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The Pratt & Whitney R-1830 Twin Wasp is an American air-cooled radial aircraft engine. It displaces 1,830 cu in (30.0 L) and its bore and stroke are both 5.5 in (140 mm). The design traces its history to 1929 experiments at Pratt & Whitney on twin-row designs. Production began in 1932 and it was widely used during the 1930s.
It was selected as the power plant for both the four-engined Consolidated B-24 Liberator heavy bomber and the twin-engined Douglas DC-3 transport, two of the most-produced aircraft. The production run of 173,618 R-1830 examples makes it the most-produced aviation engine in history.
A further developed version, the R-2000, was produced starting in 1942. The R-2000 was "bored-out" to 5.75 in (146 mm) and had a number of other minor changes to improve fuel economy and allow it to run at higher power ratings on lower-octane fuel. The primary user of the R-2000 was the Douglas DC-4.
Mostly retired today, the R-1830 is still used on Douglas DC-3 and various museum aircraft and warbirds seen at airshows. It is not manufactured anymore, but spares are still available and there is still a market for second-hand engines and parts.

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