This turboprop achieved renown as the power unit of the Vickers Viscount, it has also been flown on a limited scale in the Avro Athena and Boulton Paul Balliol advanced trainers.
The Dart is characterized by a two-stage centrifugal compressor, handling about 20 lb of air per second, and a two-stage turbine. Steel guide vanes direct the air between the 19 rotor blades, from which it is impelled at high speed. After passing through a diffuser the flow is directed through curved passages, formed by the compressor casings and inter-stage guide vanes, into the second rotor.
The two stages of the turbine are locked together on a common shaft and the blades of the high and low pressure, stages have "fir tree" roots. Both discs are cooled on their front and rear faces, and a steel-strip seal prevents gas leakage between the stages. There are seven combustion chambers.
Under tropical conditions lost take-off power is restored by water/methanol injection.
The Dart RDa.6 was in production for Viscounts, and has a new reduction gear and other refinements, making possible a maximum rating of 1,500 h.p. The RDa.5 was completely new, and designed for even greater powers. It is scheduled to power the Viscount 800 Series.
Dry weight, 1,030 lb
Max. power, 1,400 s.h.p. plus 365 lb thrust
Equivalent shaft horsepower, 1,515 at 14,500 r.p.m
Specific fuel consumption, 0.83 lb/hr/e.s.h.p.