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| Pratt & Whitney R-985 Wasp Junior | |
|---|---|
| Name | Pratt & Whitney R-985 Wasp Junior |
| Type | Air-cooled radial piston engine |
| Country | United States |
| First run | 1933 |
| Produced | 1933–1950s |
| Manufacturer | Pratt & Whitney |
| Displacement | 985 cu in (16.1 L) |
| Power | 300–450 hp |
Pratt & Whitney R-985 Wasp Junior The Pratt & Whitney R-985 Wasp Junior is a family of nine-cylinder, air-cooled radial aircraft engines produced by Pratt & Whitney beginning in 1933 for use in civil and military aircraft; it powered types used by United States Army Air Corps, Royal Air Force, and numerous commercial operators, influencing designs by Boeing, Cessna, and Beechcraft. The R-985 evolved from earlier radial developments at Pratt & Whitney under leadership associated with engineers who also worked with Sperry Corporation and suppliers like Hamilton Standard and became a mainstay through World War II and the early postwar era in liaison, trainer, and utility roles linked to programs such as those run by Curtiss-Wright and Douglas Aircraft Company.
The R-985 originated during an era when William Boeing and executives at Glenn L. Martin Company sought compact, reliable powerplants for light transports and trainers, prompting Pratt & Whitney designers influenced by work from Sikorsky Aircraft and engineers formerly at Wright Aeronautical to scale down the larger R-1340 Wasp architecture. Development involved collaboration with suppliers like Hamilton Standard for propellers, Bendix Corporation for magnetos, and testing at facilities connected to Langley Research Center and National Advisory Committee for Aeronautics. Certification trials engaged authorities analogous to Civil Aeronautics Authority and military procurement offices linked to Army Air Forces, with early prototypes bench-tested alongside engines from Lycoming Engines and Continental Motors.
The R-985 uses a single-row, nine-cylinder radial layout with a 5.75 in (146 mm) bore and 6.0 in (152 mm) stroke derived from earlier Pratt & Whitney designs; displacement is 985 cu in (16.1 L), producing nominal outputs from about 300 hp to roughly 450 hp depending on model and supercharging similar to contemporaneous units used by Grumman and Lockheed. The engine features air cooling, steel crankshafts akin to those in Allison Engine Company products, aluminum alloy crankcases, and valve gear comparable to components sourced by Wright Aeronautical; accessory drives accommodated fuel systems from Stromberg or Bendix, ignition by Delco-Remy or Wico, and carburetion variants used on aircraft by Fairchild and Bell Aircraft Corporation. Weight, dimensions, compression ratios, and power curves varied among military and civilian variants which paralleled specification practices at Douglas Aircraft Company and inspection standards used by Military Aircraft Board-type organizations.
Introduced in the 1930s, the R-985 served widely in civil aviation on types flown by Trans World Airlines, Pan American World Airways, and smaller regional carriers, and in military service with operators including the United States Navy, Royal Canadian Air Force, and Royal Australian Air Force for utility, trainer, and liaison roles. It saw frontline and rear-area use during World War II in aircraft types comparable to those flown in campaigns involving European Theatre of World War II and Pacific Theatre of World War II, supporting operations alongside aircraft powered by Pratt & Whitney R-1340 and engines from Rolls-Royce. Postwar, surplus-engined aircraft operated in civil bush flying in regions served by Alaska Airlines-like operators and aerial survey companies with logistical links to Civil Air Transport-style enterprises.
Multiple R-985 variants differed by compression ratio, supercharger gearing, accessory drives, and military designations used in procurement by entities such as United States Army Air Forces and Royal Air Force; examples include lower-rated versions for training aircraft and higher-rated certified models for transport conversions, paralleling variant practices seen in Allison V-1710 and Wright R-1820 lines. Specialized versions incorporated features for cold-weather operations used in Canadian RCAF service, or for maritime patrol aircraft akin to those flown by Royal Navy-affiliated squadrons, with some modifications inspired by collaboration with firms like Hamilton Standard and Bendix Corporation.
The R-985 powered a broad range of aircraft including types by Beechcraft (models similar to those fielded by Civil Air Patrol), Cessna light transports, Stinson Aircraft Company utility airplanes, Waco biplanes, and military trainers analogous to those produced by North American Aviation and Stearman. It was installed in civil airliners and executive transports operated by companies such as Lockheed Corporation-built conversions and in bush planes used by operators comparable to Reid and Sigrist and De Havilland-associated services. The engine's adaptability made it suitable for glider tugs, crop dusters, and amphibious conversions in fleets maintained by organizations like Pan American World Airways and regional carriers.
Manufacture occurred at Pratt & Whitney plants with supply chains involving metal suppliers such as Alcoa and component manufacturers like Hamilton Standard, Bendix Corporation, and Delco-Remy. Wartime production ramp-up paralleled industrial mobilization seen at Willow Run and other American plants, coordinated with procurement offices resembling War Production Board mechanisms and subcontracting networks that included firms such as Curtiss-Wright and General Motors divisions. After World War II, limited production and overhaul work continued at Pratt & Whitney and independent overhaul facilities similar to those run by Trans-Canada Airlines maintenance divisions.
Many R-985 engines remain airworthy in restored aircraft operated by museums such as Smithsonian Institution National Air and Space Museum, Imperial War Museum, and regional institutions affiliated with EAA AirVenture events, while static examples are displayed in collections maintained by National Museum of the United States Air Force and Royal Air Force Museum. Active preservation efforts involve restoration groups linked to Commemorative Air Force, Shuttleworth Collection, and volunteer organizations that coordinate parts and documentation comparable to archives at NASM and university libraries holding materials associated with Pratt & Whitney. Surviving airframes with R-985s participate in airshows, film productions, and historical flights honoring interwar and World War II-era aviation heritage managed by institutions like Aero Club-type societies.
Category:Aircraft piston engines