircraft engines