 The W.1 used a double-sided centrifugal compressor of Hiduminium RR.59 alloy, reverse-flow 'Lubbock' combustion chambers and a water-cooled axial-flow turbine section using 72 blades with 'fir-tree' root fixings; the turbine was later modified to use air-cooling.The turbine blades were of Firth-Vickers "Rex 78", a stainless steel developed under Dr. W. H Hatfield.Design rating was at 16,500 rpm, increased to 17,750 rpm above 4,000 feet.