Designed in 1946 by a team led by Lionel Haworth, the Dart had a two-stage centrifugal compressor design derived from the earlier Rolls-Royce Clyde. The Dart was initially rated at 890 shp and first flew in October 1947 mounted to the nose of a converted Avro Lancaster. Improvements in the design boosted power output to 1,400 shp in the RDa.3, which went into production for the Viscount in 1952. The RDa.6 increased power to 1,600 shp and the RDa.7 to 1,800 shp by adding another compressor stage.