The Pratt & Whitney R-1340 Wasp is a nine-cylinder, air-cooled radial engine that established the company's reputation in aviation. The first Wasp was completed on 24 December 1925, only months after the company was incorporated. Its combination of reliability and useful power made it important to military aircraft and early commercial transport.[1]Pratt & Whitney Wasp A, R-1300 (R-1340), Radial 9 EngineSmithsonian Institution · si.edu · Accessed 2026-09-13Open source details
First engines
Frederick Rentschler founded Pratt & Whitney Aircraft after leaving Wright, with the intention of building air-cooled radials for a market encouraged by US Navy interest. The first Wasp completed a 50-hour approval test in March 1926. A second engine flew in a Wright F3W-1 Apache on 5 May, and a contract for 200 production engines followed. Deliveries were completed before the end of that year.[1]Pratt & Whitney Wasp A, R-1300 (R-1340), Radial 9 EngineSmithsonian Institution · si.edu · Accessed 2026-09-13Open source details
Design and development
The Wasp used one row of nine cylinders with approximately equal bore and stroke. The Smithsonian's original engine has a displacement of 1,344 cubic inches and a rating of 425 horsepower at 1,900 rpm. Its later SC1 example is rated at 450 horsepower at 2,100 rpm, illustrating development within the same basic displacement class. Subsequent models reached 600 horsepower.[1]Pratt & Whitney Wasp A, R-1300 (R-1340), Radial 9 EngineSmithsonian Institution · si.edu · Accessed 2026-09-13Open source details[2]Pratt & Whitney Wasp R-1340 SC1, Radial 9 EngineSmithsonian Institution · si.edu · Accessed 2026-09-13Open source details
Expanding applications
The Boeing F2B-1 was the first operational aircraft to use the engine. The Wasp also contributed to the commercial success of the Boeing 40A. Later installations ranged from Lockheed landplanes and Fairchild utility aircraft to Sikorsky amphibians. The SC1 alone was used across numerous Bellanca, Lockheed, Fairchild and Sikorsky models, demonstrating the adaptability of a compact radial package.[2]Pratt & Whitney Wasp R-1340 SC1, Radial 9 EngineSmithsonian Institution · si.edu · Accessed 2026-09-13Open source details
Utility service
One later application was the Noorduyn Norseman. The military UC-64A used the 600-horsepower R-1340-AN1 and could operate on wheels, floats or skis. That installation extended the Wasp's usefulness into remote transport and wartime utility work. The engine family remained in production until 1960, spanning the period from open-cockpit biplanes to the arrival of jet airliners.[3]Noorduyn UC-64A NorsemanNational Museum of the United States Air Force · nationalmuseum.af.mil · Accessed 2026-09-13Open source details[2]Pratt & Whitney Wasp R-1340 SC1, Radial 9 EngineSmithsonian Institution · si.edu · Accessed 2026-09-13Open source details